Summary for Policymakers

Transcript

1 INTERGOVERNMENTAL PANEL ON climate change WG II WORKING GROUP II CONTRIBUTION TO THE FIFTH ASSESSMENT REPORT OF THE INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE

2 Summary for Policymakers SPM Drafting Authors: Christopher B. Field (USA), Vicente R. Barros (Argentina), Michael D. Mastrandrea (USA), Katharine J. Mach (USA), Mohamed A.-K. Abdrabo (Egypt), W. Neil Adger (UK), Yury A. Anokhin (Russian Federation), Oleg A. Anisimov (Russian Federation), Douglas J. Arent (USA), Jonathon Barnett (Australia), Virginia R. Burkett (USA), Rongshuo Cai (China), Monalisa Chatterjee (USA/India), Stewart J. Cohen (Canada), Wolfgang Cramer (Germany/France), Purnamita Dasgupta (India), Debra J. Davidson (Canada), Fatima Denton (Gambia), Petra Döll (Germany), Kirstin Dow (USA), Yasuaki Hijioka (Japan), Ove Hoegh-Guldberg (Australia), Richard G. Jones (UK), Roger N. Jones (Australia), Roger L. Kitching (Australia), R. Sari Kovats (UK), Joan Nymand Larsen (Iceland), Erda Lin (China), David B. Lobell (USA), Iñigo J. Losada (Spain), Graciela O. Magrin (Argentina), José A. Marengo (Brazil), Anil Markandya (Spain), Bruce A. McCarl (USA), Roger F. McLean (Australia), Linda O. Mearns (USA), Guy F. Midgley (South Africa), Nobuo Mimura (Japan), John F. Morton (UK), Isabelle Niang (Senegal), Ian R. Noble (Australia), Leonard A. Nurse (Barbados), Karen L. O’Brien (Norway), Taikan Oki (Japan), Lennart Olsson (Sweden), Michael Oppenheimer (USA), Jonathan T. Overpeck (USA), Joy J. Pereira (Malaysia), Elvira S. Poloczanska (Australia), John R. Porter (Denmark), Hans-O. Pörtner (Germany), Michael J. Prather (USA), Roger S. Pulwarty (USA), Andy Reisinger (New Zealand), Aromar Revi (India), Patricia Romero-Lankao (Mexico), Oliver C. Ruppel (Namibia), David E. Satterthwaite (UK), Daniela N. Schmidt (UK), Josef Settele (Germany), Kirk R. Smith (USA), Dáithí A. Stone (Canada/South Africa/USA), Avelino G. Suarez (Cuba), Petra Tschakert (USA), Riccardo Valentini (Italy), Alicia Villamizar (Venezuela), Rachel Warren (UK), Thomas J. Wilbanks (USA), Poh Poh Wong (Singapore), Alistair Woodward (New Zealand), Gary W. Yohe (USA) This Summary for Policymakers should be cited as: Climate Change 2014: Impacts, Adaptation, and Vulnerability. , 2014: Summary for policymakers. In: IPCC Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the [Field, C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. Mastrandrea, Intergovernmental Panel on Climate Change T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1-32. 1

3 Summary for Policymakers Contents Assessing and Managing the Risks of Climate Change ... 3 Background Box SPM.1. Context for the Assessment ... 4 Background Box SPM.2. Terms Central for Understanding the Summary ... 5 Background Box SPM.3. Communication of the Degree of Certainty in Assessment Findings ... 6 A: Observed Impacts, Vulnerability, and Adaptation in a Complex and Changing World ... 4 A-1. Observed Impacts, Vulnerability, and Exposure ... 4 A-2. Adaptation Experience ... 8 A-3. The Decision-making Context ... 9 B: Future Risks and Opportunities for Adaptation ... 11 11 B-1. Key Risks across Sectors and Regions ... 12 Assessment Box SPM.1. Human Interference with the Climate System ... B-2. Sectoral Risks and Potential for Adaptation ... 14 B-3. Regional Key Risks and Potential for Adaptation ... 20 Assessment Box SPM.2. Regional Key Risks ... 21 C: Managing Future Risks and Building Resilience ... 25 C-1. Principles for Effective Adaptation ... 25 C-2. Climate-resilient Pathways and Transformation ... 28 30 Supplementary Material ... 2

4 Summary for Policymakers ASSESSING AND MANAGING THE RISKS OF CLIMATE CHANGE 1 Human interference with the climate system is occurring, and climate change poses risks for human and natural systems (Figure SPM.1). The assessment of impacts, adaptation, and vulnerability in the Working Group II contribution to the IPCC’s Fifth Assessment Report (WGII AR5) evaluates how patterns of risks and potential benefits are shifting due to climate change. It considers how impacts and risks related to climate S M P change can be reduced and managed through adaptation and mitigation. The report assesses needs, options, opportunities, constraints, resilience, limits, and other aspects associated with adaptation. Climate change involves complex interactions and changing likelihoods of diverse impacts. A focus on risk, which is new in this report, supports decision making in the context of climate change and complements other elements of the report. People and societies may perceive or rank risks and potential benefits differently, given diverse values and goals. Compared to past WGII reports, the WGII AR5 assesses a substantially larger knowledge base of relevant scientific, technical, and socioeconomic literature. Increased literature has facilitated comprehensive assessment across a broader set of topics and sectors, with expanded coverage of 2 human systems, adaptation, and the ocean. See Background Box SPM.1. Section A of this summary characterizes observed impacts, vulnerability and exposure, and adaptive responses to date. Section B examines future risks and potential benefits. Section C considers principles for effective adaptation and the broader interactions among adaptation, mitigation, IMPACTS Vulnerability SOCIOECONOMIC CLIMATE PROCESSES onomic Socioec Natural Pathways Variability ds Hazar Adaptation and R RISK Mitigation Anthropogenic Actions Climate Change Governance osure Exp EMISSIONS and Land-use Change re SPM.1 | Illustration of the core concepts of the WGII AR5. Risk of climate-related impacts results from the interaction of climate-related hazards (including hazardous Figu sses including events and trends) with the vulnerability and exposure of human and natural systems. Changes in both the climate system (left) and socioeconomic proce adapt ation and mitigation (right) are drivers of hazards, exposure, and vulnerability. [19.2, Figure 19-1] 1 t A key finding of the WGI AR5 is, “It is e x that human influence has been the dominant cause of the observed warming since the mid-20th century.” r e m e l y l i k e l y [WGI AR5 SPM Section D.3, 2.2, 6.3, 10.3-6, 10.9] 2 1.1, Figure 1-1 3

5 Summary for Policymakers Background Box SPM.1 | Context for the Assessment For the past 2 decades, IPCC’s Working Group II has developed assessments of climate-change impacts, adaptation, and vulnerability. The WGII AR5 builds from the WGII contribution to the IPCC’s Fourth Assessment Report (WGII AR4), published in 2007, and the Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX), published in S P M 3 2012. It follows the Working Group I contribution to the AR5 (WGI AR5). The number of scientific publications available for assessing climate-change impacts, adaptation, and vulnerability more than doubled between 2005 and 2010, with especially rapid increases in publications related to adaptation. Authorship of climate-change 4 publications from developing countries has increased, although it still represents a small fraction of the total. The WGII AR5 is presented in two parts (Part A: Global and Sectoral Aspects, and Part B: Regional Aspects), reflecting the expanded literature basis and multidisciplinary approach, increased focus on societal impacts and responses, and continued regionally comprehensive coverage. and sustainable development. Background Box SPM.2 defines central concepts, and Background Box SPM.3 introduces terms used to convey the degree of certainty in key findings. Chapter references in brackets and in footnotes indicate support for findings, figures, and tables. A: OBSERVED IMPACTS, VULNERABILITY, AND ADAPTATION IN A COMPLEX AND CHANGING WORLD A-1. Observed Impacts, Vulnerability, and Exposure In recent decades, changes in climate have caused impacts on natural and human systems on all continents and across the Evidence of climate-change impacts is strongest and most comprehensive for natural systems. Some impacts on human systems have oceans. 5 to climate change, with a major or minor contribution of climate change distinguishable from other influences. See also been attributed Figure SPM.2. Attribution of observed impacts in the WGII AR5 generally links responses of natural and human systems to observed climate 6 change, regardless of its cause. In many regions, changing precipitation or melting snow and ice are altering hydrological systems, affecting water resources in ), high confidence Glaciers continue to shrink almost worldwide due to climate change ( terms of quantity and quality ( ). m e d i u m c o n f i d e n c e ). Climate change is causing permafrost warming and thawing in high- medium confidence affecting runoff and water resources downstream ( 7 ). high confidence latitude regions and in high-elevation regions ( Many terrestrial, freshwater, and marine species have shifted their geographic ranges, seasonal activities, migration patterns, See Figure SPM.2B. While only a few recent n c ). n abundances, and species interactions in response to ongoing climate change ( h i g h c o e f i d e ), natural global climate change at rates slower than current high confidence species extinctions have been attributed as yet to climate change ( 8 ). high confidence anthropogenic climate change caused significant ecosystem shifts and species extinctions during the past millions of years ( Based on many studies covering a wide range of regions and crops, negative impacts of climate change on crop yields have The smaller number of studies showing positive impacts relate mainly to c ). h g i h been more common than positive impacts ( n f i d e n c e o 3 1.2-3 4 1.1, Figure 1-1 5 The term a t t r i b u t i o n is used differently in WGI and WGII. Attribution in WGII considers the links between impacts on natural and human systems and observed climate change, regardless of its cause. By comparison, attribution in WGI quantifies the links between observed climate change and human activity, as well as other external climate drivers. 6 18.1, 18.3-6 7 3.2, 4.3, 18.3, 18.5, 24.4, 26.2, 28.2, Tables 3-1 and 25-1, Figures 18-2 and 26-1 8 4.2-4, 5.3-4, 6.1, 6.3-4, 18.3, 18.5, 22.3, 24.4, 25.6, 28.2, 30.4-5, Boxes 4-2, 4-3, 25-3, CC-CR, and CC-MB 4

6 Summary for Policymakers 9 Background Box SPM.2 | Terms Central for Understanding the Summary Climate change refers to a change in the state of the climate that can be identified (e.g., by using statistical tests) limate change C : by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forcings such as modulations of the solar cycles, volcanic S P M eruptions, and persistent anthropogenic changes in the composition of the atmosphere or in land use. Note that the Framework Convention on Climate Change (UNFCCC), in its Article 1, defines climate change as: “a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.” The UNFCCC thus makes a distinction between climate change attributable to human activities altering the atmospheric composition, and climate variability attributable to natural causes. Hazard : The potential occurrence of a natural or human-induced physical event or trend or physical impact that may cause loss of life, injury, or other health impacts, as well as damage and loss to property, infrastructure, livelihoods, service provision, ecosystems, hazard usually refers to climate-related physical events or trends or their physical and environmental resources. In this report, the term impacts. Exposure : The presence of people, livelihoods, species or ecosystems, environmental functions, services, and resources, infrastructure, or economic, social, or cultural assets in places and settings that could be adversely affected. Vulnerability : The propensity or predisposition to be adversely affected. Vulnerability encompasses a variety of concepts and elements including sensitivity or susceptibility to harm and lack of capacity to cope and adapt. Impacts : Effects on natural and human systems. In this report, the term impacts is used primarily to refer to the effects on natural and human systems of extreme weather and climate events and of climate change. Impacts generally refer to effects on lives, livelihoods, health, ecosystems, economies, societies, cultures, services, and infrastructure due to the interaction of climate changes or hazardous climate events occurring within a specific time period and the vulnerability of an exposed society or system. Impacts are also referred to as outcomes . The impacts of climate change on geophysical systems, including floods, droughts, and consequences and sea level rise, are a subset of impacts called physical impacts. Risk : The potential for consequences where something of value is at stake and where the outcome is uncertain, recognizing the diversity of values. Risk is often represented as probability of occurrence of hazardous events or trends multiplied by the impacts if these events or trends occur. Risk results from the interaction of vulnerability, exposure, and hazard (see Figure SPM.1). In this report, risk is used primarily to refer to the risks of climate-change impacts. the term Adaptation : The process of adjustment to actual or expected climate and its effects. In human systems, adaptation seeks to moderate or avoid harm or exploit beneficial opportunities. In some natural systems, human intervention may facilitate adjustment to expected climate and its effects. Transformation : A change in the fundamental attributes of natural and human systems. Within this summary, transformation could reflect strengthened, altered, or aligned paradigms, goals, or values towards promoting adaptation for sustainable development, including poverty reduction. Resilience : The capacity of social, economic, and environmental systems to cope with a hazardous event or trend or disturbance, responding or reorganizing in ways that maintain their essential function, identity, and structure, while also maintaining the capacity for adaptation, learning, and transformation. high-latitude regions, though it is not yet clear whether the balance of impacts has been negative or positive in these regions ( high confidence ). Climate change has negatively affected wheat and maize yields for many regions and in the global aggregate ( ). Effects on medium confidence rice and soybean yield have been smaller in major production regions and globally, with a median change of zero across all available data, which are fewer for soy compared to the other crops. Observed impacts relate mainly to production aspects of food security rather than access 9 The WGII AR5 glossary defines many terms used across chapters of the report. Reflecting progress in science, some definitions differ in breadth and focus from the definitions used in the AR4 and other IPCC reports. 5

