Foreword
This Synthesis Report (SYR) concludes the Sixth Assessment Report
(AR6) of the Intergovernmental Panel on Climate Change (IPCC).
The SYR synthesizes and integrates materials contained within the
three Working Groups Assessment Reports and the Special Reports
contributing to the AR6. It addresses a broad range of policy-relevant
but policy-neutral questions approved by the Panel.
The SYR is the synthesis of the most comprehensive assessment of
climate change undertaken thus far by the IPCC: Climate Change 2021:
The Physical Science Basis; Climate Change 2022: Impacts, Adaptation
and Vulnerability; and Climate Change 2022: Mitigation of Climate
Change. The SYR also draws on the findings of three Special Reports
completed as part of the Sixth Assessment – Global Warming of 1.5°C
(2018): an IPCC Special Report on the impacts of global warming of
1.5°C above pre-industrial levels and related global greenhouse gas
emission pathways, in the context of strengthening the global response
to the threat of climate change, sustainable development, and efforts
to eradicate poverty (SR1.5); Climate Change and Land (2019): an IPCC
Special Report on climate change, desertification, land degradation,
sustainable land management, food security, and greenhouse gas
fluxes in terrestrial ecosystems (SRCCL); and The Ocean and Cryosphere
in a Changing Climate (2019) (SROCC).
The AR6 SYR confirms that unsustainable and unequal energy and land use
as well as more than a century of burning fossil fuels have unequivocally
caused global warming, with global surface temperature reaching 1.1°C
above 1850–1900 in 2011–2020. This has led to widespread adverse
impacts and related losses and damages to nature and people. The
nationally determined contributions (NDCs) committed by 2030 show the
temperature will increase by 1.5°C in the first half of the 2030s, and will
make it very difficult to control temperature increase by 2.0°C towards
the end of 21st century. Every increment of global warming will intensify
multiple and concurrent hazards in all regions of the world.
The report points out that limiting human-caused global warming
requires net zero CO2 emissions. Deep, rapid, and sustained mitigation
and accelerated implementation of adaptation actions in this decade
would reduce projected losses and damages for humans and ecosystems
and deliver many co-benefits, especially for air quality and health.
Delayed mitigation and adaptation action would lock-in high-emissions
infrastructure, raise risks of stranded assets and cost-escalation, reduce
feasibility, and increase losses and damages. Near-term actions involve
high up-front investments and potentially disruptive changes that can
be lessened by a range of enabling policies.
As an intergovernmental body jointly established in 1988 by
the World Meteorological Organization (WMO) and the United
Nations Environment Programme (UNEP), the IPCC has provided
policymakers with the most authoritative and objective scientific
and technical assessments in this field. Beginning in 1990, this
series of IPCC Assessment Reports, Special Reports, Technical Papers,
Methodology Reports, and other products have become standard
works of reference.

The SYR was made possible thanks to the voluntary work, dedication
and commitment of thousands of experts and scientists from around
the globe, representing a range of views and disciplines. We would like
to express our deep gratitude to all the members of the Core Writing
Team of the SYR, members of the Extended Writing Team, Contributing
Authors, and the Review Editors, all of whom enthusiastically took on
the huge challenge of producing an outstanding SYR on top of the other
tasks they had already committed to during the AR6 cycle. We would
also like to thank the staff of the Technical Support Unit of the SYR and
the IPCC Secretariat for their dedication in organizing the production of
this IPCC report.
We also wish to acknowledge and thank the governments of the IPCC
member countries for their support of scientists in developing this
report, and for their contributions to the IPCC Trust Fund to provide the
essentials for participation of experts from developing countries and
countries with economies in transition. We would like to express our
appreciation to the government of Singapore for hosting the Scoping
Meeting of the SYR, to the government of Ireland for hosting the third
Core Writing Team meeting of the SYR, and to the government of
Switzerland for hosting the 58th Session of the IPCC where the SYR
was approved. The generous financial support from the government of
the Republic of Korea enabled the smooth operation of the Technical
Support Unit of the SYR. This is gratefully acknowledged.
We would particularly like to express our thanks to the IPCC Chair, the
IPCC Vice-Chairs and the Co-Chairs for their dedicated work throughout
the production of this report.
Petteri Taalas
Secretary-General of the World Meteorological Organization

Inger Andersen
Under-Secretary-General of the United Nations and Executive Director
of the UN Environment Programme

Preface

This Synthesis Report (SYR) constitutes the final product of the
Sixth Assessment Report (AR6) of the Intergovernmental Panel on
Climate Change (IPCC). It summarizes the state of knowledge of
climate change, its widespread impacts and risks, and climate change
mitigation and adaptation, based on the peer-reviewed scientific,
technical, and socio-economic literature since the publication of the
IPCC’s Fifth Assessment Report (AR5) in 2014.
This SYR distills, synthesizes, and integrates the key findings of the
three Working Group contributions – Climate Change 2021: The
Physical Science Basis; Climate Change 2022: Impacts, Adaptation and
Vulnerability; and Climate Change 2022: Mitigation of Climate Change.
The SYR also draws on the findings of three Special Reports completed
as part of the Sixth Assessment – Global Warming of 1.5°C (2018):
an IPCC Special Report on the impacts of global warming of 1.5°C
above pre-industrial levels and related global greenhouse gas emission
pathways, in the context of strengthening the global response to the
threat of climate change, sustainable development, and efforts to
eradicate poverty (SR1.5); Climate Change and Land (2019): an IPCC
Special Report on climate change, desertification, land degradation,
sustainable land management, food security, and greenhouse gas fluxes
in terrestrial ecosystems (SRCCL); and The Ocean and Cryosphere in a
Changing Climate (2019) (SROCC). The SYR, therefore, is a comprehensive,
timely compilation of assessments of the most recent scientific, technical,
and socio-economic literature dealing with climate change.
Scope of the report
The SYR is a self-contained synthesis of the most policy-relevant
material drawn from the scientific, technical, and socio-economic
literature assessed during the Sixth Assessment. This report integrates
the main findings of the AR6 Working Group reports and the three
AR6 Special Reports. It recognizes the interdependence of climate,
ecosystems and biodiversity, and human societies; the value of
diverse forms of knowledge; and the close linkages between climate
adaptation, mitigation, ecosystem health, human well-being, and
sustainable development. Building on multiple analytical frameworks,
including those from the physical and social sciences, this report
identifies opportunities for transformative action which are effective,
feasible, just and equitable systems transitions, and climate resilient
development pathways. Different regional classification schemes are
used for physical, social and economic aspects, reflecting the underlying
literature.
The Synthesis Report emphasizes near-term risks and options for
addressing them to give policymakers a sense of the urgency required
to address global climate change. The report also provides important
insights about how climate risks interact with not only one another
but non-climate-related risks. It describes the interaction between
mitigation and adaptation and how this combination can better confront
the climate challenge as well as produce valuable co-benefits. It
highlights the strong connection between equity and climate action and
why more equitable solutions are vital to addressing climate change. It
also emphasizes how growing urbanization provides an opportunity for
ambitious climate action to advance climate resilient development and
sustainable development for all. And it underscores how restoring and
protecting land and ocean ecosystems can bring multiple benefits to
biodiversity and other societal goals, just as a failure to do so presents
a major risk to ensuring a healthy planet.

Structure
The SYR comprises a Summary for Policymakers (SPM) and a longer report
from which the SPM is derived, as well as annexes.
To facilitate access to the findings of the SYR for a wide readership, each
part of the SPM carries highlighted headline statements. Taken together,
these 18 headline statements provide an overarching summary in
simple, non-technical language for easy assimilation by readers from
different walks of life.
The SPM follows a structure and sequence like that in the longer report,
but some issues covered in more than one section of the longer report
are summarized in a single location in the SPM. Each paragraph of the
SPM contains references to the supporting text in the longer report.
In turn, the longer report contains extensive references to relevant
portions of the Working Group Reports or Special Reports mentioned
above.
The longer report is structured around three topic headings as
mandated by the Panel. A brief Introduction (Section1) is followed by
three sections.
Section 2, ‘Current Status and Trends’, opens with the assessment of
observational evidence for our changing climate, historical and current
drivers of human-induced climate change, and its impacts. It assesses the
current implementation of adaptation and mitigation response options.
Section 3, ‘Long-Term Climate and Development Futures’, provides an
assessment of climate change to 2100 and beyond in a broad range of
socio-economic futures. It considers long-term impacts, risks and costs
in adaptation and mitigation pathways in the context of sustainable
development. Section 4, ‘Near-Term Responses in a Changing Climate’,
assesses opportunities for scaling up effective action in the period to
2040, in the context of climate pledges, and commitments, and the
pursuit of sustainable development.
Annexes containing a glossary of terms used, list of acronyms, authors,
Review Editors, the SYR Scientific Steering Committee, and Expert
Reviewers complete the report.

Process
The SYR was prepared in accordance with the procedures of the IPCC.
A scoping meeting to develop a detailed outline of the AR6 Synthesis
Report was held in Singapore from 21 to 23 October 2019 and the
outline produced in that meeting was approved by the Panel at the 52nd
IPCC Session from 24 to 28 February 2020 in Paris, France.
In accordance with IPCC procedures, the IPCC Chair, in consultation
with the Co-Chairs of the Working Groups, nominated authors for the
Core Writing Team (CWT) of the SYR. A total of 30 CWT members and
9 Review Editors were selected and accepted by the IPCC Bureau at its
58th Session on 19 May 2020. In the process of developing the SYR,
7 Extended Writing Team (EWT) authors were selected by the CWT and
approved by the Chair and the IPCC Bureau, and 28 Contributing Authors
were selected by the CWT with the approval of the Chair. These
additional authors were to enhance and deepen the expertise required
for the preparation of the Report. The Chair established at the 58th
Session of the Bureau an SYR Scientific Steering Committee (SSC) with a
mandate to advise the development of the SYR. The SYR SSC comprised
the members of the IPCC Bureau, excluding those members who served
as Review Editors for the SYR.
Due to the covid pandemic, the first two meetings of the CWT were held
virtually from 25 to 29 January 2021 and from 16 to 20 August 2021.
The First Order Draft (FOD) was released to experts and governments
for review on 10 January 2022 with comments due on 20 March 2022.
The CWT met in Dublin from 25 to 28 March 2022 to discuss how
best to revise the FOD to address the more than 10,000 comments
received. The Review Editors monitored the review process to
ensure that all comments received appropriate consideration.
The IPCC circulated a final draft of the Summary for Policymakers
and a longer report of the SYR to governments for review from
21 November 2022 to 15 January 2023 which resulted in over 6,000
comments. A final SYR draft for approval incorporating the comments
from the final government distribution was submitted to the IPCC
member governments on 8 March 2023.
The Panel at its 58th Session, held from 13 to 17 March 2023 in
Interlaken, Switzerland, approved the SPM line by line and adopted the
longer report section by section.

Acknowledgements
The SYR was made possible thanks to the hard work and commitment to
excellence shown by the Section Facilitators, members of CWT and EWT,
and Contributing Authors. Specific thanks are due to Section Facilitators
Kate Calvin, Dipak Dasgupta, Gerhard Krinner, Aditi Mukherji, Peter Thorne,
and Christopher Trisos whose work was essential in ensuring a high
standard of the longer report sections and the SPM.

We would like to express our appreciation to the IPCC member
governments, observer organizations, and expert reviewers for providing
constructive comments on the draft reports. We would like to thank
the Review Editors Paola Arias, Mercedes Bustamante, Ismail Elgizouli,
Gregory Flato, Mark Howden, Steven Rose, Yamina Saheb, Roberto Sánchez,
and Cunde Xiao for their work on the treatment of FOD comments, and
Gregory Flato, Carlos Méndez, Joy Jacqueline Pereira, Ramón Pichs-
Madruga, Diana Ürge-Vorsatz, and Noureddine Yassaa for their work
during the approval session, collaborating with author teams to ensure
consistency between the SPM and the underlying reports.
We are grateful to the members of the SSC for their thoughtful advice
and support for the SYR throughout the process: IPCC Vice-Chairs Ko
Barret, Thelma Krug, and Youba Sokona; Co-Chairs of Working
Groups (WG) and Task Force on National Greenhouse Gas Inventories
(TFI) Valérie Masson-Delmotte, Panmao Zhai, Hans-Otto Pörtner,
Debra Roberts, Priyadarshi R. Shukla, Jim Skea, Eduardo Calvo Buendía,
and Kiyoto Tanabe; WG Vice-Chairs Edvin Aldrian, Fatima Driouech,
Jan Fuglestvedt, Muhammad Tariq, Carolina Vera, Noureddine Yassaa,
Andreas Fischlin, Joy Jacqueline Pereira, Sergey Semenov, Pius Yanda,
Taha M, Zatari, Amjad Abdulla, Carlo Carraro, Diriba Korecha Dadi,
Nagmeldin G.E. Mahmoud, Ramón Pichs-Madruga, Andy Reisinger,
and Diana Ürge-Vorsatz. The IPCC Vice-Chairs and WG Co-Chairs served
also as members of the CWT and we are grateful for their contributions.
We wish to thank the IPCC Secretariat for their guidance and support
for the SYR in preparation, release and publication of the Report:
Deputy Secretary Emira Fida, Mudathir Abdallah, Jesbin Baidya,
Laura Biagioni, Oksana Ekzarkho, Judith Ewa, Joëlle Fernandez,
Emelie Larrode, Jennifer Lew Schneider, Andrej Mahecic, Nina Peeva,
Mxolisi Shongwe, Melissa Walsh, and Werani Zabula. Their support for
the successful SYR was truly outstanding throughout the entire process.
Our thanks go to José Romero, Head of the SYR Technical Support Unit
(SYR TSU) and Jinmi Kim, Director of Administration, and the members
of the SYR TSU, Arlene Birt, Meeyoung Ha, Erik Haites, Lance Ignon,
Yonghun Jung, Dan Jezreel Orendain, Robert Stavins, Semin Park, and
Youngin Park for their hard work to facilitate the development and
production of the SYR with deep commitment and dedication to ensure
an outstanding SYR. Our thanks also go to Woochong Um and his team
at the Asian Development Bank for facilitation of the SYR TSU operation.
We extend our appreciation of the enthusiasm, dedication, and
professional contributions of WG TSU members Sarah Connors,
Clotilde Péan, and Anna Pirani from WG I, Marlies Craig,
Katja Mintenbeck, Elvira Poloczanska, Melinda Tignor from WG II and
Roger Fradera, Minal Pathak, Raphael Slade, Shreya Some, and
Geninha Gabao Lisboa from WG III, working as a team with the SYR TSU,
which contributed to the successful outcome of the Session.
We are appreciative of the member governments of the IPCC who
graciously hosted the SYR scoping meeting, a CWT Meeting and
the 58th Session of the IPCC: Singapore, Ireland, and Switzerland,
respectively. We express our thanks to the IPCC member governments,
WMO, UNEP and the UNFCCC for their contributions to the Trust Fund
which supported various elements of expenditure. We wish to particularly
thank the Korea Meteorological Administration, Republic of Korea for its
generous financial support of the SYR TSU. We acknowledge the support
of IPCC’s parent organizations, UNEP and WMO, and particularly WMO
for hosting the IPCC Secretariat. Finally, may we convey our deep
gratitude to the UNFCCC for their cooperation at various stages of this
enterprise and for the prominence they give to our work in several fora.

Hoesung Lee
Chairman of the IPCC
Abdalah Mokssit
Secretary of the IPCC

Contents

Foreword -------------------------------------------------------------------------------------------------------------------------- v
Preface ---------------------------------------------------------------------------------------------------------------------------- vii
Summary for Policymakers ------------------------------------------------------------------------------------------- 1
Introduction -------------------------------------------------------------------------------------------------------------- 3
A. Current Status and Trends ----------------------------------------------------------------------------------------- 4
Box SPM.1 | Scenarios and pathways ------------------------------------------------------------------------------- 9
B. Future Climate Change, Risks, and Long-Term Responses ------------------------------------------------- 12
C. Responses in the Near Term ------------------------------------------------------------------------------------- 24
Climate Change 2023 ------------------------------------------------------------------------------------------------- 35
Section 1: Introduction ----------------------------------------------------------------------------------------------- 38
Section 2: Current Status and Trends ----------------------------------------------------------------------------- 41
2.1 Observed Changes, Impacts and Attribution ----------------------------------------------------------------42
2.1.1 Observed Warming and its Causes ---------------------------------------------------------------------- 42
2.1.2 Observed Climate System Changes and Impacts to Date ------------------------------------------ 46
2.2 Responses Undertaken to Date -------------------------------------------------------------------------------- 52
2.2.1 Global Policy Setting --------------------------------------------------------------------------------------- 52
2.2.2 Mitigation Actions to Date -------------------------------------------------------------------------------- 53
2.2.3 Adaptation Actions to Date ------------------------------------------------------------------------------- 55
2.3 Current Mitigation and Adaptation Actions and Policies are not Sufficient ------------------------- 57
2.3.1 The Gap Between Mitigation Policies, Pledges and Pathways that Limit Warming to
1.5°C or Below 2°C ---------------------------------------------------------------------------------------- 57
Cross-Section Box.1| Understanding Net Zero CO2 and Net Zero GHG Emissions ---------------------- 80
2.3.2 Adaptation Gaps and Barriers ---------------------------------------------------------------------------- 61
2.3.3 Lack of Finance as a Barrier to Climate Action ------------------------------------------------------- 63
Cross-Section Box.2 | Scenarios, Global Warming Levels, and Risks ----------------------------------------- 63
Contents
Front matter
SPM
Sections
xii
Section 3: Long-Term Climate and Development Futures---------------------------------------------------- 67
3.1 Long-Term Climate Change, Impacts and Related Risks ------------------------------------------------- 68
3.1.1 Long-term Climate Change ------------------------------------------------------------------------------- 68
3.1.2 Impacts and Related Risks -------------------------------------------------------------------------------- 71
3.1.3 The Likelihood and Risks of Abrupt and Irreversible Change -------------------------------------- 77
3.2 Long-term Adaptation Options and Limits ------------------------------------------------------------------ 78
3.3 Mitigation Pathways --------------------------------------------------------------------------------------------- 82
3.3.1 Remaining Carbon Budgets ------------------------------------------------------------------------------- 82
3.3.2 Net Zero Emissions: Timing and Implications --------------------------------------------------------- 85
3.3.3 Sectoral Contributions to Mitigation -------------------------------------------------------------------- 86
3.3.4 Overshoot Pathways: Increased Risks and Other Implications ------------------------------------- 87
3.4 Long-Term Interactions Between Adaptation, Mitigation and Sustainable Development ----------------- 88
3.4.1 Synergies and trade-offs, costs and benefits ---------------------------------------------------------- 88
3.4.2 Advancing Integrated Climate Action for Sustainable Development ----------------------------- 89
Section 4: Near-Term Responses in a Changing Climate ----------------------------------------------------- 91
4.1The Timing and Urgency of Climate Action ------------------------------------------------------------------ 92
4.2 Benefits of Strengthening Near-Term Action --------------------------------------------------------------- 95
4.3 Near-Term Risks -------------------------------------------------------------------------------------------------- 97
4.4 Equity and Inclusion in Climate Change Action ---------------------------------------------------------- 101
4.5 Near-Term Mitigation and Adaptation Actions ---------------------------------------------------------- 102
4.5.1 Energy Systems -------------------------------------------------------------------------------------------- 104
4.5.2 Industry ----------------------------------------------------------------------------------------------------- 104
4.5.3 Cities, Settlements and Infrastructure ----------------------------------------------------------------- 105
4.5.4 Land, Ocean, Food, and Water -------------------------------------------------------------------------- 106
4.5.5 Health and Nutrition -------------------------------------------------------------------------------------- 106
4.5.6 Society, Livelihoods, and Economies ------------------------------------------------------------------ 107
4.6 Co-Benefits of Adaptation and Mitigation for Sustainable Development Goals ------------------ 108
4.7 Governance and Policy for Near-Term Climate Change Action ---------------------------------------- 110
4.8 Strengthening the Response: Finance, International Cooperation and Technology --------------- 111
4.8.1 Finance for Mitigation and Adaptation Actions ----------------------------------------------------- 111
4.8.2 International Cooperation and Coordination -------------------------------------------------------- 112
4.8.3 Technology Innovation, Adoption, Diffusion and Transfer ----------------------------------------- 113
4.9 Integration of Near-Term Actions Across Sectors and Systems ---------------------------------------- 114
xiii
Annexes ---------------------------------------------------------------------------------------------------------------- 117
I. Glossary -------------------------------------------------------------------------------------------------------------------- 119
II. Acronyms, Chemical Symbols and Scientific Units ----------------------------------------------------------------- 131
III. Contributors --------------------------------------------------------------------------------------------------------------- 135
IV. Expert Reviewers --------------------------------------------------------------------------------------------------------- 143
V. Publications by the Intergovernmental Panel on Climate Change ---------------------------------------------- 161
Index -------------------------------------------------------------------------------------------------------------------- 163

Sources cited in this Synthesis Report
References for material contained in this report are given in curly brackets {} at the end of each paragraph.
In the Summary for Policymakers, the references refer to the numbers of the sections, figures, tables and boxes in the underlying
Introduction and Topics of this Synthesis Report.
In the Introduction and Sections of the longer report, the references refer to the contributions of the Working Groups I, II and
III (WGI, WGII, WGIII) to the Sixth Assessment Report and other IPCC Reports (in italicized curly brackets), or to other sections
of the Synthesis Report itself (in round brackets).
The following abbreviations have been used:
SPM: Summary for Policymakers
TS: Technical Summary
ES: Executive Summary of a chapter
Numbers denote specific chapters and sections of a report.
Other IPCC reports cited in this Synthesis Report:
SR1.5: Global Warming of 1.5°C
SRCCL: Climate Change and Land
SROCC: The Ocean and Cryosphere in a Changing Climate

Climate Change 2023
Synthesis Report
Summary for Policymakers

Introduction
This Synthesis Report (SYR) of the IPCC Sixth Assessment Report (AR6) summarises the state of knowledge of climate change,
its widespread impacts and risks, and climate change mitigation and adaptation. It integrates the main findings of the Sixth
Assessment Report (AR6) based on contributions from the three Working Groups1, and the three Special Reports2. The summary
for Policymakers (SPM) is structured in three parts: SPM.A Current Status and Trends, SPM.B Future Climate Change, Risks, and
Long-Term Responses, and SPM.C Responses in the Near Term3.
This report recognizes the interdependence of climate, ecosystems and biodiversity, and human societies; the value of diverse
forms of knowledge; and the close linkages between climate change adaptation, mitigation, ecosystem health, human well-being
and sustainable development, and reflects the increasing diversity of actors involved in climate action.
Based on scientific understanding, key findings can be formulated as statements of fact or associated with an assessed level of
confidence using the IPCC calibrated language4.
A. Current Status and Trends
Observed Warming and its Causes
A.1 Human activities, principally through emissions of greenhouse gases, have unequivocally
caused global warming, with global surface temperature reaching 1.1°C above 1850–1900
in 2011–2020. Global greenhouse gas emissions have continued to increase, with unequal
historical and ongoing contributions arising from unsustainable energy use, land use and
land-use change, lifestyles and patterns of consumption and production across regions,
between and within countries, and among individuals (high confidence). {2.1, Figure 2.1,
Figure 2.2}
A.1.1 Global surface temperature was 1.09 [0.95 to 1.20]°C5 higher in 2011–2020 than 1850–19006, with larger increases
over land (1.59 [1.34 to 1.83]°C) than over the ocean (0.88 [0.68 to 1.01]°C). Global surface temperature in the first two
decades of the 21 st century (2001–2020) was 0.99 [0.84 to 1.10]°C higher than 1850–1900. Global surface temperature
has increased faster since 1970 than in any other 50-year period over at least the last 2000 years (high confidence).
{2.1.1, Figure 2.1}
A.1.2 The likely range of total human-caused global surface temperature increase from 1850–1900 to 2010–20197 is 0.8°C to
1.3°C, with a best estimate of 1.07°C. Over this period, it is likely that well-mixed greenhouse gases (GHGs) contributed
a warming of 1.0°C to 2.0°C8, and other human drivers (principally aerosols) contributed a cooling of 0.0°C to 0.8°C,
natural (solar and volcanic) drivers changed global surface temperature by –0.1°C to +0.1°C, and internal variability
changed it by –0.2°C to +0.2°C. {2.1.1, Figure 2.1}
A.1.3 Observed increases in well-mixed GHG concentrations since around 1750 are unequivocally caused by GHG emissions
from human activities over this period. Historical cumulative net CO2 emissions from 1850 to 2019 were 2400 ± 240 GtCO2
of which more than half (58%) occurred between 1850 and 1989, and about 42% occurred between 1990 and 2019 (high
confidence). In 2019, atmospheric CO 2 concentrations (410 parts per million) were higher than at any time in at least 2
million years (high confidence), and concentrations of methane (1866 parts per billion) and nitrous oxide (332 parts per
billion) were higher than at any time in at least 800,000 years (very high confidence). {2.1.1, Figure 2.1}
A.1.4 Global net anthropogenic GHG emissions have been estimated to be 59 ± 6.6 GtCO2 -eq9 in 2019, about 12% (6.5 GtCO2-eq)
higher than in 2010 and 54% (21 GtCO2-eq) higher than in 1990, with the largest share and growth in gross GHG emissions
occurring in CO2 from fossil fuels combustion and industrial processes (CO2-FFI) followed by methane, whereas the highest
relative growth occurred in fluorinated gases (F-gases), starting from low levels in 1990. Average annual GHG emissions
during 2010–2019 were higher than in any previous decade on record, while the rate of growth between 2010 and
2019 (1.3% yr-1 ) was lower than that between 2000 and 2009 (2.1% yr-1 ). In 2019, approximately 79% of global GHG
emissions came from the sectors of energy, industry, transport, and buildings together and 22%10 from agriculture,
forestry and other land use (AFOLU). Emissions reductions in CO2 -FFI due to improvements in energy intensity of GDP
and carbon intensity of energy, have been less than emissions increases from rising global activity levels in industry,
energy supply, transport, agriculture and buildings. (high confidence) {2.1.1}
A.1.5 Historical contributions of CO2 emissions vary substantially across regions in terms of total magnitude, but also in
terms of contributions to CO 2 -FFI and net CO 2 emissions from land use, land-use change and forestry (CO 2-LULUCF).
In 2019, around 35% of the global population live in countries emitting more than 9 tCO 2-eq per capita11 (excluding
CO2 -LULUCF) while 41% live in countries emitting less than 3 tCO2 -eq per capita; of the latter a substantial share lacks
access to modern energy services. Least Developed Countries (LDCs) and Small Island Developing States (SIDS) have
much lower per capita emissions (1.7 tCO2 -eq and 4.6 tCO2-eq, respectively) than the global average (6.9 tCO2-eq),
excluding CO 2 -LULUCF. The 10% of households with the highest per capita emissions contribute 34–45% of global
consumption-based household GHG emissions, while the bottom 50% contribute 13–15%. (high confidence) {2.1.1,
Figure 2.2}
Observed Changes and Impacts
A.2 Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have
occurred. Human-caused climate change is already affecting many weather and climate
extremes in every region across the globe. This has led to widespread adverse impacts and
related losses and damages to nature and people (high confidence). Vulnerable communities
who have historically contributed the least to current climate change are disproportionately
affected (high confidence). {2.1, Table 2.1, Figure 2.2, Figure 2.3} (Figure SPM.1)
A.2.1 It is unequivocal that human influence has warmed the atmosphere, ocean and land. Global mean sea level increased by
0.20 [0.15 to 0.25] m between 1901 and 2018. The average rate of sea level rise was 1.3 [0.6 to 2.1] mm yr-1 between 1901
and 1971, increasing to 1.9 [0.8 to 2.9] mm yr-1 between 1971 and 2006, and further increasing to 3.7 [3.2 to 4.2] mm yr-1
between 2006 and 2018 (high confidence). Human influence was very likely the main driver of these increases since at
least 1971. Evidence of observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical
cyclones, and, in particular, their attribution to human influence, has further strengthened since AR5. Human influence
has likely increased the chance of compound extreme events since the 1950s, including increases in the frequency of
concurrent heatwaves and droughts (high confidence). {2.1.2, Table 2.1, Figure 2.3, Figure 3.4} (Figure SPM.1)
A.2.2 Approximately 3.3 to 3.6 billion people live in contexts that are highly vulnerable to climate change. Human and
ecosystem vulnerability are interdependent. Regions and people with considerable development constraints have high
vulnerability to climatic hazards. Increasing weather and climate extreme events have exposed millions of people
to acute food insecurity12 and reduced water security, with the largest adverse impacts observed in many locations
and/or communities in Africa, Asia, Central and South America, LDCs, Small Islands and the Arctic, and globally for
Indigenous Peoples, small-scale food producers and low-income households. Between 2010 and 2020, human mortality
from floods, droughts and storms was 15 times higher in highly vulnerable regions, compared to regions with very low
vulnerability. (high confidence) {2.1.2, 4.4} (Figure SPM.1)
A.2.3 Climate change has caused substantial damages, and increasingly irreversible losses, in terrestrial, freshwater,
cryospheric, and coastal and open ocean ecosystems (high confidence). Hundreds of local losses of species have been
driven by increases in the magnitude of heat extremes (high confidence) with mass mortality events recorded on
land and in the ocean (very high confidence). Impacts on some ecosystems are approaching irreversibility such as
the impacts of hydrological changes resulting from the retreat of glaciers, or the changes in some mountain (medium
confidence) and Arctic ecosystems driven by permafrost thaw (high confidence). {2.1.2, Figure 2.3} (Figure SPM.1)
A.2.4 Climate change has reduced food security and affected water security, hindering efforts to meet Sustainable
Development Goals (high confidence). Although overall agricultural productivity has increased, climate change has
slowed this growth over the past 50 years globally (medium confidence), with related negative impacts mainly in mid-
and low latitude regions but positive impacts in some high latitude regions (high confidence). Ocean warming and
ocean acidification have adversely affected food production from fisheries and shellfish aquaculture in some oceanic
regions (high confidence). Roughly half of the world’s population currently experience severe water scarcity for at least
part of the year due to a combination of climatic and non-climatic drivers (medium confidence). {2.1.2, Figure 2.3}
(Figure SPM.1)
A.2.5 In all regions increases in extreme heat events have resulted in human mortality and morbidity (very high confidence).
The occurrence of climate-related food-borne and water-borne diseases (very high confidence) and the incidence
of vector-borne diseases (high confidence) have increased. In assessed regions, some mental health challenges are
associated with increasing temperatures (high confidence), trauma from extreme events (very high confidence), and
loss of livelihoods and culture (high confidence). Climate and weather extremes are increasingly driving displacement
in Africa, Asia, North America (high confidence), and Central and South America (medium confidence), with small island
states in the Caribbean and South Pacific being disproportionately affected relative to their small population size (high
confidence). {2.1.2, Figure 2.3} (Figure SPM.1)
A.2.6 Climate change has caused widespread adverse impacts and related losses and damages13 to nature and people that are
unequally distributed across systems, regions and sectors. Economic damages from climate change have been detected
in climate-exposed sectors, such as agriculture, forestry, fishery, energy, and tourism. Individual livelihoods have been
affected through, for example, destruction of homes and infrastructure, and loss of property and income, human health
and food security, with adverse effects on gender and social equity. (high confidence) {2.1.2} (Figure SPM.1)
A.2.7 In urban areas, observed climate change has caused adverse impacts on human health, livelihoods and key infrastructure.
Hot extremes have intensified in cities. Urban infrastructure, including transportation, water, sanitation and energy
systems have been compromised by extreme and slow-onset events14, with resulting economic losses, disruptions of
services and negative impacts to well-being. Observed adverse impacts are concentrated amongst economically and
socially marginalised urban residents. (high confidence) {2.1.2}

Adverse impacts from human-caused
climate change will continue to intensify

a) Observed widespread and substantial impacts and
related losses and damages attributed to climate change
b) Impacts are driven by changes in multiple physical climate
conditions, which are increasingly attributed to human influence
c) The extent to which current and future generations will experience a
hotter and different world depends on choices now and in the near term

Figure SPM.1: (a) Climate change has already caused widespread impacts and related losses and damages on human systems and altered terrestrial,
freshwater and ocean ecosystems worldwide. Physical water availability includes balance of water available from various sources including ground water, water
quality and demand for water. Global mental health and displacement assessments reflect only assessed regions. Confidence levels reflect the assessment of
attribution of the observed impact to climate change. (b) Observed impacts are connected to physical climate changes including many that have been attributed
to human influence such as the selected climatic impact-drivers shown. Confidence and likelihood levels reflect the assessment of attribution of the observed
climatic impact-driver to human influence. (c) Observed (1900–2020) and projected (2021–2100) changes in global surface temperature (relative to 1850-1900),
which are linked to changes in climate conditions and impacts, illustrate how the climate has already changed and will change along the lifespan of three representative generations (born in 1950, 1980 and 2020). Future projections (2021–2100) of changes in global surface temperature are shown for very low
(SSP1-1.9), low (SSP1-2.6), intermediate (SSP2-4.5), high (SSP3-7.0) and very high (SSP5-8.5) GHG emissions scenarios. Changes in annual global surface
temperatures are presented as ‘climate stripes’, with future projections showing the human-caused long-term trends and continuing modulation by natural
variability (represented here using observed levels of past natural variability). Colours on the generational icons correspond to the global surface temperature
stripes for each year, with segments on future icons differentiating possible future experiences. {2.1, 2.1.2, Figure 2.1, Table 2.1, Figure 2.3, Cross-Section Box.2,
3.1, Figure 3.3, 4.1, 4.3} (Box SPM.1)

Current Progress in Adaptation and Gaps and Challenges
A.3 Adaptation planning and implementation has progressed across all sectors and regions,
with documented benefits and varying effectiveness. Despite progress, adaptation gaps
exist, and will continue to grow at current rates of implementation. Hard and soft limits to
adaptation have been reached in some ecosystems and regions. Maladaptation is happening
in some sectors and regions. Current global financial flows for adaptation are insufficient
for, and constrain implementation of, adaptation options, especially in developing countries
(high confidence). {2.2, 2.3}
A.3.1 Progress in adaptation planning and implementation has been observed across all sectors and regions, generating
multiple benefits (very high confidence). Growing public and political awareness of climate impacts and risks has
resulted in at least 170 countries and many cities including adaptation in their climate policies and planning processes
(high confidence). {2.2.3}
A.3.2 Effectiveness15 of adaptation in reducing climate risks16 is documented for specific contexts, sectors and regions (high
confidence). Examples of effective adaptation options include: cultivar improvements, on-farm water management and
storage, soil moisture conservation, irrigation, agroforestry, community-based adaptation, farm and landscape level
diversification in agriculture, sustainable land management approaches, use of agroecological principles and practices
and other approaches that work with natural processes (high confidence). Ecosystem-based adaptation17 approaches
such as urban greening, restoration of wetlands and upstream forest ecosystems have been effective in reducing
flood risks and urban heat (high confidence). Combinations of non-structural measures like early warning systems and
structural measures like levees have reduced loss of lives in case of inland flooding (medium confidence). Adaptation
options such as disaster risk management, early warning systems, climate services and social safety nets have broad
applicability across multiple sectors (high confidence). {2.2.3}
A.3.3 Most observed adaptation responses are fragmented, incremental18, sector-specific and unequally distributed across
regions. Despite progress, adaptation gaps exist across sectors and regions, and will continue to grow under current
levels of implementation, with the largest adaptation gaps among lower income groups. (high confidence) {2.3.2}
A.3.4 There is increased evidence of maladaptation in various sectors and regions. Maladaptation especially affects
marginalised and vulnerable groups adversely. (high confidence) {2.3.2}
A.3.5 Soft limits to adaptation are currently being experienced by small-scale farmers and households along some low-
lying coastal areas (medium confidence) resulting from financial, governance, institutional and policy constraints
(high confidence). Some tropical, coastal, polar and mountain ecosystems have reached hard adaptation limits (high
confidence). Adaptation does not prevent all losses and damages, even with effective adaptation and before reaching
soft and hard limits (high confidence). {2.3.2}

A.3.6 Key barriers to adaptation are limited resources, lack of private sector and citizen engagement, insufficient mobilization
of finance (including for research), low climate literacy, lack of political commitment, limited research and/or slow and
low uptake of adaptation science, and low sense of urgency. There are widening disparities between the estimated costs
of adaptation and the finance allocated to adaptation (high confidence). Adaptation finance has come predominantly
from public sources, and a small proportion of global tracked climate finance was targeted to adaptation and an
overwhelming majority to mitigation (very high confidence). Although global tracked climate finance has shown
an upward trend since AR5, current global financial flows for adaptation, including from public and private finance
sources, are insufficient and constrain implementation of adaptation options, especially in developing countries (high
confidence). Adverse climate impacts can reduce the availability of financial resources by incurring losses and damages
and through impeding national economic growth, thereby further increasing financial constraints for adaptation,
particularly for developing and least developed countries (medium confidence). {2.3.2, 2.3.3}

Box SPM.1 The use of scenarios and modelled pathways in the AR6 Synthesis Report
Modelled scenarios and pathways19 are used to explore future emissions, climate change, related impacts and risks, and
possible mitigation and adaptation strategies and are based on a range of assumptions, including socio-economic variables
and mitigation options. These are quantitative projections and are neither predictions nor forecasts. Global modelled emission
pathways, including those based on cost effective approaches contain regionally differentiated assumptions and outcomes,
and have to be assessed with the careful recognition of these assumptions. Most do not make explicit assumptions about
global equity, environmental justice or intra-regional income distribution. IPCC is neutral with regard to the assumptions
underlying the scenarios in the literature assessed in this report, which do not cover all possible futures.20 {Cross-Section Box.2}
WGI assessed the climate response to five illustrative scenarios based on Shared Socio-economic Pathways (SSPs)21 that
cover the range of possible future development of anthropogenic drivers of climate change found in the literature. High and
very high GHG emissions scenarios (SSP3-7.0 and SSP5-8.522) have CO 2 emissions that roughly double from current levels
by 2100 and 2050, respectively. The intermediate GHG emissions scenario (SSP2-4.5) has CO 2 emissions remaining around
current levels until the middle of the century. The very low and low GHG emissions scenarios (SSP1-1.9 and SSP1-2.6) have CO 2
emissions declining to net zero around 2050 and 2070, respectively, followed by varying levels of net negative CO 2 emissions.
In addition, Representative Concentration Pathways (RCPs)23 were used by WGI and WGII to assess regional climate changes,
impacts and risks. In WGIII, a large number of global modelled emissions pathways were assessed, of which 1202 pathways
were categorised based on their assessed global warming over the 21st century; categories range from pathways that limit
warming to 1.5°C with more than 50% likelihood (noted >50% in this report) with no or limited overshoot (C1) to pathways
that exceed 4°C (C8). {Cross-Section Box.2} (Box SPM.1, Table 1)
Global warming levels (GWLs) relative to 1850–1900 are used to integrate the assessment of climate change and related
impacts and risks since patterns of changes for many variables at a given GWL are common to all scenarios considered and
independent of timing when that level is reached. {Cross-Section Box.2}

Box SPM.1, Table 1: Description and relationship of scenarios and modelled pathways considered across AR6 Working Group
reports. {Cross-Section Box.2 Figure 1}
Category
in WGIII Category description GHG emissions scenarios
(SSPx-y*) in WGI & WGII RCPy** in WGI & WGII
C1 limit warming to 1.5°C (>50%)
with no or limited overshoot*** Very low (SSP1-1.9)
C2 return warming to 1.5°C (>50%)
after a high overshoot***
C3 limit warming to 2°C (>67%) Low (SSP1-2.6) RCP2.6
C4 limit warming to 2°C (>50%)
C5 limit warming to 2.5°C (>50%)
C6 limit warming to 3°C (>50%) Intermediate (SSP2-4.5) RCP 4.5
C7 limit warming to 4°C (>50%) High (SSP3-7.0)
C8 exceed warming of 4°C (>50%) Very high (SSP5-8.5) RCP 8.5

* See footnote 21 for the SSPx-y terminology.
** See footnote 23 for the RCPy terminology.
*** Limited overshoot refers to exceeding 1.5°C global warming by up to about 0.1°C, high overshoot by 0.1°C-0.3°C, in both
cases for up to several decades.