7 Summary for Policymakers 10 Background Box SPM.3 | Communication of the Degree of Certainty in Assessment Findings he degree of certainty in each key finding of the assessment is based on the type, amount, quality, and consistency of evidence (e.g., T data, mechanistic understanding, theory, models, expert judgment) and the degree of agreement. The summary terms to describe evidence are: limited , medium , or robust ; and agreement: low , medium , or high . S P M Confidence in the validity of a finding synthesizes the evaluation of evidence and agreement. Levels of confidence include five very high . , and high , qualifiers: , low , very low medium The likelihood, or probability, of some well-defined outcome having occurred or occurring in the future can be described quantitatively through the following terms: , 90–100%; , 95–100%; likely extremely likely , 99–100% probability; virtually certain very likely , 66–100%; , >50–100%; about as likely as not , 33–66%; unlikely , 0–33%; very unlikely , 0–10%; more likely than not , extremely unlikely 0–5%; and exceptionally unlikely , 0–1%. Unless otherwise indicated, findings assigned a likelihood term are associated with high or very high confidence . Where appropriate, findings are also formulated as statements of fact without using uncertainty qualifiers. Within paragraphs of this summary, the confidence, evidence, and agreement terms given for a bold key finding apply to subsequent statements in the paragraph, unless additional terms are provided. or other components of food security. See Figure SPM.2C. Since AR4, several periods of rapid food and cereal price increases following climate 11 extremes in key producing regions indicate a sensitivity of current markets to climate extremes among other factors ( medium confidence ). At present the worldwide burden of human ill-health from climate change is relatively small compared with effects of other However, there has been increased heat-related mortality and decreased cold-related mortality in some stressors and is not well quantified. medium confidence ). Local changes in temperature and rainfall have altered the distribution of some water- regions as a result of warming ( 12 borne illnesses and disease vectors ( ). medium confidence Differences in vulnerability and exposure arise from non-climatic factors and from multidimensional inequalities often produced See e ). These differences shape differential risks from climate change. c n e d i f by uneven development processes o c h g i h y r e v ( n Figure SPM.1. People who are socially, economically, culturally, politically, institutionally, or otherwise marginalized are especially vulnerable to medium evidence , high agreement ). This heightened vulnerability is climate change and also to some adaptation and mitigation responses ( rarely due to a single cause. Rather, it is the product of intersecting social processes that result in inequalities in socioeconomic status and income, as well as in exposure. Such social processes include, for example, discrimination on the basis of gender, class, ethnicity, age, and 13 (dis)ability. Impacts from recent climate-related extremes, such as heat waves, droughts, floods, cyclones, and wildfires, reveal significant c e ). g c o n h h f y r e v vulnerability and exposure of some ecosystems and many human systems to current climate variability ( i i e n d Impacts of such climate-related extremes include alteration of ecosystems, disruption of food production and water supply, damage to infrastructure and settlements, morbidity and mortality, and consequences for mental health and human well-being. For countries at all levels 14 of development, these impacts are consistent with a significant lack of preparedness for current climate variability in some sectors. Climate-related hazards exacerbate other stressors, often with negative outcomes for livelihoods, especially for people living in Climate-related hazards affect poor people’s lives directly through impacts on livelihoods, reductions in crop f i d e n c e ). poverty ( h i g h c o n 10 1.1, Box 1-1 11 7.2, 18.4, 22.3, 26.5, Figures 7-2, 7-3, and 7-7 12 11.4-6, 18.4, 25.8 13 8.1-2, 9.3-4, 10.9, 11.1, 11.3-5, 12.2-5, 13.1-3, 14.1-3, 18.4, 19.6, 23.5, 25.8, 26.6, 26.8, 28.4, Box CC-GC 14 3.2, 4.2-3, 8.1, 9.3, 10.7, 11.3, 11.7, 13.2, 14.1, 18.6, 22.3, 25.6-8, 26.6-7, 30.5, Tables 18-3 and 23-1, Figure 26-2, Boxes 4-3, 4-4, 25-5, 25-6, 25-8, and CC-CR 6

8 Summary for Policymakers RCTIC (A) A PE URO E S M P ORTH AMERICA N SIA A SMALL ISLANDS AFRICA CEN TRAL & SOUTH MERICA A USTRALASIA A ANTARCTIC Confidence in attribution Observed impacts attributed to climate change for climate change to Phy Human and managed systems Biological systems sical systems ciers, snow, ice, Gla Food production Terrestrial ecosystems and/or permafrost Regional-scale imp acts very very Riv ers, lakes, floods, Livelihoods, health, high med low Wildfire low high and/or drought and/or economics stal erosion Coa Marine ecosystems and/or sea level effects ind icates confidence range Minor contribution of climate change ined symbols = Outl Filled symbols = Major contribution of climate change (C) (B) ) ) e r e 2 e d d l (3) a o a c o c (13) (12) (10) (18) (27) (19) C e e Sta ndard error d d r r e e Mean p p 400 0 e ndard error Sta m g k n ( a e h c g n (13) % a ( h –2 t c c n a 100 o p (9) (29) (359) (111) i (20) t m i (46) u b (90) d i (29) l r e t −4 20 i s th (9) i Y 90 percentile D th percentile 75 0 r Median e −6 m r th entile perc 25 a –20 W th 10 percentile ) s s s s s e a n n a r k e e e n e a x o o e s t t c h h h a g a h i l s u s s k k a t t r l t a l fi fi fi n n o a l s ( o l a a c d y y y l l u i i . r A n n n m t p p h n c r t o o o o o c c e t i n c b b B o i v c y - e h l i Te m p e r ate Rice Tropical Soy Wheat Maize Z h t n h n B a i h t n t P o v n c e r n i N e a B e h B L t B n Crop Region type e B Figu Widespread impacts in a changing world. (A) Global patterns of impacts in recent decades attributed to climate change, based on studies since the AR4. Impacts re SPM.2 | are shown at a range of geographic scales. Symbols indicate categories of attributed impacts, the relative contribution of climate change (major or minor) to the observed impact, and confidence in at tribution. See supplementary Table SPM.A1 for descriptions of the impacts. (B) Average rates of change in distribution (km per decade) for marine taxonomic groups based on observations over 1900–2010. Positive distribution changes are consistent with warming (moving into previously cooler waters, generally poleward). The num ber of responses analyzed is given within parentheses for each category. (C) Summary of estimated impacts of observed climate change s on yields over 1960–2013 f or four major crops in temperate and tropical regions, with the number of data points analyzed given within parentheses for each category. [Figures 7-2, 18-3, and MB-2] 7

9 Summary for Policymakers ields, or destruction of homes and indirectly through, for example, increased food prices and food insecurity. Observed positive effects for poor y and marginalized people, which are limited and often indirect, include examples such as diversification of social networks and of agricultural 15 practices. S P M ). m d i u m e v i d e n c e , h i g h a g r e Violent conflict increases vulnerability to climate change ( m e n t e Large-scale violent conflict harms e 1 6 assets that facilitate adaptation, including infrastructure, institutions, natural resources, social capital, and livelihood opportunities. A-2. Adaptation Experience Throughout history, people and societies have adjusted to and coped with climate, climate variability, and extremes, with varying degrees of success. This section focuses on adaptive human responses to observed and projected climate-change impacts, which can also address broader risk-reduction and development objectives. h i g h c o n Adaptation is becoming embedded in some planning processes, with more limited implementation of responses ( i d e n c e ). f Engineered and technological options are commonly implemented adaptive responses, often integrated within existing programs such as disaster risk management and water management. There is increasing recognition of the value of social, institutional, and ecosystem-based measures and of the extent of constraints to adaptation. Adaptation options adopted to date continue to emphasize incremental adjustments and co- benefits and are starting to emphasize flexibility and learning ( ). Most assessments of adaptation have medium evidence , medium agreement been restricted to impacts, vulnerability, and adaptation planning, with very few assessing the processes of implementation or the effects of 17 , high agreement ). medium evidence adaptation actions ( h i g h c o n f i d e n c e ). Adaptation experience is accumulating across regions in the public and private sector and within communities ( Governments at various levels are starting to develop adaptation plans and policies and to integrate climate-change considerations Examples of adaptation across regions include the following: into broader development plans. • In Africa, most national governments are initiating governance systems for adaptation. Disaster risk management, adjustments in technologies and infrastructure, ecosystem-based approaches, basic public health measures, and livelihood diversification are reducing vulnerability, 18 although efforts to date tend to be isolated. • In Europe, adaptation policy has been developed across all levels of government, with some adaptation planning integrated into coastal 19 and water management, into environmental protection and land planning, and into disaster risk management. • In Asia, adaptation is being facilitated in some areas through mainstreaming climate adaptation action into subnational development 20 planning, early warning systems, integrated water resources management, agroforestry, and coastal reforestation of mangroves. • In Australasia, planning for sea level rise, and in southern Australia for reduced water availability, is becoming adopted widely. Planning for sea level rise has evolved considerably over the past 2 decades and shows a diversity of approaches, although its implementation remains 21 piecemeal. • In North America, governments are engaging in incremental adaptation assessment and planning, particularly at the municipal level. Some 22 proactive adaptation is occurring to protect longer-term investments in energy and public infrastructure. • In Central and South America, ecosystem-based adaptation including protected areas, conservation agreements, and community management of natural areas is occurring. Resilient crop varieties, climate forecasts, and integrated water resources management are 23 being adopted within the agricultural sector in some areas. 15 8.2-3, 9.3, 11.3, 13.1-3, 22.3, 24.4, 26.8 16 12.5, 19.2, 19.6 17 4.4, 5.5, 6.4, 8.3, 9.4, 11.7, 14.1, 14.3-4, 15.2-5, 17.2-3, 21.3, 21.5, 22.4, 23.7, 25.4, 26.8-9, 30.6, Boxes 25-1, 25-2, 25-9, and CC-EA 18 22.4 19 23.7, Boxes 5-1 and 23-3 20 24.4-6, 24.9 Box CC-TC 21 25.4, 25.10, Table 25-2, Boxes 25-1, 25-2, and 25-9 22 26.7-9 23 27.3 8