Current Mitigation Progress, Gaps and Challenges
A.4 Policies and laws addressing mitigation have consistently expanded since AR5. Global GHG
emissions in 2030 implied by nationally determined contributions (NDCs) announced by October
2021 make it likely that warming will exceed 1.5°C during the 21st century and make it harder
to limit warming below 2°C. There are gaps between projected emissions from implemented
policies and those from NDCs and finance flows fall short of the levels needed to meet climate
goals across all sectors and regions. (high confidence) {2.2, 2.3, Figure 2.5, Table 2.2}
A.4.1 The UNFCCC, Kyoto Protocol, and the Paris Agreement are supporting rising levels of national ambition. The Paris Agreement,
adopted under the UNFCCC, with near universal participation, has led to policy development and target-setting at national
and sub-national levels, in particular in relation to mitigation, as well as enhanced transparency of climate
action and support (medium confidence). Many regulatory and economic instruments have already been deployed
successfully (high confidence). In many countries, policies have enhanced energy efficiency, reduced rates of deforestation
and accelerated technology deployment, leading to avoided and in some cases reduced or removed emissions (high
confidence). Multiple lines of evidence suggest that mitigation policies have led to several24 Gt CO2-eq yr-1 of avoided
global emissions (medium confidence). At least 18 countries have sustained absolute production-based GHG and
consumption-based CO2 reductions25 for longer than 10 years. These reductions have only partly offset global emissions
growth (high confidence). {2.2.1, 2.2.2}
A.4.2 Several mitigation options, notably solar energy, wind energy, electrification of urban systems, urban green infrastructure,
energy efficiency, demand-side management, improved forest and crop / grassland management, and reduced food
waste and loss, are technically viable, are becoming increasingly cost effective and are generally supported by the
public. From 2010 to 2019 there have been sustained decreases in the unit costs of solar energy (85%), wind energy
(55%), and lithium-ion batteries (85%), and large increases in their deployment, e.g., >10× for solar and >100× for
electric vehicles (EVs), varying widely across regions. The mix of policy instruments that reduced costs and stimulated
adoption includes public R&D, funding for demonstration and pilot projects, and demand-pull instruments such as
deployment subsidies to attain scale. Maintaining emission-intensive systems may, in some regions and sectors, be
more expensive than transitioning to low emission systems. (high confidence) {2.2.2, Figure 2.4}
A.4.3 A substantial ‘emissions gap’ exists between global GHG emissions in 2030 associated with the implementation of
NDCs announced prior to COP2626 and those associated with modelled mitigation pathways that limit warming to 1.5°C
(>50%) with no or limited overshoot or limit warming to 2°C (>67%) assuming immediate action (high confidence). This
would make it likely that warming will exceed 1.5°C during the 21st century (high confidence). Global modelled mitigation
pathways that limit warming to 1.5°C (>50%) with no or limited overshoot or limit warming to 2°C (>67%) assuming
immediate action imply deep global GHG emissions reductions this decade (high confidence) (see SPM Box 1, Table 1, B.6)27.
Modelled pathways that are consistent with NDCs announced prior to COP26 until 2030 and assume no increase in
ambition thereafter have higher emissions, leading to a median global warming of 2.8 [2.1 to 3.4] °C by 2100 (medium
confidence). Many countries have signalled an intention to achieve net zero GHG or net zero CO2 by around mid-century
but pledges differ across countries in terms of scope and specificity, and limited policies are to date in place to deliver
on them. {2.3.1, Table 2.2, Figure 2.5, Table 3.1, 4.1}
A.4.4 Policy coverage is uneven across sectors (high confidence). Policies implemented by the end of 2020 are projected to
result in higher global GHG emissions in 2030 than emissions implied by NDCs, indicating an ‘implementation gap’
(high confidence). Without a strengthening of policies, global warming of 3.2 [2.2 to 3.5]°C is projected by 2100
(medium confidence). {2.2.2, 2.3.1, 3.1.1, Figure 2.5} (Box SPM.1, Figure SPM.5)
A.4.5 The adoption of low-emission technologies lags in most developing countries, particularly least developed ones, due
in part to limited finance, technology development and transfer, and capacity (medium confidence). The magnitude
of climate finance flows has increased over the last decade and financing channels have broadened but growth has
slowed since 2018 (high confidence). Financial flows have developed heterogeneously across regions and sectors
(high confidence). Public and private finance flows for fossil fuels are still greater than those for climate adaptation
and mitigation (high confidence). The overwhelming majority of tracked climate finance is directed towards mitigation,
but nevertheless falls short of the levels needed to limit warming to below 2°C or to 1.5°C across all sectors and
regions (see C7.2) (very high confidence). In 2018, public and publicly mobilised private climate finance flows from
developed to developing countries were below the collective goal under the UNFCCC and Paris Agreement to mobilise
USD 100 billion per year by 2020 in the context of meaningful mitigation action and transparency on implementation
(medium confidence). {2.2.2, 2.3.1, 2.3.3}

B. Future Climate Change, Risks, and Long-Term Responses
Future Climate Change
B.1 Continued greenhouse gas emissions will lead to increasing global warming, with the best
estimate of reaching 1.5°C in the near term in considered scenarios and modelled pathways.
Every increment of global warming will intensify multiple and concurrent hazards (high
confidence). Deep, rapid, and sustained reductions in greenhouse gas emissions would
lead to a discernible slowdown in global warming within around two decades, and also
to discernible changes in atmospheric composition within a few years (high confidence).
{Cross-Section Boxes 1 and 2, 3.1, 3.3, Table 3.1, Figure 3.1, 4.3} (Figure SPM.2, Box SPM.1)
B.1.1 Global warming28 will continue to increase in the near term (2021–2040) mainly due to increased cumulative
CO 2 emissions in nearly all considered scenarios and modelled pathways. In the near term, global warming is more
likely than not to reach 1.5°C even under the very low GHG emission scenario (SSP1-1.9) and likely or very likely to
exceed 1.5°C under higher emissions scenarios. In the considered scenarios and modelled pathways, the best estimates
of the time when the level of global warming of 1.5°C is reached lie in the near term29. Global warming declines back
to below 1.5°C by the end of the 21st century in some scenarios and modelled pathways (see B.7). The assessed
climate response to GHG emissions scenarios results in a best estimate of warming for 2081–2100 that spans a range
from 1.4°C for a very low GHG emissions scenario (SSP1-1.9) to 2.7°C for an intermediate GHG emissions scenario
(SSP2-4.5) and 4.4°C for a very high GHG emissions scenario (SSP5-8.5)30, with narrower uncertainty ranges31 than for
corresponding scenarios in AR5. {Cross-Section Boxes 1 and 2, 3.1.1, 3.3.4, Table 3.1, 4.3} (Box SPM.1)
B.1.2 Discernible differences in trends of global surface temperature between contrasting GHG emissions scenarios (SSP1-1.9
and SSP1-2.6 vs. SSP3-7.0 and SSP5-8.5) would begin to emerge from natural variability32 within around 20 years. Under
these contrasting scenarios, discernible effects would emerge within years for GHG concentrations, and sooner for air
quality improvements, due to the combined targeted air pollution controls and strong and sustained methane emissions
reductions. Targeted reductions of air pollutant emissions lead to more rapid improvements in air quality within years
compared to reductions in GHG emissions only, but in the long term, further improvements are projected in scenarios
that combine efforts to reduce air pollutants as well as GHG emissions33. (high confidence) {3.1.1} (Box SPM.1)
B.1.3 Continued emissions will further affect all major climate system components. With every additional increment of global
warming, changes in extremes continue to become larger. Continued global warming is projected to further intensify
the global water cycle, including its variability, global monsoon precipitation, and very wet and very dry weather and
climate events and seasons (high confidence). In scenarios with increasing CO2 emissions, natural land and ocean
carbon sinks are projected to take up a decreasing proportion of these emissions (high confidence). Other projected
changes include further reduced extents and/or volumes of almost all cryospheric elements34 (high confidence), further
global mean sea level rise (virtually certain), and increased ocean acidification (virtually certain) and deoxygenation
(high confidence). {3.1.1, 3.3.1, Figure 3.4} (Figure SPM.2)
B.1.4 With further warming, every region is projected to increasingly experience concurrent and multiple changes in climatic
impact-drivers. Compound heatwaves and droughts are projected to become more frequent, including concurrent
events across multiple locations (high confidence). Due to relative sea level rise, current 1-in-100 year extreme sea
level events are projected to occur at least annually in more than half of all tide gauge locations by 2100 under all
considered scenarios (high confidence). Other projected regional changes include intensification of tropical cyclones
and/or extratropical storms (medium confidence), and increases in aridity and fire weather (medium to high confidence).
{3.1.1, 3.1.3}
B.1.5 Natural variability will continue to modulate human-caused climate changes, either attenuating or amplifying projected
changes, with little effect on centennial-scale global warming (high confidence). These modulations are important to
consider in adaptation planning, especially at the regional scale and in the near term. If a large explosive volcanic
eruption were to occur35, it would temporarily and partially mask human-caused climate change by reducing global
surface temperature and precipitation for one to three years (medium confidence). {4.3}

With every increment of global warming, regional changes in mean
climate and extremes become more widespread and pronounced
Figure SPM.2: Projected changes of annual maximum daily maximum temperature, annual mean total column soil moisture and annual
maximum 1-day precipitation at global warming levels of 1.5°C, 2°C, 3°C, and 4°C relative to 1850–1900. Projected (a) annual maximum
daily temperature change (°C), (b) annual mean total column soil moisture change (standard deviation), (c) annual maximum 1-day precipitation change (%).
The panels show CMIP6 multi-model median changes. In panels (b) and (c), large positive relative changes in dry regions may correspond to small absolute
changes. In panel (b), the unit is the standard deviation of interannual variability in soil moisture during 1850–1900. Standard deviation is a widely used
metric in characterising drought severity. A projected reduction in mean soil moisture by one standard deviation corresponds to soil moisture conditions typical
of droughts that occurred about once every six years during 1850–1900. The WGI Interactive Atlas (https://interactive-atlas.ipcc.ch/) can be used to explore
additional changes in the climate system across the range of global warming levels presented in this figure. {Figure 3.1, Cross-Section Box.2}

Climate Change Impacts and Climate-Related Risks
B.2 For any given future warming level, many climate-related risks are higher than assessed in
AR5, and projected long-term impacts are up to multiple times higher than currently observed
(high confidence). Risks and projected adverse impacts and related losses and damages from
climate change escalate with every increment of global warming (very high confidence).
Climatic and non-climatic risks will increasingly interact, creating compound and cascading
risks that are more complex and difficult to manage (high confidence). {Cross-Section Box.2,
3.1, 4.3, Figure 3.3, Figure 4.3} (Figure SPM.3, Figure SPM.4)
B.2.1 In the near term, every region in the world is projected to face further increases in climate hazards (medium to
high confidence, depending on region and hazard), increasing multiple risks to ecosystems and humans (very high
confidence). Hazards and associated risks expected in the near term include an increase in heat-related human mortality
and morbidity (high confidence), food-borne, water-borne, and vector-borne diseases (high confidence), and mental
health challenges36 (very high confidence), flooding in coastal and other low-lying cities and regions (high confidence),
biodiversity loss in land, freshwater and ocean ecosystems (medium to very high confidence, depending on ecosystem),
and a decrease in food production in some regions (high confidence). Cryosphere-related changes in floods, landslides,
and water availability have the potential to lead to severe consequences for people, infrastructure and the economy in
most mountain regions (high confidence). The projected increase in frequency and intensity of heavy precipitation (high
confidence) will increase rain-generated local flooding (medium confidence). {Figure 3.2, Figure 3.3, 4.3, Figure 4.3}
(Figure SPM.3, Figure SPM.4)
B.2.2 Risks and projected adverse impacts and related losses and damages from climate change will escalate with every
increment of global warming (very high confidence). They are higher for global warming of 1.5°C than at present, and
even higher at 2°C (high confidence). Compared to the AR5, global aggregated risk levels37 (Reasons for Concern38) are
assessed to become high to very high at lower levels of global warming due to recent evidence of observed impacts,
improved process understanding, and new knowledge on exposure and vulnerability of human and natural systems,
including limits to adaptation (high confidence). Due to unavoidable sea level rise (see also B.3), risks for coastal
ecosystems, people and infrastructure will continue to increase beyond 2100 (high confidence). {3.1.2, 3.1.3, Figure 3.4,
Figure 4.3} (Figure SPM.3, Figure SPM.4)
B.2.3 With further warming, climate change risks will become increasingly complex and more difficult to manage. Multiple
climatic and non-climatic risk drivers will interact, resulting in compounding overall risk and risks cascading across
sectors and regions. Climate-driven food insecurity and supply instability, for example, are projected to increase with
increasing global warming, interacting with non-climatic risk drivers such as competition for land between urban
expansion and food production, pandemics and conflict. (high confidence) {3.1.2, 4.3, Figure 4.3}
B.2.4 For any given warming level, the level of risk will also depend on trends in vulnerability and exposure of humans and
ecosystems. Future exposure to climatic hazards is increasing globally due to socio-economic development trends
including migration, growing inequality and urbanisation. Human vulnerability will concentrate in informal settlements
and rapidly growing smaller settlements. In rural areas vulnerability will be heightened by high reliance on climate-
sensitive livelihoods. Vulnerability of ecosystems will be strongly influenced by past, present, and future patterns of
unsustainable consumption and production, increasing demographic pressures, and persistent unsustainable use and
management of land, ocean, and water. Loss of ecosystems and their services has cascading and long-term impacts on
people globally, especially for Indigenous Peoples and local communities who are directly dependent on ecosystems to
meet basic needs. (high confidence) {Cross-Section Box.2 Figure 1c, 3.1.2, 4.3}

Future climate change is projected to increase the severity of impacts
across natural and human systems and will increase regional differences
Examples of impacts without additional adaptation

a) Risk of
species losses
b) Heat-humidity
risks to
human health
c) Food production
impacts
c1) Maize yield
c2) Fisheries yield

Figure SPM.3: Projected risks and impacts of climate change on natural and human systems at different global warming levels (GWLs) relative to 1850–1900
levels. Projected risks and impacts shown on the maps are based on outputs from different subsets of Earth system and impact models that were used to project
each impact indicator without additional adaptation. WGII provides further assessment of the impacts on human and natural systems using these projections
and additional lines of evidence. (a) Risks of species losses as indicated by the percentage of assessed species exposed to potentially dangerous temperature
conditions, as defined by conditions beyond the estimated historical (1850–2005) maximum mean annual temperature experienced by each species, at GWLs
of 1.5°C, 2°C, 3°C and 4°C. Underpinning projections of temperature are from 21 Earth system models and do not consider extreme events impacting
ecosystems such as the Arctic. (b) Risks to human health as indicated by the days per year of population exposure to hyperthermic conditions that pose a risk
of mortality from surface air temperature and humidity conditions for historical period (1991–2005) and at GWLs of 1.7°C–2.3°C (mean = 1.9°C; 13 climate
models), 2.4°C–3.1°C (2.7°C; 16 climate models) and 4.2°C–5.4°C (4.7°C; 15 climate models). Interquartile ranges of GWLs by 2081–2100 under RCP2.6,
RCP4.5 and RCP8.5. The presented index is consistent with common features found in many indices included within WGI and WGII assessments. (c) Impacts
on food production: (c1) Changes in maize yield by 2080–2099 relative to 1986–2005 at projected GWLs of 1.6°C–2.4°C (2.0°C), 3.3°C–4.8°C (4.1°C) and
3.9°C–6.0°C (4.9°C). Median yield changes from an ensemble of 12 crop models, each driven by bias-adjusted outputs from 5 Earth system models, from
the Agricultural Model Intercomparison and Improvement Project (AgMIP) and the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP). Maps depict
17Summary for Policymakers
Summary for Policymakers
2080–2099 compared to 1986–2005 for current growing regions (>10 ha), with the corresponding range of future global warming levels shown under SSP1-
2.6, SSP3-7.0 and SSP5-8.5, respectively. Hatching indicates areas where <70% of the climate-crop model combinations agree on the sign of impact. (c2)
Change in maximum fisheries catch potential by 2081–2099 relative to 1986–2005 at projected GWLs of 0.9°C–2.0°C (1.5°C) and 3.4°C–5.2°C (4.3°C).
GWLs by 2081–2100 under RCP2.6 and RCP8.5. Hatching indicates where the two climate-fisheries models disagree in the direction of change. Large relative
changes in low yielding regions may correspond to small absolute changes. Biodiversity and fisheries in Antarctica were not analysed due to data limitations.
Food security is also affected by crop and fishery failures not presented here. {3.1.2, Figure 3.2, Cross-Section Box.2} (Box SPM.1)

Risks are increasing with every increment of warming

a) High risks are now assessed to occur at lower global warming levels
b) Risks differ by system
c) Risks to coastal geographies increase with sea level rise and depend on responses
d) Adaptation and socio-economic pathways affect levels of climate related risks

Figure SPM.4: Subset of assessed climate outcomes and associated global and regional climate risks. The burning embers result from a literature
based expert elicitation. Panel (a): Left – Global surface temperature changes in °C relative to 1850–1900. These changes were obtained by combining CMIP6
model simulations with observational constraints based on past simulated warming, as well as an updated assessment of equilibrium climate sensitivity. Very
likely ranges are shown for the low and high GHG emissions scenarios (SSP1-2.6 and SSP3-7.0) (Cross-Section Box.2). Right – Global Reasons for Concern
(RFC), comparing AR6 (thick embers) and AR5 (thin embers) assessments. Risk transitions have generally shifted towards lower temperatures with updated
scientific understanding. Diagrams are shown for each RFC, assuming low to no adaptation. Lines connect the midpoints of the transitions from moderate to high
risk across AR5 and AR6. Panel (b): Selected global risks for land and ocean ecosystems, illustrating general increase of risk with global warming levels with low
to no adaptation. Panel (c): Left - Global mean sea level change in centimetres, relative to 1900. The historical changes (black) are observed by tide gauges
before 1992 and altimeters afterwards. The future changes to 2100 (coloured lines and shading) are assessed consistently with observational constraints based
on emulation of CMIP, ice-sheet, and glacier models, and likely ranges are shown for SSP1-2.6 and SSP3-7.0. Right - Assessment of the combined risk of coastal
flooding, erosion and salinization for four illustrative coastal geographies in 2100, due to changing mean and extreme sea levels, under two response scenarios,
with respect to the SROCC baseline period (1986–2005). The assessment does not account for changes in extreme sea level beyond those directly induced by
mean sea level rise; risk levels could increase if other changes in extreme sea levels were considered (e.g., due to changes in cyclone intensity). “No-to-moderate
response” describes efforts as of today (i.e., no further significant action or new types of actions). “Maximum potential response” represent a combination of
responses implemented to their full extent and thus significant additional efforts compared to today, assuming minimal financial, social and political barriers.
(In this context, ‘today’ refers to 2019.) The assessment criteria include exposure and vulnerability, coastal hazards, in-situ responses and planned relocation.
Planned relocation refers to managed retreat or resettlements. The term response is used here instead of adaptation because some responses, such as retreat,
may or may not be considered to be adaptation. Panel (d): Selected risks under different socio-economic pathways, illustrating how development strategies
and challenges to adaptation influence risk. Left - Heat-sensitive human health outcomes under three scenarios of adaptation effectiveness. The diagrams are
truncated at the nearest whole ºC within the range of temperature change in 2100 under three SSP scenarios. Right - Risks associated with food security due to
climate change and patterns of socio-economic development. Risks to food security include availability and access to food, including population at risk of hunger,
food price increases and increases in disability adjusted life years attributable to childhood underweight. Risks are assessed for two contrasted socio-economic
pathways (SSP1 and SSP3) excluding the effects of targeted mitigation and adaptation policies. {Figure 3.3} (Box SPM.1)

Likelihood and Risks of Unavoidable, Irreversible or Abrupt
Changes
B.3 Some future changes are unavoidable and/or irreversible but can be limited by deep, rapid,
and sustained global greenhouse gas emissions reductions. The likelihood of abrupt and/or
irreversible changes increases with higher global warming levels. Similarly, the probability
of low-likelihood outcomes associated with potentially very large adverse impacts increases
with higher global warming levels. (high confidence) {3.1}
B.3.1 Limiting global surface temperature does not prevent continued changes in climate system components that have
multi-decadal or longer timescales of response (high confidence). Sea level rise is unavoidable for centuries to millennia
due to continuing deep ocean warming and ice sheet melt, and sea levels will remain elevated for thousands of years
(high confidence). However, deep, rapid, and sustained GHG emissions reductions would limit further sea level rise
acceleration and projected long-term sea level rise commitment. Relative to 1995–2014, the likely global mean sea
level rise under the SSP1-1.9 GHG emissions scenario is 0.15–0.23 m by 2050 and 0.28–0.55 m by 2100; while for the
SSP5-8.5 GHG emissions scenario it is 0.20–0.29 m by 2050 and 0.63–1.01 m by 2100 (medium confidence). Over the
next 2000 years, global mean sea level will rise by about 2–3 m if warming is limited to 1.5°C and 2–6 m if limited to
2°C (low confidence). {3.1.3, Figure 3.4} (Box SPM.1)
B.3.2 The likelihood and impacts of abrupt and/or irreversible changes in the climate system, including changes triggered
when tipping points are reached, increase with further global warming (high confidence). As warming levels increase, so
do the risks of species extinction or irreversible loss of biodiversity in ecosystems including forests (medium confidence),
coral reefs (very high confidence) and in Arctic regions (high confidence). At sustained warming levels between 2°C and
3°C, the Greenland and West Antarctic ice sheets will be lost almost completely and irreversibly over multiple millennia,
causing several metres of sea level rise (limited evidence). The probability and rate of ice mass loss increase with higher
global surface temperatures (high confidence). {3.1.2, 3.1.3}
B.3.3 The probability of low-likelihood outcomes associated with potentially very large impacts increases with higher global
warming levels (high confidence). Due to deep uncertainty linked to ice-sheet processes, global mean sea level rise
above the likely range – approaching 2 m by 2100 and in excess of 15 m by 2300 under the very high GHG emissions
scenario (SSP5-8.5) (low confidence) – cannot be excluded. There is medium confidence that the Atlantic Meridional
Overturning Circulation will not collapse abruptly before 2100, but if it were to occur, it would very likely cause abrupt
shifts in regional weather patterns, and large impacts on ecosystems and human activities. {3.1.3} (Box SPM.1)

Adaptation Options and their Limits in a Warmer World
B.4 Adaptation options that are feasible and effective today will become constrained and
less effective with increasing global warming. With increasing global warming, losses and
damages will increase and additional human and natural systems will reach adaptation
limits. Maladaptation can be avoided by flexible, multi-sectoral, inclusive, long-term
planning and implementation of adaptation actions, with co-benefits to many sectors and
systems. (high confidence) {3.2, 4.1, 4.2, 4.3}
B.4.1 The effectiveness of adaptation, including ecosystem-based and most water-related options, will decrease with
increasing warming. The feasibility and effectiveness of options increase with integrated, multi-sectoral solutions that
differentiate responses based on climate risk, cut across systems and address social inequities. As adaptation options
often have long implementation times, long-term planning increases their efficiency. (high confidence) {3.2, Figure 3.4,
4.1, 4.2}
B.4.2 With additional global warming, limits to adaptation and losses and damages, strongly concentrated among vulnerable
populations, will become increasingly difficult to avoid (high confidence). Above 1.5°C of global warming, limited
freshwater resources pose potential hard adaptation limits for small islands and for regions dependent on glacier
and snow melt (medium confidence). Above that level, ecosystems such as some warm-water coral reefs, coastal
wetlands, rainforests, and polar and mountain ecosystems will have reached or surpassed hard adaptation limits and as
a consequence, some Ecosystem-based Adaptation measures will also lose their effectiveness (high confidence). {2.3.2,
3.2, 4.3}
B.4.3 Actions that focus on sectors and risks in isolation and on short-term gains often lead to maladaptation over the long
term, creating lock-ins of vulnerability, exposure and risks that are difficult to change. For example, seawalls effectively
reduce impacts to people and assets in the short term but can also result in lock-ins and increase exposure to climate
risks in the long term unless they are integrated into a long-term adaptive plan. Maladaptive responses can worsen
existing inequities especially for Indigenous Peoples and marginalised groups and decrease ecosystem and biodiversity
resilience. Maladaptation can be avoided by flexible, multi-sectoral, inclusive, long-term planning and implementation
of adaptation actions, with co-benefits to many sectors and systems. (high confidence) {2.3.2, 3.2}

Carbon Budgets and Net Zero Emissions
B.5 Limiting human-caused global warming requires net zero CO2 emissions. Cumulative carbon
emissions until the time of reaching net zero CO2 emissions and the level of greenhouse
gas emission reductions this decade largely determine whether warming can be limited to
1.5°C or 2°C (high confidence). Projected CO2 emissions from existing fossil fuel infrastructure
without additional abatement would exceed the remaining carbon budget for 1.5°C (50%)
(high confidence). {2.3, 3.1, 3.3, Table 3.1}
B.5.1 From a physical science perspective, limiting human-caused global warming to a specific level requires limiting cumulative
CO2 emissions, reaching at least net zero CO2 emissions, along with strong reductions in other greenhouse gas emissions.
Reaching net zero GHG emissions primarily requires deep reductions in CO2 , methane, and other GHG emissions, and
implies net negative CO2 emissions39. Carbon dioxide removal (CDR) will be necessary to achieve net negative CO2
emissions (see B.6). Net zero GHG emissions, if sustained, are projected to result in a gradual decline in global surface
temperatures after an earlier peak. (high confidence) {3.1.1, 3.3.1, 3.3.2, 3.3.3, Table 3.1, Cross-Section Box.1}
B.5.2 For every 1000 GtCO2 emitted by human activity, global surface temperature rises by 0.45°C (best estimate, with a likely
range from 0.27°C to 0.63°C). The best estimates of the remaining carbon budgets from the beginning of 2020 are
500 GtCO2 for a 50% likelihood of limiting global warming to 1.5°C and 1150 GtCO2 for a 67% likelihood of limiting
warming to 2°C40. The stronger the reductions in non-CO2 emissions, the lower the resulting temperatures are for a given
remaining carbon budget or the larger remaining carbon budget for the same level of temperature change41. {3.3.1}

B.5.3 If the annual CO2 emissions between 2020–2030 stayed, on average, at the same level as 2019, the resulting cumulative
emissions would almost exhaust the remaining carbon budget for 1.5°C (50%), and deplete more than a third of the
remaining carbon budget for 2°C (67%). Estimates of future CO2 emissions from existing fossil fuel infrastructures
without additional abatement42 already exceed the remaining carbon budget for limiting warming to 1.5°C (50%)
(high confidence). Projected cumulative future CO 2 emissions over the lifetime of existing and planned fossil fuel
infrastructure, if historical operating patterns are maintained and without additional abatement43, are approximately
equal to the remaining carbon budget for limiting warming to 2°C with a likelihood of 83%44 (high confidence). {2.3.1,
3.3.1, Figure 3.5}
B.5.4 Based on central estimates only, historical cumulative net CO 2 emissions between 1850 and 2019 amount to about
four fifths45 of the total carbon budget for a 50% probability of limiting global warming to 1.5°C (central estimate about
2900 GtCO2 ), and to about two thirds46 of the total carbon budget for a 67% probability to limit global warming to 2°C
(central estimate about 3550 GtCO2 ). {3.3.1, Figure 3.5}

Mitigation Pathways
B.6 All global modelled pathways that limit warming to 1.5°C (>50%) with no or limited overshoot,
and those that limit warming to 2°C (>67%), involve rapid and deep and, in most cases,
immediate greenhouse gas emissions reductions in all sectors this decade. Global net zero CO2
emissions are reached for these pathway categories, in the early 2050s and around the early
2070s, respectively. (high confidence) {3.3, 3.4, 4.1, 4.5, Table 3.1} (Figure SPM.5, Box SPM.1)
B.6.1 Global modelled pathways provide information on limiting warming to different levels; these pathways, particularly
their sectoral and regional aspects, depend on the assumptions described in Box SPM.1. Global modelled pathways that
limit warming to 1.5°C (>50%) with no or limited overshoot or limit warming to 2°C (>67%) are characterized by deep,
rapid, and, in most cases, immediate GHG emissions reductions. Pathways that limit warming to 1.5°C (>50%) with no
or limited overshoot reach net zero CO2 in the early 2050s, followed by net negative CO2 emissions. Those pathways that
reach net zero GHG emissions do so around the 2070s. Pathways that limit warming to 2°C (>67%) reach net zero CO2
emissions in the early 2070s. Global GHG emissions are projected to peak between 2020 and at the latest before 2025
in global modelled pathways that limit warming to 1.5°C (>50%) with no or limited overshoot and in those that limit
warming to 2°C (>67%) and assume immediate action. (high confidence) {3.3.2, 3.3.4, 4.1, Table 3.1, Figure 3.6} (Table
SPM.1)

Table SPM.1: Greenhouse gas and CO2 emission reductions from 2019, median and 5-95 percentiles. {3.3.1, 4.1, Table 3.1, Figure 2.5, Box SPM.1}
Reductions from 2019 emission levels (%)
2030 2035 2040 2050
Limit warming to1.5°C (>50%) with no or
limited overshoot
GHG 43 [34-60] 60 [49-77] 69 [58-90] 84 [73-98]
CO 2 48 [36-69] 65 [50-96] 80 [61-109] 99 [79-119]
Limit warming to 2°C (>67%) GHG 21 [1-42] 35 [22-55] 46 [34-63] 64 [53-77]
CO 2 22 [1-44] 37 [21-59] 51 [36-70] 73 [55-90]

B.6.2 Reaching net zero CO2 or GHG emissions primarily requires deep and rapid reductions in gross emissions of CO 2, as well
as substantial reductions of non-CO 2 GHG emissions (high confidence). For example, in modelled pathways that limit
warming to 1.5°C (>50%) with no or limited overshoot, global methane emissions are reduced by 34 [21–57]% by 2030
relative to 2019. However, some hard-to-abate residual GHG emissions (e.g., some emissions from agriculture, aviation,
shipping, and industrial processes) remain and would need to be counterbalanced by deployment of CDR methods to
achieve net zero CO2 or GHG emissions (high confidence). As a result, net zero CO2 is reached earlier than net zero GHGs
(high confidence). {3.3.2, 3.3.3, Table 3.1, Figure 3.5} (Figure SPM.5)
B.6.3 Global modelled mitigation pathways reaching net zero CO2 and GHG emissions include transitioning from fossil fuels
without carbon capture and storage (CCS) to very low- or zero-carbon energy sources, such as renewables or fossil fuels
with CCS, demand-side measures and improving efficiency, reducing non-CO 2 GHG emissions, and CDR47. In most global
modelled pathways, land-use change and forestry (via reforestation and reduced deforestation) and the energy supply
sector reach net zero CO2 emissions earlier than the buildings, industry and transport sectors. (high confidence) {3.3.3,
4.1, 4.5, Figure 4.1} (Figure SPM.5, Box SPM.1)
B.6.4 Mitigation options often have synergies with other aspects of sustainable development, but some options can also
have trade-offs. There are potential synergies between sustainable development and, for instance, energy efficiency
and renewable energy. Similarly, depending on the context48, biological CDR methods like reforestation, improved
forest management, soil carbon sequestration, peatland restoration and coastal blue carbon management can enhance
biodiversity and ecosystem functions, employment and local livelihoods. However, afforestation or production of
biomass crops can have adverse socio-economic and environmental impacts, including on biodiversity, food and water
security, local livelihoods and the rights of Indigenous Peoples, especially if implemented at large scales and where land
tenure is insecure. Modelled pathways that assume using resources more efficiently or that shift global development
towards sustainability include fewer challenges, such as less dependence on CDR and pressure on land and biodiversity.
(high confidence) {3.4.1}

Limiting warming to 1.5°C and 2°C involves rapid, deep and
in most cases immediate greenhouse gas emission reductions
Net zero CO2 and net zero GHG emissions can be achieved through strong reductions across all sectors

Figure SPM.5: Global emissions pathways consistent with implemented policies and mitigation strategies. Panels (a), (b) and (c) show the
development of global GHG, CO2 and methane emissions in modelled pathways, while panel (d) shows the associated timing of when GHG and CO2 emissions
reach net zero. Coloured ranges denote the 5th to 95th percentile across the global modelled pathways falling within a given category as described in Box SPM.1.
The red ranges depict emissions pathways assuming policies that were implemented by the end of 2020. Ranges of modelled pathways that limit warming to
1.5°C (>50%) with no or limited overshoot are shown in light blue (category C1) and pathways that limit warming to 2°C (>67%) are shown in green (category
C3). Global emission pathways that would limit warming to 1.5°C (>50%) with no or limited overshoot and also reach net zero GHG in the second half of the
century do so between 2070–2075. Panel (e) shows the sectoral contributions of CO 2 and non-CO 2 emissions sources and sinks at the time when net zero
CO2 emissions are reached in illustrative mitigation pathways (IMPs) consistent with limiting warming to 1.5°C with a high reliance on net negative emissions
(IMP-Neg) (“high overshoot”), high resource efficiency (IMP-LD), a focus on sustainable development (IMP-SP), renewables (IMP-Ren) and limiting warming to
2°C with less rapid mitigation initially followed by a gradual strengthening (IMP-GS). Positive and negative emissions for different IMPs are compared to GHG
emissions from the year 2019. Energy supply (including electricity) includes bioenergy with carbon dioxide capture and storage and direct air carbon dioxide
capture and storage. CO 2 emissions from land-use change and forestry can only be shown as a net number as many models do not report emissions and sinks
of this category separately. {Figure 3.6, 4.1} (Box SPM.1)

Overshoot: Exceeding a Warming Level and Returning
B.7 If warming exceeds a specified level such as 1.5°C, it could gradually be reduced again by
achieving and sustaining net negative global CO2 emissions. This would require additional
deployment of carbon dioxide removal, compared to pathways without overshoot, leading
to greater feasibility and sustainability concerns. Overshoot entails adverse impacts, some
irreversible, and additional risks for human and natural systems, all growing with the
magnitude and duration of overshoot. (high confidence) {3.1, 3.3, 3.4, Table 3.1, Figure 3.6}
B.7.1 Only a small number of the most ambitious global modelled pathways limit global warming to 1.5°C (>50%) by 2100
without exceeding this level temporarily. Achieving and sustaining net negative global CO 2 emissions, with annual rates
of CDR greater than residual CO 2 emissions, would gradually reduce the warming level again (high confidence). Adverse
impacts that occur during this period of overshoot and cause additional warming via feedback mechanisms, such as
increased wildfires, mass mortality of trees, drying of peatlands, and permafrost thawing, weakening natural land
carbon sinks and increasing releases of GHGs would make the return more challenging (medium confidence). {3.3.2,
3.3.4, Table 3.1, Figure 3.6} (Box SPM.1)
B.7.2 The higher the magnitude and the longer the duration of overshoot, the more ecosystems and societies are exposed
to greater and more widespread changes in climatic impact-drivers, increasing risks for many natural and human
systems. Compared to pathways without overshoot, societies would face higher risks to infrastructure, low-lying
coastal settlements, and associated livelihoods. Overshooting 1.5°C will result in irreversible adverse impacts on certain
ecosystems with low resilience, such as polar, mountain, and coastal ecosystems, impacted by ice-sheet melt, glacier
melt, or by accelerating and higher committed sea level rise. (high confidence) {3.1.2, 3.3.4}
B.7.3 The larger the overshoot, the more net negative CO2 emissions would be needed to return to 1.5°C by 2100. Transitioning
towards net zero CO 2 emissions faster and reducing non-CO 2 emissions such as methane more rapidly would limit
peak warming levels and reduce the requirement for net negative CO2 emissions, thereby reducing feasibility and
sustainability concerns, and social and environmental risks associated with CDR deployment at large scales. (high
confidence) {3.3.3, 3.3.4, 3.4.1, Table 3.1}

C. Responses in the Near Term
Urgency of Near-Term Integrated Climate Action
C.1 Climate change is a threat to human well-being and planetary health (very high confidence).
There is a rapidly closing window of opportunity to secure a liveable and sustainable future for
all (very high confidence). Climate resilient development integrates adaptation and mitigation
to advance sustainable development for all, and is enabled by increased international
cooperation including improved access to adequate financial resources, particularly for
vulnerable regions, sectors and groups, and inclusive governance and coordinated policies
(high confidence). The choices and actions implemented in this decade will have impacts now
and for thousands of years (high confidence). {3.1, 3.3, 4.1, 4.2, 4.3, 4.4, 4.7, 4.8, 4.9, Figure 3.1,
Figure 3.3, Figure 4.2} (Figure SPM.1, Figure SPM.6)
C.1.1 Evidence of observed adverse impacts and related losses and damages, projected risks, levels and trends in vulnerability
and adaptation limits, demonstrate that worldwide climate resilient development action is more urgent than previously
assessed in AR5. Climate resilient development integrates adaptation and GHG mitigation to advance sustainable
development for all. Climate resilient development pathways have been constrained by past development, emissions
and climate change and are progressively constrained by every increment of warming, in particular beyond 1.5°C.
(very high confidence) {3.4, 3.4.2, 4.1}
C.1.2 Government actions at sub-national, national and international levels, with civil society and the private sector, play a
crucial role in enabling and accelerating shifts in development pathways towards sustainability and climate resilient
development (very high confidence). Climate resilient development is enabled when governments, civil society and
the private sector make inclusive development choices that prioritize risk reduction, equity and justice, and when
decision-making processes, finance and actions are integrated across governance levels, sectors, and timeframes (very
high confidence). Enabling conditions are differentiated by national, regional and local circumstances and geographies,
according to capabilities, and include: political commitment and follow-through, coordinated policies, social and
international cooperation, ecosystem stewardship, inclusive governance, knowledge diversity, technological innovation,
monitoring and evaluation, and improved access to adequate financial resources, especially for vulnerable regions,
sectors and communities (high confidence). {3.4, 4.2, 4.4, 4.5, 4.7, 4.8} (Figure SPM.6)
C.1.3 Continued emissions will further affect all major climate system components, and many changes will be irreversible on
centennial to millennial time scales and become larger with increasing global warming. Without urgent, effective, and
equitable mitigation and adaptation actions, climate change increasingly threatens ecosystems, biodiversity, and the
livelihoods, health and well-being of current and future generations. (high confidence) {3.1.3, 3.3.3, 3.4.1, Figure 3.4,
4.1, 4.2, 4.3, 4.4} (Figure SPM.1, Figure SPM.6)

There is a rapidly narrowing window of opportunity
to enable climate resilient development
Multiple interacting choices and actions can shift
development pathways towards sustainability

Figure SPM.6: The illustrative development pathways (red to green) and associated outcomes (right panel) show that there is a rapidly narrowing window
of opportunity to secure a liveable and sustainable future for all. Climate resilient development is the process of implementing greenhouse gas mitigation and
adaptation measures to support sustainable development. Diverging pathways illustrate that interacting choices and actions made by diverse government,
private sector and civil society actors can advance climate resilient development, shift pathways towards sustainability, and enable lower emissions and
adaptation. Diverse knowledge and values include cultural values, Indigenous Knowledge, local knowledge, and scientific knowledge. Climatic and non-climatic
events, such as droughts, floods or pandemics, pose more severe shocks to pathways with lower climate resilient development (red to yellow) than to pathways
with higher climate resilient development (green). There are limits to adaptation and adaptive capacity for some human and natural systems at global warming
of 1.5°C, and with every increment of warming, losses and damages will increase. The development pathways taken by countries at all stages of economic
development impact GHG emissions and mitigation challenges and opportunities, which vary across countries and regions. Pathways and opportunities for
action are shaped by previous actions (or inactions and opportunities missed; dashed pathway) and enabling and constraining conditions (left panel), and
take place in the context of climate risks, adaptation limits and development gaps. The longer emissions reductions are delayed, the fewer effective adaptation
options. {Figure 4.2, 3.1, 3.2, 3.4, 4.2, 4.4, 4.5, 4.6, 4.9}

The Benefits of Near-Term Action
C.2 Deep, rapid, and sustained mitigation and accelerated implementation of adaptation actions
in this decade would reduce projected losses and damages for humans and ecosystems
(very high confidence), and deliver many co-benefits, especially for air quality and health
(high confidence). Delayed mitigation and adaptation action would lock in high-emissions
infrastructure, raise risks of stranded assets and cost-escalation, reduce feasibility, and
increase losses and damages (high confidence). Near-term actions involve high up-front
investments and potentially disruptive changes that can be lessened by a range of enabling
policies (high confidence). {2.1, 2.2, 3.1, 3.2, 3.3, 3.4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8}
C.2.1 Deep, rapid, and sustained mitigation and accelerated implementation of adaptation actions in this decade would
reduce future losses and damages related to climate change for humans and ecosystems (very high confidence). As
adaptation options often have long implementation times, accelerated implementation of adaptation in this decade is
important to close adaptation gaps (high confidence). Comprehensive, effective, and innovative responses integrating
adaptation and mitigation can harness synergies and reduce trade-offs between adaptation and mitigation (high
confidence). {4.1, 4.2, 4.3}

C.2.2 Delayed mitigation action will further increase global warming and losses and damages will rise and additional human
and natural systems will reach adaptation limits. Challenges from delayed adaptation and mitigation actions include the
risk of cost escalation, lock-in of infrastructure, stranded assets, and reduced feasibility and effectiveness of adaptation
and mitigation options. Without rapid, deep and sustained mitigation and accelerated adaptation actions, losses
and damages will continue to increase, including projected adverse impacts in Africa, LDCs, SIDS, Central and South
America49, Asia and the Arctic, and will disproportionately affect the most vulnerable populations. (high confidence)
{2.1.2, 3.1.2, 3.2, 3.3.1, 3.3.3, 4.1, 4.2, 4.3} (Figure SPM.3, Figure SPM.4)
C.2.3 Accelerated climate action can also provide co-benefits (see also C.4) (high confidence). Many mitigation actions would
have benefits for health through lower air pollution, active mobility (e.g., walking, cycling), and shifts to sustainable
healthy diets (high confidence). Strong, rapid and sustained reductions in methane emissions can limit near-term
warming and improve air quality by reducing global surface ozone (high confidence). Adaptation can generate multiple
additional benefits such as improving agricultural productivity, innovation, health and well-being, food security,
livelihood, and biodiversity conservation (very high confidence). {4.2, 4.5.4, 4.5.5, 4.6}
C.2.4 Cost-benefit analysis remains limited in its ability to represent all avoided damages from climate change (high
confidence). The economic benefits for human health from air quality improvement arising from mitigation action can
be of the same order of magnitude as mitigation costs, and potentially even larger (medium confidence). Even without
accounting for all the benefits of avoiding potential damages, the global economic and social benefit of limiting global
warming to 2°C exceeds the cost of mitigation in most of the assessed literature (medium confidence)50. More rapid
climate change mitigation, with emissions peaking earlier, increases co-benefits and reduces feasibility risks and costs
in the long-term, but requires higher up-front investments (high confidence). {3.4.1, 4.2}
C.2.5 Ambitious mitigation pathways imply large and sometimes disruptive changes in existing economic structures, with
significant distributional consequences within and between countries. To accelerate climate action, the adverse
consequences of these changes can be moderated by fiscal, financial, institutional and regulatory reforms and by
integrating climate actions with macroeconomic policies through (i) economy-wide packages, consistent with national
circumstances, supporting sustainable low-emission growth paths; (ii) climate resilient safety nets and social protection;
and (iii) improved access to finance for low-emissions infrastructure and technologies, especially in developing countries.
(high confidence) {4.2, 4.4, 4.7, 4.8.1}

There are multiple opportunities for scaling up climate action
a) Feasibility of climate responses and adaptation, and potential of mitigation options in the near term
b) Potential of demand-side mitigation options by 2050

Figure SPM.7: Multiple Opportunities for scaling up climate action. Panel (a) presents selected mitigation and adaptation options across different
systems. The left-hand side of panel a shows climate responses and adaptation options assessed for their multidimensional feasibility at global scale, in the near
term and up to 1.5°C global warming. As literature above 1.5°C is limited, feasibility at higher levels of warming may change, which is currently not possible
to assess robustly. The term response is used here in addition to adaptation because some responses, such as migration, relocation and resettlement may or
may not be considered to be adaptation. Forest based adaptation includes sustainable forest management, forest conservation and restoration, reforestation
and afforestation. WASH refers to water, sanitation and hygiene. Six feasibility dimensions (economic, technological, institutional, social, environmental and
geophysical) were used to calculate the potential feasibility of climate responses and adaptation options, along with their synergies with mitigation. For
potential feasibility and feasibility dimensions, the figure shows high, medium, or low feasibility. Synergies with mitigation are identified as high, medium, and
low. The right-hand side of Panel a provides an overview of selected mitigation options and their estimated costs and potentials in 2030. Costs are net lifetime
discounted monetary costs of avoided GHG emissions calculated relative to a reference technology. Relative potentials and costs will vary by place, context and
time and in the longer term compared to 2030. The potential (horizontal axis) is the net GHG emission reduction (sum of reduced emissions and/or enhanced
sinks) broken down into cost categories (coloured bar segments) relative to an emission baseline consisting of current policy (around 2019) reference scenarios
from the AR6 scenarios database. The potentials are assessed independently for each option and are not additive. Health system mitigation options are included
mostly in settlement and infrastructure (e.g., efficient healthcare buildings) and cannot be identified separately. Fuel switching in industry refers to switching
to electricity, hydrogen, bioenergy and natural gas. Gradual colour transitions indicate uncertain breakdown into cost categories due to uncertainty or heavy
context dependency. The uncertainty in the total potential is typically 25–50%. Panel (b) displays the indicative potential of demand-side mitigation options
for 2050. Potentials are estimated based on approximately 500 bottom-up studies representing all global regions. The baseline (white bar) is provided by the
sectoral mean GHG emissions in 2050 of the two scenarios (IEA-STEPS and IP_ModAct) consistent with policies announced by national governments until 2020.
The green arrow represents the demand-side emissions reductions potentials. The range in potential is shown by a line connecting dots displaying the highest
and the lowest potentials reported in the literature. Food shows demand-side potential of socio-cultural factors and infrastructure use, and changes in land-use
patterns enabled by change in food demand. Demand-side measures and new ways of end-use service provision can reduce global GHG emissions in end-use
sectors (buildings, land transport, food) by 40–70% by 2050 compared to baseline scenarios, while some regions and socioeconomic groups require additional
energy and resources. The last row shows how demand-side mitigation options in other sectors can influence overall electricity demand. The dark grey bar shows
the projected increase in electricity demand above the 2050 baseline due to increasing electrification in the other sectors. Based on a bottom-up assessment,
this projected increase in electricity demand can be avoided through demand-side mitigation options in the domains of infrastructure use and socio-cultural
factors that influence electricity usage in industry, land transport, and buildings (green arrow). {Figure 4.4}

Mitigation and Adaptation Options across Systems
C.3 Rapid and far-reaching transitions across all sectors and systems are necessary to achieve
deep and sustained emissions reductions and secure a liveable and sustainable future for all.
These system transitions involve a significant upscaling of a wide portfolio of mitigation and
adaptation options. Feasible, effective, and low-cost options for mitigation and adaptation
are already available, with differences across systems and regions. (high confidence) {4.1, 4.5,
4.6} (Figure SPM.7)
C.3.1 The systemic change required to achieve rapid and deep emissions reductions and transformative adaptation to climate
change is unprecedented in terms of scale, but not necessarily in terms of speed (medium confidence). Systems transitions
include: deployment of low- or zero-emission technologies; reducing and changing demand through infrastructure
design and access, socio-cultural and behavioural changes, and increased technological efficiency and adoption; social
protection, climate services or other services; and protecting and restoring ecosystems (high confidence). Feasible,
effective, and low-cost options for mitigation and adaptation are already available (high confidence). The availability,
feasibility and potential of mitigation and adaptation options in the near term differs across systems and regions (very
high confidence). {4.1, 4.5.1 to 4.5.6} (Figure SPM.7)
Energy Systems
C.3.2 Net zero CO 2 energy systems entail: a substantial reduction in overall fossil fuel use, minimal use of unabated fossil
fuels51, and use of carbon capture and storage in the remaining fossil fuel systems; electricity systems that emit no
net CO2; widespread electrification; alternative energy carriers in applications less amenable to electrification; energy
conservation and efficiency; and greater integration across the energy system (high confidence). Large contributions
to emissions reductions with costs less than USD 20 tCO 2 -eq-1 come from solar and wind energy, energy efficiency
improvements, and methane emissions reductions (coal mining, oil and gas, waste) (medium confidence). There are
feasible adaptation options that support infrastructure resilience, reliable power systems and efficient water use for
existing and new energy generation systems (very high confidence). Energy generation diversification (e.g., via wind,
solar, small scale hydropower) and demand-side management (e.g., storage and energy efficiency improvements) can
increase energy reliability and reduce vulnerabilities to climate change (high confidence). Climate responsive energy
markets, updated design standards on energy assets according to current and projected climate change, smart-grid
technologies, robust transmission systems and improved capacity to respond to supply deficits have high feasibility in
the medium to long term, with mitigation co-benefits (very high confidence). {4.5.1} (Figure SPM.7)

Industry and Transport
C.3.3 Reducing industry GHG emissions entails coordinated action throughout value chains to promote all mitigation
options, including demand management, energy and materials efficiency, circular material flows, as well as abatement
technologies and transformational changes in production processes (high confidence). In transport, sustainable
biofuels, low-emissions hydrogen, and derivatives (including ammonia and synthetic fuels) can support mitigation of
CO2 emissions from shipping, aviation, and heavy-duty land transport but require production process improvements
and cost reductions (medium confidence). Sustainable biofuels can offer additional mitigation benefits in land-based
transport in the short and medium term (medium confidence). Electric vehicles powered by low-GHG emissions
electricity have large potential to reduce land-based transport GHG emissions, on a life cycle basis (high confidence).
Advances in battery technologies could facilitate the electrification of heavy-duty trucks and compliment conventional
electric rail systems (medium confidence). The environmental footprint of battery production and growing concerns
about critical minerals can be addressed by material and supply diversification strategies, energy and material efficiency
improvements, and circular material flows (medium confidence). {4.5.2, 4.5.3} (Figure SPM.7)
Cities, Settlements and Infrastructure
C.3.4 Urban systems are critical for achieving deep emissions reductions and advancing climate resilient development (high
confidence). Key adaptation and mitigation elements in cities include considering climate change impacts and risks
(e.g., through climate services) in the design and planning of settlements and infrastructure; land use planning to
achieve compact urban form, co-location of jobs and housing; supporting public transport and active mobility (e.g.,
walking and cycling); the efficient design, construction, retrofit, and use of buildings; reducing and changing energy
and material consumption; sufficiency52; material substitution; and electrification in combination with low emissions
sources (high confidence). Urban transitions that offer benefits for mitigation, adaptation, human health and well-
being, ecosystem services, and vulnerability reduction for low-income communities are fostered by inclusive long-term
planning that takes an integrated approach to physical, natural and social infrastructure (high confidence). Green/
natural and blue infrastructure supports carbon uptake and storage and either singly or when combined with grey
infrastructure can reduce energy use and risk from extreme events such as heatwaves, flooding, heavy precipitation and
droughts, while generating co-benefits for health, well-being and livelihoods (medium confidence). {4.5.3}
Land, Ocean, Food, and Water
C.3.5 Many agriculture, forestry, and other land use (AFOLU) options provide adaptation and mitigation benefits that could
be upscaled in the near term across most regions. Conservation, improved management, and restoration of forests
and other ecosystems offer the largest share of economic mitigation potential, with reduced deforestation in tropical
regions having the highest total mitigation potential. Ecosystem restoration, reforestation, and afforestation can lead to
trade-offs due to competing demands on land. Minimizing trade-offs requires integrated approaches to meet multiple
objectives including food security. Demand-side measures (shifting to sustainable healthy diets53 and reducing food loss/
waste) and sustainable agricultural intensification can reduce ecosystem conversion, and methane and nitrous oxide
emissions, and free up land for reforestation and ecosystem restoration. Sustainably sourced agricultural and forest
products, including long-lived wood products, can be used instead of more GHG-intensive products in other sectors.
Effective adaptation options include cultivar improvements, agroforestry, community-based adaptation, farm and
landscape diversification, and urban agriculture. These AFOLU response options require integration of biophysical,
socioeconomic and other enabling factors. Some options, such as conservation of high-carbon ecosystems (e.g., peatlands,
wetlands, rangelands, mangroves and forests), deliver immediate benefits, while others, such as restoration of high-carbon
ecosystems, take decades to deliver measurable results. (high confidence) {4.5.4} (Figure SPM.7)
C.3.6 Maintaining the resilience of biodiversity and ecosystem services at a global scale depends on effective and equitable
conservation of approximately 30% to 50% of Earth’s land, freshwater and ocean areas, including currently near-
natural ecosystems (high confidence). Conservation, protection and restoration of terrestrial, freshwater, coastal and
ocean ecosystems, together with targeted management to adapt to unavoidable impacts of climate change reduces
the vulnerability of biodiversity and ecosystem services to climate change (high confidence), reduces coastal erosion
and flooding (high confidence), and could increase carbon uptake and storage if global warming is limited (medium
confidence). Rebuilding overexploited or depleted fisheries reduces negative climate change impacts on fisheries
(medium confidence) and supports food security, biodiversity, human health and well-being (high confidence). Land
restoration contributes to climate change mitigation and adaptation with synergies via enhanced ecosystem services
and with economically positive returns and co-benefits for poverty reduction and improved livelihoods (high confidence).
Cooperation, and inclusive decision making, with Indigenous Peoples and local communities, as well as recognition of
inherent rights of Indigenous Peoples, is integral to successful adaptation and mitigation across forests and other
ecosystems (high confidence). {4.5.4, 4.6} (Figure SPM.7)
Health and Nutrition
C.3.7 Human health will benefit from integrated mitigation and adaptation options that mainstream health into food,
infrastructure, social protection, and water policies (very high confidence). Effective adaptation options exist to help
protect human health and well-being, including: strengthening public health programs related to climate-sensitive
diseases, increasing health systems resilience, improving ecosystem health, improving access to potable water,
reducing exposure of water and sanitation systems to flooding, improving surveillance and early warning systems,
vaccine development (very high confidence), improving access to mental healthcare, and Heat Health Action Plans that
include early warning and response systems (high confidence). Adaptation strategies which reduce food loss and waste
or support balanced, sustainable healthy diets contribute to nutrition, health, biodiversity and other environmental
benefits (high confidence). {4.5.5} (Figure SPM.7)
Society, Livelihoods, and Economies
C.3.8 Policy mixes that include weather and health insurance, social protection and adaptive social safety nets, contingent
finance and reserve funds, and universal access to early warning systems combined with effective contingency plans, can
reduce vulnerability and exposure of human systems. Disaster risk management, early warning systems, climate services
and risk spreading and sharing approaches have broad applicability across sectors. Increasing education including
capacity building, climate literacy, and information provided through climate services and community approaches can
facilitate heightened risk perception and accelerate behavioural changes and planning. (high confidence) {4.5.6}
Synergies and Trade-Offs with Sustainable Development
C.4 Accelerated and equitable action in mitigating and adapting to climate change impacts is
critical to sustainable development. Mitigation and adaptation actions have more synergies
than trade-offs with Sustainable Development Goals. Synergies and trade-offs depend on
context and scale of implementation. (high confidence) {3.4, 4.2, 4.4, 4.5, 4.6, 4.9, Figure 4.5}
C.4.1 Mitigation efforts embedded within the wider development context can increase the pace, depth and breadth of emission
reductions (medium confidence). Countries at all stages of economic development seek to improve the well-being of
people, and their development priorities reflect different starting points and contexts. Different contexts include but
are not limited to social, economic, environmental, cultural, political circumstances, resource endowment, capabilities,
international environment, and prior development (high confidence). In regions with high dependency on fossil fuels for,
among other things, revenue and employment generation, mitigating risk for sustainable development requires policies
that promote economic and energy sector diversification and considerations of just transitions principles, processes
and practices (high confidence). Eradicating extreme poverty, energy poverty, and providing decent living standards in
low-emitting countries / regions in the context of achieving sustainable development objectives, in the near term, can
be achieved without significant global emissions growth (high confidence). {4.4, 4.6, Annex I: Glossary}
C.4.2 Many mitigation and adaptation actions have multiple synergies with Sustainable Development Goals (SDGs) and
sustainable development generally, but some actions can also have trade-offs. Potential synergies with SDGs exceed
potential trade-offs; synergies and trade-offs depend on the pace and magnitude of change and the development
context including inequalities with consideration of climate justice. Trade-offs can be evaluated and minimised by
giving emphasis to capacity building, finance, governance, technology transfer, investments, development, context
specific gender-based and other social equity considerations with meaningful participation of Indigenous Peoples, local
communities and vulnerable populations. (high confidence) {3.4.1, 4.6, Figure 4.5, 4.9}
C.4.3 Implementing both mitigation and adaptation actions together and taking trade-offs into account supports co-benefits
and synergies for human health and well-being. For example, improved access to clean energy sources and technologies
generates health benefits especially for women and children; electrification combined with low-GHG energy, and shifts
to active mobility and public transport can enhance air quality, health, employment, and can elicit energy security and
deliver equity. (high confidence) {4.2, 4.5.3, 4.5.5, 4.6, 4.9}
Equity and Inclusion
C.5 Prioritising equity, climate justice, social justice, inclusion and just transition processes can
enable adaptation and ambitious mitigation actions and climate resilient development.
Adaptation outcomes are enhanced by increased support to regions and people with the
highest vulnerability to climatic hazards. Integrating climate adaptation into social protection
programs improves resilience. Many options are available for reducing emission-intensive
consumption, including through behavioural and lifestyle changes, with co-benefits for
societal well-being. (high confidence) {4.4, 4.5}
C.5.1 Equity remains a central element in the UN climate regime, notwithstanding shifts in differentiation between states
over time and challenges in assessing fair shares. Ambitious mitigation pathways imply large and sometimes disruptive
changes in economic structure, with significant distributional consequences, within and between countries. Distributional
consequences within and between countries include shifting of income and employment during the transition from
high- to low-emissions activities. (high confidence) {4.4}
C.5.2 Adaptation and mitigation actions that prioritise equity, social justice, climate justice, rights-based approaches, and
inclusivity, lead to more sustainable outcomes, reduce trade-offs, support transformative change and advance climate
resilient development. Redistributive policies across sectors and regions that shield the poor and vulnerable, social
safety nets, equity, inclusion and just transitions, at all scales can enable deeper societal ambitions and resolve trade-
offs with sustainable development goals. Attention to equity and broad and meaningful participation of all relevant
actors in decision making at all scales can build social trust which builds on equitable sharing of benefits and burdens
of mitigation that deepen and widen support for transformative changes. (high confidence) {4.4}
C.5.3 Regions and people (3.3 to 3.6 billion in number) with considerable development constraints have high vulnerability to
climatic hazards (see A.2.2). Adaptation outcomes for the most vulnerable within and across countries and regions are
enhanced through approaches focusing on equity, inclusivity and rights-based approaches. Vulnerability is exacerbated
by inequity and marginalisation linked to e.g., gender, ethnicity, low incomes, informal settlements, disability, age,
and historical and ongoing patterns of inequity such as colonialism, especially for many Indigenous Peoples and local
communities. Integrating climate adaptation into social protection programs, including cash transfers and public works
programs, is highly feasible and increases resilience to climate change, especially when supported by basic services
and infrastructure. The greatest gains in well-being in urban areas can be achieved by prioritising access to finance to
reduce climate risk for low-income and marginalised communities including people living in informal settlements. (high
confidence) {4.4, 4.5.3, 4.5.5, 4.5.6}
C.5.4 The design of regulatory instruments and economic instruments and consumption-based approaches, can advance equity.
Individuals with high socio-economic status contribute disproportionately to emissions, and have the highest potential
for emissions reductions. Many options are available for reducing emission-intensive consumption while improving
societal well-being. Socio-cultural options, behaviour and lifestyle changes supported by policies, infrastructure, and
technology can help end-users shift to low-emissions-intensive consumption, with multiple co-benefits. A substantial
share of the population in low-emitting countries lack access to modern energy services. Technology development,
transfer, capacity building and financing can support developing countries / regions leapfrogging or transitioning to
low-emissions transport systems thereby providing multiple co-benefits. Climate resilient development is advanced
when actors work in equitable, just and inclusive ways to reconcile divergent interests, values and worldviews, toward
equitable and just outcomes. (high confidence) {2.1, 4.4}
Governance and Policies
C.6 Effective climate action is enabled by political commitment, well-aligned multilevel
governance, institutional frameworks, laws, policies and strategies and enhanced access
to finance and technology. Clear goals, coordination across multiple policy domains, and
inclusive governance processes facilitate effective climate action. Regulatory and economic
instruments can support deep emissions reductions and climate resilience if scaled up and
applied widely. Climate resilient development benefits from drawing on diverse knowledge.
(high confidence) {2.2, 4.4, 4.5, 4.7}
C.6.1 Effective climate governance enables mitigation and adaptation. Effective governance provides overall direction on
setting targets and priorities and mainstreaming climate action across policy domains and levels, based on national
circumstances and in the context of international cooperation. It enhances monitoring and evaluation and regulatory
certainty, prioritising inclusive, transparent and equitable decision-making, and improves access to finance and
technology (see C.7). (high confidence) {2.2.2, 4.7}
C.6.2 Effective local, municipal, national and subnational institutions build consensus for climate action among diverse
interests, enable coordination and inform strategy setting but require adequate institutional capacity. Policy support is
influenced by actors in civil society, including businesses, youth, women, labour, media, Indigenous Peoples, and local
communities. Effectiveness is enhanced by political commitment and partnerships between different groups in society.
(high confidence) {2.2, 4.7}
C.6.3 Effective multilevel governance for mitigation, adaptation, risk management, and climate resilient development is
enabled by inclusive decision processes that prioritise equity and justice in planning and implementation, allocation of
appropriate resources, institutional review, and monitoring and evaluation. Vulnerabilities and climate risks are often
reduced through carefully designed and implemented laws, policies, participatory processes, and interventions that
address context specific inequities such as those based on gender, ethnicity, disability, age, location and income. (high
confidence) {4.4, 4.7}
C.6.4 Regulatory and economic instruments could support deep emissions reductions if scaled up and applied more widely
(high confidence). Scaling up and enhancing the use of regulatory instruments can improve mitigation outcomes in
sectoral applications, consistent with national circumstances (high confidence). Where implemented, carbon pricing
instruments have incentivized low-cost emissions reduction measures but have been less effective, on their own and
at prevailing prices during the assessment period, to promote higher-cost measures necessary for further reductions
(medium confidence). Equity and distributional impacts of such carbon pricing instruments, e.g., carbon taxes and
emissions trading, can be addressed by using revenue to support low-income households, among other approaches.
Removing fossil fuel subsidies would reduce emissions54 and yield benefits such as improved public revenue,
macroeconomic and sustainability performance; subsidy removal can have adverse distributional impacts, especially
on the most economically vulnerable groups which, in some cases can be mitigated by measures such as redistributing
revenue saved, all of which depend on national circumstances (high confidence). Economy-wide policy packages, such
as public spending commitments and pricing reforms, can meet short-term economic goals while reducing emissions and
shifting development pathways towards sustainability (medium confidence). Effective policy packages would be comprehensive,
consistent, balanced across objectives, and tailored to national circumstances (high confidence). {2.2.2, 4.7}
C.6.5 Drawing on diverse knowledges and cultural values, meaningful participation and inclusive engagement processes—
including Indigenous Knowledge, local knowledge, and scientific knowledge—facilitates climate resilient development,
builds capacity and allows locally appropriate and socially acceptable solutions. (high confidence) {4.4, 4.5.6, 4.7}
Finance, Technology and International Cooperation
C.7 Finance, technology and international cooperation are critical enablers for accelerated climate
action. If climate goals are to be achieved, both adaptation and mitigation financing would
need to increase many-fold. There is sufficient global capital to close the global investment
gaps but there are barriers to redirect capital to climate action. Enhancing technology
innovation systems is key to accelerate the widespread adoption of technologies and
practices. Enhancing international cooperation is possible through multiple channels. (high
confidence) {2.3, 4.8}
C.7.1 Improved availability of and access to finance55 would enable accelerated climate action (very high confidence).
Addressing needs and gaps and broadening equitable access to domestic and international finance, when combined
with other supportive actions, can act as a catalyst for accelerating adaptation and mitigation, and enabling climate
resilient development (high confidence). If climate goals are to be achieved, and to address rising risks and accelerate
investments in emissions reductions, both adaptation and mitigation finance would need to increase many-fold (high
confidence). {4.8.1}
C.7.2 Increased access to finance can build capacity and address soft limits to adaptation and avert rising risks, especially for
developing countries, vulnerable groups, regions and sectors (high confidence). Public finance is an important enabler
of adaptation and mitigation, and can also leverage private finance (high confidence). Average annual modelled
mitigation investment requirements for 2020 to 2030 in scenarios that limit warming to 2°C or 1.5°C are a factor of
three to six greater than current levels56, and total mitigation investments (public, private, domestic and international)
would need to increase across all sectors and regions (medium confidence). Even if extensive global mitigation efforts
are implemented, there will be a need for financial, technical, and human resources for adaptation (high confidence).
{4.3, 4.8.1}
C.7.3 There is sufficient global capital and liquidity to close global investment gaps, given the size of the global financial
system, but there are barriers to redirect capital to climate action both within and outside the global financial sector and
in the context of economic vulnerabilities and indebtedness facing developing countries. Reducing financing barriers for
scaling up financial flows would require clear signalling and support by governments, including a stronger alignment
of public finances in order to lower real and perceived regulatory, cost and market barriers and risks and improving
the risk-return profile of investments. At the same time, depending on national contexts, financial actors, including
investors, financial intermediaries, central banks and financial regulators can shift the systemic underpricing of climate-
related risks, and reduce sectoral and regional mismatches between available capital and investment needs. (high
confidence) {4.8.1}
C.7.4 Tracked financial flows fall short of the levels needed for adaptation and to achieve mitigation goals across all sectors
and regions. These gaps create many opportunities and the challenge of closing gaps is largest in developing countries.
Accelerated financial support for developing countries from developed countries and other sources is a critical enabler
to enhance adaptation and mitigation actions and address inequities in access to finance, including its costs, terms
and conditions, and economic vulnerability to climate change for developing countries. Scaled-up public grants for
mitigation and adaptation funding for vulnerable regions, especially in Sub-Saharan Africa, would be cost-effective and
have high social returns in terms of access to basic energy. Options for scaling up mitigation in developing countries
include: increased levels of public finance and publicly mobilised private finance flows from developed to developing
countries in the context of the USD 100 billion-a-year goal; increased use of public guarantees to reduce risks and
leverage private flows at lower cost; local capital markets development; and building greater trust in international
cooperation processes. A coordinated effort to make the post-pandemic recovery sustainable over the longer-term
can accelerate climate action, including in developing regions and countries facing high debt costs, debt distress and
macroeconomic uncertainty. (high confidence) {4.8.1}
C.7.5 Enhancing technology innovation systems can provide opportunities to lower emissions growth, create social and
environmental co-benefits, and achieve other SDGs. Policy packages tailored to national contexts and technological
characteristics have been effective in supporting low-emission innovation and technology diffusion. Public policies can
support training and R&D, complemented by both regulatory and market-based instruments that create incentives and
market opportunities. Technological innovation can have trade-offs such as new and greater environmental impacts,
social inequalities, overdependence on foreign knowledge and providers, distributional impacts and rebound effects57,
requiring appropriate governance and policies to enhance potential and reduce trade-offs. Innovation and adoption of
low-emission technologies lags in most developing countries, particularly least developed ones, due in part to weaker
enabling conditions, including limited finance, technology development and transfer, and capacity building. (high
confidence) {4.8.3}
C.7.6 International cooperation is a critical enabler for achieving ambitious climate change mitigation, adaptation, and climate
resilient development (high confidence). Climate resilient development is enabled by increased international cooperation
including mobilising and enhancing access to finance, particularly for developing countries, vulnerable regions, sectors
and groups and aligning finance flows for climate action to be consistent with ambition levels and funding needs (high
confidence). Enhancing international cooperation on finance, technology and capacity building can enable greater
ambition and can act as a catalyst for accelerating mitigation and adaptation, and shifting development pathways
towards sustainability (high confidence). This includes support to NDCs and accelerating technology development and
deployment (high confidence). Transnational partnerships can stimulate policy development, technology diffusion,
adaptation and mitigation, though uncertainties remain over their costs, feasibility and effectiveness (medium
confidence). International environmental and sectoral agreements, institutions and initiatives are helping, and in some
cases may help, to stimulate low GHG emissions investments and reduce emissions (medium confidence). {2.2.2, 4.8.2}

Climate Change 2023
Synthesis Report

Section 1
Introduction

1. Introduction
This Synthesis Report (SYR) of the IPCC Sixth Assessment Report (AR6)
summarises the state of knowledge of climate change, its widespread
impacts and risks, and climate change mitigation and adaptation, based
on the peer-reviewed scientific, technical and socio-economic literature
since the publication of the IPCC’s Fifth Assessment Report (AR5) in
2014.
The assessment is undertaken within the context of the evolving
international landscape, in particular, developments in the UN
Framework Convention on Climate Change (UNFCCC) process,
including the outcomes of the Kyoto Protocol and the adoption of the
Paris Agreement. It reflects the increasing diversity of those involved in
climate action.
This report integrates the main findings of the AR6 Working Group
reports58 and the three AR6 Special Reports59. It recognizes the
interdependence of climate, ecosystems and biodiversity, and human
societies; the value of diverse forms of knowledge; and the close
linkages between climate change adaptation, mitigation, ecosystem
health, human well-being and sustainable development. Building on
multiple analytical frameworks, including those from the physical and
social sciences, this report identifies opportunities for transformative
action which are effective, feasible, just and equitable using concepts
of systems transitions and resilient development pathways60. Different
regional classification schemes61 are used for physical, social and
economic aspects, reflecting the underlying literature.
After this introduction, Section 2, ‘Current Status and Trends’, opens
with the assessment of observational evidence for our changing
climate, historical and current drivers of human-induced climate
change, and its impacts. It assesses the current implementation of
adaptation and mitigation response options. Section 3, ‘Long-Term
Climate and Development Futures’, provides a long-term assessment of
climate change to 2100 and beyond in a broad range of socio-economic
futures. It considers long-term characteristics, impacts, risks and costs
in adaptation and mitigation pathways in the context of sustainable
development. Section 4, ‘Near- Term Responses in a Changing Climate’,
assesses opportunities for scaling up effective action in the period up
to 2040, in the context of climate pledges, and commitments, and the
pursuit of sustainable development.
Based on scientific understanding, key findings can be formulated as
statements of fact or associated with an assessed level of confidence
using the IPCC calibrated language62. The scientific findings are
drawn from the underlying reports and arise from their Summary for
Policymakers (hereafter SPM), Technical Summary (hereafter TS), and
underlying chapters and are indicated by {} brackets. Figure 1.1 shows
the Synthesis Report Figures Key, a guide to visual icons that are used
across multiple figures within this report.