10 Summary for Policymakers In the Arctic, some communities have begun to deploy adaptive co-management strategies and communications infrastructure, combining • 2 4 traditional and scientific knowledge. • In small islands, which have diverse physical and human attributes, community-based adaptation has been shown to generate larger 25 benefits when delivered in conjunction with other development activities. S M P • In the ocean, international cooperation and marine spatial planning are starting to facilitate adaptation to climate change, with constraints 2 6 from challenges of spatial scale and governance issues. A-3. The Decision-making Context Climate variability and extremes have long been important in many decision-making contexts. Climate-related risks are now evolving over time due to both climate change and development. This section builds from existing experience with decision making and risk management. It creates a foundation for understanding the report’s assessment of future climate-related risks and potential responses. Responding to climate-related risks involves decision making in a changing world, with continuing uncertainty about the severity Iterative risk management i g h c o n f i d e n c e ). and timing of climate-change impacts and with limits to the effectiveness of adaptation ( h is a useful framework for decision making in complex situations characterized by large potential consequences, persistent uncertainties, long timeframes, potential for learning, and multiple climatic and non-climatic influences changing over time. See Figure SPM.3. Assessment of the widest possible range of potential impacts, including low-probability outcomes with large consequences, is central to understanding the benefits and trade-offs of alternative risk management actions. The complexity of adaptation actions across scales and contexts means that monitoring 27 and learning are important components of effective adaptation. h i g h Adaptation and mitigation choices in the near term will affect the risks of climate change throughout the 21st century ( Figure SPM.4 illustrates projected warming under a low-emission mitigation scenario and a high-emission scenario [Representative o n f i d e n c e ). c Concentration Pathways (RCPs) 2.6 and 8.5], along with observed temperature changes. The benefits of adaptation and mitigation occur over different but overlapping timeframes. Projected global temperature increase over the next few decades is similar across emission scenarios 28 During this near-term period, risks will evolve as socioeconomic trends interact with the changing climate. Societal (Figure SPM.4B). Sco ping g g g in p p op Sc Identify risks, Establish decision- vulnerabilities, maki ng criteria & objectives Analysis Implementation Identify options Implement Review decision & learn Evaluate Assess tradeoffs risks Figure SPM.3 | Climate-change adaptation Monitor as an iterative risk management process with multiple feedbacks. People and knowledge shape the process and its outcomes. [Figure 2-1] 24 28.2, 28.4 25 29.3, 29.6, Table 29-3, Figure 29-1 26 30.6 27 2.1-4, 3.6, 14.1-3, 15.2-4, 16.2-4, 17.1-3, 17.5, 20.6, 22.4, 25.4, Figure 1-5 28 WGI AR5 11.3 9

11 Summary for Policymakers (A) S T ignificant rend not Observed Temperature Change Diagonal Lines Solid Color trend statistically Base d on trend over significant C over period) 1901–2012 ( Insufficient ̊ White –0.5 11.7 0246 data P M S ) e 6 5 g 0 (B) n 0 a 2 h – c 6 8 e 4 r 9 1 u t o a Observed t r e e p v RCP8.5 i 2 t m a e l t Overlap e r n C a ̊ RCP2.6 e ( 0 m l a b o l –2 G 2050 2000 2100 1900 1950 (C) Projected Temperature Change Strong Very strong White Dots Solid Color Difference from agreement agreement C) 1986–2005 mean ( ̊ Little or Div ergent Gray Diagonal Lines –0.5 11.7 no change 0246 changes 2081–2100 RCP2.6 2081–2100 RCP8.5 erved and projected changes in annual average surface temperature. This figure informs understanding of climate-related risks in the WGII AR5. It illustrates Obs Figu re SPM.4 | temperature change observed to date and projected warming under continued high emissions and under ambitious mitigation. 10

12 Summary for Policymakers re SPM.4 Technical Details Figu (A) Map of observed annual average temperature change from 1901–2012, derived from a linear trend where sufficient data permit a robust estimate; other areas are white. . Observed data (range of grid-point values: Solid colors indicate areas where trends are significant at the 10% level. Diagonal lines indicate areas where trends are not significant –0.53 to 2.50°C ove r period) are from WGI AR5 Figures SPM.1 and 2.21. (B) Observed and projected future global annual average temperature relative to 1986–2005. Observed warming from 1850–1900 to 1986–2005 is 0.61°C (5–95% confidence interval: 0.55 to 0.67°C). Black lines show temperature estimates from three datasets. Blue and red line ls for RCP8.5. (C) s and shading denote the ensemble mean and ±1.64 standard deviation range, based on CMIP5 simulations from 32 models for RCP2.6 and 39 mode P S M CMIP5 mult i-model mean projections of annual average temperature changes for 2081–2100 under RCP2.6 and 8.5, relative to 1986–2005. Solid color s indicate areas with very strong agreement, where the multi-model mean change is greater than twice the baseline variability (natural internal variability in 20- yr means) and ≥90% of models agree on sign of change. Colors with white dots indicate areas with strong agreement, where ≥66% of models show change greater than the bas eline variability and ≥66% of models ee on sign of change. Gray indicates areas with divergent changes, where ≥66% of models show change greater than the baseline variability, but <66% agree on sign of agr . Colors with diagonal lines indicate areas with little or no change, where <66% of models show change greater than the baseline variability, although there may be change significant change at shorter timescales such as seasons, months, or days. Analysis uses model data (range of grid-point values across RCP2.6 and 8.5: 0.06 to 11.71°C) from WGI AR5 Figure SPM.8, with full description of methods in Box CC-RC. See also Annex I of WGI AR5. [Boxes 21-2 and CC-RC; WGI AR5 2.4, Fi gures SPM.1, SPM.7, and 2.21] responses, particularly adaptations, will influence near-term outcomes. In the second half of the 21st century and beyond, global temperature 29 For this longer-term period, near-term and longer-term adaptation and increase diverges across emission scenarios (Figure SPM.4B and 4C). 30 mitigation, as well as development pathways, will determine the risks of climate change. Assessment of risks in the WGII AR5 relies on diverse forms of evidence. Expert judgment is used to integrate evidence into Forms of evidence include, for example, empirical observations, experimental results, process-based understanding, evaluations of risks. statistical approaches, and simulation and descriptive models. Future risks related to climate change vary substantially across plausible alternative development pathways, and the relative importance of development and climate change varies by sector, region, and time period ). Scenarios are useful tools for characterizing possible future socioeconomic pathways, climate change and its risks, and policy ( high confidence implications. Climate-model projections informing evaluations of risks in this report are generally based on the RCPs (Figure SPM.4), as well as 31 the older IPCC (SRES) scenarios. Special Report on Emission Scenarios Uncertainties about future vulnerability, exposure, and responses of interlinked human and natural systems are large ( i g h h Understanding future n c o n c ). This motivates exploration of a wide range of socioeconomic futures in assessments of risks. e f e d i vulnerability, exposure, and response capacity of interlinked human and natural systems is challenging due to the number of interacting social, economic, and cultural factors, which have been incompletely considered to date. These factors include wealth and its distribution across society, demographics, migration, access to technology and information, employment patterns, the quality of adaptive responses, societal values, governance structures, and institutions to resolve conflicts. International dimensions such as trade and relations among states are also 32 important for understanding the risks of climate change at regional scales. B: FUTURE RISKS AND OPPORTUNITIES FOR ADAPTATION This section presents future risks and more limited potential benefits across sectors and regions, over the next few decades and in the second half of the 21st century and beyond. It examines how they are affected by the magnitude and rate of climate change and by socioeconomic choices. It also assesses opportunities for reducing impacts and managing risks through adaptation and mitigation. B-1. Key Risks across Sectors and Regions Key risks are potentially severe impacts relevant to Article 2 of the United Nations Framework Convention on Climate Change, which refers to “dangerous anthropogenic interference with the climate system.” Risks are considered key due to high hazard or high vulnerability of societies and systems exposed, or both. Identification of key risks was based on expert judgment using the following specific criteria: large magnitude, 29 WGI AR5 12.4 and Table SPM.2 30 2.5, 21.2-3, 21.5, Box CC-RC 31 1.1, 1.3, 2.2-3, 19.6, 20.2, 21.3, 21.5, 26.2, Box CC-RC; WGI AR5 Box SPM.1 32 11.3, 12.6, 21.3-5, 25.3-4, 25.11, 26.2 11

13 Summary for Policymakers Assessment Box SPM.1 | Human Interference with the Climate System 3 3 et determining whether such influence constitutes “dangerous anthropogenic uman influence on the climate system is clear. Y H interference” in the words of Article 2 of the UNFCCC involves both risk assessment and value judgments. This report assesses risks S M P across contexts and through time, providing a basis for judgments about the level of climate change at which risks become dangerous. Five integrative reasons for concern (RFCs) provide a framework for summarizing key risks across sectors and regions. First identified in the IPCC Third Assessment Report, the RFCs illustrate the implications of warming and of adaptation limits for people, economies, and ecosystems. They provide one starting point for evaluating dangerous anthropogenic interference with the climate system. Risks for each RFC, updated based on assessment of the literature and expert judgments, are presented below and in Assessment Box 34 SPM.1 Figure 1. All temperatures below are given as global average temperature change relative to 1986–2005 (“recent”). 1) Unique and threatened systems : Some unique and threatened systems, including ecosystems and cultures, are already at risk from climate change ( high confidence ). The number of such systems at risk of severe consequences is higher with additional warming of around 1°C. Many species and systems with limited adaptive capacity are subject to very high risks with additional warming of 2°C, particularly Arctic-sea-ice and coral-reef systems. 2) Extreme weather events : Climate-change-related risks from extreme events, such as heat waves, extreme precipitation, and coastal flooding, are already moderate ( high confidence ) and high with 1°C additional warming ( medium confidence ). Risks associated with some types of extreme events (e.g., extreme heat) increase further at higher temperatures ( high confidence ). 3) Distribution of impacts : Risks are unevenly distributed and are generally greater for disadvantaged people and communities in countries at all levels of development. Risks are already moderate because of regionally differentiated climate-change impacts on high confidence crop production in particular ( ). Based on projected decreases in regional crop yields and water medium to availability, risks of unevenly distributed impacts are high for additional warming above 2°C ( medium confidence ). : Risks of global aggregate impacts are moderate for additional warming between 1–2°C, reflecting 4) Global aggregate impacts impacts to both Earth’s biodiversity and the overall global economy ( ). Extensive biodiversity loss with associated medium confidence loss of ecosystem goods and services results in high risks around 3°C additional warming ( high confidence ). Aggregate economic damages accelerate with increasing temperature ( limited evidence , high agreement ), but few quantitative estimates have been completed for additional warming around 3°C or above. 5) Large-scale singular events : With increasing warming, some physical systems or ecosystems may be at risk of abrupt and irreversible changes. Risks associated with such tipping points become moderate between 0–1°C additional warming, due to early warning signs that both warm-water coral reef and Arctic ecosystems are already experiencing irreversible regime shifts ( medium confidence ). Risks increase disproportionately as temperature increases between 1–2°C additional warming and become high above 3°C, due to the potential for a large and irreversible sea level rise from ice sheet loss. For sustained warming greater than 35 near-complete loss of the Greenland ice sheet would occur over a millennium or more, contributing up to 7 m of some threshold, global mean sea level rise. high probability, or irreversibility of impacts; timing of impacts; persistent vulnerability or exposure contributing to risks; or limited potential to reduce risks through adaptation or mitigation. Key risks are integrated into five complementary and overarching reasons for concern (RFCs) in Assessment Box SPM.1. c h The key risks that follow, all of which are identified with h i g o n f i d e n c e , span sectors and regions. Each of these key risks 36 contributes to one or more RFCs. 33 WGI AR5 SPM, 2.2, 6.3, 10.3-6, 10.9 34 18.6, 19.6; observed warming from 1850–1900 to 1986–2005 is 0.61°C (5–95% confidence interval: 0.55 to 0.67°C). [WGI AR5 2.4] 35 w e m ) but less than about 4°C ( e c f e d i f n o c o o l Current estimates indicate that this threshold is greater than about 1°C ( n c m u i d i d e n c e ) sustained global mean warming above n preindustrial levels. [WGI AR5 SPM, 5.8, 13.4-5] 36 19.2-4, 19.6, Table 19-4, Boxes 19-2 and CC-KR 12

14 Summary for Policymakers ) ) ) ) n n e e s s 5 5 l l 6 a a g g e e 0 0 n n v v s s 0 0 a a e e a a l l 2 2 h h l l , , – – c c a a 5 5 0 0 i i 6 6 e e r r 0 0 t t r r 8 8 s s 9 9 u u 9 9 u u t t 1 1 1 1 5 5 d d a a – – r r n n o o i i 0 0 e e t t e e 4 4 5 5 p p r r e e 8 8 p p v v m m i i f f 1 1 e e t t o o t t a a 4 4 o o l l t t n n n n e e o o r r a a i i e e 3 3 t t e e v v a a i i C C t t ̊ ̊ m m ( ( m m P M S a a i i l l l l x x 3 3 a a e e o o r r b b r r o o p p 2 2 l l C C p p ̊ ̊ G G ( ( a a 2 2 1 1 1 1 2003 –2012 0 0 0 0 0.61 0.61 - - Large-scale Distribution Global Extreme Unique & singular of impacts aggregate weather threatened °C °C °C °C 1950 2000 2050 1900 2100 events impacts events systems Observed RCP8.5 (a high-emission scenario) L evel of additional risk due to climate change Overlap igh H V ery high Moderate Undetectable RCP2.6 (a low-emission mitigation scenario) A global perspective on climate-related risks. Risks associated with reasons for concern are shown at right for increasing levels of climate Assessment Box SPM.1 Figure 1 | . The color shading indicates the additional risk due to climate change when a temperature level is reached and then sustained or exceeded. Undetectable risk (white) change es no associated impacts are detectable and attributable to climate change. Moderate risk (yellow) indicates that associated impact indicat s are both detectable and attributable to climate change with at least medium confidence , also accounting for the other specific criteria for key risks. High risk (red) indicates severe and widespread impacts, also or the other specific criteria for key risks. Purple, introduced in this assessment, shows that very high risk is indicated by all s pecific criteria for key risks. [Figure 19-4] accounting f x CC-RC; WGI AR5 Figures SPM.1 and SPM.7] For reference, past and projected global annual average surface temperature is shown at left, as in Figure SPM.4. [Figure RC-1, Bo the AR5 reference period ed on the longest global surface temperature dataset available, the observed change between the average of the period 1850–1900 and of Bas (1986–2005) is 0.61°C (5–95% confidence interval: 0.55 to 0.67°C) [WGI AR5 SPM, 2.4], which is used here as an approximation of the change in global mean surface temperature since preindustrial times, referred to as the period before 1750. [WGI and WGII AR5 glossaries] i) Risk of death, injury, ill-health, or disrupted livelihoods in low-lying coastal zones and small island developing states and other small 37 [RFC 1-5] islands, due to storm surges, coastal flooding, and sea level rise. 38 [RFC 2 and 3] ii) Risk of severe ill-health and disrupted livelihoods for large urban populations due to inland flooding in some regions. iii) Systemic risks due to extreme weather events leading to breakdown of infrastructure networks and critical services such as electricity, 39 [RFC 2-4] water supply, and health and emergency services. iv) Risk of mortality and morbidity during periods of extreme heat, particularly for vulnerable urban populations and those working outdoors 40 [RFC 2 and 3] in urban or rural areas. v) Risk of food insecurity and the breakdown of food systems linked to warming, drought, flooding, and precipitation variability and extremes, 41 [RFC 2-4] particularly for poorer populations in urban and rural settings. vi) Risk of loss of rural livelihoods and income due to insufficient access to drinking and irrigation water and reduced agricultural productivity, 42 [RFC 2 and 3] particularly for farmers and pastoralists with minimal capital in semi-arid regions. vii) Risk of loss of marine and coastal ecosystems, biodiversity, and the ecosystem goods, functions, and services they provide for coastal 43 [RFC 1, 2, and 4] livelihoods, especially for fishing communities in the tropics and the Arctic. viii) Risk of loss of terrestrial and inland water ecosystems, biodiversity, and the ecosystem goods, functions, and services they provide for 44 [RFC 1, 3, and 4] livelihoods. Many key risks constitute particular challenges for the least developed countries and vulnerable communities, given their limited ability to cope. 37 5.4, 8.2, 13.2, 19.2-4, 19.6-7, 24.4-5, 26.7-8, 29.3, 30.3, Tables 19-4 and 26-1, Figure 26-2, Boxes 25-1, 25-7, and CC-KR 38 3.4-5, 8.2, 13.2, 19.6, 25.10, 26.3, 26.8, 27.3, Tables 19-4 and 26-1, Boxes 25-8 and CC-KR 39 5.4, 8.1-2, 9.3, 10.2-3, 12.6, 19.6, 23.9, 25.10, 26.7-8, 28.3, Table 19-4, Boxes CC-KR and CC-HS 40 8.1-2, 11.3-4, 11.6, 13.2, 19.3, 19.6, 23.5, 24.4, 25.8, 26.6, 26.8, Tables 19-4 and 26-1, Boxes CC-KR and CC-HS 41 3.5, 7.4-5, 8.2-3, 9.3, 11.3, 11.6, 13.2, 19.3-4, 19.6, 22.3, 24.4, 25.5, 25.7, 26.5, 26.8, 27.3, 28.2, 28.4, Table 19-4, Box CC-KR 42 3.4-5, 9.3, 12.2, 13.2, 19.3, 19.6, 24.4, 25.7, 26.8, Table 19-4, Boxes 25-5 and CC-KR 43 5.4, 6.3, 7.4, 9.3, 19.5-6, 22.3, 25.6, 27.3, 28.2-3, 29.3, 30.5-7, Table 19-4, Boxes CC-OA, CC-CR, CC-KR, and CC-HS 44 4.3, 9.3, 19.3-6, 22.3, 25.6, 27.3, 28.2-3, Table 19-4, Boxes CC-KR and CC-WE 13

15 Summary for Policymakers ncreasing magnitudes of warming increase the likelihood of severe, pervasive, and irreversible impacts. ome risks of climate I S change are considerable at 1 or 2°C above preindustrial levels (as shown in Assessment Box SPM.1). Global climate change risks are high to very high with global mean temperature increase of 4°C or more above preindustrial levels in all reasons for concern (Assessment Box SPM.1), and include severe and widespread impacts on unique and threatened systems, substantial species extinction, large risks to global and regional S P M food security, and the combination of high temperature and humidity compromising normal human activities, including growing food or working outdoors in some areas for parts of the year ( high confidence ). The precise levels of climate change sufficient to trigger tipping points (thresholds for abrupt and irreversible change) remain uncertain, but the risk associated with crossing multiple tipping points in the earth 45 medium confidence system or in interlinked human and natural systems increases with rising temperature ( ). The overall risks of climate change impacts can be reduced by limiting the rate and magnitude of climate change. Risks are reduced substantially under the assessed scenario with the lowest temperature projections (RCP2.6 – low emissions) compared to the highest ). Reducing climate temperature projections (RCP8.5 – high emissions), particularly in the second half of the 21st century ( very high confidence change can also reduce the scale of adaptation that might be required. Under all assessed scenarios for adaptation and mitigation, some risk 46 very high confidence ). from adverse impacts remains ( B-2. Sectoral Risks and Potential for Adaptation Climate change is projected to amplify existing climate-related risks and create new risks for natural and human systems. Some of these risks will be limited to a particular sector or region, and others will have cascading effects. To a lesser extent, climate change is also projected to have some potential benefits. Freshwater resources r o b u s Freshwater-related risks of climate change increase significantly with increasing greenhouse gas concentrations ( e v i d e n c e , t The fraction of global population experiencing water scarcity and the fraction affected by major river floods increase with g h a g r e e i e n t ). h m 47 the level of warming in the 21st century. Climate change over the 21st century is projected to reduce renewable surface water and groundwater resources significantly in d most dry subtropical regions ( r o b u s t e v i d e n c e , h i g h a g r e e m e n t ), intensifying competition for water among sectors ( l i m i t e In presently dry regions, drought frequency will likely increase by the end of the 21st century under RCP8.5 n c e , m e d i u m i a g r e e m e n t ). e d e v ( medium confidence ). In contrast, water resources are projected to increase at high latitudes ( robust evidence , high agreement ). Climate change is projected to reduce raw water quality and pose risks to drinking water quality even with conventional treatment, due to interacting factors: increased temperature; increased sediment, nutrient, and pollutant loadings from heavy rainfall; increased concentration of pollutants during droughts; and disruption of treatment facilities during floods ( medium evidence , high agreement ). Adaptive water management techniques, including scenario planning, learning-based approaches, and flexible and low-regret solutions, can help create resilience to 48 limited evidence , high agreement ). uncertain hydrological changes and impacts due to climate change ( Terrestrial and freshwater ecosystems A large fraction of both terrestrial and freshwater species faces increased extinction risk under projected climate change during and beyond the 21st century, especially as climate change interacts with other stressors, such as habitat modification, over- 45 4.2-3, 11.8, 19.5, 19.7, 26.5, Box CC-HS 46 3.4-5, 16.6, 17.2, 19.7, 20.3, 25.10, Tables 3-2, 8-3, and 8-6, Boxes 16-3 and 25-1 47 3.4-5, 26.3, Table 3-2, Box 25-8 14

16 Summary for Policymakers d xploitation, pollution, and invasive species ( h i g h c o n f i xtinction risk is increased under all RCP scenarios, with risk increasing e n c e ). E e with both magnitude and rate of climate change. Many species will be unable to track suitable climates under mid- and high-range rates of climate change (i.e., RCP4.5, 6.0, and 8.5) during the 21st century ( medium confidence ). Lower rates of change (i.e., RCP2.6) will pose fewer problems. See Figure SPM.5. Some species will adapt to new climates. Those that cannot adapt sufficiently fast will decrease in abundance or S P M go extinct in part or all of their ranges. Management actions, such as maintenance of genetic diversity, assisted species migration and dispersal, manipulation of disturbance regimes (e.g., fires, floods), and reduction of other stressors, can reduce, but not eliminate, risks of impacts to terrestrial and freshwater ecosystems due to climate change, as well as increase the inherent capacity of ecosystems and their species to adapt 49 high confidence ). to a changing climate ( Within this century, magnitudes and rates of climate change associated with medium- to high-emission scenarios (RCP4.5, 6.0, and 8.5) pose high risk of abrupt and irreversible regional-scale change in the composition, structure, and function of terrestrial Examples that could lead to substantial impact on climate are the d i u m c o n f i d e n and freshwater ecosystems, including wetlands ( e ). m e c medium confidence low confidence ). Carbon stored in the terrestrial biosphere (e.g., in boreal-tundra Arctic system ( ) and the Amazon forest ( peatlands, permafrost, and forests) is susceptible to loss to the atmosphere as a result of climate change, deforestation, and ecosystem high confidence degradation ( ). Increased tree mortality and associated forest dieback is projected to occur in many regions over the 21st ). Forest dieback poses risks for carbon storage, biodiversity, wood century, due to increased temperatures and drought ( medium confidence 50 production, water quality, amenity, and economic activity. ) 100 e Average climate velocity d a 2050–2090 c e d r e p 80 m k ( 8.5 flat areas RCP e Upper v bound o m n 60 Median a c s e i Lower c e bound p s h 40 RCP 6.0 flat areas c i h w t a d e RCP 4.5 flat areas e 20 p RCP 8.5 global average s m 6.0 global average RCP u m i RCP 4.5 global average x a RCP 2.6 flat areas and global average 0 M r s s s s s s s s s s g d l l t t t e e k e u u e n t a c a t n n s i f e o o e a r a e a r d u o m e m l s l T d e l o c o w m p n m i m e o v i o a h h i r f - a a s R b - t n P m r t i e r m l m r e n a p F a H l C S P re SPM.5 | Max imum speeds at which species can move across landscapes (based on observations and models; vertical axis on left), compared with s peeds at which Figu temperatures are projected to move across landscapes (climate velocities for temperature; vertical axis on right). Human interventions, such as transport or habitat fragmentation, can gr eatly increase or decrease speeds of movement. White boxes with black bars indicate ranges and medians of maximum movement speeds for trees, plants, mammals, -feeding insects (median not estimated), and freshwater mollusks. For RCP2.6, 4.5, 6.0, and 8.5 for 2050–2090, horizontal line plant s show climate velocity for the area average and for large flat regions. Species with maximum speeds below each line are expected to be unable to track warming in t he absence of human global-land- intervention. [Figure 4-5] 48 3.2, 3.4-6, 22.3, 23.9, 25.5, 26.3, Table 3-2, Table 23-3, Boxes 25-2, CC-RF, and CC-WE; WGI AR5 12.4 49 4.3-4, 25.6, 26.4, Box CC-RF 50 4.2-3, Figure 4-8, Boxes 4-2, 4-3, and 4-4 15