Section 2
Current Status and Trends

2.1 Observed Changes, Impacts and Attribution
Human activities, principally through emissions of greenhouse gases, have unequivocally caused global warming,
with global surface temperature reaching 1.1°C above 1850–1900 in 2011–2020. Global greenhouse gas emissions
have continued to increase over 2010–2019, with unequal historical and ongoing contributions arising from
unsustainable energy use, land use and land-use change, lifestyles and patterns of consumption and production
across regions, between and within countries, and between individuals (high confidence). Human-caused climate
change is already affecting many weather and climate extremes in every region across the globe. This has led to
widespread adverse impacts on food and water security, human health and on economies and society and related
losses and damages63 to nature and people (high confidence). Vulnerable communities who have historically
contributed the least to current climate change are disproportionately affected (high confidence).

2.1.1. Observed Warming and its Causes
Global surface temperature was around 1.1°C above 1850–1900 in
2011–2020 (1.09 [0.95 to 1.20]°C)64, with larger increases
over land (1.59 [1.34 to 1.83]°C) than over the ocean
(0.88 [0.68 to 1.01]°C)65. Observed warming is human-caused, with
warming from greenhouse gases (GHG), dominated by CO2 and
methane (CH4), partly masked by aerosol cooling (Figure 2.1).
Global surface temperature in the first two decades of the 21st century
(2001–2020) was 0.99 [0.84 to 1.10]°C higher than 1850–1900. Global
surface temperature has increased faster since 1970 than in any other
50-year period over at least the last 2000 years (high confidence). The
likely range of total human-caused global surface temperature increase
from 1850–1900 to 2010–201966 is 0.8°C to 1.3°C, with a best estimate
of 1.07°C. It is likely that well-mixed GHGs67 contributed a warming
of 1.0°C to 2.0°C, and other human drivers (principally aerosols)
contributed a cooling of 0.0°C to 0.8°C, natural (solar and volcanic)
drivers changed global surface temperature by ±0.1°C and internal
variability changed it by ±0.2°C. {WGI SPM A.1, WGI SPM A.1.2,
WGI SPM A.1.3, WGI SPM A.2.2, WGI Figure SPM.2; SRCCL TS.2}
Observed increases in well-mixed GHG concentrations since around
1750 are unequivocally caused by GHG emissions from human activities.
Land and ocean sinks have taken up a near-constant proportion
(globally about 56% per year) of CO2 emissions from human activities over
the past six decades, with regional differences (high confidence). In 2019,
atmospheric CO2 concentrations reached 410 parts per million (ppm), CH 4
reached 1866 parts per billion (ppb) and nitrous oxide (N2O) reached 332 ppb68.
Other major contributors to warming are tropospheric ozone (O 3 ) and
halogenated gases. Concentrations of CH 4 and N2 O have increased to
levels unprecedented in at least 800,000 years (very high confidence),
and there is high confidence that current CO 2 concentrations are
higher than at any time over at least the past two million years. Since
1750, increases in CO 2 (47%) and CH4 (156%) concentrations far
exceed – and increases in N2 O (23%) are similar to – the natural
multi-millennial changes between glacial and interglacial periods over at
least the past 800,000 years (very high confidence). The net cooling effect
which arises from anthropogenic aerosols peaked in the late 20th century
(high confidence). {WGI SPM A1.1, WGI SPM A1.3, WGI SPM A.2.1,
WGI Figure SPM.2, WGI TS 2.2, WGI 2ES, WGI Figure 6.1}

Human activities are responsible for global warming
Figure 2.1: The causal chain from emissions to resulting
warming of the climate system. Emissions of GHG have
increased rapidly over recent decades (panel (a)). Global net
anthropogenic GHG emissions include CO 2 from fossil fuel
combustion and industrial processes (CO 2 -FFI) (dark green);
net CO2 from land use, land-use change and forestry (CO2 -LULUCF)
(green); CH 4 ; N 2 O; and fluorinated gases (HFCs, PFCs, SF 6 , NF 3 )
(light blue). These emissions have led to increases in the atmospheric
concentrations of several GHGs including the three major well-mixed
GHGs CO2, CH4 and N2O (panel (b), annual values). To indicate their
relative importance each subpanel’s vertical extent for CO2 , CH4 and
N 2O is scaled to match the assessed individual direct effect (and,
in the case of CH4 indirect effect via atmospheric chemistry impacts
on tropospheric ozone) of historical emissions on temperature
change from 1850–1900 to 2010–2019. This estimate arises from
an assessment of effective radiative forcing and climate sensitivity.
The global surface temperature (shown as annual anomalies from
a 1850–1900 baseline) has increased by around 1.1°C since
1850–1900 (panel (c)). The vertical bar on the right shows the
estimated temperature (very likely range) during the warmest
multi-century period in at least the last 100,000 years, which
occurred around 6500 years ago during the current interglacial
period (Holocene). Prior to that, the next most recent warm period
was about 125,000 years ago, when the assessed multi-century
temperature range [0.5°C to 1.5°C] overlaps the observations of
the most recent decade. These past warm periods were caused
by slow (multi-millennial) orbital variations. Formal detection and
attribution studies synthesise information from climate models
and observations and show that the best estimate is that all the
warming observed between 1850–1900 and 2010–2019 is caused
by humans (panel (d)). The panel shows temperature change
attributed to: total human influence; its decomposition into changes
in GHG concentrations and other human drivers (aerosols, ozone
and land-use change (land-use reflectance)); solar and volcanic
drivers; and internal climate variability. Whiskers show likely ranges.
{WGI SPM A.2.2, WGI Figure SPM.1, WGI Figure SPM.2, WGI TS2.2,
WGI 2.1; WGIII Figure SPM.1, WGIII A.III.II.2.5.1}

Average annual GHG emissions during 2010–2019 were higher
than in any previous decade, but the rate of growth between
2010 and 2019 (1.3% yr -1 ) was lower than that between 2000
and 2009 (2.1% yr -1
)69. Historical cumulative net CO 2 emissions from
1850 to 2019 were 2400 ±240 GtCO2. Of these, more than half (58%)
occurred between 1850 and 1989 [1400 ±195 GtCO 2], and about 42%
between 1990 and 2019 [1000 ±90 GtCO2]. Global net anthropogenic
GHG emissions have been estimated to be 59±6.6 GtCO 2 -eq in 2019,
about 12% (6.5 GtCO2 -eq) higher than in 2010 and 54% (21 GtCO2 -eq)
higher than in 1990. By 2019, the largest growth in gross emissions
occurred in CO2 from fossil fuels and industry (CO2-FFI) followed by
CH4, whereas the highest relative growth occurred in fluorinated
gases (F-gases), starting from low levels in 1990. (high confidence)
{WGIII SPM B1.1, WGIII SPM B.1.2, WGIII SPM B.1.3, WGIII Figure SPM.1,
WGIII Figure SPM.2}

Regional contributions to global human-caused GHG emissions
continue to differ widely. Historical contributions of CO2 emissions
vary substantially across regions in terms of total magnitude, but also
in terms of contributions to CO 2 -FFI (1650 ± 73 GtCO 2 -eq) and net
CO2 -LULUCF (760 ± 220 GtCO 2-eq) emissions (Figure 2.2). Variations
in regional and national per capita emissions partly reflect different
development stages, but they also vary widely at similar income
levels. Average per capita net anthropogenic GHG emissions in 2019
ranged from 2.6 tCO 2-eq to 19 tCO 2-eq across regions (Figure 2.2).
Least Developed Countries (LDCs) and Small Island Developing States (SIDS)
have much lower per capita emissions (1.7 tCO2-eq and 4.6 tCO2-eq,
respectively) than the global average (6.9 tCO 2 -eq), excluding
CO2 -LULUCF. Around 48% of the global population in 2019 lives in countries
emitting on average more than 6 tCO 2-eq per capita, 35% of the global
population live in countries emitting more than 9 tCO2 -eq per capita70
(excluding CO2 -LULUCF) while another 41% live in countries emitting less
than 3 tCO 2 -eq per capita. A substantial share of the population in these
low-emitting countries lack access to modern energy services. (high confidence)
{WGIII SPM B.3, WGIII SPM B3.1, WGIII SPM B.3.2, WGIII SPM B.3.3}
Net GHG emissions have increased since 2010 across all major
sectors (high confidence). In 2019, approximately 34% (20 GtCO2 -eq)
of net global GHG emissions came from the energy sector, 24%
(14 GtCO 2 -eq) from industry, 22% (13 GtCO 2-eq) from AFOLU, 15%
(8.7 GtCO2-eq) from transport and 6% (3.3 GtCO 2-eq) from buildings71
(high confidence). Average annual GHG emissions growth between
2010 and 2019 slowed compared to the previous decade in energy
supply (from 2.3% to 1.0%) and industry (from 3.4% to 1.4%) but
remained roughly constant at about 2% yr –1 in the transport sector
(high confidence). About half of total net AFOLU emissions are from
CO2 LULUCF, predominantly from deforestation (medium confidence).
Land overall constituted a net sink of –6.6 (±4.6) GtCO 2 yr–1 for the period
2010–201972 (medium confidence). {WGIII SPM B.2, WGIII SPM B.2.1,
WGIII SPM B.2.2, WGIII TS 5.6.1}
Human-caused climate change is a consequence of more than
a century of net GHG emissions from energy use, land-use and
land use change, lifestyle and patterns of consumption, and
production. Emissions reductions in CO2 from fossil fuels and industrial
processes (CO2 -FFI), due to improvements in energy intensity of GDP
and carbon intensity of energy, have been less than emissions increases
from rising global activity levels in industry, energy supply, transport,
agriculture and buildings. The 10% of households with the highest per
capita emissions contribute 34–45% of global consumption-based
household GHG emissions, while the middle 40% contribute 40–53%,
and the bottom 50% contribute 13–15%. An increasing share of
emissions can be attributed to urban areas (a rise from about 62%
to 67–72% of the global share between 2015 and 2020). The drivers
of urban GHG emissions73 are complex and include population size,
income, state of urbanisation and urban form. (high confidence)
{WGIII SPM B.2, WGIII SPM B.2.3, WGIII SPM B.3.4, WGIII SPM D.1.1}

Emissions have grown in most regions but are distributed unevenly,
both in the present day and cumulatively since 1850

a) Historical cumulative net anthropogenic
CO 2 emissions per region (1850–2019)

b) Net anthropogenic GHG emissions per capita
and for total population, per region (2019)

c) Global net anthropogenic GHG emissions by region (1990–2019)
d) Regional indicators (2019) and regional production vs consumption accounting (2018)

Figure 2.2: Regional GHG emissions, and the regional proportion of total cumulative production-based CO 2 emissions from 1850 to 2019. Panel (a) shows the
share of historical cumulative net anthropogenic CO2 emissions per region from 1850 to 2019 in GtCO2. This includes CO2 -FFI and CO2 -LULUCF. Other GHG emissions are not included.
CO2-LULUCF emissions are subject to high uncertainties, reflected by a global uncertainty estimate of ±70% (90% confidence interval). Panel (b) shows the distribution of regional
GHG emissions in tonnes CO2-eq per capita by region in 2019. GHG emissions are categorised into: CO2 -FFI; net CO2 -LULUCF; and other GHG emissions (CH4, N 2 O, fluorinated gases,
expressed in CO2-eq using GWP100-AR6). The height of each rectangle shows per capita emissions, the width shows the population of the region, so that the area of the rectangles
refers to the total emissions for each region. Emissions from international aviation and shipping are not included. In the case of two regions, the area for CO2 -LULUCF is below the
axis, indicating net CO 2 removals rather than emissions. Panel (c) shows global net anthropogenic GHG emissions by region (in GtCO 2 -eq yr –1 (GWP100-AR6)) for the time period
1990–2019. Percentage values refer to the contribution of each region to total GHG emissions in each respective time period. The single-year peak of emissions in 1997 was due to
higher CO 2-LULUCF emissions from a forest and peat fire event in South East Asia. Regions are as grouped in Annex II of WGIII. Panel (d) shows population, gross domestic product
(GDP) per person, emission indicators by region in 2019 for total GHG per person, and total GHG emissions intensity, together with production-based and consumption-based CO2-FFI data,
which is assessed in this report up to 2018. Consumption-based emissions are emissions released to the atmosphere in order to generate the goods and services consumed by a
certain entity (e.g., region). Emissions from international aviation and shipping are not included. {WGIII Figure SPM.2}

2.1.2. Observed Climate System Changes and Impacts to
Date

It is unequivocal that human influence has warmed the
atmosphere, ocean and land. Widespread and rapid changes in
the atmosphere, ocean, cryosphere and biosphere have occurred
(Table 2.1). The scale of recent changes across the climate system as
a whole and the present state of many aspects of the climate system
are unprecedented over many centuries to many thousands of years. It
is very likely that GHG emissions were the main driver74 of tropospheric
warming and extremely likely that human-caused stratospheric ozone
depletion was the main driver of stratospheric cooling between 1979
and the mid-1990s. It is virtually certain that the global upper ocean
(0-700m) has warmed since the 1970s and extremely likely that
human influence is the main driver. Ocean warming accounted for
91% of the heating in the climate system, with land warming, ice loss
and atmospheric warming accounting for about 5%, 3% and 1%,
respectively (high confidence). Global mean sea level increased by 0.20
[0.15 to 0.25] m between 1901 and 2018. The average rate of sea level
rise was 1.3 [0.6 to 2.1]mm yr-1 between 1901 and 1971, increasing to
1.9 [0.8 to 2.9] mm yr-1 between 1971 and 2006, and further increasing
to 3.7 [3.2 to –4.2] mm yr -1 between 2006 and 2018 (high confidence).
Human influence was very likely the main driver of these increases
since at least 1971 (Figure 3.4). Human influence is very likely the main
driver of the global retreat of glaciers since the 1990s and the decrease
in Arctic sea ice area between 1979–1988 and 2010–2019. Human
influence has also very likely contributed to decreased Northern Hemisphere
spring snow cover and surface melting of the Greenland ice sheet. It is
virtually certain that human-caused CO2 emissions are the main driver
of current global acidification of the surface open ocean. {WGI SPM A.1,
WGI SPM A.1.3, WGI SPM A.1.5, WGI SPM A.1.6, WG1 SPM A1.7,
WGI SPM A.2, WG1.SPM A.4.2; SROCC SPM.A.1, SROCC SPM A.2}
Human-caused climate change is already affecting many weather and
climate extremes in every region across the globe. Evidence of observed
changes in extremes such as heatwaves, heavy precipitation, droughts,
and tropical cyclones, and, in particular, their attribution to human
influence, has strengthened since AR5 (Figure 2.3). It is virtually certain
that hot extremes (including heatwaves) have become more frequent and
more intense across most land regions since the 1950s (Figure 2.3), while cold
extremes (including cold waves) have become less frequent and less severe,
with high confidence that human-caused climate change is the main
driver of these changes. Marine heatwaves have approximately doubled
in frequency since the 1980s (high confidence), and human influence
has very likely contributed to most of them since at least 2006. The
frequency and intensity of heavy precipitation events have increased
since the 1950s over most land areas for which observational data
are sufficient for trend analysis (high confidence), and human-caused
climate change is likely the main driver (Figure 2.3). Human-caused
climate change has contributed to increases in agricultural and ecological
droughts in some regions due to increased land evapotranspiration
(medium confidence) (Figure 2.3). It is likely that the global proportion
of major (Category 3–5) tropical cyclone occurrence has increased over
the last four decades. {WGI SPM A.3, WGI SPM A3.1, WGI SPM A3.2;
WGI SPM A3.4; SRCCL SPM.A.2.2; SROCC SPM. A.2}
Climate change has caused substantial damages, and increasingly
irreversible75 losses, in terrestrial, freshwater, cryospheric and
coastal and open ocean ecosystems (high confidence). The extent
and magnitude of climate change impacts are larger than estimated
in previous assessments (high confidence). Approximately half of the
species assessed globally have shifted polewards or, on land, also to
higher elevations (very high confidence). Biological responses including
changes in geographic placement and shifting seasonal timing are often
not sufficient to cope with recent climate change (very high confidence).
Hundreds of local losses of species have been driven by increases in
the magnitude of heat extremes (high confidence) and mass mortality
events on land and in the ocean (very high confidence). Impacts on
some ecosystems are approaching irreversibility such as the impacts
of hydrological changes resulting from the retreat of glaciers, or the
changes in some mountain (medium confidence) and Arctic ecosystems
driven by permafrost thaw (high confidence). Impacts in ecosystems
from slow-onset processes such as ocean acidification, sea level rise
or regional decreases in precipitation have also been attributed to
human-caused climate change (high confidence). Climate change
has contributed to desertification and exacerbated land degradation,
particularly in low lying coastal areas, river deltas, drylands and in
permafrost areas (high confidence). Nearly 50% of coastal wetlands
have been lost over the last 100 years, as a result of the combined
effects of localised human pressures, sea level rise, warming
and extreme climate events (high confidence). {WGII SPM B.1.1,
WGII SPM B.1.2, WGII Figure SPM.2.A, WGII TS.B.1; SRCCL SPM A.1.5,
SRCCL SPM A.2, SRCCL SPM A.2.6, SRCCL Figure SPM.1; SROCC SPM A.6.1,
SROCC SPM, A.6.4, SROCC SPM A.7}

Table 2.1: Assessment of observed changes in large-scale indicators of mean climate across climate system components, and their attribution to human
influence. The colour coding indicates the assessed confidence in / likelihood76 of the observed change and the human contribution as a driver or main driver (specified in that case)
where available (see colour key). Otherwise, explanatory text is provided. {WGI Table TS.1}

Climate change has impacted human and natural systems across the
world with those who have generally least contributed to climate
change being most vulnerable

a) Synthesis of assessment of observed change in hot extremes, heavy precipitation and
drought, and confidence in human contribution to the observed changes in the world’s regions
b) Vulnerability of population & per capita emissions per country in 2019
c) Observed impacts and related losses and damages of climate change

Figure 2.3: Both vulnerability to current climate extremes and historical contribution to climate change are highly heterogeneous with many of those who have
least contributed to climate change to date being most vulnerable to its impacts. Panel (a) The IPCC AR6 WGI inhabited regions are displayed as hexagons with identical size
in their approximate geographical location (see legend for regional acronyms). All assessments are made for each region as a whole and for the 1950s to the present. Assessments made
on different time scales or more local spatial scales might differ from what is shown in the figure. The colours in each panel represent the four outcomes of the assessment on observed
changes. Striped hexagons (white and light-grey) are used where there is low agreement in the type of change for the region as a whole, and grey hexagons are used when there is limited
data and/or literature that prevents an assessment of the region as a whole. Other colours indicate at least medium confidence in the observed change. The confidence level for the human
influence on these observed changes is based on assessing trend detection and attribution and event attribution literature, and it is indicated by the number of dots: three dots for
high confidence, two dots for medium confidence and one dot for low confidence (single, filled dot: limited agreement; single, empty dot: limited evidence). For hot extremes, the evidence
is mostly drawn from changes in metrics based on daily maximum temperatures; regional studies using other indices (heatwave duration, frequency and intensity) are used in addition. For
heavy precipitation, the evidence is mostly drawn from changes in indices based on one-day or five-day precipitation amounts using global and regional studies. Agricultural and
ecological droughts are assessed based on observed and simulated changes in total column soil moisture, complemented by evidence on changes in surface soil moisture, water
balance (precipitation minus evapotranspiration) and indices driven by precipitation and atmospheric evaporative demand. Panel (b) shows the average level of vulnerability amongst a
country’s population against 2019 CO2-FFI emissions per- capita per country for the 180 countries for which both sets of metrics are available. Vulnerability information is based on two
global indicator systems, namely INFORM and World Risk Index. Countries with a relatively low average vulnerability often have groups with high vulnerability within their population and
vice versa. The underlying data includes, for example, information on poverty, inequality, health care infrastructure or insurance coverage. Panel (c) Observed impacts on ecosystems
and human systems attributed to climate change at global and regional scales. Global assessments focus on large studies, multi-species, meta-analyses and large reviews. Regional
assessments consider evidence on impacts across an entire region and do not focus on any country in particular. For human systems, the direction of impacts is assessed and both
adverse and positive impacts have been observed e.g., adverse impacts in one area or food item may occur with positive impacts in another area or food item (for more details and
methodology see WGII SMTS.1). Physical water availability includes balance of water available from various sources including ground water, water quality and demand for water.
Global mental health and displacement assessments reflect only assessed regions. Confidence levels reflect the assessment of attribution of the observed impact to climate change.
{WGI Figure SPM.3, Table TS.5, Interactive Atlas; WGII Figure SPM.2, WGII SMTS.1, WGII 8.3.1, Figure 8.5; ; WGIII 2.2.3}

Climate change has reduced food security and affected water
security due to warming, changing precipitation patterns,
reduction and loss of cryospheric elements, and greater frequency
and intensity of climatic extremes, thereby hindering efforts to
meet Sustainable Development Goals (high confidence). Although
overall agricultural productivity has increased, climate change has slowed
this growth in agricultural productivity over the past 50 years globally
(medium confidence), with related negative crop yield impacts mainly
recorded in mid- and low latitude regions, and some positive impacts
in some high latitude regions (high confidence). Ocean warming in
the 20th century and beyond has contributed to an overall decrease
in maximum catch potential (medium confidence), compounding the
impacts from overfishing for some fish stocks (high confidence). Ocean
warming and ocean acidification have adversely affected food production
from shellfish aquaculture and fisheries in some oceanic regions (high
confidence). Current levels of global warming are associated with
moderate risks from increased dryland water scarcity (high confidence).
Roughly half of the world’s population currently experiences severe water
scarcity for at least some part of the year due to a combination of climatic
and non-climatic drivers (medium confidence) (Figure 2.3). Unsustainable
agricultural expansion, driven in part by unbalanced diets77, increases
ecosystem and human vulnerability and leads to competition for land
and/or water resources (high confidence). Increasing weather and climate
extreme events have exposed millions of people to acute food insecurity78
and reduced water security, with the largest impacts observed in many
locations and/or communities in Africa, Asia, Central and South America,
LDCs, Small Islands and the Arctic, and for small-scale food producers,
low-income households and Indigenous Peoples globally (high confidence).
{WGII SPM B.1.3, WGII SPM.B.2.3, WGII Figure SPM.2, WGII TS B.2.3,
WGII TS Figure TS. 6; SRCCL SPM A.2.8, SRCCL SPM A.5.3; SROCC SPM A.5.4.,
SROCC SPM A.7.1, SROCC SPM A.8.1, SROCC Figure SPM.2}

In urban settings, climate change has caused adverse impacts on
human health, livelihoods and key infrastructure (high confidence).
Hot extremes including heatwaves have intensified in cities (high
confidence), where they have also worsened air pollution events
(medium confidence) and limited functioning of key infrastructure
(high confidence). Urban infrastructure, including transportation, water,
sanitation and energy systems have been compromised by extreme
and slow-onset events79, with resulting economic losses, disruptions of
services and impacts to well-being (high confidence). Observed impacts
are concentrated amongst economically and socially marginalised urban
residents, e.g., those living in informal settlements (high confidence).
Cities intensify human-caused warming locally (very high confidence),
while urbanisation also increases mean and heavy precipitation over and/or
downwind of cities (medium confidence) and resulting runoff intensity
(high confidence). {WGI SPM C.2.6; WGII SPM B.1.5, WGII Figure TS.9,
WGII 6 ES}
Climate change has adversely affected human physical health globally
and mental health in assessed regions (very high confidence), and is
contributing to humanitarian crises where climate hazards interact
with high vulnerability (high confidence). In all regions increases in
extreme heat events have resulted in human mortality and morbidity
(very high confidence). The occurrence of climate-related food-borne and
water-borne diseases has increased (very high confidence). The incidence
of vector-borne diseases has increased from range expansion and/or
increased reproduction of disease vectors (high confidence). Animal and
human diseases, including zoonoses, are emerging in new areas (high
confidence). In assessed regions, some mental health challenges are
associated with increasing temperatures (high confidence), trauma from
extreme events (very high confidence), and loss of livelihoods and culture
(high confidence) (Figure 2.3). Climate change impacts on health are
mediated through natural and human systems, including economic
and social conditions and disruptions (high confidence). Climate and
weather extremes are increasingly driving displacement in Africa,
Asia, North America (high confidence), and Central and South America
(medium confidence) (Figure 2.3), with small island states in the
Caribbean and South Pacific being disproportionately affected relative
to their small population size (high confidence). Through displacement
and involuntary migration from extreme weather and climate
events, climate change has generated and perpetuated vulnerability
(medium confidence). {WGII SPM B.1.4, WGII SPM B.1.7}

Human influence has likely increased the chance of compound
extreme events80 since the 1950s. Concurrent and repeated climate
hazards have occurred in all regions, increasing impacts and
risks to health, ecosystems, infrastructure, livelihoods and food
(high confidence). Compound extreme events include increases in the
frequency of concurrent heatwaves and droughts (high confidence); fire
weather in some regions (medium confidence); and compound flooding in
some locations (medium confidence). Multiple risks interact, generating
new sources of vulnerability to climate hazards, and compounding
overall risk (high confidence). Compound climate hazards can overwhelm
adaptive capacity and substantially increase damage (high confidence)).
{WGI SPM A.3.5; WGII SPM. B.5.1, WGII TS.C.11.3}
Economic impacts attributable to climate change are increasingly
affecting peoples’ livelihoods and are causing economic and
societal impacts across national boundaries (high confidence).
Economic damages from climate change have been detected in
climate-exposed sectors, with regional effects to agriculture, forestry,
fishery, energy, and tourism, and through outdoor labour productivity
(high confidence) with some exceptions of positive impacts in regions
with low energy demand and comparative advantages in agricultural
markets and tourism (high confidence). Individual livelihoods have been
affected through changes in agricultural productivity, impacts on human
health and food security, destruction of homes and infrastructure, and loss
of property and income, with adverse effects on gender and social equity
(high confidence). Tropical cyclones have reduced economic growth in
the short-term (high confidence). Event attribution studies and physical
understanding indicate that human-caused climate change increases
heavy precipitation associated with tropical cyclones (high confidence).
Wildfires in many regions have affected built assets, economic activity,
and health (medium to high confidence). In cities and settlements, climate
impacts to key infrastructure are leading to losses and damages across water
and food systems, and affect economic activity, with impacts extending
beyond the area directly impacted by the climate hazard (high confidence).
{WGI SPM A.3.4; WGII SPM B.1.6, WGII SPM B.5.2, WGII SPM B.5.3}

Climate change has caused widespread adverse impacts
and related losses and damages to nature and people (high
confidence). Losses and damages are unequally distributed across
systems, regions and sectors (high confidence). Cultural losses, related
to tangible and intangible heritage, threaten adaptive capacity and may
result in irrevocable losses of sense of belonging, valued cultural practices,
identity and home, particularly for Indigenous Peoples and those more
directly reliant on the environment for subsistence (medium confidence).
For example, changes in snow cover, lake and river ice, and permafrost
in many Arctic regions, are harming the livelihoods and cultural identity
of Arctic residents including Indigenous populations (high confidence).
Infrastructure, including transportation, water, sanitation and energy
systems have been compromised by extreme and slow-onset events,
with resulting economic losses, disruptions of services and impacts
to well-being (high confidence). {WGII SPM B.1, WGII SPM B.1.2,
WGII SPM.B.1.5, WGII SPM C.3.5, WGII TS.B.1.6; SROCC SPM A.7.1}
Across sectors and regions, the most vulnerable people and
systems have been disproportionately affected by the impacts
of climate change (high confidence). LDCs and SIDS who have much
lower per capita emissions (1.7 tCO2-eq, 4.6 tCO2 -eq, respectively) than
the global average (6.9 tCO2-eq) excluding CO2-LULUCF, also have high
vulnerability to climatic hazards, with global hotspots of high human
vulnerability observed in West-, Central- and East Africa, South Asia,
Central and South America, SIDS and the Arctic (high confidence).
Regions and people with considerable development constraints have
high vulnerability to climatic hazards (high confidence). Vulnerability is
higher in locations with poverty, governance challenges and limited
access to basic services and resources, violent conflict and high levels
of climate-sensitive livelihoods (e.g., smallholder farmers, pastoralists,
fishing communities) (high confidence). Vulnerability at different spatial
levels is exacerbated by inequity and marginalisation linked to gender,
ethnicity, low income or combinations thereof (high confidence), especially
for many Indigenous Peoples and local communities (high confidence).
Approximately 3.3 to 3.6 billion people live in contexts that are highly
vulnerable to climate change (high confidence). Between 2010 and
2020, human mortality from floods, droughts and storms was 15 times
higher in highly vulnerable regions, compared to regions with very low
vulnerability (high confidence). In the Arctic and in some high mountain
regions, negative impacts of cryosphere change have been especially felt
among Indigenous Peoples (high confidence). Human and ecosystem
vulnerability are interdependent (high confidence). Vulnerability of
ecosystems and people to climate change differs substantially among and
within regions (very high confidence), driven by patterns of intersecting
socio-economic development, unsustainable ocean and land use,
inequity, marginalisation, historical and ongoing patterns of inequity
such as colonialism, and governance81 (high confidence). {WGII SPM B.1,
WGII SPM B.2, WGII SPM B.2.4; WGIII SPM B.3.1; SROCC SPM A.7.1,
SROCC SPM A.7.2}

2.2 Responses Undertaken to Date

International climate agreements, rising national ambitions for climate action, along with rising public awareness
are accelerating efforts to address climate change at multiple levels of governance. Mitigation policies have
contributed to a decrease in global energy and carbon intensity, with several countries achieving GHG emission
reductions for over a decade. Low-emission technologies are becoming more affordable, with many low or
zero emissions options now available for energy, buildings, transport, and industry. Adaptation planning and
implementation progress has generated multiple benefits, with effective adaptation options having the potential
to reduce climate risks and contribute to sustainable development. Global tracked finance for mitigation and
adaptation has seen an upward trend since AR5, but falls short of needs. (high confidence)

2.2.1. Global Policy Setting

The United Nations Framework Convention on Climate Change (UNFCCC),
Kyoto Protocol, and Paris Agreement are supporting rising levels of
national ambition and encouraging the development and implementation
of climate policies at multiple levels of governance (high confidence).
The Kyoto Protocol led to reduced emissions in some countries and
was instrumental in building national and international capacity
for GHG reporting, accounting and emissions markets (high
confidence). The Paris Agreement, adopted under the UNFCCC, with
near universal participation, has led to policy development and
target-setting at national and sub-national levels, particularly in
relation to mitigation but also for adaptation, as well as enhanced
transparency of climate action and support (medium confidence).
Nationally Determined Contributions (NDCs), required under
the Paris Agreement, have required countries to articulate their
priorities and ambition with respect to climate action. {WGII 17.4,
WGII TS D.1.1; WGIII SPM B.5.1, WGIII SPM E.6}

Loss & Damage82 was formally recognized in 2013 through establishment
of the Warsaw International Mechanism on Loss and Damage (WIM),
and in 2015, Article 8 of the Paris Agreement provided a legal basis
for the WIM. There is improved understanding of both economic and
non-economic losses and damages, which is informing international
climate policy and which has highlighted that losses and damages are
not comprehensively addressed by current financial, governance and
institutional arrangements, particularly in vulnerable developing countries
(high confidence). {WGII SPM C.3.5, WGII Cross-Chapter Box LOSS}
Other recent global agreements that influence responses to climate
change include the Sendai Framework for Disaster Risk Reduction
(2015-2030), the finance-oriented Addis Ababa Action Agenda (2015)
and the New Urban Agenda (2016), and the Kigali Amendment to
the Montreal Protocol on Substances that Deplete the Ozone Layer
(2016), among others. In addition, the 2030 Agenda for Sustainable
Development, adopted in 2015 by UN member states, sets out 17
Sustainable Development Goals (SDGs) and seeks to align efforts
globally to prioritise ending extreme poverty, protect the planet and
promote more peaceful, prosperous and inclusive societies. If achieved,
these agreements would reduce climate change, and the impacts on
health, well-being, migration, and conflict, among others (very high
confidence). {WGII TS.A.1, WGII 7 ES}
Since AR5, rising public awareness and an increasing diversity
of actors, have overall helped accelerate political commitment
and global efforts to address climate change (medium
confidence). Mass social movements have emerged as catalysing
agents in some regions, often building on prior movements including
Indigenous Peoples-led movements, youth movements, human
rights movements, gender activism, and climate litigation, which is
raising awareness and, in some cases, has influenced the outcome
and ambition of climate governance (medium confidence). Engaging
Indigenous Peoples and local communities using just-transition and
rights-based decision-making approaches, implemented through
collective and participatory decision-making processes has enabled
deeper ambition and accelerated action in different ways, and at all
scales, depending on national circumstances (medium confidence).
The media helps shape the public discourse about climate change. This
can usefully build public support to accelerate climate action (medium
evidence, high agreement). In some instances, public discourses of
media and organised counter movements have impeded climate
action, exacerbating helplessness and disinformation and fuelling
polarisation, with negative implications for climate action (medium
confidence). {WGII SPM C.5.1, WGII SPM D.2, WGII TS.D.9, WGII TS.D.9.7,
WGII TS.E.2.1, WGII 18.4; WGIII SPM D.3.3, WGIII SPM E.3.3, WGIII TS.6.1,
WGIII 6.7, WGIII 13 ES, WGIII Box.13.7}

2.2.2. Mitigation Actions to Date

There has been a consistent expansion of policies and laws
addressing mitigation since AR5 (high confidence). Climate
governance supports mitigation by providing frameworks through
which diverse actors interact, and a basis for policy development and
implementation (medium confidence). Many regulatory and economic
instruments have already been deployed successfully (high confidence).
By 2020, laws primarily focussed on reducing GHG emissions existed in
56 countries covering 53% of global emissions (medium confidence).
The application of diverse policy instruments for mitigation at the
national and sub-national levels has grown consistently across a
range of sectors (high confidence). Policy coverage is uneven across
sectors and remains limited for emissions from agriculture, and from
industrial materials and feedstocks (high confidence). {WGIII SPM B.5,
WGIII SPM B.5.2, WGIII SPM E.3, WGIII SPM E.4}
Practical experience has informed economic instrument design
and helped to improve predictability, environmental effectiveness,
economic efficiency, alignment with distributional goals, and social
acceptance (high confidence). Low-emission technological innovation
is strengthened through the combination of technology-push policies,
together with policies that create incentives for behaviour change and
market opportunities (high confidence) (Section 4.8.3). Comprehensive
and consistent policy packages have been found to be more effective
than single policies (high confidence). Combining mitigation with
policies to shift development pathways, policies that induce lifestyle or
behaviour changes, for example, measures promoting walkable urban
areas combined with electrification and renewable energy can create
health co-benefits from cleaner air and enhanced active mobility (high
confidence). Climate governance enables mitigation by providing an
overall direction, setting targets, mainstreaming climate action across
policy domains and levels, based on national circumstances and in the
context of international cooperation. Effective governance enhances
regulatory certainty, creating specialised organisations and creating the
context to mobilise finance (medium confidence). These functions can
be promoted by climate-relevant laws, which are growing in number, or
climate strategies, among others, based on national and sub-national
context (medium confidence). Effective and equitable climate
governance builds on engagement with civil society actors, political
actors, businesses, youth, labour, media, Indigenous Peoples and local
communities (medium confidence). {WGIII SPM E.2.2, WGIII SPM E.3,
WGIII SPM E.3.1, WGIII SPM E.4.2, WGIII SPM E.4.3, WGIII SPM E.4.4}
The unit costs of several low-emission technologies, including
solar, wind and lithium-ion batteries, have fallen consistently
since 2010 (Figure 2.4). Design and process innovations in
combination with the use of digital technologies have led to
near-commercial availability of many low or zero emissions
options in buildings, transport and industry. From 2010-2019,
there have been sustained decreases in the unit costs of solar energy
(by 85%), wind energy (by 55%), and lithium-ion batteries (by 85%),
and large increases in their deployment, e.g., >10× for solar and >100× for
electric vehicles (EVs), albeit varying widely across regions (Figure 2.4).
Electricity from PV and wind is now cheaper than electricity from
fossil sources in many regions, electric vehicles are increasingly
competitive with internal combustion engines, and large-scale
battery storage on electricity grids is increasingly viable. In
comparison to modular small-unit size technologies, the empirical
record shows that multiple large-scale mitigation technologies, with
fewer opportunities for learning, have seen minimal cost reductions
and their adoption has grown slowly. Maintaining emission-intensive
systems may, in some regions and sectors, be more expensive than
transitioning to low emission systems. (high confidence) {WGIII SPM B.4,
WGIII SPM B.4.1, WGIII SPM C.4.2, WGIII SPM C.5.2, WGIII SPM C.7.2,
WGIII SPM C.8, WGIII Figure SPM.3, WGIII Figure SPM.3}
For almost all basic materials – primary metals, building materials and
chemicals – many low- to zero-GHG intensity production processes are
at the pilot to near-commercial and in some cases commercial stage
but they are not yet established industrial practice. Integrated design
in construction and retrofit of buildings has led to increasing examples
of zero energy or zero carbon buildings. Technological innovation
made possible the widespread adoption of LED lighting. Digital
technologies including sensors, the internet of things, robotics, and
artificial intelligence can improve energy management in all sectors;
they can increase energy efficiency, and promote the adoption of many
low-emission technologies, including decentralised renewable energy,
while creating economic opportunities. However, some of these climate
change mitigation gains can be reduced or counterbalanced by growth in
demand for goods and services due to the use of digital devices. Several
mitigation options, notably solar energy, wind energy, electrification of
urban systems, urban green infrastructure, energy efficiency, demand
side management, improved forest- and crop/grassland management,
and reduced food waste and loss, are technically viable, are becoming
increasingly cost effective and are generally supported by the public, and
this enables expanded deployment in many regions. (high confidence)
{WGIII SPM B.4.3, WGIII SPM C.5.2, WGIII SPM C.7.2, WGIII SPM E.1.1,
WGIII TS.6.5}
The magnitude of global climate finance flows has increased
and financing channels have broadened (high confidence).
Annual tracked total financial flows for climate mitigation and
adaptation increased by up to 60% between 2013/14 and 2019/20,
but average growth has slowed since 2018 (medium confidence) and
most climate finance stays within national borders (high confidence).
Markets for green bonds, environmental, social and governance and
sustainable finance products have expanded significantly since AR5
(high confidence). Investors, central banks, and financial regulators are
driving increased awareness of climate risk to support climate policy
development and implementation (high confidence). Accelerated
international financial cooperation is a critical enabler of low-GHG and
just transitions (high confidence). {WGIII SPM B.5.4, WGIII SPM E.5,
WGIII TS.6.3, WGIII TS.6.4}
Economic instruments have been effective in reducing emissions,
complemented by regulatory instruments mainly at the national
and also sub-national and regional level (high confidence). By 2020,
over 20% of global GHG emissions were covered by carbon taxes or
emissions trading systems, although coverage and prices have been
insufficient to achieve deep reductions (medium confidence). Equity and
distributional impacts of carbon pricing instruments can be addressed
by using revenue from carbon taxes or emissions trading to support
low-income households, among other approaches (high confidence).
The mix of policy instruments which reduced costs and stimulated
adoption of solar energy, wind energy and lithium-ion batteries
includes public R&D, funding for demonstration and pilot projects, and
demand-pull instruments such as deployment subsidies to attain scale
(high confidence) (Figure 2.4). {WGIII SPM B.4.1, WGIII SPM B.5.2,
WGIII SPM E.4.2, WG III TS.3}
Mitigation actions, supported by policies, have contributed
to a decrease in global energy and carbon intensity between
2010 and 2019, with a growing number of countries achieving
absolute GHG emission reductions for more than a decade (high
confidence). While global net GHG emissions have increased since
2010, global energy intensity (total primary energy per unit GDP)
decreased by 2% yr –1 between 2010 and 2019. Global carbon
intensity (CO2 -FFI per unit primary energy) also decreased by 0.3%
yr –1
, mainly due to fuel switching from coal to gas, reduced expansion
of coal capacity, and increased use of renewables, and with large
regional variations over the same period. In many countries, policies
have enhanced energy efficiency, reduced rates of deforestation and
accelerated technology deployment, leading to avoided and in some
cases reduced or removed emissions (high confidence). At least
18 countries have sustained production-based CO2 and GHG and
consumption-based CO2 absolute emission reductions for longer than
10 years since 2005 through energy supply decarbonization, energy
efficiency gains, and energy demand reduction, which resulted from
both policies and changes in economic structure (high confidence).
Some countries have reduced production-based GHG emissions by a
third or more since peaking, and some have achieved reduction rates
of around 4% yr–1 for several years consecutively (high confidence).
Multiple lines of evidence suggest that mitigation policies have led to
avoided global emissions of several GtCO 2-eq yr–1 (medium confidence).

Renewable electricity generation
is increasingly price-competitive
and some sectors are electrifying

a) Market Cost
Since AR5, the unit costs of some
forms of renewable energy and
of batteries for passenger EVs
have fallen.

b) Market Adoption
Since AR5, the installed capacity
of renewable energies has
increased multiple times.

Figure 2.4: Unit cost reductions and use in some rapidly changing mitigation technologies. The top panel (a) shows global costs per unit of energy (USD per MWh)
for some rapidly changing mitigation technologies. Solid blue lines indicate average unit cost in each year. Light blue shaded areas show the range between the 5th and 95th
percentiles in each year. Yellow shading indicates the range of unit costs for new fossil fuel (coal and gas) power in 2020 (corresponding to USD 55 to 148 per MWh).
In 2020, the levelised costs of energy (LCOE) of the three renewable energy technologies could compete with fossil fuels in many places. For batteries, costs shown are for 1 kWh
of battery storage capacity; for the others, costs are LCOE, which includes installation, capital, operations, and maintenance costs per MWh of electricity produced. The literature uses
LCOE because it allows consistent comparisons of cost trends across a diverse set of energy technologies to be made. However, it does not include the costs of grid integration
or climate impacts. Further, LCOE does not take into account other environmental and social externalities that may modify the overall (monetary and non-monetary) costs of
technologies and alter their deployment. The bottom panel (b) shows cumulative global adoption for each technology, in GW of installed capacity for renewable energy and
in millions of vehicles for battery-electric vehicles. A vertical dashed line is placed in 2010 to indicate the change over the past decade. The electricity production share reflects
different capacity factors; for example, for the same amount of installed capacity, wind produces about twice as much electricity as solar PV. Renewable energy and battery
technologies were selected as illustrative examples because they have recently shown rapid changes in costs and adoption, and because consistent data are available. Other
mitigation options assessed in the WGIII report are not included as they do not meet these criteria. {WGIII Figure SPM.3, WGIII 2.5, 6.4}

At least 1.8 GtCO2-eq yr–1 of avoided emissions can be accounted for
by aggregating separate estimates for the effects of economic and
regulatory instruments (medium confidence). Growing numbers of
laws and executive orders have impacted global emissions and are
estimated to have resulted in 5.9 GtCO2 -eq yr–1 of avoided emissions
in 2016 (medium confidence). These reductions have only partly offset
global emissions growth (high confidence). {WGIII SPM B.1,
WGIII SPM B.2.4, WGIII SPM B.3.5, WGIII SPM B.5.1, WGIII SPM B.5.3,
WGIII 1.3.2, WGIII 2.2.3}

2.2.3. Adaptation Actions to Date

Progress in adaptation planning and implementation has been
observed across all sectors and regions, generating multiple
benefits (very high confidence). The ambition, scope and progress
on adaptation have risen among governments at the local, national and
international levels, along with businesses, communities and civil society
(high confidence). Various tools, measures and processes are available
that can enable, accelerate and sustain adaptation implementation
(high confidence). Growing public and political awareness of climate
impacts and risks has resulted in at least 170 countries and many cities
including adaptation in their climate policies and planning processes
(high confidence). Decision support tools and climate services are
increasingly being used (very high confidence) and pilot projects and
local experiments are being implemented in different sectors (high
confidence). {WGII SPM C.1, WGII SPM.C.1.1, WGII TS.D.1.3, WGII TS.D.10}
Adaptation to water-related risks and impacts make up the majority (~60%)
of all documented83 adaptation (high confidence). A large number of
these adaptation responses are in the agriculture sector and these
include on-farm water management, water storage, soil moisture
conservation, and irrigation. Other adaptations in agriculture include
cultivar improvements, agroforestry, community-based adaptation and
farm and landscape diversification among others (high confidence).
For inland flooding, combinations of non-structural measures like
early warning systems, enhancing natural water retention such as by
restoring wetlands and rivers, and land use planning such as no build
zones or upstream forest management, can reduce flood risk (medium
confidence). Some land-related adaptation actions such as sustainable
food production, improved and sustainable forest management,
soil organic carbon management, ecosystem conservation and land
restoration, reduced deforestation and degradation, and reduced
food loss and waste are being undertaken, and can have mitigation
co-benefits (high confidence). Adaptation actions that increase the
resilience of biodiversity and ecosystem services to climate change
include responses like minimising additional stresses or disturbances,
reducing fragmentation, increasing natural habitat extent, connectivity
and heterogeneity, and protecting small-scale refugia where
microclimate conditions can allow species to persist (high confidence).
Most innovations in urban adaptation have occurred through advances
in disaster risk management, social safety nets and green/blue
infrastructure (medium confidence). Many adaptation measures that
benefit health and well-being are found in other sectors (e.g., food,
livelihoods, social protection, water and sanitation, infrastructure)
(high confidence). {WGII SPM C.2.1, WGII SPM C.2.2, WGII TS.D.1.2,
WGII TS.D.1.4, WGII TS.D.4.2, WGII TS.D.8.3, WGII 4 ES; SRCCL SPM B.1.1}
Adaptation can generate multiple additional benefits such as improving
agricultural productivity, innovation, health and well-being, food
security, livelihood, and biodiversity conservation as well as reduction
of risks and damages (very high confidence). {WGII SPM C1.1}
Globally tracked adaptation finance has shown an upward trend
since AR5, but represents only a small portion of total climate
finance, is uneven and has developed heterogeneously across
regions and sectors (high confidence). Adaptation finance has come
predominantly from public sources, largely through grants, concessional
and non-concessional instruments (very high confidence). Globally,
private-sector financing of adaptation from a variety of sources such
as commercial financial institutions, institutional investors, other
private equity, non-financial corporations, as well as communities
and households has been limited, especially in developing countries
(high confidence). Public mechanisms and finance can leverage
private sector finance for adaptation by addressing real and perceived
regulatory, cost and market barriers, for example via public-private
partnerships (high confidence). Innovations in adaptation and
resilience finance, such as forecast-based/anticipatory financing
systems and regional risk insurance pools, have been piloted and are
growing in scale (high confidence). {WGII SPM C.3.2, WGII SPM C.5.4;
WGII TS.D.1.6, WGII Cross-Chapter Box FINANCE; WGIII SPM E.5.4}
There are adaptation options which are effective84 in reducing
climate risks85 for specific contexts, sectors and regions and
contribute positively to sustainable development and other
societal goals. In the agriculture sector, cultivar improvements,
on-farm water management and storage, soil moisture conservation,
irrigation86, agroforestry, community-based adaptation, and farm and
landscape level diversification, and sustainable land management
approaches, provide multiple benefits and reduce climate risks.
Reduction of food loss and waste, and adaptation measures in support
of balanced diets contribute to nutrition, health, and biodiversity benefits.
(high confidence) {WGII SPM C.2, WGII SPM C.2.1, WGII SPM C.2.2;
SRCCL B.2, SRCCL SPM C.2.1}
Ecosystem-based Adaptation87 approaches such as urban greening,
restoration of wetlands and upstream forest ecosystems reduce
a range of climate change risks, including flood risks, urban heat
and provide multiple co-benefits. Some land-based adaptation
options provide immediate benefits (e.g., conservation of peatlands,
wetlands, rangelands, mangroves and forests); while afforestation and
reforestation, restoration of high-carbon ecosystems, agroforestry, and
the reclamation of degraded soils take more time to deliver measurable
results. Significant synergies exist between adaptation and mitigation,
for example through sustainable land management approaches.
Agroecological principles and practices and other approaches
that work with natural processes support food security, nutrition,
health and well-being, livelihoods and biodiversity, sustainability and
ecosystem services. (high confidence) {WGII SPM C.2.1, WGII SPM C.2.2,
WGII SPM C.2.5, WGII TS.D.4.1; SRCCL SPM B.1.2, SRCCL SPM.B.6.1;
SROCC SPM C.2}
Combinations of non-structural measures like early warning systems
and structural measures like levees have reduced loss of lives in case
of inland flooding (medium confidence) and early warning systems
along with flood-proofing of buildings have proven to be cost-effective
in the context of coastal flooding under current sea level rise (high
confidence). Heat Health Action Plans that include early warning and
response systems are effective adaptation options for extreme heat
(high confidence). Effective adaptation options for water, food and
vector-borne diseases include improving access to potable water,
reducing exposure of water and sanitation systems to extreme weather
events, and improved early warning systems, surveillance, and vaccine
development (very high confidence). Adaptation options such as
disaster risk management, early warning systems, climate services
and social safety nets have broad applicability across multiple sectors
(high confidence). {WGII SPM C.2.1, WGII SPM C.2.5, WGII SPM C.2.9,
WGII SPM C.2.11, WGII SPM C.2.13; SROCC SPM C.3.2}
Integrated, multi-sectoral solutions that address social inequities,
differentiate responses based on climate risk and cut across systems,
increase the feasibility and effectiveness of adaptation in multiple
sectors (high confidence). {WGII SPM C.2}

2.3 Current Mitigation and Adaptation Actions and Policies are not Sufficient

At the time of the present assessment88 there are gaps between global ambitions and the sum of declared
national ambitions. These are further compounded by gaps between declared national ambitions and current
implementation for all aspects of climate action. For mitigation, global GHG emissions in 2030 implied by NDCs
announced by October 2021 would make it likely that warming will exceed 1.5°C during the 21st century and would
make it harder to limit warming below 2°C.89 Despite progress, adaptation gaps90 persist, with many initiatives
prioritising short-term risk reduction, hindering transformational adaptation. Hard and soft limits to adaptation
are being reached in some sectors and regions, while maladaptation is also increasing and disproportionately
affecting vulnerable groups. Systemic barriers such as funding, knowledge, and practice gaps, including lack of
climate literacy and data hinders adaptation progress. Insufficient financing, especially for adaptation, constraints
climate action in particular in developing countries. (high confidence)

2.3.1. The Gap Between Mitigation Policies, Pledges and
Pathways that Limit Warming to 1.5°C or Below 2°C

Global GHG emissions in 2030 associated with the implementation
of NDCs announced prior to COP2691 would make it likely that
warming will exceed 1.5°C during the 21st century and would
make it harder to limit warming below 2°C – if no additional
commitments are made or actions taken (Figure 2.5, Table 2.2).
A substantial ‘emissions gap’ exists as global GHG emissions in 2030
associated with the implementation of NDCs announced prior to COP26
would be similar to or only slightly below 2019 emission levels and
higher than those associated with modelled mitigation pathways that
limit warming to 1.5°C (>50%) with no or limited overshoot or to
2°C (>67%), assuming immediate action, which implies deep, rapid,
and sustained global GHG emission reductions this decade (high
confidence) (Table 2.2, Table 3.1, 4.1).92 The magnitude of the emissions
gap depends on the global warming level considered and whether only
unconditional or also conditional elements of NDCs93 are considered
(high confidence) (Table 2.2). Modelled pathways that are consistent
with NDCs announced prior to COP26 until 2030 and assume no
increase in ambition thereafter have higher emissions, leading
to a median global warming of 2.8 [2.1 to 3.4]°C by 2100 (medium
confidence). If the ‘emission gap’ is not reduced, global GHG emissions
in 2030 consistent with NDCs announced prior to COP26 make it likely
that warming will exceed 1.5°C during the 21st century, while limiting
warming to 2°C (>67%) would imply an unprecedented acceleration of
mitigation efforts during 2030–2050 (medium confidence) (see Section 4.1,
Cross-Section Box.2). {WGIII SPM B.6, WGIII SPM B.6.1, WGIII SPM B.6.3,
WGIII SPM B.6.4, WGIII SPM C.1.1}
Policies implemented by the end of 2020 are projected to result in
higher global GHG emissions in 2030 than those implied by NDCs,
indicating an ‘implementation gap94’ (high confidence) (Table 2.2,
Figure 2.5). Projected global emissions implied by policies implemented
by the end of 2020 are 57 (52–60) GtCO2 -eq in 2030 (Table 2.2). This
points to an implementation gap compared with the NDCs of 4 to
7 GtCO 2-eq in 2030 (Table 2.2); without a strengthening of policies,
emissions are projected to rise, leading to a median global warming
of 2.2°C to 3.5°C (very likely range) by 2100 (medium confidence)
(see Section 3.1.1). {WGIII SPM B.6.1, WGIII SPM C.1}
Projected cumulative future CO2 emissions over the lifetime of existing
fossil fuel infrastructure without additional abatement95 exceed the
total cumulative net CO2 emissions in pathways that limit warming to
1.5°C (>50%) with no or limited overshoot. They are approximately
equal to total cumulative net CO2 emissions in pathways that limit
warming to 2°C with a likelihood of 83%96 (see Figure 3.5). Limiting
warming to 2°C (>67%) or lower will result in stranded assets.
About 80% of coal, 50% of gas, and 30% of oil reserves cannot be
burned and emitted if warming is limited to 2°C. Significantly more
reserves are expected to remain unburned if warming is limited to
1.5°C. (high confidence) {WGIII SPM B.7, WGIII Box 6.3}

Table 2.2 Projected global emissions in 2030 associated with policies implemented by the end of 2020 and NDCs announced prior to COP26, and associated
emissions gaps. Emissions projections for 2030 and gross differences in emissions are based on emissions of 52–56 GtCO 2 -eq yr–1 in 2019 as assumed in underlying model
studies97. (medium confidence) {WGIII Table SPM.1} (Table 3.1, Cross-Section Box.2)

Emission and implementation gaps associated with projected
global emissions in 2030 under Nationally Determined
Contributions (NDCs) and implemented policies

Implied by policies
implemented by the end
of 2020 (GtCO2 -eq/yr)
Implied by Nationally Determined Contributions
(NDCs) announced prior to COP26
Unconditional
elements (GtCO2-eq/yr)
Including conditional
elements (GtCO 2 -eq/yr)

Median projected global emissions (min-max) 57 [52–60] 53 [50–57] 50 [47–55]
Implementation gap between
implemented policies and NDCs
(median) 4 7

Emissions gap between NDCs and
pathways that limit warming to
2°C (>67%) with immediate action - 10-16 6-14

Emissions gap between NDCs and
pathways that limit warming to
1.5°C (>50%) with no or limited
overshoot with immediate action - 19-26 16-23

Projected global GHG emissions from NDCs announced prior to
COP26 would make it likely that warming will exceed 1.5°C and
also make it harder after 2030 to limit warming to below 2°C
a) Global GHG emissions
b) 2030

Figure 2.5 Global GHG emissions of modelled pathways (funnels in Panel a), and projected emission outcomes from near-term policy assessments for 2030 (Panel b).
Panel a shows global GHG emissions over 2015-2050 for four types of assessed modelled global pathways:
- Trend from implemented policies: Pathways with projected near-term GHG emissions in line with policies implemented until the end of 2020 and extended with comparable
ambition levels beyond 2030 (29 scenarios across categories C5–C7, WGIII Table SPM.2).
- Limit to 2°C (>67%) or return warming to 1.5°C (>50%) after a high overshoot, NDCs until 2030: Pathways with GHG emissions until 2030 associated with the
implementation of NDCs announced prior to COP26, followed by accelerated emissions reductions likely to limit warming to 2°C (C3b, WGIII Table SPM.2) or to return
warming to 1.5°C with a probability of 50% or greater after high overshoot (subset of 42 scenarios from C2, WGIII Table SPM.2).
- Limit to 2°C (>67%) with immediate action: Pathways that limit warming to 2°C (>67%) with immediate action after 2020 (C3a, WGIII Table SPM.2).
- Limit to 1.5°C (>50%) with no or limited overshoot: Pathways limiting warming to 1.5°C with no or limited overshoot (C1, WGIII Table SPM.2 C1).
All these pathways assume immediate action after 2020. Past GHG emissions for 2010-2015 used to project global warming outcomes of the modelled pathways are shown by a
black line. Panel b shows a snapshot of the GHG emission ranges of the modelled pathways in 2030 and projected emissions outcomes from near-term policy assessments in 2030
from WGIII Chapter 4.2 (Tables 4.2 and 4.3; median and full range). GHG emissions are CO2 -equivalent using GWP100 from AR6 WGI. {WGIII Figure SPM.4, WGIII 3.5, 4.2, Table 4.2,
Table 4.3, Cross-Chapter Box 4 in Chapter 4} (Table 3.1, Cross-Section Box.2)

Cross-Section Box.1: Understanding Net Zero CO2 and Net Zero GHG Emissions
Limiting human-caused global warming to a specific level requires limiting cumulative CO2 emissions, reaching net zero or net negative
CO2 emissions, along with strong reductions in other GHG emissions (see 3.3.2). Future additional warming will depend on future emissions,
with total warming dominated by past and future cumulative CO2 emissions. {WGI SPM D.1.1, WGI Figure SPM.4; SR1.5 SPM A.2.2}
Reaching net zero CO2 emissions is different from reaching net zero GHG emissions. The timing of net zero for a basket of GHGs depends
on the emissions metric, such as global warming potential over a 100-year period, chosen to convert non-CO2 emissions into CO2 -equivalent (high
confidence). However, for a given emissions pathway, the physical climate response is independent of the metric chosen (high confidence).
{WGI SPM D.1.8; WGIII Box TS.6, WGIII Cross-Chapter Box 2}
Achieving global net zero GHG emissions requires all remaining CO2 and metric-weighted98 non-CO2 GHG emissions to be
counterbalanced by durably stored CO2 removals (high confidence). Some non-CO 2 emissions, such as CH4 and N 2O from agriculture,
cannot be fully eliminated using existing and anticipated technical measures. {WGIII SPM C.2.4, WGIII SPM C.11.4, WGIII Cross-Chapter Box 3}
Global net zero CO 2 or GHG emissions can be achieved even if some sectors and regions are net emitters, provided that
others reach net negative emissions (see Figure 4.1). The potential and cost of achieving net zero or even net negative emissions
vary by sector and region. If and when net zero emissions for a given sector or region are reached depends on multiple factors, including
the potential to reduce GHG emissions and undertake carbon dioxide removal, the associated costs, and the availability of policy
mechanisms to balance emissions and removals between sectors and countries. (high confidence) {WGIII Box TS.6, WGIII Cross-Chapter Box 3}
The adoption and implementation of net zero emission targets by countries and regions also depend on equity and capacity
considerations (high confidence). The formulation of net zero pathways by countries will benefit from clarity on scope, plans-of-action, and
fairness. Achieving net zero emission targets relies on policies, institutions, and milestones against which to track progress. Least-cost global
modelled pathways have been shown to distribute the mitigation effort unevenly, and the incorporation of equity principles could change the
country-level timing of net zero (high confidence). The Paris Agreement also recognizes that peaking of emissions will occur later in developing
countries than developed countries (Article 4.1). {WGIII Box TS.6, WGIII Cross-Chapter Box 3, WGIII 14.3}
More information on country-level net zero pledges is provided in Section 2.3.1, on the timing of global net zero emissions in Section 3.3.2, and
on sectoral aspects of net zero in Section 4.1.

Many countries have signalled an intention to achieve net
zero GHG or net zero CO 2 emissions by around mid-century
(Cross-Section Box.1). More than 100 countries have either adopted,
announced or are discussing net zero GHG or net zero CO 2 emissions
commitments, covering more than two-thirds of global GHG emissions.
A growing number of cities are setting climate targets, including net zero
GHG targets. Many companies and institutions have also announced
net zero emissions targets in recent years. The various net zero emission
pledges differ across countries in terms of scope and specificity, and
limited policies are to date in place to deliver on them. {WGIII SPM C.6.4,
WGIII TS.4.1, WGIII Table TS.1, WGIII 13.9, WGIII 14.3, WGIII 14.5}
All mitigation strategies face implementation challenges,
including technology risks, scaling, and costs (high confidence).
Almost all mitigation options also face institutional barriers that
need to be addressed to enable their application at scale (medium
confidence). Current development pathways may create behavioural,
spatial, economic and social barriers to accelerated mitigation at all
scales (high confidence). Choices made by policymakers, citizens, the
private sector and other stakeholders influence societies’ development
pathways (high confidence). Structural factors of national circumstances
and capabilities (e.g., economic and natural endowments, political
systems and cultural factors and gender considerations) affect the
breadth and depth of climate governance (medium confidence). The
extent to which civil society actors, political actors, businesses, youth,
labour, media, Indigenous Peoples, and local communities are engaged
influences political support for climate change mitigation and eventual
policy outcomes (medium confidence). {WGIII SPM C.3.6, WGIII SPM E.1.1,
WGIII SPM E.2.1, WGIII SPM E.3.3}
The adoption of low-emission technologies lags in most
developing countries, particularly least developed ones,
due in part to weaker enabling conditions, including limited
finance, technology development and transfer, and capacity
(medium confidence). In many countries, especially those with
limited institutional capacity, several adverse side-effects have
been observed as a result of diffusion of low-emission technology,
e.g., low-value employment, and dependency on foreign knowledge
and suppliers (medium confidence). Low-emission innovation along
with strengthened enabling conditions can reinforce development
benefits, which can, in turn, create feedbacks towards greater public
support for policy (medium confidence). Persistent and region-specific
barriers also continue to hamper the economic and political feasibility
of deploying AFOLU mitigation options (medium confidence). Barriers to
implementation of AFOLU mitigation include insufficient institutional and
financial support, uncertainty over long-term additionality and trade-offs,
weak governance, insecure land ownership, low incomes and the lack
of access to alternative sources of income, and the risk of reversal (high
confidence). {WGIII SPM B.4.2, WGIII SPM C.9.1, WGIII SPM C.9.3}

2.3.2. Adaptation Gaps and Barriers

Despite progress, adaptation gaps exist between current
levels of adaptation and levels needed to respond to impacts
and reduce climate risks (high confidence). While progress in
adaptation implementation is observed across all sectors and regions
(very high confidence), many adaptation initiatives prioritise immediate
and near-term climate risk reduction, e.g., through hard flood protection,
which reduces the opportunity for transformational adaptation99 (high
confidence). Most observed adaptation is fragmented, small in scale,
incremental, sector-specific, and focused more on planning rather than
implementation (high confidence). Further, observed adaptation is
unequally distributed across regions and the largest adaptation gaps
exist among lower population income groups (high confidence). In the
urban context, the largest adaptation gaps exist in projects that manage
complex risks, for example in the food–energy–water–health nexus or
the inter-relationships of air quality and climate risk (high confidence).
Many funding, knowledge and practice gaps remain for effective
implementation, monitoring and evaluation and current adaptation
efforts are not expected to meet existing goals (high confidence).
At current rates of adaptation planning and implementation the
adaptation gap will continue to grow (high confidence). {WGII SPM C.1,
WGII SPM C.1.2, WGII SPM C.4.1, WGII TS.D.1.3, WGII TS.D.1.4}
Soft and hard adaptation limits100 have already been reached in
some sectors and regions, in spite of adaptation having buffered
some climate impacts (high confidence). Ecosystems already
reaching hard adaptation limits include some warm water coral reefs,
some coastal wetlands, some rainforests, and some polar and mountain
ecosystems (high confidence). Individuals and households in low lying
coastal areas in Australasia and Small Islands and smallholder farmers
in Central and South America, Africa, Europe and Asia have reached
soft limits (medium confidence), resulting from financial, governance,
institutional and policy constraints and can be overcome by addressing
these constraints (high confidence). Transitioning from incremental to
transformational adaptation can help overcome soft adaptation limits
(high confidence). {WGII SPM C.3, WGII SPM C.3.1, WGII SPM C.3.2,
WGII SPM C.3.3, WGII SPM.C.3.4, WGII 16 ES}
Adaptation does not prevent all losses and damages, even with
effective adaptation and before reaching soft and hard limits. Losses
and damages are unequally distributed across systems, regions and
sectors and are not comprehensively addressed by current financial,
governance and institutional arrangements, particularly in vulnerable
developing countries. (high confidence) {WGII SPM.C.3.5}
There is increased evidence of maladaptation101 in various sectors
and regions. Examples of maladaptation are observed in urban areas
(e.g., new urban infrastructure that cannot be adjusted easily or affordably),
agriculture (e.g., using high-cost irrigation in areas projected to have more
intense drought conditions), ecosystems (e.g. fire suppression in naturally
fire-adapted ecosystems, or hard defences against flooding) and human
settlements (e.g. stranded assets and vulnerable communities that
cannot afford to shift away or adapt and require an increase in social
safety nets). Maladaptation especially affects marginalised and vulnerable
groups adversely (e.g., Indigenous Peoples, ethnic minorities, low-income
households, people living in informal settlements), reinforcing and
entrenching existing inequities. Maladaptation can be avoided by flexible,
multi-sectoral, inclusive and long-term planning and implementation of
adaptation actions with benefits to many sectors and systems. (high
confidence) {WGII SPM C.4, WGII SPM C.4.3, WGII TS.D.3.1}