17 Summary for Policymakers (A) Chang e in maximum catch potential (2051–2060 compared to 2001–2010, SRES A1B) > 100 % < –50 % –21 to –50 % –6 to –20 % 20 to 49 % 0 to 4 % 50 to 100 % no data –1 to –5 % 5 to 19 % P M S (B) Change in pH (2081–2100 compared to 1986–2005, RCP8.5) Cold-water Warm-water Mollusk and crustacean fisheries 0 0 5 5 0 5 0 5 0 0 5 5 -2 ≥ corals corals ) (present-day annual catch rate 0.005 tonnes km 2 1 4 6 5 5 3 1 2 0 3 4 . . . . . . . . . . . . 0 0 0 0 0 0 0 0 0 0 0 0 – – – – – – – – – – – – Warm-water corals Cold-water corals Mollusks Crustaceans 29 40 16 15 31 37 23 49 18 7475 26 9 3 15 23 20 100 100 100 100 ) 80 80 80 80 % ( Positive effect s 60 60 60 60 e i c e No effect p 40 40 40 40 S Negative effect 20 20 20 20 0 0 0 0 l l l l 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 o o o o 0 0 0 r r 5 7 5 r 0 7 5 5 7 5 5 r 5 5 7 t t t t 9 9 9 9 6 3 8 3 6 8 3 8 6 6 8 3 n n n n 2 2 2 – – 2 – – – – 1 – – 1 1 1 – o – – o o o – 0 – 1 – 0 1 – 1 0 0 1 – 1 1 1 1 C C C C 0 1 5 1 5 0 1 5 0 5 0 1 7 7 7 7 5 6 5 5 6 5 5 6 5 6 5 5 3 3 3 3 8 8 8 8 1 1 1 1 CO p atm) μ ( 2 16

18 Summary for Policymakers Clim re SPM.6 | Figu ate change risks for fisheries. (A) Projected global redistribution of maximum catch potential of ~1000 exploited fish and invertebrate species. Projections e the 10-year averages 2001–2010 and 2051–2060 using SRES A1B, without analysis of potential impacts of overfishing or ocean acidification. (B) Marine mollusk and compar -2 ) and known locations of cold- and warm-water corals, depicted on a global map showing the crustacean fisheries (present-day estimated annual catch rates ≥0.005 tonnes km rojected distribution of ocean acidification under RCP8.5 (pH change from 1986–2005 to 2081–2100). [WGI AR5 Figure SPM.8] The bottom panel compares sensitivity to p ocean acidification acr oss mollusks, crustaceans, and corals, vulnerable animal phyla with socioeconomic relevance (e.g., for coastal protection and fisheries). The number of category are as follows: CO p tial pressure ( For 2100, RCP scenarios falling within each CO par . ) pecies analyzed across studies is given for each category of elevated CO s 2 2 2 atm. By 2150, RCP8.5 falls within the or 500–650 μ atm (approximately equivalent to ppm in the atmosphere), RCP6.0 for 651–850 μ atm, and RCP8.5 for 851–1370 μ RCP4.5 f S P M μ 1371–2900 atm category. The control category corresponds to 380 μ atm. [6.1, 6.3, 30.5, Figures 6-10 and 6-14; WGI AR5 Box SPM.1] Coastal systems and low-lying areas Due to sea level rise projected throughout the 21st century and beyond, coastal systems and low-lying areas will increasingly The population and h i g h c o n f i d e n c e ). experience adverse impacts such as submergence, coastal flooding, and coastal erosion ( v e r y assets projected to be exposed to coastal risks as well as human pressures on coastal ecosystems will increase significantly in the coming high confidence decades due to population growth, economic development, and urbanization ( ). The relative costs of coastal adaptation vary strongly among and within regions and countries for the 21st century. Some low-lying developing countries and small island states are expected 5 1 to face very high impacts that, in some cases, could have associated damage and adaptation costs of several percentage points of GDP. Marine systems Due to projected climate change by the mid 21st century and beyond, global marine-species redistribution and marine-biodiversity h h i reduction in sensitive regions will challenge the sustained provision of fisheries productivity and other ecosystem services ( g Spatial shifts of marine species due to projected warming will cause high-latitude invasions and high local-extinction rates in the d o n f i c e n c e ). ). Species richness and fisheries catch potential are projected to increase, on average, at medium confidence tropics and semi-enclosed seas ( mid and high latitudes ( ) and decrease at tropical latitudes ( medium confidence ). See Figure SPM.6A. The progressive expansion high confidence of oxygen minimum zones and anoxic “dead zones” is projected to further constrain fish habitat. Open-ocean net primary production is projected to redistribute and, by 2100, fall globally under all RCP scenarios. Climate change adds to the threats of over-fishing and other non- 52 climatic stressors, thus complicating marine management regimes ( high confidence ). For medium- to high-emission scenarios (RCP4.5, 6.0, and 8.5), ocean acidification poses substantial risks to marine ecosystems, especially polar ecosystems and coral reefs, associated with impacts on the physiology, behavior, and population dynamics of Highly calcified mollusks, echinoderms, and reef-building i d e n c e ). individual species from phytoplankton to animals ( m e d i u m to h i g h c o n f corals are more sensitive than crustaceans ( ) and fishes ( low confidence ), with potentially detrimental consequences for fisheries high confidence and livelihoods. See Figure SPM.6B. Ocean acidification acts together with other global changes (e.g., warming, decreasing oxygen levels) and with local changes (e.g., pollution, eutrophication) ( high confidence ). Simultaneous drivers, such as warming and ocean acidification, can lead 53 to interactive, complex, and amplified impacts for species and ecosystems. Food security and food production systems For the major crops (wheat, rice, and maize) in tropical and temperate regions, climate change without adaptation is projected to negatively impact production for local temperature increases of 2°C or more above late-20th-century levels, although individual Projected impacts vary across crops and regions and adaptation scenarios, with about 10% of o d ). m locations may benefit ( u m c i n f i d e n c e e projections for the period 2030–2049 showing yield gains of more than 10%, and about 10% of projections showing yield losses of more than 51 5.3-5, 8.2, 22.3, 24.4, 25.6, 26.3, 26.8, Table 26-1, Box 25-1 52 6.3-5, 7.4, 25.6, 28.3, 30.6-7, Boxes CC-MB and CC-PP 53 5.4, 6.3-5, 22.3, 25.6, 28.3, 30.5, Boxes CC-CR, CC-OA, and TS.7 17

19 Summary for Policymakers s 100 n o i t c Color Legend e j Range of yield change o r 80 p 50 to 100% d l e S M P 25 to 50% i y f incr ease 10 to 25% o 60 n yield i e 5 to 10% g a t 0 to 5% n e 40 c r 0 to –5% e P –5 to –10% ecr ease d –10 to –25% 20 n yield i –25 to –50% –50 to –100% 0 2070–2089 2090–2109 2030–2049 2010–2029 2050–2069 Figu re SPM.7 | Summary of projected changes in crop yields, due to climate change over the 21st century. The figure includes projections for different emission scenarios, for tropical and temperate regions, and for adaptation and no-adaptation cases combined. Relatively few studies have considered impact s on cropping systems for scenarios where more. For five timeframes in the near term and long term, data (n=1090) are plotted in the 20-year period on the horizontal axis ° C or global m ean temperatures increase by 4 that includes the midpoint of each future projection period. Changes in crop yields are relative to late-20th-century levels. Data for each timeframe sum to 100%. [Figure 7-5] 25%, compared to the late 20th century. After 2050 the risk of more severe yield impacts increases and depends on the level of warming. See Figure SPM.7. Climate change is projected to progressively increase inter-annual variability of crop yields in many regions. These projected 54 impacts will occur in the context of rapidly rising crop demand. All aspects of food security are potentially affected by climate change, including food access, utilization, and price stability ( i g h h Redistribution of marine fisheries catch potential towards higher latitudes poses risk of reduced supplies, income, and employment f i d e c c e ). o n n medium confidence ). Global temperature increases of ~4°C or more above in tropical countries, with potential implications for food security ( late-20th-century levels, combined with increasing food demand, would pose large risks to food security globally and regionally ( high 55 ). Risks to food security are generally greater in low-latitude areas. confidence Urban areas n Many global risks of climate change are concentrated in urban areas ( i m e u c o n f i d e d c e ). Steps that build resilience and enable m Heat stress, extreme precipitation, inland and sustainable development can accelerate successful climate-change adaptation globally. coastal flooding, landslides, air pollution, drought, and water scarcity pose risks in urban areas for people, assets, economies, and ecosystems ( very high confidence ). Risks are amplified for those lacking essential infrastructure and services or living in poor-quality housing and exposed areas. Reducing basic service deficits, improving housing, and building resilient infrastructure systems could significantly reduce vulnerability and exposure in urban areas. Urban adaptation benefits from effective multi-level urban risk governance, alignment of policies and incentives, strengthened local government and community adaptation capacity, synergies with the private sector, and appropriate financing and institutional development ( medium confidence ). Increased capacity, voice, and influence of low-income groups and vulnerable communities 56 and their partnerships with local governments also benefit adaptation. 54 7.4-5, 22.3, 24.4, 25.7, 26.5, Table 7-2, Figures 7-4, 7-5, 7-6, 7-7, and 7-8 55 6.3-5, 7.4-5, 9.3, 22.3, 24.4, 25.7, 26.5, Table 7-3, Figures 7-1, 7-4, and 7-7, Box 7-1 56 3.5, 8.2-4, 22.3, 24.4-5, 26.8, Table 8-2, Boxes 25-9 and CC-HS 18