Systemic barriers constrain the implementation of adaptation
options in vulnerable sectors, regions and social groups (high
confidence). Key barriers include limited resources, lack of private-sector
and civic engagement, insufficient mobilisation of finance, lack of political
commitment, limited research and/or slow and low uptake of adaptation
science and a low sense of urgency. Inequity and poverty also constrain
adaptation, leading to soft limits and resulting in disproportionate
exposure and impacts for most vulnerable groups (high confidence). The
largest adaptation gaps exist among lower income population groups
(high confidence). As adaptation options often have long implementation
times, long-term planning and accelerated implementation, particularly
in this decade, is important to close adaptation gaps, recognising that
constraints remain for some regions (high confidence). Prioritisation of
options and transitions from incremental to transformational adaptation
are limited due to vested interests, economic lock-ins, institutional
path dependencies and prevalent practices, cultures, norms and belief
systems (high confidence). Many funding, knowledge and practice
gaps remain for effective implementation, monitoring and evaluation
of adaptation (high confidence), including, lack of climate literacy at
all levels and limited availability of data and information (medium
confidence); for example for Africa, severe climate data constraints and
inequities in research funding and leadership reduce adaptive capacity
(very high confidence). {WGII SPM C.1.2, WGII SPM C.3.1, WGII TS.D.1.3,
WGII TS.D.1.5, WGII TS.D.2.4}
2.3.3. Lack of Finance as a Barrier to Climate Action
Insufficient financing, and a lack of political frameworks and
incentives for finance, are key causes of the implementation
gaps for both mitigation and adaptation (high confidence).
Financial flows remained heavily focused on mitigation, are
uneven, and have developed heterogeneously across regions
and sectors (high confidence). In 2018, public and publicly mobilised
private climate finance flows from developed to developing countries
were below the collective goal under the UNFCCC and Paris Agreement
to mobilise USD 100 billion per year by 2020 in the context of
meaningful mitigation action and transparency on implementation
(medium confidence). Public and private finance flows for fossil fuels
are still greater than those for climate adaptation and mitigation (high
confidence). The overwhelming majority of tracked climate finance
is directed towards mitigation (very high confidence). Nevertheless,
average annual modelled investment requirements for 2020 to 2030
in scenarios that limit warming to 2°C or 1.5°C are a factor of three
to six greater than current levels, and total mitigation investments
(public, private, domestic and international) would need to increase
across all sectors and regions (medium confidence). Challenges
remain for green bonds and similar products, in particular around
integrity and additionality, as well as the limited applicability of
these markets to many developing countries (high confidence).
{WGII SPM C.3.2, WGII SPM C.5.4; WGIII SPM B.5.4, WGIII SPM E.5.1}
Current global financial flows for adaptation including from public
and private finance sources, are insufficient for and constrain
implementation of adaptation options, especially in developing
countries (high confidence). There are widening disparities between
the estimated costs of adaptation and the documented finance
allocated to adaptation (high confidence). Adaptation finance
needs are estimated to be higher than those assessed in AR5, and
the enhanced mobilisation of and access to financial resources are
essential for implementation of adaptation and to reduce adaptation
gaps (high confidence). Annual finance flows targeting adaptation for
Africa, for example, are billions of USD less than the lowest adaptation
cost estimates for near-term climate change (high confidence). Adverse
climate impacts can further reduce the availability of financial resources
by causing losses and damages and impeding national economic
growth, thereby further increasing financial constraints for adaptation
particularly for developing countries and LDCs (medium confidence).
{WGII SPM C.1.2, WGII SPM C.3.2, WGII SPM C.5.4, WGII TS.D.1.6}
Without effective mitigation and adaptation, losses and damages will
continue to disproportionately affect the poorest and most vulnerable
populations. Accelerated financial support for developing countries
from developed countries and other sources is a critical enabler to
enhance mitigation action {WGIII SPM. E.5.3}. Many developing
countries lack comprehensive data at the scale needed and lack adequate
financial resources needed for adaptation for reducing associated
economic and non-economic losses and damages. (high confidence)
{WGII Cross-Chapter Box LOSS, WGII SPM C.3.1, WGII SPM C.3.2,
WGII TS.D.1.3, WGII TS.D.1.5; WGIII SPM E.5.3}
There are barriers to redirecting capital towards climate action both
within and outside the global financial sector. These barriers include:
the inadequate assessment of climate-related risks and investment
opportunities, regional mismatch between available capital and
investment needs, home bias factors, country indebtedness levels,
economic vulnerability, and limited institutional capacities. Challenges
from outside the financial sector include: limited local capital markets;
unattractive risk-return profiles, in particular due to missing or weak
regulatory environments that are inconsistent with ambition levels;
limited institutional capacity to ensure safeguards; standardisation,
aggregation, scalability and replicability of investment opportunities
and financing models; and, a pipeline ready for commercial investments.
(high confidence) {WGII SPM C.5.4; WGIII SPM E.5.2; SR1.5 SPM D.5.2}

Cross-Section Box.2: Scenarios, Global Warming Levels, and Risks
Modelled scenarios and pathways102 are used to explore future emissions, climate change, related impacts and risks, and possible mitigation and
adaptation strategies and are based on a range of assumptions, including socio-economic variables and mitigation options. These are quantitative
projections and are neither predictions nor forecasts. Global modelled emission pathways, including those based on cost effective approaches
contain regionally differentiated assumptions and outcomes, and have to be assessed with the careful recognition of these assumptions. Most
do not make explicit assumptions about global equity, environmental justice or intra-regional income distribution. IPCC is neutral with regard
to the assumptions underlying the scenarios in the literature assessed in this report, which do not cover all possible futures103. {WGI Box SPM.1;
WGII Box SPM.1; WGIII Box SPM.1; SROCC Box SPM.1; SRCCL Box SPM.1}
Socio-economic Development, Scenarios, and Pathways
The five Shared Socio-economic Pathways (SSP1 to SSP5) were designed to span a range of challenges to climate change mitigation and adaptation.
For the assessment of climate impacts, risk and adaptation, the SSPs are used for future exposure, vulnerability and challenges to adaptation.
Depending on levels of GHG mitigation, modelled emissions scenarios based on the SSPs can be consistent with low or high warming levels104.
There are many different mitigation strategies that could be consistent with different levels of global warming in 2100 (see Figure 4.1).
{WGI Box SPM.1; WGII Box SPM.1; WGIII Box SPM.1, WGIII Box TS.5, WGIII Annex III; SRCCL Box SPM.1, SRCCL Figure SPM.2}
WGI assessed the climate response to five illustrative scenarios based on SSPs105 that cover the range of possible future development of anthropogenic
drivers of climate change found in the literature. These scenarios combine socio-economic assumptions, levels of climate mitigation, land use and
air pollution controls for aerosols and non-CH4 ozone precursors. The high and very high GHG emissions scenarios (SSP3-7.0 and SSP5-8.5) have
CO2 emissions that roughly double from current levels by 2100 and 2050, respectively106. The intermediate GHG emissions scenario (SSP2-4.5)
has CO2 emissions remaining around current levels until the middle of the century. The very low and low GHG emissions scenarios (SSP1-1.9 and
SSP1-2.6) have CO2 emissions declining to net zero around 2050 and 2070, respectively, followed by varying levels of net negative CO2
emissions. In addition, Representative Concentration Pathways (RCPs)107 were used by WGI and WGII to assess regional climate changes,
impacts and risks. {WGI Box SPM.1} (Cross-Section Box.2 Figure 1)
In WGIII, a large number of global modelled emissions pathways were assessed, of which 1202 pathways were categorised based on their
projected global warming over the 21st century, with categories ranging from pathways that limit warming to 1.5°C with more than 50%
likelihood108 with no or limited overshoot (C1) to pathways that exceed 4°C (C8). Methods to project global warming associated with the
modelled pathways were updated to ensure consistency with the AR6 WGI assessment of the climate system response109. {WGIII Box SPM.1,WGIII
Table 3.1} (Table 3.1, Cross-Section Box.2 Figure 1)

Global Warming Levels (GWLs)
For many climate and risk variables, the geographical patterns of changes in climatic impact-drivers110 and climate impacts for a level of global
warming111 are common to all scenarios considered and independent of timing when that level is reached. This motivates the use of GWLs as a
dimension of integration. {WGI Box SPM.1.4, WGI TS.1.3.2; WGII Box SPM.1} (Figure 3.1, Figure 3.2)
Risks
Dynamic interactions between climate-related hazards, exposure and vulnerability of the affected human society, species, or ecosystems result
in risks arising from climate change. AR6 assesses key risks across sectors and regions as well as providing an updated assessment of the
Reasons for Concern (RFCs) – five globally aggregated categories of risk that evaluate risk accrual with increasing global surface temperature.
Risks can also arise from climate change mitigation or adaptation responses when the response does not achieve its intended objective, or when
it results in adverse effects for other societal objectives. {WGII SPM A, WGII Figure SPM.3, WGII Box TS.1, WGII Figure TS.4; SR1.5 Figure SPM.2;
SROCC Errata Figure SPM.3; SRCCL Figure SPM.2} (3.1.2, Cross-Section Box.2 Figure 1, Figure 3.3)

Scenarios and warming levels structure our understanding across the
cause-effect chain from emissions to climate change and risks
a) AR6 integrated assessment framework on future climate, impacts and mitigation
Cross-Section Box.2 Figure 1: Schematic of the AR6 framework for assessing future greenhouse gas emissions, climate change,
risks, impacts and mitigation. Panel (a) The integrated framework encompasses socio-economic development and policy, emissions pathways
and global surface temperature responses to the five scenarios considered by WGI (SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) and
eight global mean temperature change categorisations (C1–C8) assessed by WGIII, and the WGII risk assessment. The dashed arrow indicates
that the influence from impacts/risks to socio-economic changes is not yet considered in the scenarios assessed in the AR6. Emissions include
GHGs, aerosols, and ozone precursors. CO2 emissions are shown as an example on the left. The assessed global surface temperature changes
across the 21st century relative to 1850-1900 for the five GHG emissions scenarios are shown as an example in the centre. Very likely ranges
are shown for SSP1-2.6 and SSP3-7.0. Projected temperature outcomes at 2100 relative to 1850-1900 are shown for C1 to C8 categories with
median (line) and the combined very likely range across scenarios (bar). On the right, future risks due to increasing warming are represented by
an example ‘burning ember’ figure (see 3.1.2 for the definition of RFC1). Panel (b) Description and relationship of scenarios considered across
AR6 Working Group reports. Panel (c) Illustration of risk arising from the interaction of hazard (driven by changes in climatic impact-drivers)
with vulnerability, exposure and response to climate change. {WGI TS1.4, Figure 4.11; WGII Figure 1.5, WGII Figure 14.8; WGIII Table SPM.2,
WGIII Figure 3.11}

Section 3: Long-Term Climate and Development Futures
3.1 Long-Term Climate Change, Impacts and Related Risks
Future warming will be driven by future emissions and will affect all major climate system components, with
every region experiencing multiple and co-occurring changes. Many climate-related risks are assessed to be
higher than in previous assessments, and projected long-term impacts are up to multiple times higher than
currently observed. Multiple climatic and non-climatic risks will interact, resulting in compounding and cascading
risks across sectors and regions. Sea level rise, as well as other irreversible changes, will continue for thousands
of years, at rates depending on future emissions. (high confidence)
3.1.1. Long-term Climate Change
The uncertainty range on assessed future changes in global
surface temperature is narrower than in the AR5. For the first
time in an IPCC assessment cycle, multi-model projections of global
surface temperature, ocean warming and sea level are constrained
using observations and the assessed climate sensitivity. The likely
range of equilibrium climate sensitivity has been narrowed to 2.5°C
to 4.0°C (with a best estimate of 3.0°C) based on multiple lines of
evidence112, including improved understanding of cloud feedbacks. For
related emissions scenarios, this leads to narrower uncertainty ranges
for long-term projected global temperature change than in AR5.
{WGI A.4, WGI Box SPM.1, WGI TS.3.2, WGI 4.3}
Future warming depends on future GHG emissions, with
cumulative net CO 2 dominating. The assessed best estimates and
very likely ranges of warming for 2081-2100 with respect to 1850–1900
vary from 1.4 [1.0 to 1.8]°C in the very low GHG emissions scenario
(SSP1-1.9) to 2.7 [2.1 to 3.5]°C in the intermediate GHG emissions
scenario (SSP2-4.5) and 4.4 [3.3 to 5.7]°C in the very high GHG emissions
scenario (SSP5-8.5)113. {WGI SPM B.1.1, WGI Table SPM.1, WGI Figure
SPM.4} (Cross-Section Box.2 Figure 1)
Modelled pathways consistent with the continuation of policies
implemented by the end of 2020 lead to global warming of
3.2 [2.2 to 3.5]°C (5–95% range) by 2100 (medium confidence)
(see also Section 2.3.1). Pathways of >4°C (≥50%) by 2100 would
imply a reversal of current technology and/or mitigation policy trends
(medium confidence). However, such warming could occur in emissions
pathways consistent with policies implemented by the end of 2020 if
climate sensitivity or carbon cycle feedbacks are higher than the best
estimate (high confidence). {WGIII SPM C.1.3}
Global warming will continue to increase in the near term in
nearly all considered scenarios and modelled pathways. Deep,
rapid, and sustained GHG emissions reductions, reaching net
zero CO2 emissions and including strong emissions reductions
of other GHGs, in particular CH4, are necessary to limit warming
to 1.5°C (>50%) or less than 2°C (>67%) by the end of century
(high confidence). The best estimate of reaching 1.5°C of global
warming lies in the first half of the 2030s in most of the considered
scenarios and modelled pathways114. In the very low GHG emissions
scenario (SSP1-1.9), CO 2 emissions reach net zero around 2050 and the
best-estimate end-of-century warming is 1.4°C, after a temporary overshoot
(see Section 3.3.4) of no more than 0.1°C above 1.5°C global warming.
Global warming of 2°C will be exceeded during the 21st century unless
deep reductions in CO 2 and other GHG emissions occur in the coming
decades. Deep, rapid, and sustained reductions in GHG emissions would
lead to improvements in air quality within a few years, to reductions in
trends of global surface temperature discernible after around 20 years,
and over longer time periods for many other climate impact-drivers115
(high confidence). Targeted reductions of air pollutant emissions lead
to more rapid improvements in air quality compared to reductions
in GHG emissions only, but in the long term, further improvements are
projected in scenarios that combine efforts to reduce air pollutants as
well as GHG emissions (high confidence)116. {WGI SPM B.1, WGI SPM B.1.3,
WGI SPM D.1, WGI SPM D.2, WGI Figure SPM.4, WGI Table SPM.1,
WGI Cross-Section Box TS.1; WGIII SPM C.3, WGIII Table SPM.2,
WGIII Figure SPM.5, WGIII Box SPM.1 Figure 1, WGIII Table 3.2} (Table 3.1,
Cross-Section Box.2 Figure 1)
Changes in short-lived climate forcers (SLCF) resulting from the
five considered scenarios lead to an additional net global warming
in the near and long term (high confidence). Simultaneous
stringent climate change mitigation and air pollution control
policies limit this additional warming and lead to strong benefits
for air quality (high confidence). In high and very high GHG
emissions scenarios (SSP3-7.0 and SSP5-8.5), combined changes
in SLCF emissions, such as CH 4, aerosol and ozone precursors, lead to a
net global warming by 2100 of likely 0.4°C to 0.9°C relative to 2019.
This is due to projected increases in atmospheric concentration of CH4 ,
tropospheric ozone, hydrofluorocarbons and, when strong air pollution
control is considered, reductions of cooling aerosols. In low and very
low GHG emissions scenarios (SSP1-1.9 and SSP1-2.6), air pollution
control policies, reductions in CH 4 and other ozone precursors lead to a
net cooling, whereas reductions in anthropogenic cooling aerosols lead
to a net warming (high confidence). Altogether, this causes a likely net
warming of 0.0°C to 0.3°C due to SLCF changes in 2100 relative to 2019
and strong reductions in global surface ozone and particulate matter
(high confidence). {WGI SPM D.1.7, WGI Box TS.7} (Cross-Section Box.2)
Continued GHG emissions will further affect all major climate
system components, and many changes will be irreversible on
centennial to millennial time scales. Many changes in the climate
system become larger in direct relation to increasing global warming.
With every additional increment of global warming, changes in
extremes continue to become larger. Additional warming will lead to
more frequent and intense marine heatwaves and is projected to further
amplify permafrost thawing and loss of seasonal snow cover, glaciers,
land ice and Arctic sea ice (high confidence). Continued global warming
is projected to further intensify the global water cycle, including its
variability, global monsoon precipitation117, and very wet and very dry
weather and climate events and seasons (high confidence). The portion
of global land experiencing detectable changes in seasonal mean
precipitation is projected to increase (medium confidence) with more
variable precipitation and surface water flows over most land regions
within seasons (high confidence) and from year to year (medium
confidence). Many changes due to past and future GHG emissions are
irreversible118 on centennial to millennial time scales, especially in the
ocean, ice sheets and global sea level (see 3.1.3). Ocean acidification
(virtually certain), ocean deoxygenation (high confidence) and global
mean sea level (virtually certain) will continue to increase in the 21st century,
at rates dependent on future emissions. {WGI SPM B.2, WGI SPM B.2.2,
WGI SPM B.2.3, WGI SPM B.2.5, WGI SPM B.3, WGI SPM B.3.1,
WGI SPM B.3.2, WGI SPM B.4, WGI SPM B.5, WGI SPM B.5.1, WGI SPM B.5.3,
WGI Figure SPM.8} (Figure 3.1)
With further global warming, every region is projected to
increasingly experience concurrent and multiple changes
in climatic impact-drivers. Increases in hot and decreases in
cold climatic impact-drivers, such as temperature extremes, are
projected in all regions (high confidence). At 1.5°C global warming,
heavy precipitation and flooding events are projected to intensify
and become more frequent in most regions in Africa, Asia (high
confidence), North America (medium to high confidence) and Europe
(medium confidence). At 2°C or above, these changes expand to more
regions and/or become more significant (high confidence), and more
frequent and/or severe agricultural and ecological droughts are projected
in Europe, Africa, Australasia and North, Central and South America
(medium to high confidence). Other projected regional changes include
intensification of tropical cyclones and/or extratropical storms
(medium confidence), and increases in aridity and fire weather119
(medium to high confidence). Compound heatwaves and droughts
become likely more frequent, including concurrently at multiple
locations (high confidence). {WGI SPM C.2, WGI SPM C.2.1, WGI SPM C.2.2,
WGI SPM C.2.3, WGI SPM C.2.4, WGI SPM C.2.7}

With every increment of global warming, regional changes in mean
climate and extremes become more widespread and pronounced
a) Annual hottest-day temperature change
Annual hottest day temperature is projected to increase most
(1.5-2 times the GWL) in some mid-latitude and semi-arid
regions, and in the South American Monsoon region.

b) Annual mean total column soil moisture change
Projections of annual mean soil moisture largely follow
projections in annual mean precipitation but also show
some differences due to the influence of evapotranspiration.

c) Annual wettest-day precipitation change
Annual wettest day precipitation is projected to increase
in almost all continental regions, even in regions where
projected annual mean soil moisture declines.

Figure 3.1: Projected changes of annual maximum daily temperature, annual mean total column soil moisture CMIP and annual maximum daily precipitation
at global warming levels of 1.5°C, 2°C, 3°C, and 4°C relative to 1850-1900. Simulated (a) annual maximum temperature change (°C), (b) annual mean total column
soil moisture (standard deviation), (c) annual maximum daily precipitation change (%). Changes correspond to CMIP6 multi-model median changes. In panels (b) and (c), large
positive relative changes in dry regions may correspond to small absolute changes. In panel (b), the unit is the standard deviation of interannual variability in soil moisture during
1850-1900. Standard deviation is a widely used metric in characterising drought severity. A projected reduction in mean soil moisture by one standard deviation corresponds to soil
moisture conditions typical of droughts that occurred about once every six years during 1850-1900. The WGI Interactive Atlas (https://interactive-atlas.ipcc.ch/) can be used to explore
additional changes in the climate system across the range of global warming levels presented in this figure. {WGI Figure SPM.5, WGI Figure TS.5, WGI Figure 11.11, WGI Figure 11.16,
WGI Figure 11.19} (Cross-Section Box.2)

3.1.2 Impacts and Related Risks
For a given level of warming, many climate-related risks are
assessed to be higher than in AR5 (high confidence). Levels of
risk120 for all Reasons for Concern121 (RFCs) are assessed to become high
to very high at lower global warming levels compared to what was
assessed in AR5 (high confidence). This is based upon recent evidence
of observed impacts, improved process understanding, and new
knowledge on exposure and vulnerability of human and natural
systems, including limits to adaptation. Depending on the level
of global warming, the assessed long-term impacts will be up to
multiple times higher than currently observed (high confidence) for
127 identified key risks, e.g., in terms of the number of affected people
and species. Risks, including cascading risks (see 3.1.3) and risks from
overshoot (see 3.3.4), are projected to become increasingly severe
with every increment of global warming (very high confidence).
{WGII SPM B.3.3, WGII SPM B.4, WGII SPM B.5, WGII 16.6.3; SRCCL SPM A5.3}
(Figure 3.2, Figure 3.3)
Climate-related risks for natural and human systems are higher for
global warming of 1.5°C than at present (1.1°C) but lower than at 2°C
(high confidence) (see Section 2.1.2). Climate-related risks to health,
livelihoods, food security, water supply, human security, and economic
growth are projected to increase with global warming of 1.5°C. In
terrestrial ecosystems, 3 to 14% of the tens of thousands of species
assessed will likely face a very high risk of extinction at a GWL of 1.5°C.
Coral reefs are projected to decline by a further 70–90% at 1.5°C of
global warming (high confidence). At this GWL, many low-elevation
and small glaciers around the world would lose most of their mass or
disappear within decades to centuries (high confidence). Regions at
disproportionately higher risk include Arctic ecosystems, dryland regions,
small island developing states and Least Developed Countries (high
confidence). {WGII SPM B.3, WGII SPM B.4.1, WGII TS.C.4.2; SR1.5 SPM A.3,
SR1.5 SPM B.4.2, SR1.5 SPM B.5, SR1.5 SPM B.5.1} (Figure 3.3)
At 2°C of global warming, overall risk levels associated with the unequal
distribution of impacts (RFC3), global aggregate impacts (RFC4) and
large-scale singular events (RFC5) would be transitioning to high (medium
confidence), those associated with extreme weather events (RFC2) would
be transitioning to very high (medium confidence), and those associated
with unique and threatened systems (RFC1) would be very high (high
confidence) (Figure 3.3, panel a). With about 2°C warming, climate-related
changes in food availability and diet quality are estimated to increase
nutrition-related diseases and the number of undernourished people,
affecting tens (under low vulnerability and low warming) to hundreds of
millions of people (under high vulnerability and high warming), particularly
among low-income households in low- and middle-income countries in
sub-Saharan Africa, South Asia and Central America (high confidence).
For example, snowmelt water availability for irrigation is projected
to decline in some snowmelt dependent river basins by up to 20%
(medium confidence). Climate change risks to cities, settlements
and key infrastructure will rise sharply in the mid and long term with
further global warming, especially in places already exposed to high
temperatures, along coastlines, or with high vulnerabilities (high
confidence). {WGII SPM B.3.3, WGII SPM B.4.2, WGII SPM B.4.5, WGII TS C.3.3,
WGII TS.C.12.2} (Figure 3.3)
At global warming of 3°C, additional risks in many sectors and regions
reach high or very high levels, implying widespread systemic impacts,
irreversible change and many additional adaptation limits (see Section 3.2)
(high confidence). For example, very high extinction risk for endemic
species in biodiversity hotspots is projected to increase at least tenfold
if warming rises from 1.5°C to 3°C (medium confidence). Projected
increases in direct flood damages are higher by 1.4 to 2 times at 2°C
and 2.5 to 3.9 times at 3°C, compared to 1.5°C global warming without
adaptation (medium confidence). {WGII SPM B.4.1, WGII SPM B.4.2,
WGII Figure SPM.3, WGII TS Appendix AII, WGII Appendix I Global to
Regional Atlas Figure AI.46} (Figure 3.2, Figure 3.3)
Global warming of 4°C and above is projected to lead to far-reaching
impacts on natural and human systems (high confidence). Beyond
4°C of warming, projected impacts on natural systems include local
extinction of ~50% of tropical marine species (medium confidence)
and biome shifts across 35% of global land area (medium confidence).
At this level of warming, approximately 10% of the global land area
is projected to face both increasing high and decreasing low extreme
streamflow, affecting, without additional adaptation, over 2.1 billion people
(medium confidence) and about 4 billion people are projected to
experience water scarcity (medium confidence). At 4°C of warming, the
global burned area is projected to increase by 50 to 70% and the
fire frequency by ~30% compared to today (medium confidence).
{WGII SPM B.4.1, WGII SPM B.4.2, WGII TS.C.1.2, WGII TS.C.2.3,
WGII TS.C.4.1, WGII TS.C.4.4} (Figure 3.2, Figure 3.3)

Projected adverse impacts and related losses and damages from
climate change escalate with every increment of global warming
(very high confidence), but they will also strongly depend on
socio-economic development trajectories and adaptation actions
to reduce vulnerability and exposure (high confidence). For
example, development pathways with higher demand for food, animal
feed, and water, more resource-intensive consumption and production,
and limited technological improvements result in higher risks from
water scarcity in drylands, land degradation and food insecurity (high
confidence). Changes in, for example, demography or investments in
health systems have effect on a variety of health-related outcomes
including heat-related morbidity and mortality (Figure 3.3 Panel d).
{WGII SPM B.3, WGII SPM B.4, WGII Figure SPM.3; SRCCL SPM A.6}
With every increment of warming, climate change impacts and
risks will become increasingly complex and more difficult to
manage. Many regions are projected to experience an increase in
the probability of compound events with higher global warming, such
as concurrent heatwaves and droughts, compound flooding and fire
weather. In addition, multiple climatic and non-climatic risk drivers
such as biodiversity loss or violent conflict will interact, resulting
in compounding overall risk and risks cascading across sectors and
regions. Furthermore, risks can arise from some responses that are
intended to reduce the risks of climate change, e.g., adverse side effects
of some emission reduction and carbon dioxide removal (CDR) measures
(see 3.4.1). (high confidence) {WGI SPM C.2.7, WGI Figure SPM.6,
WGI TS.4.3; WGII SPM B.1.7, WGII B.2.2, WGII SPM B.5, WGII SPM B.5.4,
WGII SPM C.4.2, WGII SPM B.5, WGII CCB2}
Solar Radiation Modification (SRM) approaches, if they were
to be implemented, introduce a widespread range of new risks
to people and ecosystems, which are not well understood.
SRM has the potential to offset warming within one or two decades
and ameliorate some climate hazards but would not restore climate to
a previous state, and substantial residual or overcompensating climate
change would occur at regional and seasonal scales (high confidence).
Effects of SRM would depend on the specific approach used122, and
a sudden and sustained termination of SRM in a high CO 2 emissions
scenario would cause rapid climate change (high confidence). SRM
would not stop atmospheric CO 2 concentrations from increasing nor
reduce resulting ocean acidification under continued anthropogenic
emissions (high confidence). Large uncertainties and knowledge
gaps are associated with the potential of SRM approaches to reduce
climate change risks. Lack of robust and formal SRM governance
poses risks as deployment by a limited number of states could create
international tensions. {WGI 4.6; WGII SPM B.5.5; WGIII 14.4.5.1;
WGIII 14 Cross-Working Group Box Solar Radiation Modification;
SR1.5 SPM C.1.4}

Future climate change is projected to increase the severity of impacts
across natural and human systems and will increase regional differences
Examples of impacts without additional adaptation
a) Risk of species losses
Percentage of animal species and seagrasses exposed to potentially dangerous temperature conditions
b) Heat-humidity risks to human health
Days per year where combined temperature and humidity conditions pose a risk of mortality to individuals
c) Food production impacts
c1) Maize yield
c2) Fisheries yield
Figure 3.2: Projected risks and impacts of climate change on natural and human systems at different global warming levels (GWLs) relative to 1850-1900 levels.
Projected risks and impacts shown on the maps are based on outputs from different subsets of Earth system models that were used to project each impact indicator without
additional adaptation. WGII provides further assessment of the impacts on human and natural systems using these projections and additional lines of evidence. (a) Risks of species
losses as indicated by the percentage of assessed species exposed to potentially dangerous temperature conditions, as defined by conditions beyond the estimated historical
(1850–2005) maximum mean annual temperature experienced by each species, at GWLs of 1.5°C, 2°C, 3°C and 4°C. Underpinning projections of temperature are from 21 Earth
system models and do not consider extreme events impacting ecosystems such as the Arctic. (b) Risk to human health as indicated by the days per year of population exposure
to hypothermic conditions that pose a risk of mortality from surface air temperature and humidity conditions for historical period (1991 –2005) and at GWLs of 1.7°C to 2.3°C
(mean = 1.9°C; 13 climate models), 2.4°C to 3.1°C (2.7°C; 16 climate models) and 4.2°C to 5.4°C (4.7°C; 15 climate models). Interquartile ranges of WGLs by 2081 –2100
under RCP2.6, RCP4.5 and RCP8.5. The presented index is consistent with common features found in many indices included within WGI and WGII assessments. (c) Impacts
on food production: (c1) Changes in maize yield at projected GWLs of 1.6°C to 2.4°C (2.0°C), 3.3°C to 4.8°C (4.1°C) and 3.9°C to 6.0°C (4.9°C). Median yield changes
from an ensemble of 12 crop models, each driven by bias-adjusted outputs from 5 Earth system models from the Agricultural Model Intercomparison and Improvement Project
(AgMIP) and the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP). Maps depict 2080–2099 compared to 1986–2005 for current growing regions (>10 ha), with the
corresponding range of future global warming levels shown under SSP1-2.6, SSP3-7.0 and SSP5-8.5, respectively. Hatching indicates areas where <70% of the climate-crop model
combinations agree on the sign of impact. (c2) Changes in maximum fisheries catch potential by 2081 –2099 relative to 1986-2005 at projected GWLs of 0.9°C to 2.0°C (1.5°C)
and 3.4°C to 5.2°C (4.3°C). GWLs by 2081 –2100 under RCP2.6 and RCP8.5. Hatching indicates where the two climate-fisheries models disagree in the direction of change. Large
relative changes in low yielding regions may correspond to small absolute changes. Biodiversity and fisheries in Antarctica were not analysed due to data limitations. Food security
is also affected by crop and fishery failures not presented here. {WGII Fig. TS.5, WGII Fig TS.9, WGII Annex I: Global to Regional Atlas Figure AI.15, Figure AI.22, Figure AI.23, Figure
AI.29; WGII 7.3.1.2, 7.2.4.1, SROCC Figure SPM.3} (3.1.2, Cross-Section Box.2)

Risks are increasing with every increment of warming
a) High risks are now assessed to occur at lower global warming levels
b) Risks differ by system
c) Risks to coastal geographies increase with sea level rise and depend on responses
d) Adaptation and socio-economic pathways affect levels of climate related risks
e) Examples of key risks in different regions
Absence of risk diagrams does not imply absence of risks within a region. The development of synthetic diagrams for Small
Islands, Asia and Central and South America was limited due to the paucity of adequately downscaled climate projections, with
uncertainty in the direction of change, the diversity of climatologies and socioeconomic contexts across countries within a region, and
the resulting few numbers of impact and risk projections for different warming levels
The risks listed are of at least medium confidence level:

Small Islands
- Loss of terrestrial, marine and coastal biodiversity and ecosystem services
- Loss of lives and assets, risk to food security and economic disruption due to
destruction of settlements and infrastructure
- Economic decline and livelihood failure of fisheries, agriculture, tourism and from
biodiversity loss from traditional agroecosystems
- Reduced habitability of reef and non-reef islands leading to increased displacement
- Risk to water security in almost every small island

North America
- Climate-sensitive mental health outcomes, human mortality and morbidity due to
increasing average temperature, weather and climate extremes, and compound
climate hazards
- Risk of degradation of marine, coastal and terrestrial ecosystems, including loss of
biodiversity, function, and protective services
- Risk to freshwater resources with consequences for ecosystems, reduced surface water
availability for irrigated agriculture, other human uses, and degraded water quality
- Risk to food and nutritional security through changes in agriculture, livestock, hunting,
fisheries, and aquaculture productivity and access
- Risks to well-being, livelihoods and economic activities from cascading and
compounding climate hazards, including risks to coastal cities, settlements and
infrastructure from sea level rise

Europe
- Risks to people, economies and infrastructures due to coastal and inland flooding
- Stress and mortality to people due to increasing temperatures and heat extremes
- Marine and terrestrial ecosystems disruptions
- Water scarcity to multiple interconnected sectors
- Losses in crop production, due to compound heat and dry conditions, and extreme
weather

Central and South America
- Risk to water security
- Severe health effects due to increasing epidemics, in particular vector-borne diseases
- Coral reef ecosystems degradation due to coral bleaching
- Risk to food security due to frequent/extreme droughts
- Damages to life and infrastructure due to floods, landslides, sea level rise, storm
surges and coastal erosion

Australasia
- Degradation of tropical shallow coral reefs and associated biodiversity and
ecosystem service values
- Loss of human and natural systems in low-lying coastal areas due to sea level rise
- Impact on livelihoods and incomes due to decline in agricultural production
- Increase in heat-related mortality and morbidity for people and wildlife
- Loss of alpine biodiversity in Australia due to less snow

Asia
- Urban infrastructure damage and impacts on human well-being and health due to
flooding, especially in coastal cities and settlements
- Biodiversity loss and habitat shifts as well as associated disruptions in dependent
human systems across freshwater, land, and ocean ecosystems
- More frequent, extensive coral bleaching and subsequent coral mortality induced by
ocean warming and acidification, sea level rise, marine heat waves and resource
extraction
- Decline in coastal fishery resources due to sea level rise, decrease in precipitation in
some parts and increase in temperature
- Risk to food and water security due to increased temperature extremes, rainfall
variability and drought

Africa
- Species extinction and reduction or irreversible loss of ecosystems and their services,
including freshwater, land and ocean ecosystems
- Risk to food security, risk of malnutrition (micronutrient deficiency), and loss of
livelihood due to reduced food production from crops, livestock and fisheries
- Risks to marine ecosystem health and to livelihoods in coastal communities
- Increased human mortality and morbidity due to increased heat and infectious diseases
(including vector-borne and diarrhoeal diseases)
- Reduced economic output and growth, and increased inequality and poverty rates
- Increased risk to water and energy security due to drought and heat

Figure 3.3: Synthetic risk diagrams of global and sectoral assessments and examples of regional key risks. The burning embers result from a literature based
expert elicitation. Panel (a): Left - Global surface temperature changes in °C relative to 1850–1900. These changes were obtained by combining CMIP6 model simulations with
observational constraints based on past simulated warming, as well as an updated assessment of equilibrium climate sensitivity. Very likely ranges are shown for the low and high
GHG emissions scenarios (SSP1-2.6 and SSP3-7.0). Right - Global Reasons for Concern, comparing AR6 (thick embers) and AR5 (thin embers) assessments. Diagrams are shown for
each RFC, assuming low to no adaptation (i.e., adaptation is fragmented, localised and comprises incremental adjustments to existing practices). However, the transition to a very
high-risk level has an emphasis on irreversibility and adaptation limits. The horizontal line denotes the present global warming of 1.1°C which is used to separate the observed, past
impacts below the line from the future projected risks above it. Lines connect the midpoints of the transition from moderate to high risk across AR5 and AR6. Panel (b): Risks for
land-based systems and ocean/coastal ecosystems. Diagrams shown for each risk assume low to no adaptation. Text bubbles indicate examples of impacts at a given warming level.
Panel (c): Left - Global mean sea level change in centimetres, relative to 1900. The historical changes (black) are observed by tide gauges before 1992 and altimeters afterwards.
The future changes to 2100 (coloured lines and shading) are assessed consistently with observational constraints based on emulation of CMIP, ice-sheet, and glacier models, and
likely ranges are shown for SSP1-2.6 and SSP3-7.0. Right - Assessment of the combined risk of coastal flooding, erosion and salinization for four illustrative coastal geographies in
2100, due to changing mean and extreme sea levels, under two response scenarios, with respect to the SROCC baseline period (1986–2005) and indicating the IPCC AR6 baseline
period (1995–2014). The assessment does not account for changes in extreme sea level beyond those directly induced by mean sea level rise; risk levels could increase if other changes in
extreme sea levels were considered (e.g., due to changes in cyclone intensity). “No-to-moderate response” describes efforts as of today (i.e., no further significant action or new types of actions).
“Maximum potential response” represents a combination of responses implemented to their full extent and thus significant additional efforts compared to today, assuming minimal
financial, social and political barriers. The assessment criteria include exposure and vulnerability (density of assets, level of degradation of terrestrial and marine buffer ecosystems),
coastal hazards (flooding, shoreline erosion, salinization), in-situ responses (hard engineered coastal defences, ecosystem restoration or creation of new natural buffers areas, and
subsidence management) and planned relocation. Planned relocation refers to managed retreat or resettlement. Forced displacement is not considered in this assessment. The term
response is used here instead of adaptation because some responses, such as retreat, may or may not be considered to be adaptation. Panel (d): Left - Heat-sensitive human
health outcomes under three scenarios of adaptation effectiveness. The diagrams are truncated at the nearest whole ºC within the range of temperature change in 2100 under
three SSP scenarios. Right - Risks associated with food security due to climate change and patterns of socio-economic development. Risks to food security include availability and
access to food, including population at risk of hunger, food price increases and increases in disability adjusted life years attributable to childhood underweight. Risks are assessed
for two contrasted socio-economic pathways (SSP1 and SSP3) excluding the effects of targeted mitigation and adaptation policies. Panel (e): Examples of regional key risks. Risks
identified are of at least medium confidence level. Key risks are identified based on the magnitude of adverse consequences (pervasiveness of the consequences, degree of change,
irreversibility of consequences, potential for impact thresholds or tipping points, potential for cascading effects beyond system boundaries); likelihood of adverse consequences;
temporal characteristics of the risk; and ability to respond to the risk, e.g., by adaptation. {WGI Figure SPM.8; WGII SPM B.3.3, WGII Figure SPM.3, WGII SM 16.6, WGII SM 16.7.4;
SROCC Figure SPM.3d, SROCC SPM.5a, SROCC 4SM; SRCCL Figure SPM.2, SRCCL 7.3.1, SRCCL 7 SM} (Cross-Section Box.2)