20 Summary for Policymakers Rural areas Major future rural impacts are expected in the near term and beyond through impacts on water availability and supply, food security, and agricultural incomes, including shifts in production areas of food and non-food crops across the world ( h i g h S P M These impacts are expected to disproportionately affect the welfare of the poor in rural areas, such as female-headed households o i d e n c e ). n f c and those with limited access to land, modern agricultural inputs, infrastructure, and education. Further adaptations for agriculture, water, forestry, and biodiversity can occur through policies taking account of rural decision-making contexts. Trade reform and investment can improve 57 market access for small-scale farms ( medium confidence ). Key economic sectors and services For most economic sectors, the impacts of drivers such as changes in population, age structure, income, technology, relative prices, m e d i u m e v i d e n c lifestyle, regulation, and governance are projected to be large relative to the impacts of climate change ( , h i g h e Climate change is projected to reduce energy demand for heating and increase energy demand for cooling in the residential and r e e m e n t ). a g robust evidence high agreement commercial sectors ( ). Climate change is projected to affect energy sources and technologies differently, , depending on resources (e.g., water flow, wind, insolation), technological processes (e.g., cooling), or locations (e.g., coastal regions, floodplains) involved. More severe and/or frequent extreme weather events and/or hazard types are projected to increase losses and loss variability in various regions and challenge insurance systems to offer affordable coverage while raising more risk-based capital, particularly in developing 58 countries. Large-scale public-private risk reduction initiatives and economic diversification are examples of adaptation actions. Global economic impacts from climate change are difficult to estimate. Economic impact estimates completed over the past 20 years vary in their coverage of subsets of economic sectors and depend on a large number of assumptions, many of which are disputable, and many 59 With these recognized limitations, the incomplete estimates do not account for catastrophic changes, tipping points, and many other factors. estimates of global annual economic losses for additional temperature increases of ~2°C are between 0.2 and 2.0% of income (±1 standard deviation around the mean) ( medium evidence , medium agreement ). Losses are more likely than not to be greater, rather than smaller, than this range ( limited evidence high agreement ). Additionally, there are large differences between and within countries. Losses accelerate with , limited evidence high agreement ), but few quantitative estimates have been completed for additional warming around 3°C greater warming ( , or above. Estimates of the incremental economic impact of emitting carbon dioxide lie between a few dollars and several hundreds of dollars 60 61 robust evidence , medium agreement ). Estimates vary strongly with the assumed damage function and discount rate. ( per tonne of carbon Human health Until mid-century, projected climate change will impact human health mainly by exacerbating health problems that already exist ( v e r y h i g h c o n f i d e n c e ). Throughout the 21st century, climate change is expected to lead to increases in ill-health in many regions d and especially in developing countries with low income, as compared to a baseline without climate change ( g h c o n f i i e n c e ). h Examples include greater likelihood of injury, disease, and death due to more intense heat waves and fires ( very high confidence ); increased likelihood of under-nutrition resulting from diminished food production in poor regions ( high confidence ); risks from lost work capacity and reduced labor productivity in vulnerable populations; and increased risks from food- and water-borne diseases ( ) and very high confidence 57 9.3, 25.9, 26.8, 28.2, 28.4, Box 25-5 58 3.5, 10.2, 10.7, 10.10, 17.4-5, 25.7, 26.7-9, Box 25-7 59 Disaster loss estimates are lower-bound estimates because many impacts, such as loss of human lives, cultural heritage, and ecosystem services, are difficult to value and monetize, and thus they are poorly reflected in estimates of losses. Impacts on the informal or undocumented economy as well as indirect economic effects can be very important in some areas and sectors, but are generally not counted in reported estimates of losses. [SREX 4.5] 60 1 tonne of carbon = 3.667 tonne of CO 2 61 10.9 19

21 Summary for Policymakers ector-borne diseases ( medium confidence ). Positive effects are expected to include modest reductions in cold-related mortality and morbidity v in some areas due to fewer cold extremes ( low confidence ), geographical shifts in food production ( medium confidence ), and reduced capacity of vectors to transmit some diseases. But globally over the 21st century, the magnitude and severity of negative impacts are projected to ). The most effective vulnerability reduction measures for health in the near term are increasingly outweigh positive impacts ( high confidence S M P programs that implement and improve basic public health measures such as provision of clean water and sanitation, secure essential health very high care including vaccination and child health services, increase capacity for disaster preparedness and response, and alleviate poverty ( confidence ). By 2100 for the high-emission scenario RCP8.5, the combination of high temperature and humidity in some areas for parts of the 62 year is projected to compromise normal human activities, including growing food or working outdoors ( high confidence ). Human security Climate change over the 21st century is projected to increase displacement of people ( m e d i u m ). e v i d e n c e h i g h a g r e e m e n t , Displacement risk increases when populations that lack the resources for planned migration experience higher exposure to extreme weather events, in both rural and urban areas, particularly in developing countries with low income. Expanding opportunities for mobility can reduce vulnerability for such populations. Changes in migration patterns can be responses to both extreme weather events and longer-term climate variability and change, and migration can also be an effective adaptation strategy. There is low confidence in quantitative projections of 63 changes in mobility, due to its complex, multi-causal nature. Climate change can indirectly increase risks of violent conflicts in the form of civil war and inter-group violence by amplifying Multiple lines of evidence well-documented drivers of these conflicts such as poverty and economic shocks ( m e d i u m c o n f i d e n c e ). 64 relate climate variability to these forms of conflict. The impacts of climate change on the critical infrastructure and territorial integrity of many states are expected to influence For example, land inundation due to sea level rise poses risks to the e d i u m e v i d e n c e , national security policies ( m d i u m a g r e e m e n t ). e m territorial integrity of small island states and states with extensive coastlines. Some transboundary impacts of climate change, such as changes in sea ice, shared water resources, and pelagic fish stocks, have the potential to increase rivalry among states, but robust national and 65 intergovernmental institutions can enhance cooperation and manage many of these rivalries. Livelihoods and poverty Throughout the 21st century, climate-change impacts are projected to slow down economic growth, make poverty reduction more difficult, further erode food security, and prolong existing and create new poverty traps, the latter particularly in urban Climate-change impacts are expected to exacerbate poverty in most m e d i u m c o n f i d e n c e ). areas and emerging hotspots of hunger ( developing countries and create new poverty pockets in countries with increasing inequality, in both developed and developing countries. In urban and rural areas, wage-labor-dependent poor households that are net buyers of food are expected to be particularly affected due to food price increases, including in regions with high food insecurity and high inequality (particularly in Africa), although the agricultural self- employed could benefit. Insurance programs, social protection measures, and disaster risk management may enhance long-term livelihood 66 resilience among poor and marginalized people, if policies address poverty and multidimensional inequalities. B-3. Regional Key Risks and Potential for Adaptation Risks will vary through time across regions and populations, dependent on myriad factors including the extent of adaptation and mitigation. A selection of key regional risks identified with medium to high confidence is presented in Assessment Box SPM.2. For extended summary of regional risks and potential benefits, see Technical Summary Section B-3 and WGII AR5 Part B: Regional Aspects. 20

22 Summary for Policymakers Assessment Box SPM.2 | Regional Key Risks The accompanying Assessment Box SPM.2 Table 1 highlights several representative key risks for each region. Key risks have been identified based on assessment of the relevant scientific, technical, and socioeconomic literature detailed in supporting chapter sections. Identification of key risks was based on expert judgment using the following specific criteria: large magnitude, high probability, or S P M irreversibility of impacts; timing of impacts; persistent vulnerability or exposure contributing to risks; or limited potential to reduce risks through adaptation or mitigation. For each key risk, risk levels were assessed for three timeframes. For the present, risk levels were estimated for current adaptation and a hypothetical highly adapted state, identifying where current adaptation deficits exist. For two future timeframes, risk levels were estimated for a continuation of current adaptation and for a highly adapted state, representing the potential for and limits to adaptation. The risk levels integrate probability and consequence over the widest possible range of potential outcomes, based on available literature. These potential outcomes result from the interaction of climate-related hazards, vulnerability, and exposure. Each risk level reflects total risk from climatic and non-climatic factors. Key risks and risk levels vary across regions and over time, given differing socioeconomic development pathways, vulnerability and exposure to hazards, adaptive capacity, and risk perceptions. Risk levels are not necessarily comparable, especially across regions, because the assessment considers potential impacts and adaptation in different physical, biological, and human systems across diverse contexts. This assessment of risks acknowledges the importance of differences in values and objectives in interpretation of the assessed risk levels. Assessment Box SPM.2 Table 1 | Key regional risks from climate change and the potential for reducing risks through adaptation and mitigation. Each key risk is charact erized as for three timeframes: the present, near term (here, assessed over 2030–2040), and longer term (here, assessed over 2080–2100). In the near term, very low to very high projected levels of global mean temperature increase do not diverge substantially for different emission scenarios. For the longer term, risk levels are presented for two scenarios of global mean temperature increase (2°C and 4°C above preindustrial levels). These scenarios illustrate the potential for mitigation and adaptation to reduce the risks related to clim ate change. Climate-related drivers of impacts are indicated by icons. Level of risk & potential for adaptation Climate-related drivers of impacts P otential for additional adaptation to reduce risk OO OO C C Warming Ocean Sea Snow Extreme Carbon dioxide Drying Damaging Extreme Risk level with Risk level with Precipitation acidification precipitation trend cover fertiliz level trend temperature cyclone ation high current adaptation adaptation Africa Risk & potential for Climatic Timeframe Adaptation issues & prospects Key risk drivers adaptation Very Very • Reducing non-climate stressors on water resources ounded stress on water resources facing Comp Medium high low significant strain from overexploitation and • Strengthening institutional capacities for demand management, Present degradation at present and increased demand in the groundwater assessment, integrated water-wastewater planning, future, with drought stress exacerbated in Near term and integrated land and water governance high confidence ) drought-prone regions of Africa ( (2030–2040) • Sustainable urban development 2°C [22.3-4] Long term (2080–2100) 4°C Very Very • Technological adaptation responses (e.g., stress-tolerant crop uced crop productivity associated with heat and Red Medium high low varieties, irrigation, enhanced observation systems) drought stress, with strong adverse effects on Present • Enhancing smallholder access to credit and other critical production ional, national, and household livelihood and food reg Diversifying livelihoods resources; rity, also given increased pest and disease secu Near term damage and flood impacts on food system (2030–2040) • Strengthening institutions at local, national, and regional levels to support agriculture (including early warning systems) and ) infrastructure ( high confidence 2°C gender-oriented policy Long term [22.3-4] (2080–2100) • Agronomic adaptation responses (e.g., agroforestry, conservation 4°C agriculture) Very Very Changes in the incidence and geographic range of • Achieving development goals, particularly improved access to safe Medium high low - and water-borne diseases due to changes in and improved sanitation, and enhancement of public health water vector Present functions such as surveillance the mean and variability of temperature and precipitation, particularly along the edges of their Near term • Vulnerability mapping and early warning systems distribution ( med ium confidence ) (2030–2040) • Coordination across sectors 2°C • Sustainable urban development 3] [22. Long term (2080–2100) 4°C 62 Continued next page 8.2, 11.3-8, 19.3, 22.3, 25.8, 26.6, Figure 25-5, Box CC-HS 63 9.3, 12.4, 19.4, 22.3, 25.9 64 12.5, 13.2, 19.4 65 12.5-6, 23.9, 25.9 66 8.1, 8.3-4, 9.3, 10.9, 13.2-4, 22.3, 26.8 21