3.1.3 The Likelihood and Risks of Abrupt and Irreversible
Change

The likelihood of abrupt and irreversible changes and their impacts
increase with higher global warming levels (high confidence).
As warming levels increase, so do the risks of species extinction or
irreversible loss of biodiversity in ecosystems such as forests (medium
confidence), coral reefs (very high confidence) and in Arctic regions
(high confidence). Risks associated with large-scale singular events
or tipping points, such as ice sheet instability or ecosystem loss from
tropical forests, transition to high risk between 1.5°C to 2.5°C (medium
confidence) and to very high risk between 2.5°C to 4°C (low confidence).
The response of biogeochemical cycles to anthropogenic perturbations
can be abrupt at regional scales and irreversible on decadal to century
time scales (high confidence). The probability of crossing uncertain
regional thresholds increases with further warming (high confidence).
{WGI SPM C.3.2, WGI Box TS.9, WGI TS.2.6; WGII Figure SPM.3,
WGII SPM B.3.1, WGII SPM B.4.1, WGII SPM B.5.2, WGII Table TS.1,
WGII TS.C.1, WGII TS.C.13.3; SROCC SPM B.4}
Sea level rise is unavoidable for centuries to millennia due
to continuing deep ocean warming and ice sheet melt, and
sea levels will remain elevated for thousands of years (high
confidence). Global mean sea level rise will continue in the 21st
century (virtually certain), with projected regional relative sea level rise
within 20% of the global mean along two-thirds of the global coastline
(medium confidence). The magnitude, the rate, the timing of threshold
exceedances, and the long-term commitment of sea level rise depend
on emissions, with higher emissions leading to greater and faster rates
of sea level rise. Due to relative sea level rise, extreme sea level events
that occurred once per century in the recent past are projected to occur
at least annually at more than half of all tide gauge locations by 2100
and risks for coastal ecosystems, people and infrastructure will continue
to increase beyond 2100 (high confidence). At sustained warming
levels between 2°C and 3°C, the Greenland and West Antarctic ice
sheets will be lost almost completely and irreversibly over multiple
millennia (limited evidence). The probability and rate of ice mass loss
increase with higher global surface temperatures (high confidence).
Over the next 2000 years, global mean sea level will rise by about
2 to 3 m if warming is limited to 1.5°C and 2 to 6 m if limited to 2°C
(low confidence). Projections of multi-millennial global mean sea level
rise are consistent with reconstructed levels during past warm climate
periods: global mean sea level was very likely 5 to 25 m higher than today
roughly 3 million years ago, when global temperatures were 2.5°C to
4°C higher than 1850–1900 (medium confidence). Further examples
of unavoidable changes in the climate system due to multi-decadal
or longer response timescales include continued glacier melt (very high
confidence) and permafrost carbon loss (high confidence). {WGI SPM B.5.2,
WGI SPM B.5.3, WGI SPM B.5.4, WGI SPM C.2.5, WGI Box TS.4,
WGI Box TS.9, WGI 9.5.1; WGII TS C.5; SROCC SPM B.3, SROCC SPM B.6,
SROCC SPM B.9} (Figure 3.4)
The probability of low-likelihood outcomes associated with
potentially very large impacts increases with higher global
warming levels (high confidence). Warming substantially above the
assessed very likely range for a given scenario cannot be ruled out, and
there is high confidence this would lead to regional changes greater
than assessed in many aspects of the climate system. Low-likelihood,
high-impact outcomes could occur at regional scales even for global warming
within the very likely assessed range for a given GHG emissions scenario.
Global mean sea level rise above the likely range – approaching 2 m by
2100 and in excess of 15 m by 2300 under a very high GHG emissions
scenario (SSP5-8.5) (low confidence) – cannot be ruled out due to
deep uncertainty in ice-sheet processes123 and would have severe
impacts on populations in low elevation coastal zones. If global
warming increases, some compound extreme events124 will
become more frequent, with higher likelihood of unprecedented
intensities, durations or spatial extent (high confidence). The
Atlantic Meridional Overturning Circulation is very likely to weaken
over the 21st century for all considered scenarios (high confidence),
however an abrupt collapse is not expected before 2100 (medium
confidence). If such a low probability event were to occur, it would very
likely cause abrupt shifts in regional weather patterns and water cycle,
such as a southward shift in the tropical rain belt, and large impacts
on ecosystems and human activities. A sequence of large explosive
volcanic eruptions within decades, as have occurred in the past, is a
low-likelihood high-impact event that would lead to substantial cooling
globally and regional climate perturbations over several decades.
{WGI SPM B.5.3, WGI SPM C.3, WGI SPM C.3.1, WGI SPM C.3.2,
WGI SPM C.3.3, WGI SPM C.3.4, WGI SPM C.3.5, WGI Figure SPM.8,
WGI Box TS.3, WGI Figure TS.6, WGI Box 9.4; WGII SPM B.4.5, WGII SPM C.2.8;
SROCC SPM B.2.7} (Figure 3.4, Cross-Section Box.2)

3.2 Long-term Adaptation Options and Limits

With increasing warming, adaptation options will become more constrained and less effective. At higher levels
of warming, losses and damages will increase, and additional human and natural systems will reach adaptation
limits. Integrated, cross-cutting multi-sectoral solutions increase the effectiveness of adaptation. Maladaptation
can create lock-ins of vulnerability, exposure and risks but can be avoided by long-term planning and the
implementation of adaptation actions that are flexible, multi-sectoral and inclusive. (high confidence)

The effectiveness of adaptation to reduce climate risk is documented
for specific contexts, sectors and regions and will decrease with
increasing warming (high confidence)125. For example, common
adaptation responses in agriculture – adopting improved cultivars and
agronomic practices, and changes in cropping patterns and crop
systems – will become less effective from 2°C to higher levels of
warming (high confidence). The effectiveness of most water-related
adaptation options to reduce projected risks declines with increasing
warming (high confidence). Adaptations for hydropower and
thermo-electric power generation are effective in most regions up to
1.5°C to 2°C, with decreasing effectiveness at higher levels of warming
(medium confidence). Ecosystem-based Adaptation is vulnerable to
climate change impacts, with effectiveness declining with increasing
global warming (high confidence). Globally, adaptation options related
to agroforestry and forestry have a sharp decline in effectiveness at 3°C,
with a substantial increase in residual risk (medium confidence).
{WGII SPM C.2, WGII SPM C.2.1, WGII SPM C.2.5, WGII SPM C.2.10,
WGII Figure TS.6 Panel (e), 4.7.2}
With increasing global warming, more limits to adaptation will be
reached and losses and damages, strongly concentrated among the
poorest vulnerable populations, will increase (high confidence).
Already below 1.5°C, autonomous and evolutionary adaptation
responses by terrestrial and aquatic ecosystems will increasingly
face hard limits (high confidence) (Section 2.1.2). Above 1.5°C, some
ecosystem-based adaptation measures will lose their effectiveness
in providing benefits to people as these ecosystems will reach hard
adaptation limits (high confidence). Adaptation to address the risks of
heat stress, heat mortality and reduced capacities for outdoor work
for humans face soft and hard limits across regions that become
significantly more severe at 1.5°C, and are particularly relevant for
regions with warm climates (high confidence). Above 1.5°C global
warming level, limited freshwater resources pose potential hard limits
for small islands and for regions dependent on glacier and snow melt
(medium confidence). By 2°C, soft limits are projected for multiple
staple crops, particularly in tropical regions (high confidence). By 3°C,
soft limits are projected for some water management measures for
many regions, with hard limits projected for parts of Europe (medium
confidence). {WGII SPM C.3, WGII SPM C.3.3, WGII SPM C.3.4, WGII SPM C.3.5,
WGII TS.D.2.2, WGII TS.D.2.3; SR1.5 SPM B.6; SROCC SPM C.1}
Integrated, cross-cutting multi-sectoral solutions increase the
effectiveness of adaptation. For example, inclusive, integrated
and long-term planning at local, municipal, sub-national and national
scales, together with effective regulation and monitoring systems
and financial and technological resources and capabilities foster
urban and rural system transition. There are a range of cross-cutting
adaptation options, such as disaster risk management, early warning
systems, climate services and risk spreading and sharing that have
broad applicability across sectors and provide greater benefits to other
adaptation options when combined. Transitioning from incremental to
transformational adaptation, and addressing a range of constraints,
primarily in the financial, governance, institutional and policy domains,
can help overcome soft adaptation limits. However, adaptation does
not prevent all losses and damages, even with effective adaptation and
before reaching soft and hard limits. (high confidence) {WGII SPM C.2,
WGII SPM C.2.6, WGII SPM.C.2.13, WGII SPM C.3.1, WGII SPM.C.3.4,
WGII SPM C.3.5, WGII Figure TS.6 Panel (e)}
Maladaptive responses to climate change can create lock-ins of
vulnerability, exposure and risks that are difficult and expensive
to change and exacerbate existing inequalities. Actions that focus
on sectors and risks in isolation and on short-term gains often lead
to maladaptation. Adaptation options can become maladaptive due
to their environmental impacts that constrain ecosystem services and
decrease biodiversity and ecosystem resilience to climate change or by
causing adverse outcomes for different groups, exacerbating inequity.
Maladaptation can be avoided by flexible, multi-sectoral, inclusive and
long-term planning and implementation of adaptation actions with
benefits to many sectors and systems. (high confidence) {WGII SPM C.4,
WGII SPM.C.4.1, WGII SPM C.4.2, WGII SPM C.4.3}
Sea level rise poses a distinctive and severe adaptation challenge
as it implies both dealing with slow onset changes and increases
in the frequency and magnitude of extreme sea level events (high
confidence). Such adaptation challenges would occur much earlier
under high rates of sea level rise (high confidence). Responses to ongoing
sea level rise and land subsidence include protection, accommodation,
advance and planned relocation (high confidence). These responses
are more effective if combined and/or sequenced, planned well ahead,
aligned with sociocultural values and underpinned by inclusive
community engagement processes (high confidence). Ecosystem-based
solutions such as wetlands provide co-benefits for the environment
and climate mitigation, and reduce costs for flood defences (medium
confidence), but have site-specific physical limits, at least above 1.5ºC
of global warming (high confidence) and lose effectiveness at high
rates of sea level rise beyond 0.5 to 1 cm yr -1 (medium confidence).
Seawalls can be maladaptive as they effectively reduce impacts in the
short term but can also result in lock-ins and increase exposure to climate
risks in the long term unless they are integrated into a long-term adaptive
plan (high confidence). {WGI SPM C.2.5; WGII SPM C.2.8, WGII SPM C.4.1;
WGII 13.10, WGII Cross-Chapter Box SLR; SROCC SPM B.9, SROCC SPM C.3.2,
SROCC Figure SPM.4, SROCC Figure SPM.5c} (Figure 3.4)

Sea level rise will continue for millennia, but how
fast and how much depends on future emissions

Sea level rise greater than 15m cannot be ruled out with very high emissions

a) Sea level rise: observations and projections 2020-2100, 2150, 2300 (relative to 1900)
Unavoidable sea level rise will cause:
Losses of coastal ecosystems and ecosystem services
Groundwater salinisation
Flooding and damages to coastal infrastructure

By 2050 1 Billion people exposed. Extreme sea level events that occured once per century will be 20-30 times more frequent

Responding to sea level rise requires long-term planning

b) Typical timescales of coastal risk-management measures
Ecosystem-based adaptation = 15 years
Sediment-based adaptation = 15 years
Elevating houses = 30 years
Long-living societal legacy:
- Protect levees = 50 years
- Protect barriers = 100 years
- Planned relocation => 100 years

Higher greenhouse gas emissions lead to larger and faster sea level rise, demanding earlier and stronger responses, and reducing the lifetime of some options

Figure 3.4: Observed and projected global mean sea level change and its impacts, and time scales of coastal risk management. Panel (a): Global mean sea
level change in metres relative to 1900. The historical changes (black) are observed by tide gauges before 1992 and altimeters afterwards. The future changes to 2100 and for
2150 (coloured lines and shading) are assessed consistently with observational constraints based on emulation of CMIP, ice-sheet, and glacier models, and median values and
likely ranges are shown for the considered scenarios. Relative to 1995-2014, the likely global mean sea level rise by 2050 is between 0.15 to 0.23 m in the very low
GHG emissions scenario (SSP1-1.9) and 0.20 to 0.29 m in the very high GHG emissions scenario (SSP5-8.5); by 2100 between 0.28 to 0.55 m under SSP1-1.9 and 0.63 to 1.01 m under
SSP5-8.5; and by 2150 between 0.37 to 0.86 m under SSP1-1.9 and 0.98 to 1.88 m under SSP5-8.5 (medium confidence). Changes relative to 1900 are calculated by adding 0.158
m (observed global mean sea level rise from 1900 to 1995-2014) to simulated changes relative to 1995-2014. The future changes to 2300 (bars) are based on literature assessment,
representing the 17th–83rd percentile range for SSP1-2.6 (0.3 to 3.1 m) and SSP5-8.5 (1.7 to 6.8 m). Red dashed lines: Low-likelihood, high-impact storyline, including ice sheet
instability processes. These indicate the potential impact of deeply uncertain processes, and show the 83rd percentile of SSP5-8.5 projections that include low-likelihood, high-
impact processes that cannot be ruled out; because of low confidence in projections of these processes, this is not part of a likely range. IPCC AR6 global and regional sea level
projections are hosted at https://sealevel.nasa.gov/ipcc-ar6-sea-level-projection-tool. The low-lying coastal zone is currently home to around 896 million people (nearly 11% of the
2020 global population), projected to reach more than one billion by 2050 across all five SSPs. Panel (b): Typical time scales for the planning, implementation (dashed bars) and
operational lifetime of current coastal risk-management measures (blue bars). Higher rates of sea level rise demand earlier and stronger responses and reduce the lifetime of measures (inset).
As the scale and pace of sea level rise accelerates beyond 2050, long-term adjustments may in some locations be beyond the limits of current adaptation options and for some small
islands and low-lying coasts could be an existential risk. {WGI SPM B.5, WGI C.2.5, WGI Figure SPM.8, WGI 9.6; WGII SPM B.4.5, WGII B.5.2, WGII C.2.8, WGII D.3.3, WGII TS.D.7,
WGII Cross-Chapter Box SLR} (Cross-Section Box.2)

3.3 Mitigation Pathways

Limiting human-caused global warming requires net zero anthropogenic CO2 emissions. Pathways consistent
with 1.5°C and 2°C carbon budgets imply rapid, deep, and in most cases immediate GHG emission reductions in
all sectors (high confidence). Exceeding a warming level and returning (i.e. overshoot) implies increased risks
and potential irreversible impacts; achieving and sustaining global net negative CO2 emissions would reduce
warming (high confidence).

3.3.1 Remaining Carbon Budgets

Limiting global temperature increase to a specific level requires
limiting cumulative net CO2 emissions to within a finite carbon
budget126, along with strong reductions in other GHGs. For every
1000 GtCO2 emitted by human activity, global mean temperature rises
by likely 0.27°C to 0.63°C (best estimate of 0.45°C). This relationship
implies that there is a finite carbon budget that cannot be exceeded in
order to limit warming to any given level. {WGI SPM D.1, WGI SPM D.1.1;
SR1.5 SPM C.1.3} (Figure 3.5)

The best estimates of the remaining carbon budget (RCB) from
the beginning of 2020 for limiting warming to 1.5°C with a 50%
likelihood127 is estimated to be 500 GtCO2; for 2°C (67% likelihood)
this is 1150 GtCO2.128 Remaining carbon budgets have been quantified
based on the assessed value of TCRE and its uncertainty, estimates of
historical warming, climate system feedbacks such as emissions from
thawing permafrost, and the global surface temperature change after
global anthropogenic CO 2 emissions reach net zero, as well as variations
in projected warming from non-CO2 emissions due in part to mitigation
action. The stronger the reductions in non-CO2 emissions the lower the
resulting temperatures are for a given RCB or the larger RCB for the
same level of temperature change. For instance, the RCB for limiting
warming to 1.5°C with a 50% likelihood could vary between 300 to
600 GtCO 2 depending on non-CO 2 warming129. Limiting warming to 2°C
with a 67% (or 83%) likelihood would imply a RCB of 1150 (900) GtCO2
from the beginning of 2020. To stay below 2°C with a 50% likelihood,
the RCB is higher, i.e., 1350 GtCO 2130. {WGI SPM D.1.2, WGI Table SPM.2;
WGIII Box SPM.1, WGIII Box 3.4; SR1.5 SPM C.1.3}
If the annual CO2 emissions between 2020–2030 stayed, on average,
at the same level as 2019, the resulting cumulative emissions would
almost exhaust the remaining carbon budget for 1.5°C (50%), and
exhaust more than a third of the remaining carbon budget for 2°C
(67%) (Figure 3.5). Based on central estimates only, historical cumulative
net CO2 emissions between 1850 and 2019 (2400 ±240 GtCO2 ) amount
to about four-fifths131 of the total carbon budget for a 50% probability of
limiting global warming to 1.5°C (central estimate about 2900 GtCO2) and
to about two-thirds132 of the total carbon budget for a 67% probability
to limit global warming to 2°C (central estimate about 3550 GtCO2 ).
{WGI Table SPM.2; WGIII SPM B.1.3, WGIII Table 2.1}
In scenarios with increasing CO 2 emissions, the land and ocean
carbon sinks are projected to be less effective at slowing the
accumulation of CO2 in the atmosphere (high confidence). While
natural land and ocean carbon sinks are projected to take up, in absolute
terms, a progressively larger amount of CO 2 under higher compared to
lower CO2 emissions scenarios, they become less effective, that is, the
proportion of emissions taken up by land and ocean decreases with
increasing cumulative net CO2 emissions (high confidence). Additional
ecosystem responses to warming not yet fully included in climate models,
such as GHG fluxes from wetlands, permafrost thaw, and wildfires,
would further increase concentrations of these gases in the atmosphere
(high confidence). In scenarios where CO2 concentrations peak and
decline during the 21st century, the land and ocean begin to take up less
carbon in response to declining atmospheric CO2 concentrations (high
confidence) and turn into a weak net source by 2100 in the very low
GHG emissions scenario (medium confidence)133. {WGI SPM B.4,
WGI SPM B.4.1, WGI SPM B.4.2, WGI SPM B.4.3}

Remaining carbon budgets to limit warming to 1.5°C could
soon be exhausted, and those for 2°C largely depleted
Remaining carbon budgets are similar to emissions from use of existing
and planned fossil fuel infrastructure, without additional abatement

a) Carbon budgets and emissions
Every ton of CO2 adds to global warming
b) Cumulative CO 2 emissions and warming until 2050

Figure 3.5: Cumulative past, projected, and committed emissions, and associated global temperature changes. Panel (a) Assessed remaining carbon budgets to limit
warming more likely than not to 1.5°C, to 2°C with a 83% and 67% likelihood, compared to cumulative emissions corresponding to constant 2019 emissions until 2030, existing and
planned fossil fuel infrastructures (in GtCO2 ). For remaining carbon budgets, thin lines indicate the uncertainty due to the contribution of non-CO2 warming. For lifetime emissions from
fossil fuel infrastructure, thin lines indicate the assessed sensitivity range. Panel (b) Relationship between cumulative CO2 emissions and the increase in global surface temperature.
Historical data (thin black line) shows historical CO2 emissions versus observed global surface temperature increase relative to the period 1850-1900. The grey range with its central
line shows a corresponding estimate of the human-caused share of historical warming. Coloured areas show the assessed very likely range of global surface temperature projections,
and thick coloured central lines show the median estimate as a function of cumulative CO2 emissions for the selected scenarios SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5.
Projections until 2050 use the cumulative CO2 emissions of each respective scenario, and the projected global warming includes the contribution from all anthropogenic forcers. {WGI SPM D.1,
WGI Figure SPM.10, WGI Table SPM.2; WGIII SPM B.1, WGIII SPM B.7, WGIII 2.7; SR1.5 SPM C.1.3}

Table 3.1: Key characteristics of the modelled global emissions pathways. Summary of projected CO2 and GHG emissions, projected net zero timings and the resulting global
warming outcomes. Pathways are categorised (columns), according to their likelihood of limiting warming to different peak warming levels (if peak temperature occurs before 2100)
and 2100 warming levels. Values shown are for the median [p50] and 5–95th percentiles [p5–p95], noting that not all pathways achieve net zero CO2 or GHGs. {WGIII Table SPM.2}

1 Detailed explanations on the Table are provided in WGIII Box SPM.1 and WGIII Table SPM.2. The relationship between the temperature categories and SSP/RCPs is discussed
in Cross-Section Box.2. Values in the table refer to the 50th and [5–95th] percentile values across the pathways falling within a given category as defined in WGIII Box SPM.1.
The three dots (…) sign denotes that the value cannot be given (as the value is after 2100 or, for net zero, net zero is not reached). Based on the assessment of climate emulators
in AR6 WG I (Chapter 7, Box 7.1), two climate emulators were used for the probabilistic assessment of the resulting warming of the pathways. For the ‘Temperature Change’
and ‘Likelihood’ columns, the non-bracketed values represent the 50th percentile across the pathways in that category and the median [50th percentile] across the warming
estimates of the probabilistic MAGICC climate model emulator. For the bracketed ranges in the “likelihood” column, the median warming for every pathway in that category
is calculated for each of the two climate model emulators (MAGICC and FaIR). These ranges cover both the uncertainty of the emissions pathways as well as the climate
emulators’ uncertainty. All global warming levels are relative to 1850-1900.
2 C3 pathways are sub-categorised according to the timing of policy action to match the emissions pathways in WGIII Figure SPM.4.
3 Global emission reductions in mitigation pathways are reported on a pathway-by-pathway basis relative to harmonised modelled global emissions in 2019 rather than
the global emissions reported in WGIII SPM Section B and WGIII Chapter 2; this ensures internal consistency in assumptions about emission sources and activities, as well as
consistency with temperature projections based on the physical climate science assessment by WGI (see WGIII SPM Footnote 49). Negative values (e.g., in C5, C6) represent
an increase in emissions. The modelled GHG emissions in 2019 are 55 [53–58] GtCO 2 -eq, thus within the uncertainty ranges of estimates for 2019 emissions [53-66] GtCO 2-eq
(see 2.1.1).
4 Emissions milestones are provided for 5-year intervals in order to be consistent with the underlying 5-year time-step data of the modelled pathways. Ranges in square
brackets underneath refer to the range across the pathways, comprising the lower bound of the 5th percentile 5-year interval and the upper bound of the 95th percentile
5-year interval. Numbers in round brackets signify the fraction of pathways that reach specific milestones over the 21st century. Percentiles reported across all pathways in
that category include those that do not reach net zero before 2100.
5 For cases where models do not report all GHGs, missing GHG species are infilled and aggregated into a Kyoto basket of GHG emissions in CO2-eq defined by the 100-year
global warming potential. For each pathway, reporting of CO2, CH4, and N2O emissions was the minimum required for the assessment of the climate response and the assignment
to a climate category. Emissions pathways without climate assessment are not included in the ranges presented here. See WGIII Annex III.II.5.
6 Cumulative emissions are calculated from the start of 2020 to the time of net zero and 2100, respectively. They are based on harmonised net CO2 emissions, ensuring
consistency with the WG I assessment of the remaining carbon budget. {WGIII Box 3.4, WGIII SPM Footnote 50}

3.3.2 Net Zero Emissions: Timing and Implications

From a physical science perspective, limiting human-caused
global warming to a specific level requires limiting cumulative
CO2 emissions, reaching net zero or net negative CO2 emissions,
along with strong reductions of other GHG emissions
(see Cross-Section Box.1). Global modelled pathways that reach
and sustain net zero GHG emissions are projected to result in
a gradual decline in surface temperature (high confidence).
Reaching net zero GHG emissions primarily requires deep reductions in
CO2 , methane, and other GHG emissions, and implies net negative
CO2 emissions.134 Carbon dioxide removal (CDR) will be necessary to
achieve net negative CO2 emissions135. Achieving global net zero
CO2 emissions, with remaining anthropogenic CO 2 emissions balanced by
durably stored CO 2 from anthropogenic removal, is a requirement to
stabilise CO2-induced global surface temperature increase (see 3.3.3)
(high confidence). This is different from achieving net zero GHG
emissions, where metric-weighted anthropogenic GHG emissions (see
Cross-Section Box.1) equal CO 2 removal (high confidence). Emissions
pathways that reach and sustain net zero GHG emissions defined by the
100-year global warming potential imply net negative CO2 emissions
and are projected to result in a gradual decline in surface temperature
after an earlier peak (high confidence). While reaching net zero CO2 or net
zero GHG emissions requires deep and rapid reductions in gross
emissions, the deployment of CDR to counterbalance hard-
to-abate residual emissions (e.g., some emissions from agriculture,
aviation, shipping, and industrial processes) is unavoidable (high
confidence). {WGI SPM D.1, WGI SPM D.1.1, WGI SPM D.1.8; WGIII SPM C.2,
WGIII SPM C.3, WGIII SPM C.11, WGIII Box TS.6; SR1.5 SPM A.2.2}
In modelled pathways, the timing of net zero CO2 emissions,
followed by net zero GHG emissions, depends on several
variables, including the desired climate outcome, the mitigation
strategy and the gases covered (high confidence). Global net zero
CO2 emissions are reached in the early 2050s in pathways that limit
warming to 1.5°C (>50%) with no or limited overshoot, and around
the early 2070s in pathways that limit warming to 2°C (>67%). While
non-CO2 GHG emissions are strongly reduced in all pathways that limit
warming to 2°C (>67%) or lower, residual emissions of CH4 and N2O
and F-gases of about 8 [5–11] GtCO2 -eq yr -1 remain at the time of
net zero GHG, counterbalanced by net negative CO2 emissions.
As a result, net zero CO2 would be reached before net zero GHGs
(high confidence). {WGIII SPM C.2, WGIII SPM C.2.3, WGIII SPM C.2.4,
WGIII Table SPM.2, WGIII 3.3} (Figure 3.6)

Global modelled pathways that limit warming to 1.5°C (>50%) with
no or limited overshoot reach net zero CO2 emissions around 2050
Total greenhouse gases (GHG) reach net zero later

Figure 3.6: Total GHG, CO2 and CH4 emissions and timing of reaching net zero in different mitigation pathways. Top row: GHG, CO2 and CH4 emissions over time (in
GtCO2eq) with historical emissions, projected emissions in line with policies implemented until the end of 2020 (grey), and pathways consistent with temperature goals in colour
(blue, purple, and brown, respectively). Panel (a) (left) shows pathways that limit warming to 1.5°C (>50%) with no or limited overshoot (C1) and Panel (b) (right) shows
pathways that limit warming to 2°C (>67%) (C3). Bottom row: Panel (c) shows median (vertical line), likely (bar) and very likely (thin lines) timing of reaching net zero GHG
and CO2 emissions for global modelled pathways that limit warming to 1.5°C (>50%) with no or limited overshoot (C1) (left) or 2°C (>67%) (C3) (right). {WGIII Figure SPM.5}

3.3.3 Sectoral Contributions to Mitigation

All global modelled pathways that limit warming to 2°C (>67%) or
lower by 2100 involve rapid and deep and in most cases immediate
GHG emissions reductions in all sectors (see also 4.1, 4.5). Reductions
in GHG emissions in industry, transport, buildings, and urban areas
can be achieved through a combination of energy efficiency and
conservation and a transition to low-GHG technologies and energy
carriers (see also 4.5, Figure 4.4). Socio-cultural options and behavioural
change can reduce global GHG emissions of end-use sectors, with most
of the potential in developed countries, if combined with improved
infrastructure design and access. (high confidence) {WGIII SPM C.3,
WGIII SPM C.5, WGIII SPM C.6, WGIII SPM C.7.3, WGIII SPM C.8,
WGIII SPM C.10.2}
Global modelled mitigation pathways reaching net zero CO2 and
GHG emissions include transitioning from fossil fuels without
carbon capture and storage (CCS) to very low- or zero-carbon
energy sources, such as renewables or fossil fuels with CCS,
demand-side measures and improving efficiency, reducing
non-CO2 GHG emissions, and CDR136. In global modelled pathways
that limit warming to 2°C or below, almost all electricity is supplied
from zero or low-carbon sources in 2050, such as renewables or
fossil fuels with CO2 capture and storage, combined with increased
electrification of energy demand. Such pathways meet energy service
demand with relatively low energy use, through e.g., enhanced energy
efficiency and behavioural changes and increased electrification of
energy end use. Modelled global pathways limiting global warming to
1.5°C (>50%) with no or limited overshoot generally implement such
changes faster than pathways limiting global warming to 2°C (>67%).
(high confidence) {WGIII SPM C.3, WGIII SPM C.3.2, WGIII SPM C.4,
WGIII TS.4.2; SR1.5 SPM C.2.2}
AFOLU mitigation options, when sustainably implemented, can
deliver large-scale GHG emission reductions and enhanced CO2
removal; however, barriers to implementation and trade-offs
may result from the impacts of climate change, competing
demands on land, conflicts with food security and livelihoods,
the complexity of land ownership and management systems,
and cultural aspects (see 3.4.1). All assessed modelled pathways
that limit warming to 2°C (>67%) or lower by 2100 include land-based
mitigation and land-use change, with most including different
combinations of reforestation, afforestation, reduced deforestation, and
bioenergy. However, accumulated carbon in vegetation and soils is at
risk from future loss (or sink reversal) triggered by climate change and
disturbances such as flood, drought, fire, or pest outbreaks, or future
poor management. (high confidence) {WGI SPM B.4.3; WGII SPM B.2.3,
WGII SPM B.5.4; WGIII SPM C.9, WGIII SPM C.11.3, WGIII SPM D.2.3,
WGIII TS.4.2, 3.4; SR1.5 SPM C.2.5; SRCCL SPM B.1.4, SRCCL SPM B.3,
SRCCL SPM B.7}
In addition to deep, rapid, and sustained emission reductions,
CDR can fulfil three complementary roles: lowering net CO2
or net GHG emissions in the near term; counterbalancing
‘hard-to-abate’ residual emissions (e.g., some emissions from
agriculture, aviation, shipping, industrial processes) to help reach
net zero CO2 or GHG emissions, and achieving net negative
CO 2 or GHG emissions if deployed at levels exceeding annual
residual emissions (high confidence). CDR methods vary in terms
of their maturity, removal process, time scale of carbon storage, storage
medium, mitigation potential, cost, co-benefits, impacts and risks, and
governance requirements (high confidence). Specifically, maturity
ranges from lower maturity (e.g., ocean alkalinisation) to higher
maturity (e.g., reforestation); removal and storage potential ranges
from lower potential (<1 Gt CO2 yr-1 , e.g., blue carbon management)
to higher potential (>3 Gt CO 2 yr -1 , e.g., agroforestry); costs range from
lower cost (e.g., –45 to 100 USD tCO2-1 for soil carbon sequestration)
to higher cost (e.g., 100 to 300 USD tCO2-1 for direct air carbon dioxide
capture and storage) (medium confidence). Estimated storage timescales
vary from decades to centuries for methods that store carbon in
vegetation and through soil carbon management, to ten thousand years
or more for methods that store carbon in geological formations (high
confidence). Afforestation, reforestation, improved forest management,
agroforestry and soil carbon sequestration are currently the only widely
practiced CDR methods (high confidence). Methods and levels of CDR
deployment in global modelled mitigation pathways vary depending on
assumptions about costs, availability and constraints (high confidence).
{WGIII SPM C.3.5, WGIII SPM C.11.1, WGIII SPM C.11.4}
3.3.4 Overshoot Pathways: Increased Risks and Other
Implications
Exceeding a specific remaining carbon budget results in
higher global warming. Achieving and sustaining net negative
global CO 2 emissions could reverse the resulting temperature
exceedance (high confidence). Continued reductions in emissions of
short-lived climate forcers, particularly methane, after peak temperature
has been reached, would also further reduce warming (high confidence).
Only a small number of the most ambitious global modelled pathways
limit global warming to 1.5°C (>50%) without overshoot. {WGI SPM D.1.1,
WGI SPM D.1.6, WGI SPM D.1.7; WGIII TS.4.2}
Overshoot of a warming level results in more adverse impacts, some
irreversible, and additional risks for human and natural systems
compared to staying below that warming level, with risks growing
with the magnitude and duration of overshoot (high confidence).
Compared to pathways without overshoot, societies and ecosystems
would be exposed to greater and more widespread changes in climatic
impact-drivers, such as extreme heat and extreme precipitation, with
increasing risks to infrastructure, low-lying coastal settlements, and
associated livelihoods (high confidence). Overshooting 1.5°C will result
in irreversible adverse impacts on certain ecosystems with low resilience,
such as polar, mountain, and coastal ecosystems, impacted by ice-sheet
melt, glacier melt, or by accelerating and higher committed sea level
rise (high confidence). Overshoot increases the risks of severe impacts,
such as increased wildfires, mass mortality of trees, drying of peatlands,
thawing of permafrost and weakening natural land carbon sinks; such
impacts could increase releases of GHGs making temperature reversal
more challenging (medium confidence). {WGI SPM C.2, WGI SPM C.2.1,
WGI SPM C.2.3; WGII SPM B.6, WGII SPM B.6.1, WGII SPM B.6.2; SR1.5 3.6}
The larger the overshoot, the more net negative CO2 emissions needed
to return to a given warming level (high confidence). Reducing global
temperature by removing CO 2 would require net negative emissions of
220 GtCO 2 (best estimate, with a likely range of 160 to 370 GtCO2 )
for every tenth of a degree (medium confidence). Modelled pathways
that limit warming to 1.5°C (>50%) with no or limited overshoot reach
median values of cumulative net negative emissions of 220 GtCO2
by 2100, pathways that return warming to 1.5°C (>50%) after high
overshoot reach median values of 360 GtCO2 (high confidence).137
More rapid reduction in CO 2 and non-CO2 emissions, particularly
methane, limits peak warming levels and reduces the requirement
for net negative CO2 emissions and CDR, thereby reducing feasibility
and sustainability concerns, and social and environmental risks (high
confidence). {WGI SPM D.1.1; WGIII SPM B.6.4, WGIII SPM C.2,
WGIII SPM C.2.2, WGIII Table SPM.2}

3.4 Long-Term Interactions Between Adaptation, Mitigation and Sustainable Development

Mitigation and adaptation can lead to synergies and trade-offs with sustainable development (high confidence).
Accelerated and equitable mitigation and adaptation bring benefits from avoiding damages from climate
change and are critical to achieving sustainable development (high confidence). Climate resilient development138
pathways are progressively constrained by every increment of further warming (very high confidence). There is a
rapidly closing window of opportunity to secure a liveable and sustainable future for all (very high confidence).

3.4.1 Synergies and trade-offs, costs and benefits

Mitigation and adaptation options can lead to synergies and
trade-offs with other aspects of sustainable development
(see also Section 4.6, Figure 4.4). Synergies and trade-offs depend
on the pace and magnitude of changes and the development context
including inequalities, with consideration of climate justice. The
potential or effectiveness of some adaptation and mitigation options
decreases as climate change intensifies (see also Sections 3.2, 3.3.3,
4.5). (high confidence) {WGII SPM C.2, WGII Figure SPM.4b; WGIII SPM D.1,
WGIII SPM D.1.2, WGIII TS.5.1, WGIII Figure SPM.8; SR1.5 SPM D.3,
SR1.5 SPM D.4; SRCCL SPM B.2, SRCCL SPM B.3, SRCCL SPM D.3.2,
SRCCL Figure SPM.3}
In the energy sector, transitions to low-emission systems will have
multiple co-benefits, including improvements in air quality and health.
There are potential synergies between sustainable development and,
for instance, energy efficiency and renewable energy. (high confidence)
{WGIII SPM C.4.2, WGIII SPM D.1.3}
For agriculture, land, and food systems, many land management
options and demand-side response options (e.g., dietary choices,
reduced post-harvest losses, reduced food waste) can contribute to
eradicating poverty and eliminating hunger while promoting good health
and well-being, clean water and sanitation, and life on land (medium
confidence). In contrast, certain adaptation options that promote
intensification of production, such as irrigation, may have negative
effects on sustainability (e.g., for biodiversity, ecosystem services,
groundwater depletion, and water quality) (high confidence). {WGII
TS.D.5.5; WGIII SPM D.10; SRCCL SPM B.2.3}
Reforestation, improved forest management, soil carbon sequestration,
peatland restoration and coastal blue carbon management are
examples of CDR methods that can enhance biodiversity and ecosystem
functions, employment and local livelihoods, depending on context139.
However, afforestation or production of biomass crops for bioenergy
with carbon dioxide capture and storage or biochar can have adverse
socio-economic and environmental impacts, including on biodiversity,
food and water security, local livelihoods and the rights of Indigenous
Peoples, especially if implemented at large scales and where land
tenure is insecure. (high confidence) {WGII SPM B.5.4, WGII SPM C.2.4;
WGIII SPM C.11.2; SR1.5 SPM C.3.4, SR1.5 SPM C.3.5; SRCCL SPM B.3,
SRCCL SPM B.7.3, SRCCL Figure SPM.3}

Modelled pathways that assume using resources more efficiently or shift
global development towards sustainability include fewer challenges, such
as dependence on CDR and pressure on land and biodiversity, and have
the most pronounced synergies with respect to sustainable development
(high confidence). {WGIII SPM C.3.6; SR1.5 SPM D.4.2}

Strengthening climate change mitigation action entails more
rapid transitions and higher up-front investments, but brings
benefits from avoiding damages from climate change and
reduced adaptation costs. The aggregate effects of climate change
mitigation on global GDP (excluding damages from climate change and
adaptation costs) are small compared to global projected GDP growth.
Projected estimates of global aggregate net economic damages and
the costs of adaptation generally increase with global warming level.
(high confidence) {WGII SPM B.4.6, WGII TS.C.10; WGIII SPM C.12.2,
WGIII SPM C.12.3}
Cost-benefit analysis remains limited in its ability to represent all
damages from climate change, including non-monetary damages,
or to capture the heterogeneous nature of damages and the risk of
catastrophic damages (high confidence). Even without accounting for
these factors or for the co-benefits of mitigation, the global benefits
of limiting warming to 2°C exceed the cost of mitigation (medium
confidence). This finding is robust against a wide range of assumptions
about social preferences on inequalities and discounting over time
(medium confidence). Limiting global warming to 1.5°C instead of 2°C
would increase the costs of mitigation, but also increase the benefits
in terms of reduced impacts and related risks (see 3.1.1, 3.1.2) and
reduced adaptation needs (high confidence)140. {WGII SPM B.4, WGII
SPM B.6; WGIII SPM C.12, WGIII SPM C.12.2, WGIII SPM C.12.3 WGIII Box TS.7;
SR1.5 SPM B.3, SR1.5 SPM B.5, SR1.5 SPM B.6}
Considering other sustainable development dimensions, such as the
potentially strong economic benefits on human health from air quality
improvement, may enhance the estimated benefits of mitigation
(medium confidence). The economic effects of strengthened mitigation
action vary across regions and countries, depending notably on economic
structure, regional emissions reductions, policy design and level of
international cooperation (high confidence). Ambitious mitigation
pathways imply large and sometimes disruptive changes in economic
structure, with implications for near-term actions (Section 4.2), equity
(Section 4.4), sustainability (Section 4.6), and finance (Section 4.8)
(high confidence). {WGIII SPM C.12.2, WGIII SPM D.3.2, WGIII TS.4.2}

3.4.2 Advancing Integrated Climate Action for Sustainable
Development

An inclusive, equitable approach to integrating adaptation, mitigation
and development can advance sustainable development in the long
term (high confidence). Integrated responses can harness synergies for
sustainable development and reduce trade-offs (high confidence). Shifting
development pathways towards sustainability and advancing climate
resilient development is enabled when governments, civil society
and the private sector make development choices that prioritise risk
reduction, equity and justice, and when decision-making processes,
finance and actions are integrated across governance levels, sectors
and timeframes (very high confidence) (see also Figure 4.2). Inclusive
processes involving local knowledge and Indigenous Knowledge
increase these prospects (high confidence). However, opportunities
for action differ substantially among and within regions, driven by
historical and ongoing patterns of development (very high confidence).
Accelerated financial support for developing countries is critical to enhance
mitigation and adaptation action (high confidence). {WGII SPM C.5.4,
WGII SPM D.1, WGII SPM D.1.1, WGII SPM D.1.2, WGII SPM D.2,
WGII SPM D.3, WGII SPM D.5, WGII SPM D.5.1, WGII SPM D.5.2;
WGIII SPM D.1, WGIII SPM D.2, WGIII SPM D.2.4, WGIII SPM E.2.2,
WGIII SPM E.2.3, WGIII SPM E.5.3, WGIII Cross-Chapter Box 5}
Policies that shift development pathways towards sustainability
can broaden the portfolio of available mitigation and adaptation
responses (medium confidence). Combining mitigation with action
to shift development pathways, such as broader sectoral policies,
approaches that induce lifestyle or behaviour changes, financial
regulation, or macroeconomic policies can overcome barriers and
open up a broader range of mitigation options (high confidence).
Integrated, inclusive planning and investment in everyday decision-
making about urban infrastructure can significantly increase the
adaptive capacity of urban and rural settlements. Coastal cities and
settlements play an important role in advancing climate resilient
development due to the high number of people living in the Low
Elevation Coastal Zone, the escalating and climate compounded risk
that they face, and their vital role in national economies and beyond
(high confidence). {WGII SPM.D.3, WGII SPM D.3.3; WGIII SPM E.2,
WGIII SPM E.2.2; SR1.5 SPM D.6}
Observed adverse impacts and related losses and damages,
projected risks, trends in vulnerability, and adaptation limits
demonstrate that transformation for sustainability and climate
resilient development action is more urgent than previously
assessed (very high confidence). Climate resilient development
integrates adaptation and GHG mitigation to advance
sustainable development for all. Climate resilient development
pathways have been constrained by past development, emissions and
climate change and are progressively constrained by every increment
of warming, in particular beyond 1.5°C (very high confidence).
Climate resilient development will not be possible in some regions
and sub-regions if global warming exceeds 2°C (medium confidence).
Safeguarding biodiversity and ecosystems is fundamental to climate
resilient development, but biodiversity and ecosystem services have
limited capacity to adapt to increasing global warming levels, making
climate resilient development progressively harder to achieve beyond
1.5°C warming (very high confidence). {WGII SPM D.1, WGII SPM D.1.1,
WGII SPM D.4, WGII SPM D.4.3, WGII SPM D.5.1; WGIII SPM D.1.1}
The cumulative scientific evidence is unequivocal: climate change
is a threat to human well-being and planetary health (very
high confidence). Any further delay in concerted anticipatory
global action on adaptation and mitigation will miss a brief and
rapidly closing window of opportunity to secure a liveable and
sustainable future for all (very high confidence). Opportunities for
near-term action are assessed in the following section. {WGII SPM D.5.3;
WGIII SPM D.1.1}

Section 4 : Near-Term Responses in a Changing Climate

4.1 The Timing and Urgency of Climate Action

Deep, rapid, and sustained mitigation and accelerated implementation of adaptation reduces the risks of climate
change for humans and ecosystems. In modelled pathways that limit warming to 1.5°C (>50%) with no or limited
overshoot and in those that limit warming to 2°C (>67%) and assume immediate action, global GHG emissions
are projected to peak in the early 2020s followed by rapid and deep reductions. As adaptation options often have
long implementation times, accelerated implementation of adaptation, particularly in this decade, is important
to close adaptation gaps. (high confidence)

The magnitude and rate of climate change and associated risks
depend strongly on near-term mitigation and adaptation actions
(very high confidence). Global warming is more likely than not to reach
1.5°C between 2021 and 2040 even under the very low GHG emission
scenarios (SSP1-1.9), and likely or very likely to exceed 1.5°C under
higher emissions scenarios141. Many adaptation options have medium
or high feasibility up to 1.5°C (medium to high confidence, depending
on option), but hard limits to adaptation have already been reached
in some ecosystems and the effectiveness of adaptation to reduce
climate risk will decrease with increasing warming (high confidence).
Societal choices and actions implemented in this decade determine the
extent to which medium- and long-term pathways will deliver higher or
lower climate resilient development (high confidence). Climate resilient
development prospects are increasingly limited if current greenhouse
gas emissions do not rapidly decline, especially if 1.5°C global warming
is exceeded in the near term (high confidence). Without urgent, effective
and equitable adaptation and mitigation actions, climate change
increasingly threatens the health and livelihoods of people around
the globe, ecosystem health, and biodiversity, with severe adverse
consequences for current and future generations (high confidence).
{WGI SPM B.1.3, WGI SPM B.5.1, WGI SPM B.5.2; WGII SPM A, WGII
SPM B.4, WGII SPM C.2, WGII SPM C.3.3, WGII Figure SPM.4, WGII SPM
D.1, WGII SPM D.5, WGIII SPM D.1.1 SR1.5 SPM D.2.2}. (Cross-Section
Box.2, Figure 2.1, Figure 2.3)

In modelled pathways that limit warming to 1.5°C (>50%) with
no or limited overshoot and in those that limit warming to
2°C (>67%), assuming immediate actions, global GHG emissions
are projected to peak in the early 2020s followed by rapid and
deep GHG emissions reductions (high confidence) 142
. In pathways
that limit warming to 1.5°C (>50%) with no or limited overshoot, net
global GHG emissions are projected to fall by 43 [34 to 60]%143 below
2019 levels by 2030, 60 [49 to 77]% by 2035, 69 [58 to 90]% by 2040
and 84 [73 to 98]% by 2050 (high confidence) (Section 2.3.1, Table 2.2,
Figure 2.5, Table 3.1)144. Global modelled pathways that limit warming
to 2°C (>67%) have reductions in GHG emissions below 2019 levels
of 21 [1 to 42]% by 2030, 35 [22 to 55] % by 2035, 46 [34 to 63]
% by 2040 and 64 [53 to 77]% by 2050145 (high confidence). Global
GHG emissions associated with NDCs announced prior to COP26 would
make it likely that warming would exceed 1.5°C (high confidence)
and limiting warming to 2°C (>67%) would then imply a rapid
acceleration of emission reductions during 2030–2050, around
70% faster than in pathways where immediate action is taken to
limit warming to 2°C (>67%) (medium confidence) (Section 2.3.1)
Continued investments in unabated high-emitting infrastructure146 and
limited development and deployment of low-emitting alternatives
prior to 2030 would act as barriers to this acceleration and increase
feasibility risks (high confidence). {WGIII SPM B.6.3, WGIII 3.5.2,
WGIII SPM B.6, WGIII SPM B.6., WGIII SPM C.1, WGIII SPM C1.1,
WGIII Table SPM.2} (Cross-Section Box.2)

All global modelled pathways that limit warming to 2°C (>67%)
or lower by 2100 involve reductions in both net CO 2 emissions
and non-CO 2 emissions (see Figure 3.6) (high confidence).
For example, in pathways that limit warming to 1.5°C (>50%)
with no or limited overshoot, global CH4 (methane) emissions are
reduced by 34 [21 to 57]% below 2019 levels by 2030 and by
44 [31 to 63]% in 2040 (high confidence). Global CH 4 emissions
are reduced by 24 [9 to 53]% below 2019 levels by 2030 and by
37 [20 to 60]% in 2040 in modelled pathways that limit warming to
2°C with action starting in 2020 (>67%) (high confidence). {WGIII SPM
C1.2, WGIII Table SPM.2, WGIII 3.3; SR1.5 SPM C.1, SR1.5 SPM C.1.2}
(Cross-Section Box.2)
All global modelled pathways that limit warming to 2°C (>67%)
or lower by 2100 involve GHG emission reductions in all sectors
(high confidence). The contributions of different sectors vary across
modelled mitigation pathways. In most global modelled mitigation
pathways, emissions from land-use, land-use change and forestry, via
reforestation and reduced deforestation, and from the energy supply
sector reach net zero CO2 emissions earlier than the buildings, industry
and transport sectors (Figure 4.1). Strategies can rely on combinations
of different options (Figure 4.1, Section 4.5), but doing less in one
sector needs to be compensated by further reductions in other sectors if
warming is to be limited. (high confidence) {WGIII SPM C.3, WGIII SPM
C.3.1, WGIII SPM 3.2, WGIII SPM C.3.3} (Cross-Section Box.2)
Without rapid, deep and sustained mitigation and accelerated
adaptation actions, losses and damages will continue to
increase, including projected adverse impacts in Africa, LDCs,
SIDS, Central and South America147
, Asia and the Arctic, and will
disproportionately affect the most vulnerable populations (high
confidence). {WGII SPM C.3.5, WGII SPM B.2.4, WGII 12.2, WGII 10.
Box 10.6, WGII TS D.7.5, WGII Cross-Chapter Box 6 ES, WGII Global
to Regional Atlas Annex A1.15, WGII Global to Regional Atlas Annex
A1.27; SR1.5 SPM B.5.3, SR 1.5 SPM B.5.7; SRCCL A.5.6} (Figure 3.2;
Figure 3.3)

The transition towards net zero CO2 will
have different pace across different sectors
CO2 emissions from the electricity/fossil fuel industries sector and
land-use change generally reach net zero earlier than other sectors

a) Sectoral emissions in pathways that limit warming to 1.5°C
b) Greenhouse gas emissions by sector at the time of net zero CO2 , compared to 2019

Figure 4.1: Sectoral emissions in pathways that limit warming to 1.5°C. Panel (a) shows sectoral CO2 and non-CO2 emissions in global modelled pathways that limit
warming to 1.5°C (>50%) with no or limited overshoot. The horizontal lines illustrate halving 2015 emissions (base year of the pathways) (dashed) and reaching net zero emissions
(solid line). The range shows the 5–95th percentile of the emissions across the pathways. The timing strongly differs by sector, with the CO2 emissions from the electricity/fossil fuel
industries sector and land-use change generally reaching net zero earlier. Non-CO2 emissions from agriculture are also substantially reduced compared to pathways without climate
policy but do not typically reach zero. Panel (b) Although all pathways include strongly reduced emissions, there are different pathways as indicated by the illustrative mitigation
pathways used in IPCC WGIII. The pathways emphasise routes consistent with limiting warming to 1.5°C with a high reliance on net negative emissions (IMP-Neg), high resource
efficiency (IMP-LD), a focus on sustainable development (IMP-SP) or renewables (IMP-Ren) and consistent with 2°C based on a less rapid introduction of mitigation measures followed
by a subsequent gradual strengthening (IMP-GS). Positive (solid filled bars) and negative emissions (hatched bars) for different illustrative mitigation pathways are compared to
GHG emissions from the year 2019. The category “energy supply (including electricity)” includes bioenergy with carbon capture and storage and direct air carbon capture and storage.
{WGIII Box TS.5, WGIII 3.3, WGIII 3.4, WGIII 6.6, WGIII 10.3, WGIII 11.3} (Cross-Section Box.2)

4.2 Benefits of Strengthening Near-Term Action

Accelerated implementation of adaptation will improve well-being by reducing losses and damages, especially
for vulnerable populations. Deep, rapid, and sustained mitigation actions would reduce future adaptation costs
and losses and damages, enhance sustainable development co-benefits, avoid locking-in emission sources,
and reduce stranded assets and irreversible climate changes. These near-term actions involve higher up-front
investments and disruptive changes, which can be moderated by a range of enabling conditions and removal or
reduction of barriers to feasibility. (high confidence)

Accelerated implementation of adaptation responses will bring
benefits to human well-being (high confidence) (Section 4.3). As
adaptation options often have long implementation times, long-term
planning and accelerated implementation, particularly in this decade, is
important to close adaptation gaps, recognising that constraints remain
for some regions. The benefits to vulnerable populations would be high
(see Section 4.4). (high confidence) {WGI SPM B.1, WGI SPM B.1.3, WGI
SPM B.2.2, WGI SPM B.3; WGII SPM C.1.1, WGII SPM C.1.2, WGII SPM
C.2, WGII SPM C.3.1, WGII Figure SPM.4b; SROCC SPM C.3.4, SROCC
Figure 3.4, SROCC Figure SPM.5}
Near-term actions that limit global warming to close to 1.5°C
would substantially reduce projected losses and damages related
to climate change in human systems and ecosystems, compared
to higher warming levels, but cannot eliminate them all (very
high confidence). The magnitude and rate of climate change and
associated risks depend strongly on near-term mitigation and adaptation
actions, and projected adverse impacts and related losses and damages
escalate with every increment of global warming (very high confidence).
Delayed mitigation action will further increase global warming which
will decrease the effectiveness of many adaptation options, including
Ecosystem-based Adaptation and many water-related options, as well
as increasing mitigation feasibility risks, such as for options based on
ecosystems (high confidence). Comprehensive, effective, and innovative
responses integrating adaptation and mitigation can harness synergies
and reduce trade-offs between adaptation and mitigation, as well as in
meeting requirements for financing (very high confidence) (see Section
4.5, 4.6, 4.8 and 4.9). {WGII SPM B.3, WGII SPM B.4, WGII SPM B.6.2,
WGII SPM C.2, WGII SPM C.3, WGII SPM D.1, WGII SPM D.4.3, WGII SPM D.5,
WG II TS D.1.4, WG II TS.D.5, WGII TS D.7.5; WGIII SPM B.6.3,WGIII SPM B.6.4,
WGIII SPM C.9, WGIII SPM D.2, WGIII SPM E.13; SR1.5 SPM C.2.7,
SR1.5 D.1.3, SR1.5 D.5.2}
Mitigation actions will have other sustainable development
co-benefits (high confidence). Mitigation will improve air quality and
human health in the near term notably because many air pollutants are
co-emitted by GHG emitting sectors and because methane emissions
leads to surface ozone formation (high confidence). The benefits from
air quality improvement include prevention of air pollution-related
premature deaths, chronic diseases and damages to ecosystems
and crops. The economic benefits for human health from air quality
improvement arising from mitigation action can be of the same order
of magnitude as mitigation costs, and potentially even larger (medium
confidence). As methane has a short lifetime but is a potent GHG,
strong, rapid and sustained reductions in methane emissions can limit
near-term warming and improve air quality by reducing global surface
ozone (high confidence). {WGI SPM D.1.7, WGI SPM D.2.2, WGI 6.7,
WGI TS Box TS.7, WGI 6 Box 6.2, WGI Figure 6.3, WGI Figure 6.16,
WGI Figure 6.17; WGII TS.D.8.3, WGII Cross-Chapter Box HEALTH,
WGII 5 ES, WGII 7 ES; WGII 7.3.1.2; WGIII Figure SPM.8, WGIII SPM
C.2.3, WGIII SPM C.4.2, WGIII TS.4.2}
Challenges from delayed adaptation and mitigation actions
include the risk of cost escalation, lock-in of infrastructure,
stranded assets, and reduced feasibility and effectiveness
of adaptation and mitigation options (high confidence). The
continued installation of unabated fossil fuel148 infrastructure
will ‘lock-in’ GHG emissions (high confidence). Limiting global
warming to 2°C or below will leave a substantial amount of fossil fuels
unburned and could strand considerable fossil fuel infrastructure
(high confidence), with globally discounted value projected to be
around USD 1 to 4 trillion from 2015 to 2050 (medium confidence).
Early actions would limit the size of these stranded assets, whereas
delayed actions with continued investments in unabated high-emitting
infrastructure and limited development and deployment of low-emitting
alternatives prior to 2030 would raise future stranded assets to the
higher end of the range – thereby acting as barriers and increasing
political economy feasibility risks that may jeopardise efforts to limit
global warming. (high confidence). {WGIII SPM B.6.3, WGIII SPM C.4,
WGIII Box TS.8}

Scaling-up near-term climate actions (Section 4.1) will mobilise a
mix of low-cost and high-cost options. High-cost options, as in energy
and infrastructure, are needed to avoid future lock-ins, foster innovation
and initiate transformational changes (Figure 4.4). Climate resilient
development pathways in support of sustainable development for all are
shaped by equity, and social and climate justice (very high confidence).
Embedding effective and equitable adaptation and mitigation in
development planning can reduce vulnerability, conserve and restore
ecosystems, and enable climate resilient development. This is especially
challenging in localities with persistent development gaps and limited
resources. (high confidence) {WGII SPM C.5, WGII SPM D1; WGIII TS.5.2,
WGIII 8.3.1, WGIII 8.3.4, WGIII 8.4.1, WGIII 8.6}
Scaling-up climate action may generate disruptive changes in
economic structure with distributional consequences and need
to reconcile divergent interests, values and worldviews, within
and between countries. Deeper fiscal, financial, institutional and
regulatory reforms can offset such adverse effects and unlock mitigation
potentials. Societal choices and actions implemented in this decade will
determine the extent to which medium and long-term development
pathways will deliver higher or lower climate resilient development
outcomes. (high confidence) {WGII SPM D.2, WGII SPM D.5, WGII Box TS.8;
WGIII SPM D.3, WGIII SPM E.2, WGIII SPM E.3, WGIII SPM E.4, WGIII TS.2,
WGIII TS.4.1, WGIII TS.6.4, WGIII 15.2, WGIII 15.6}
Enabling conditions would need to be strengthened in the near-
term and barriers reduced or removed to realise opportunities
for deep and rapid adaptation and mitigation actions and
climate resilient development (high confidence) (Figure 4.2).
These enabling conditions are differentiated by national, regional
and local circumstances and geographies, according to capabilities,
and include: equity and inclusion in climate action (see Section 4.4),
rapid and far-reaching transitions in sectors and system (see Section
4.5), measures to achieve synergies and reduce trade-
offs with sustainable development goals (see Section 4.6),
governance and policy improvements (see Section 4.7), access
to finance, improved international cooperation and technology
improvements (see Section 4.8), and integration of near-term
actions across sectors, systems and regions (see Section 4.9).
{WGII SPM D.2; WGIII SPM E.1, WGIII SPM E.2}
Barriers to feasibility would need to be reduced or removed
to deploy mitigation and adaptation options at scale. Many
limits to feasibility and effectiveness of responses can be overcome
by addressing a range of barriers, including economic, technological,
institutional, social, environmental and geophysical barriers. The
feasibility and effectiveness of options increase with integrated,
multi-sectoral solutions that differentiate responses based on climate
risk, cut across systems and address social inequities. Strengthened
near-term actions in modelled cost-effective pathways that limit global
warming to 2°C or lower, reduce the overall risk to the feasibility of the
system transitions, compared to modelled pathways with delayed or
uncoordinated action. (high confidence) {WGII SPM C.2, WGII SPM C.3,
WGII SPM C.5; WGIII SPM E.1, WGIII SPM E.1.3}
Integrating ambitious climate actions with macroeconomic
policies under global uncertainty would provide benefits
(high confidence). This encompasses three main directions:
(a) economy-wide mainstreaming packages supporting options to
improved sustainable low-emission economic recovery, development
and job creation programs (Sections 4.4, 4.5, 4.6, 4.8, 4.9) (b) safety
nets and social protection in the transition (Section 4.4, 4.7); and
(c) broadened access to finance, technology and capacity-building
and coordinated support to low-emission infrastructure (‘leap-frog’
potential), especially in developing regions, and under debt stress
(high confidence). (Section 4.8) {WGII SPM C.2, WGII SPM C.4.1,
WGII SPM D.1.3, WGII SPM D.2, WGII SPM D.3.2, WGII SPM E.2.2,
WGII SPM E.4, WGII SPM TS.2, WGII SPM TS.5.2, WGII TS.6.4,
WGII TS.15, WGII TS Box TS.3; WGIII SPM B.4.2, WGIII SPM C.5.4,
WGIII SPM C.6.2, WGIII SPM C.12.2, WGIII SPM D.3.4, WGIII SPM E.4.2,
WGIII SPM E.4.5, WGIII SPM E.5.2, WGIII SPM E.5.3, WGIII TS.1, WGIII Box TS.15,
WGIII 15.2, WGIII Cross-Chapter Box 1 on COVID in Chapter 1}

There is a rapidly narrowing window of opportunity to enable climate resilient development
Multiple interacting choices and actions can shift development pathways towards sustainability

Conditions that enable individual and collective actions:
• Inclusive governance
• Diverse knowledges and values
• Finance and innovation
• Integration across sectors and time scales
• Ecosystem stewardship
• Synergies between climate and development actions
• Behavioural change supported by policy, infrastructure and socio-cultural factors

Conditions that constrain individual and collective actions
• Poverty, inequity and injustice
• Economic, institutional, social and capacity barriers
• Siloed responses
• Lack of finance, and barriers to finance and technology
• Tradeoffs with SDGs

Figure 4.2: The illustrative development pathways (red to green) and associated outcomes (right panel) show that there is a rapidly narrowing window of
opportunity to secure a liveable and sustainable future for all. Climate resilient development is the process of implementing greenhouse gas mitigation and adaptation
measures to support sustainable development. Diverging pathways illustrate that interacting choices and actions made by diverse government, private sector and civil society actors
can advance climate resilient development, shift pathways towards sustainability, and enable lower emissions and adaptation. Diverse knowledges and values include cultural values,
Indigenous Knowledge, local knowledge, and scientific knowledge. Climatic and non-climatic events, such as droughts, floods or pandemics, pose more severe shocks to pathways
with lower climate resilient development (red to yellow) than to pathways with higher climate resilient development (green). There are limits to adaptation and adaptive capacity
for some human and natural systems at global warming of 1.5°C, and with every increment of warming, losses and damages will increase. The development pathways taken by
countries at all stages of economic development impact GHG emissions and hence shape mitigation challenges and opportunities, which vary across countries and regions.
Pathways and opportunities for action are shaped by previous actions (or inactions and opportunities missed, dashed pathway), and enabling and constraining conditions
(left panel), and take place in the context of climate risks, adaptation limits and development gaps. The longer emissions reductions are delayed, the fewer effective
adaptation options. {WGI SPM B.1; WGII SPM B.1 to B.5, WGII SPM C.2 to 5, WGII SPM D.1 to 5, WGII Figure SPM.3, WGII Figure SPM.4, WGII Figure SPM.5, WGII TS.D.5, WGII 3.1,
WGII 3.2, WGII 3.4, WGII 4.2, WGII Figure 4.4, WGII 4.5, WGII 4.6, WGII 4.9; WGIII SPM A, WGIII SPM B1, WGIII SPM B.3, WGIII SPM B.6, WGIII SPM C.4, WGIII SPM D1 to 3,
WGIII SPM E.1, WGIII SPM E.2, WGIII SPM E.4, WGIII SPM E.5, WGIII Figure TS.1, WGIII Figure TS.7, WGIII Box TS.3, WGIII Box TS.8, Cross-Working Group Box 1 in Chapter 3,
WGIII Cross-Chapter Box 5 in Chapter 4; SR1.5 SPM D.1 to 6; SRCCL SPM D.3}

4.3 Near-Term Risks

Many changes in the climate system, including extreme events, will become larger in the near term with increasing
global warming (high confidence). Multiple climatic and non-climatic risks will interact, resulting in increased
compounding and cascading impacts becoming more difficult to manage (high confidence). Losses and damages
will increase with increasing global warming (very high confidence), while strongly concentrated among the
poorest vulnerable populations (high confidence). Continuing with current unsustainable development patterns
would increase exposure and vulnerability of ecosystems and people to climate hazards (high confidence).

Global warming will continue to increase in the near term (2021–2040)
mainly due to increased cumulative CO 2 emissions in nearly all
considered scenarios and pathways. In the near term, every
region in the world is projected to face further increases in
climate hazards (medium to high confidence, depending on
region and hazard), increasing multiple risks to ecosystems
and humans (very high confidence). In the near term, natural
variability149 will modulate human-caused changes, either attenuating
or amplifying projected changes, especially at regional scales, with little
effect on centennial global warming. Those modulations are important
to consider in adaptation planning. Global surface temperature in any
single year can vary above or below the long-term human-induced
trend, due to natural variability. By 2030, global surface temperature
in any individual year could exceed 1.5°C relative to 1850–1900 with a
probability between 40% and 60%, across the five scenarios assessed
in WGI (medium confidence). The occurrence of individual years with
global surface temperature change above a certain level does not
imply that this global warming level has been reached. If a large
explosive volcanic eruption were to occur in the near term150 , it
would temporarily and partially mask human-caused climate change
by reducing global surface temperature and precipitation, especially
over land, for one to three years (medium confidence). {WGI SPM B.1.3,
WGI SPM B.1.4, WGI SPM C.1, WGI SPM C.2, WGI Cross-Section Box TS.1,
WGI Cross-Chapter Box 4.1; WGII SPM B.3, WGII SPM B.3.1;
WGIII Box SPM.1 Figure 1}

The level of risk for humans and ecosystems will depend on near-term
trends in vulnerability, exposure, level of socio-economic
development and adaptation (high confidence). In the near term,
many climate-associated risks to natural and human systems depend
more strongly on changes in these systems’ vulnerability and exposure
than on differences in climate hazards between emissions scenarios
(high confidence). Future exposure to climatic hazards is increasing
globally due to socio-economic development trends including growing
inequality, and when urbanisation or migration increase exposure
(high confidence). Urbanisation increases hot extremes (very high
confidence) and precipitation runoff intensity (high confidence).
Increasing urbanisation in low-lying and coastal zones will be a major
driver of increasing exposure to extreme riverflow events and sea level
rise hazards, increasing risks (high confidence) (Figure 4.3). Vulnerability
will also rise rapidly in low-lying Small Island Developing States and
atolls in the context of sea level rise (high confidence) (see Figure 3.4 and
Figure 4.3). Human vulnerability will concentrate in informal settlements
and rapidly growing smaller settlements; and vulnerability in rural
areas will be heightened by reduced habitability and high reliance on
climate-sensitive livelihoods (high confidence). Human and ecosystem
vulnerability are interdependent (high confidence). Vulnerability to
climate change for ecosystems will be strongly influenced by past,
present, and future patterns of human development, including from
unsustainable consumption and production, increasing demographic
pressures, and persistent unsustainable use and management of
land, ocean, and water (high confidence). Several near-term risks can
be moderated with adaptation (high confidence). {WGI SPM C.2.6;
WGII SPM B.2, WGII SPM B.2.3, WGII SPM B.2.5, WGII SPM B.3,
WGII SPM B.3.2, WGII TS.C.5.2} (Section 4.5 and 3.2)

Principal hazards and associated risks expected in the near term
(at 1.5°C global warming) are:
• Increased intensity and frequency of hot extremes and dangerous
heat-humidity conditions, with increased human mortality, morbidity,
and labour productivity loss (high confidence). {WGI SPM B.2.2,
WGI TS Figure TS.6; WGII SPM B.1.4, WGII SPM B.4.4,
WGII Figure SPM.2}
• Increasing frequency of marine heatwaves will increase risks
of biodiversity loss in the oceans, including from mass mortality
events (high confidence). {WGI SPM B.2.3; WGII SPM B.1.2,
WGII Figure SPM.2; SROCC SPM B.5.1}
• Near-term risks for biodiversity loss are moderate to high in
forest ecosystems (medium confidence) and kelp and seagrass
ecosystems (high to very high confidence) and are high to very
high in Arctic sea-ice and terrestrial ecosystems (high confidence)
and warm-water coral reefs (very high confidence). {WGII SPM B.3.1}
• More intense and frequent extreme rainfall and associated flooding
in many regions including coastal and other low-lying cities
(medium to high confidence), and increased proportion of and
peak wind speeds of intense tropical cyclones (high confidence).
{WGI SPM B.2.4, WGI SPM C.2.2, WGI SPM C.2.6, WGI 11.7}
• High risks from dryland water scarcity, wildfire damage, and
permafrost degradation (medium confidence). {SRCCL SPM A.5.3.}
• Continued sea level rise and increased frequency and
magnitude of extreme sea level events encroaching on coastal
human settlements and damaging coastal infrastructure (high
confidence), committing low-lying coastal ecosystems to
submergence and loss (medium confidence), expanding land
salinization (very high confidence), with cascading to risks to
livelihoods, health, well-being, cultural values, food and water
security (high confidence). {WGI SPM C.2.5, WGI SPM C.2.6;
WGII SPM B.3.1, WGII SPM B.5.2; SRCCL SPM A.5.6; SROCC SPM B.3.4,
SROCC SPM 3.6, SROCC SPM B.9.1} (Figure 3.4, 4.3)
• Climate change will significantly increase ill health and premature
deaths from the near to long term (high confidence). Further
warming will increase climate-sensitive food-borne, water-borne,
and vector-borne disease risks (high confidence), and mental health
challenges including anxiety and stress (very high confidence).
{WGII SPM B.4.4}
• Cryosphere-related changes in floods, landslides, and water
availability have the potential to lead to severe consequences for
people, infrastructure and the economy in most mountain regions
(high confidence). {WGII TS C.4.2}
• The projected increase in frequency and intensity of heavy
precipitation (high confidence) will increase rain-generated local
flooding (medium confidence). {WGI Figure SPM.6, WGI SPM B.2.2;
WGII TS C.4.5}

Multiple climate change risks will increasingly compound and
cascade in the near term (high confidence). Many regions are
projected to experience an increase in the probability of compound
events with higher global warming (high confidence) including
concurrent heatwaves and drought. Risks to health and food
production will be made more severe from the interaction of sudden
food production losses from heat and drought, exacerbated by heat-
induced labour productivity losses (high confidence) (Figure 4.3). These
interacting impacts will increase food prices, reduce household incomes,
and lead to health risks of malnutrition and climate-related mortality
with no or low levels of adaptation, especially in tropical regions (high
confidence). Concurrent and cascading risks from climate change to
food systems, human settlements, infrastructure and health will make
these risks more severe and more difficult to manage, including when
interacting with non-climatic risk drivers such as competition for land
between urban expansion and food production, and pandemics (high
confidence). Loss of ecosystems and their services has cascading and
long-term impacts on people globally, especially for Indigenous Peoples
and local communities who are directly dependent on ecosystems, to
meet basic needs (high confidence). Increasing transboundary risks
are projected across the food, energy and water sectors as impacts
from weather and climate extremes propagate through supply-chains,
markets, and natural resource flows (high confidence) and may interact
with impacts from other crises such as pandemics. Risks also arise from
some responses intended to reduce the risks of climate change, including
risks from maladaptation and adverse side effects of some emissions
reduction and carbon dioxide removal measures, such as afforestation of
naturally unforested land or poorly implemented bioenergy compounding
climate-related risks to biodiversity, food and water security, and
livelihoods (high confidence) (see Section 3.4.1 and 4.5). {WGI SPM.2.7;
WGII SPM B.2.1, WGII SPM B.5, WGII SPM B.5.1, WGII SPM B.5.2,
WGII SPM B.5.3, WGII SPM B.5.4, WGII Cross-Chapter Box COVID in Chapter 7;
WGIII SPM C.11.2; SRCCL SPM A.5, SRCCL SPM A.6.5} (Figure 4.3)
With every increment of global warming losses and damages will
increase (very high confidence), become increasingly difficult
to avoid and be strongly concentrated among the poorest
vulnerable populations (high confidence). Adaptation does not
prevent all losses and damages, even with effective adaptation and
before reaching soft and hard limits. Losses and damages will be
unequally distributed across systems, regions and sectors and are
not comprehensively addressed by current financial, governance and
institutional arrangements, particularly in vulnerable developing
countries. (high confidence). {WGII SPM B.4, WGII SPM C.3, WGII SPM C.3.5}