23 Summary for Policymakers Continued next page Assessment Box SPM.2 Table 1 (continued) Europe Climatic Risk & potential for Timeframe Key risk Adaptation issues & prospects drivers adaptation Very Very high daptation can prevent most of the projected damages ( ncreased economic losses and people affected by A I Medium high low onfidence ). ooding in river basins and coasts, driven by c fl M S P resent P increasing urbanization, increasing sea levels, • Significant experience in hard flood-protection technologies and coastal erosion, and peak river discharges ear term N increasing experience with restoring wetlands ) high confidence ( 2030–2040) ( High costs for increasing flood protection • 2 °C Potential barriers to implementation: demand for land in Europe • 23.7] 23.2-3, [ ong term L and environmental and landscape concerns 2080–2100) ( 4°C ery V Very Increased water restrictions. Significant reduction in • Proven adaptation potential from adoption of more water-efficient M edium high ow l ater availability from river abstraction and from w nologies and of water-saving strategies (e.g., for irrigation, crop ech t Present groundwater resources, combined with increased species, land cover, industries, domestic use) water demand (e.g., for irrigation, energy and industry, Near term • Implementation of best practices and governance instruments in omestic use) and with reduced water drainage and d (2030–2040) iver basin management plans and integrated water management r runoff as a result of increased evaporative demand, 2°C ) high confidence particularly in southern Europe ( Long term (2080–2100) 4°C [23. 4, 23.7] ery V ery V Medium Increased economic losses and people affected by • Implementation of warning systems high low xtreme heat events: impacts on health and e Adaptation of dwellings and workplaces and of transport and • resent P l-being, labor productivity, crop production, air wel nergy infrastructure e quality, and increasing risk of wildfires in southern ear term N • Reductions in emissions to improve air quality 2030–2040) ( urope and in Russian boreal region E Improved wildfire management • ium confidence med ( ) 2°C ong term L Development of insurance products against weather-related yield • (2080–2100) [23.3-7, Table 23-1] variati ons 4°C Asia Risk & potential for Climatic Timeframe Key risk Adaptation issues & prospects drivers adaptation Very Very Medium Increased riverine, coastal, and urban • Exposure reduction via structural and non-structural measures, effective high low flooding leading to widespread damage land-use planning, and selective relocation Present infrastructure, livelihoods, and to • Reduction in the vulnerability of lifeline infrastructure and services (e.g., water, ium confidence ) settlements in Asia ( med Near term energy, waste management, food, biomass, mobility, local ecosystems, (2030–2040) nications) telecommu [24. 4] • Construction of monitoring and early warning systems; Measures to identify 2 °C Long term exposed areas, assist vulnerable areas and households, and diversify livelihoods (2080–2100) 4°C • Economic diversification Very Very • Heat health warning systems Increased risk of heat-related mortality Medium igh h low ) high confidence ( • Urban planning to reduce heat islands; Improvement of the built environment; Present opment of sustainable cities Devel 4] [24. Near term • New work practices to avoid heat stress among outdoor workers (2030–2040) 2°C Long term (2080–2100) 4°C Very Very • Disaster preparedness including early-warning systems and local coping Medium Increased risk of drought-related water high low ies strateg and food shortage causing malnutrition Present ( high confidence ) • Adaptive/integrated water resource management Near term • Water infrastructure and reservoir development (2030–2040) [24. 4] • Diversification of water sources including water re-use 2°C Long term • More efficient use of water (e.g., improved agricultural practices, irrigation (2080–2100) man agement, and resilient agriculture) 4°C 22

24 Summary for Policymakers Assessment Box SPM.2 Table 1 (continued) ont inued next page C Australasia Climatic Risk & potential for Timeframe Key risk Adaptation issues & prospects rivers d daptation a Very Very • S Ability of corals to adapt naturally appears limited and insufficient to offset the ignificant change in community Medium igh h ow l detrimental effects of rising temperatures and acidification. tion and structure of coral reef composi S M P Present ) high confidence systems in Australia ( • Other options are mostly limited to reducing other stresses (water quality, N ear term t ourism, fishing) and early warning systems; direct interventions such as assisted (2030–2040) [ 25. 6, 30.5, Boxes CC-CR and CC-OA] c olonization and shading have been proposed but remain untested at scale. 2 °C Long term OO C ( 2080–2100) 4°C ery V Very • Significant adaptation deficit in some regions to current flood risk. I ncreased frequency and intensity of flood Medium igh h low damage to infrastructure and settlements • Effective adaptation includes land-use controls and relocation as well as Present in Australia and New Zealand protection and accommodation of increased risk to ensure flexibility. ( high confidence ) Near term ( 2030–2040) [Table 25-1, Boxes 25-8 and 25-9] 2 °C L ong term ( 2080–2100) 4°C ery V Very • I Adaptation deficit in some locations to current coastal erosion and flood risk. ncreasing risks to coastal infrastructure Medium high low S a uccessive building and protection cycles constrain flexible responses. nd low-lying ecosystems in Australia and P resent New Zeal and, with widespread damage • Effective adaptation includes land-use controls and ultimately relocation as well toward s the upper end of projected Near term a s protection and accommodation. s ea-level-rise ranges ( high confidence ) (2030–2040) 2 °C Long term 6, 25.10, Box 25-1] [25. ( 2080–2100) 4°C North America Risk & potential for Climatic Timeframe Key risk Adaptation issues & prospects adaptation drivers Very Very Medium • Some ecosystems are more fire-adapted than others. Forest managers and Wildfire-induced loss of ecosystem high low municipal planners are increasingly incorporating fire protection measures (e.g., integrity, property loss, human morbidity, Present prescribed burning, introduction of resilient vegetation). Institutional capacity to and mortality as a result of increased support ecosystem adaptation is limited. drying trend and temperature trend Near term (2030–2040) ) high confidence ( • Adaptation of human settlements is constrained by rapid private property development in high-risk areas and by limited household-level adaptive capacity. 2 °C Long term [26. 4, 26.8, Box 26-2] • Agroforestry can be an effective strategy for reduction of slash and burn (2080–2100) 4°C practices in Mexico. Very Very human mortality • Residential air conditioning (A/C) can effectively reduce risk. However, Heat-related Medium igh h low lability and usage of A/C is highly variable and is subject to complete loss avai high confidence ) ( Present during power failures. Vulnerable populations include athletes and outdoor whom A/C is not available. workers for Near term [26. 6, 26.8] (2030–2040) • Community- and household-scale adaptations have the potential to reduce heat extremes via family support, early heat warning systems, exposure to 2°C Long term ing centers, greening, and high-albedo surfaces. cool (2080–2100) 4°C Very Very Urb an floods in riverine and coastal areas, • Implementing management of urban drainage is expensive and disruptive to Medium high low urban areas. inducing property and infrastructure damage; supply chain, ecosystem, and Present • Low-regret strategies with co-benefits include less impervious surfaces leading al system disruption; public health soci to more groundwater recharge, green infrastructure, and rooftop gardens. Near term impacts; and water quality impairment, due (2030–2040) • Sea level rise increases water elevations in coastal outfalls, which impedes level rise, extreme precipitation, and to sea drainage. In many cases, older rainfall design standards are being used that need 2°C cycl high confidence ones ( ) to be updated to reflect current climate conditions. Long term (2080–2100) • Conservation of wetlands, including mangroves, and land-use planning 4°C [26.2-4, 26.8] strateg ies can reduce the intensity of flood events. 23

25 Summary for Policymakers ssessment Box SPM.2 Table 1 (continued) A inued next page Cont Central and South America Climatic Risk & potential for Timeframe Key risk Adaptation issues & prospects drivers adaptation V ery Very Water avai lability in semi-arid and • Integrated water resource management edium M high low glacier-melt-dependent regions and Central • Urban and rural flood management (including infrastructure), early warning Present America; flooding and landslides in urban better weather and runoff forecasts, and infectious disease control systems, and rural areas due to extreme precipitation Near term S M P ( ) high confidence (2030–2040) 2°C Long term [27. 3] (2080–2100) 4°C V ery Very food production and food quality Decreased • Development of new crop varieties more adapted to climate change Medium high low med ( ium confidence ) (temperature and drought) Present • Offsetting of human and animal health impacts of reduced food quality Near term [27. 3] • Offsetting of economic impacts of land-use change (2030–2040) • Strengthening traditional indigenous knowledge systems and practices 2°C OO Long term C (2080–2100) 4°C Very Very Spread of vector-borne diseases in altitude • Development of early warning systems for disease control and mitigation Medium low high ) and latitude ( high confidence based on climatic and other relevant inputs. Many factors augment Present vulnerability. Near term • Establishing programs to extend basic public health services [27. 3] (2030–2040) 2°C n ot available Long term (2080–2100) 4°C not available Polar Regions Risk & potential for Climatic Timeframe Key risk Adaptation issues & prospects adaptation drivers V ery Very • Improved understanding through scientific and indigenous knowledge, Risks for freshwater and terrestrial ecosystems edium M high low producing more effective solutions and/or technological innovations ( high confidence ) and marine ecosystems Present medium confidence ( ), due to changes in ice, • Enhanced monitoring, regulation, and warning systems that achieve safe and snow cover, permafrost, and freshwater/ocean Near term sustainable use of ecosystem resources conditions, affecting species ́ habitat quality, (2030–2040) • Hunting or fishing for different species, if possible, and diversifying income ranges, phenology, and productivity, as well as sources 2°C dependent economies Long term OO C (2080–2100) 4°C [28.2-4] Very V ery • Co-production of more robust solutions that combine science and technology Risks for the health and well-being of Arctic Medium h igh low with indigenous knowledge resi dents, resulting from injuries and illness Present • Enhanced observation, monitoring, and warning systems from the changing physical environment, food insecurity, lack of reliable and safe Near term • Improved communications, education, and training drinking water, and damage to (2030–2040) • Shifting resource bases, land use, and/or settlement areas infrastructure, including infrastructure in 2°C high confidence ) permafrost regions ( Long term (2080–2100) 4°C [28.2-4] Very Very • Co-production of more robust solutions that combine science and Unprecedented challenges for northern Medium high low nology with indigenous knowledge tech nities due to complex inter-linkages commu Present • Enhanced observation, monitoring, and warning systems between climate-related hazards and societal factors , particularly if rate of change is faster Near term • Improved communications, education, and training than social systems can adapt (2030–2040) • Adaptive co-management responses developed through the settlement of ( high confidence ) land claims 2°C Long term [28.2-4] (2080–2100) 4°C Small Islands Risk & potential for Climatic Timeframe Key risk Adaptation issues & prospects adaptation drivers Very Very • Significant potential exists for adaptation in islands, but additional external livelihoods, coastal settlements, Loss of Medium high low resources and technologies will enhance response. infrastructure, ecosystem services, and Present high confidence ) economi c stability ( • Maintenance and enhancement of ecosystem functions and services and of Near term and food security water 6, 29.8, Figure 29-4] [29. (2030–2040) OO C • Efficacy of traditional community coping strategies is expected to be substantially reduced in the future. 2°C Long term (2080–2100) 4°C Very Very • High ratio of coastal area to land mass will make adaptation a significant The interaction of rising global mean sea level Medium high low financial and resource challenge for islands. in the 21st century with high-water-level Present will threaten low-lying coastal areas events • Adaptation options include maintenance and restoration of coastal landforms ( high confidence ) Near term and ecosystems, improved management of soils and freshwater resources, and (2030–2040) appropriate building codes and settlement patterns. 4, Table 29-1; WGI AR5 13.5, Table 13.5] [29. 2°C Long term (2080–2100) 4°C 24

26 Summary for Policymakers Assessment Box SPM.2 Table 1 (continued) The Ocean Climatic Risk & potential for T imeframe A daptation issues & prospects K ey risk d rivers a daptation Very Very • Evolutionary adaptation potential of fish and invertebrate species to warming Distributional shift in fish and invertebrate Medium igh h low is limited as indicated by their changes in distribution to maintain temperatures. s pecies, and decrease in fisheries catch P resent potential at low latitudes, e.g., in equatorial • Human adaptation options: Large-scale translocation of industrial fishing upwelling and coastal boundary systems and vities following the regional decreases (low latitude) vs. possibly transient acti Near term S M P sub-tropical gyres ( high confidence ) (2030–2040) increases (high latitude) in catch potential; Flexible management that can react to vari ability and change; Improvement of fish resilience to thermal stress by 2°C [ 6.3, 30.5-6, Tables 6-6 and 30-3, Box L ong term ucing other stressors such as pollution and eutrophication; Expansion of red CC-M B] (2080–2100) sustainable aquaculture and the development of alternative livelihoods in some 4°C r egions. Very Very • Evidence of rapid evolution by corals is very limited. Some corals may migrate R educed biodiversity, fisheries abundance, Medium igh h ow l to higher latitudes, but entire reef systems are not expected to be able to track and coastal protection by coral reefs due to P resent the high rates of temperature shifts. heat-induced mass coral bleaching and m ortal ity increases, exacerbated by ocean N ear term • Human adaptation options are limited to reducing other stresses, mainly by dification, e.g., in coastal boundary systems aci (2030–2040) enhancing water quality, and limiting pressures from tourism and fishing. These a nd sub-tropical gyres ( high confidence ) o ptions will delay human impacts of climate change by a few decades, but their 2°C Long term efficacy will be severely reduced as thermal stress increases. OO C [5. 4, 6.4, 30.3, 30.5-6, Tables 6-6 and 30-3, (2080–2100) 4°C Box CC-CR] ery V Very • Human adaptation options are limited to reducing other stresses, mainly by Coastal inundation and habitat loss due to Medium igh h ow l ucing pollution and limiting pressures from tourism, fishing, physical red sea level rise, extreme events, changes in OO C Present destruction, and unsustainable aquaculture. precipitation, and reduced ecological resi lience, e.g., in coastal boundary systems Near term • Reducing deforestation and increasing reforestation of river catchments and and sub-tropical gyres (2030–2040) coastal areas to retain sediments and nutrients ) ium med to ( high confidence • Increased mangrove, coral reef, and seagrass protection, and restoration to 2°C Long term p rotect numerous ecosystem goods and services such as coastal protection, [5. 5, 30.5-6, Tables 6-6 and 30-3, Box (2080–2100) tou rist value, and fish habitat 4°C CC-CR] C: MANAGING FUTURE RISKS AND BUILDING RESILIENCE Managing the risks of climate change involves adaptation and mitigation decisions with implications for future generations, economies, and environments. This section evaluates adaptation as a means to build resilience and to adjust to climate-change impacts. It also considers limits to adaptation, climate-resilient pathways, and the role of transformation. See Figure SPM.8 for an overview of responses for addressing risk related to climate change. C-1. Principles for Effective Adaptation Adaptation is place- and context-specific, with no single approach for reducing risks appropriate across all settings ( h i g h Effective risk reduction and adaptation strategies consider the dynamics of vulnerability and exposure and their linkages with o n f i d e n c e ). c socioeconomic processes, sustainable development, and climate change. Specific examples of responses to climate change are presented in 67 Table SPM.1. Adaptation planning and implementation can be enhanced through complementary actions across levels, from individuals to National governments can coordinate adaptation efforts of local and subnational governments, for example i g h c o n f i d e n c e ). governments ( h by protecting vulnerable groups, by supporting economic diversification, and by providing information, policy and legal frameworks, and financial support ( robust evidence , high agreement ). Local government and the private sector are increasingly recognized as critical to progress in adaptation, given their roles in scaling up adaptation of communities, households, and civil society and in managing risk information and 68 medium evidence , high agreement ). financing ( A first step towards adaptation to future climate change is reducing vulnerability and exposure to present climate variability Available strategies and actions can increase h i g h c o n f i ( e n c e ). Strategies include actions with co-benefits for other objectives. d resilience across a range of possible future climates while helping to improve human health, livelihoods, social and economic well-being, and 67 2.1, 8.3-4, 13.1, 13.3-4, 15.2-3, 15.5, 16.2-3, 16.5, 17.2, 17.4, 19.6, 21.3, 22.4, 26.8-9, 29.6, 29.8 68 2.1-4, 3.6, 5.5, 8.3-4, 9.3-4, 14.2, 15.2-3, 15.5, 16.2-5, 17.2-3, 22.4, 24.4, 25.4, 26.8-9, 30.7, Tables 21-1, 21-5, & 21-6, Box 16-2 25

27 Summary for Policymakers ulnerability & Exposure V ocioeconomic Pathways S • Vulnerability & exposure • I MPACTS iverse values & objectives A-3] D [ reduction C-1] [ • lima te-resilient pathways [C-2] C • Low-regrets strategies & • ransformation [C-2] T C-1] actions [ Addressing multidimensional • M P S inequalities A-1, C-1] [ ulnerability V OCIOECONOMIC S CLIMATE ROCESSES P daptation & Interactions A Natural ith Mitigation w Socioeconomic Variability Pathways • Incremental & transformational isk R adaptation [A-2, A-3, C-2] ds azar H Risk assessment B] [ • • Adaptation and R R K R IS ISK benefits, synergies, & Co- Iterative risk management • Mitigation radeoffs [A-2, C-1, C-2] t Actions [A-3] • ont ext-specific adaptation C [C-1] Anthr opogenic Risk perception A-3, C-1] [ • • Climate Change omp lementary actions [C-1] C • Governance imits to adaptation [C-2] L Exposure nthropogenic A Governance Climate Change • EMISSIONS ecision making under D Mitigation [WGIII AR5] • uncertainty [A-3] and Land-use Change • earning, monitoring, & flexibility L [A-2, A-3, C-1] • oordination across scales C [A-2, C-1] Figu re SPM.8 | The solution space. Core concepts of the WGII AR5, illustrating overlapping entry points and approaches, as well as key considerations, in managing risks related to climate change, as assessed in this report and presented throughout this SPM. Bracketed references indicate sections of this summary with corresponding assessment findings. environmental quality. See Table SPM.1. Integration of adaptation into planning and decision making can promote synergies with development 69 and disaster risk reduction. Adaptation planning and implementation at all levels of governance are contingent on societal values, objectives, and risk perceptions ( h i g h c o n f i d e n c e ). Recognition of diverse interests, circumstances, social-cultural contexts, and expectations can Indigenous, local, and traditional knowledge systems and practices, including indigenous peoples’ benefit decision-making processes. holistic view of community and environment, are a major resource for adapting to climate change, but these have not been used consistently in 70 existing adaptation efforts. Integrating such forms of knowledge with existing practices increases the effectiveness of adaptation. Decision support is most effective when it is sensitive to context and the diversity of decision types, decision processes, and Organizations bridging science and decision making, including climate services, play constituencies ( r o b u s t e v i d e n c e , h i g h a g r e m e ). t n e an important role in the communication, transfer, and development of climate-related knowledge, including translation, engagement, and 71 medium evidence , high agreement ). knowledge exchange ( Existing and emerging economic instruments can foster adaptation by providing incentives for anticipating and reducing impacts Instruments include public-private finance partnerships, loans, payments for environmental services, improved resource m e d i u m c o n f i d e n c e ). ( pricing, charges and subsidies, norms and regulations, and risk sharing and transfer mechanisms. Risk financing mechanisms in the public and private sector, such as insurance and risk pools, can contribute to increasing resilience, but without attention to major design challenges, they can also provide disincentives, cause market failure, and decrease equity. Governments often play key roles as regulators, providers, or insurers 72 of last resort. Constraints can interact to impede adaptation planning and implementation ( h i g h c o n f i d e n c e ). Common constraints on implementation arise from the following: limited financial and human resources; limited integration or coordination of governance; uncertainties 69 3.6, 8.3, 9.4, 14.3, 15.2-3, 17.2, 20.4, 20.6, 22.4, 24.4-5, 25.4, 25.10, 27.3-5, 29.6, Boxes 25-2 and 25-6 70 2.2-4, 9.4, 12.3, 13.2, 15.2, 16.2-4, 16.7, 17.2-3, 21.3, 22.4, 24.4, 24.6, 25.4, 25.8, 26.9, 28.2, 28.4, Table 15-1, Box 25-7 71 2.1-4, 8.4, 14.4, 16.2-3, 16.5, 21.2-3, 21.5, 22.4, Box 9-4 72 10.7, 10.9, 13.3, 17.4-5, Box 25-7 26

28 Summary for Policymakers Table SPM.1 | Approaches for managing the risks of climate change . These approaches should be considered overlapping rather than discrete, and they are often pursued . It is not addressed in this table as mitigation is the focus of WGIII AR5. Examples are simultaneously. Mitigation is considered essential for managing the risks of climate change c order and can be relevant to more than one category. [14.2-3, Table 14-1] presented in no specifi Overlapping Category Examples Chapter Reference(s) Approaches S M P s .3, 9.3, 13.1-3, 14.2-3, 22.4 8 n , energy, safe housing & settlement structures, Improved access to education, nutrition, health facilities e Human r o u i social support structures; Reduced gender inequality & marginalization in other forms. & development s t a c e 8.3-4, 9.3, 13.1-3 u m mproved access to & control of local resources; Land tenure; Disaster risk reduction; Social safety nets I Poverty alleviation s d t & social protection; Insurance schemes. e e r R g e .5, 9.4, 13.1-3, 22.3-4, 23.4, 26.5, 7 ncome , asset, & livelihood diversifi cation; Improved infrastructure; Access to technology & decision- I r e - r 27.3, 29.6, Table SM24-7 making fora; Increased decision-making power; Changed cropping, livestock, & aquaculture practices; Livelihood security w u o l eliance on social networks. R s y o n a p .2-4, 11.7, 14.3, 15.4, 22.4, 24.4, 8 Early warning systems; Hazard & vulnerability mapping; Diversifying water resources; Improved m x Disaster risk Table 3-3 26.6, 28.4, Box 25-1, drainage; Flood & cyclone shelters; Building codes & practices; Storm & wastewater management; g E n management i ransport & road infrastructure improvements. T d & u l c y .3-4, 8.3, 22.4, Table 3-3, Boxes 4-3, 4 Maintaining wetlands & urban green spaces; Coastal afforestation; Watershed & reservoir n t i i l s 8-2, 15-1, 25-8, 25-9, & CC-EA anagement; Reduction of other stressors on ecosystems & of habitat fragmentation; Maintenance m Ecosystem i e c b i of genetic diversity; Manipulation of disturbance regimes; Community-based natural resource management t a c r anagement. m a r e p n 4.4, 8.1-4, 22.4, 23.7-8, 27.3, Box 25-8 & l , & services; Managing development in fl ood prone & Provisioning of adequate housing, infrastructure , Spatial or land-use u g other high risk areas; Urban planning & upgrading programs; Land zoning laws; Easements; Protected n V i planning n reas. a n a l p 3.5-6, 5.5, 8.2-3, 10.2, 11.7, 23.3, : Sea walls & coastal protection structures; Flood levees; Engineered & built-environment options , t 24.4, 25.7, 26.3, 26.8, Boxes 15-1, ater storage; Improved drainage; Flood & cyclone shelters; Building codes & practices; Storm & W n e 5-1, 25-2, & 25-8 2 wastewater management; Transport & road infrastructure improvements; Floating houses; Power plant m p electricity grid adjustments. & o l e v 7.5, 8.3, 9.4, 10.3, 15.4, 22.4, 24.4, e : New crop & animal varieties; Indigenous, traditional, & local knowledge, Technological options d 6.3, 26.5, 27.3, 28.2, 28.4, 29.6-7, 2 , & methods; Effi cient irrigation; Water-saving technologies; Desalinization; Conservation technologies h g Tables 3-3 & 15-1 Boxes 20-5 & 25-2, agriculture; Food storage & preservation facilities; Hazard & vulnerability mapping & monitoring; Early u o r warning systems; Building insulation; Mechanical & passive cooling; Technology development, transfer, h t s & diffusion. t Structural/physical n e 4.4, 5.5, 6.4, 8.3, 9.4, 11.7, 15.4, 22.4, : Ecological restoration; Soil conservation; Afforestation & reforestation; Ecosystem-based options m t 23.6-7, 24.4, 25.6, 27.3, 28.2, 29.7, , green roofs); Mangrove conservation & replanting; Green infrastructure (e.g., shade trees s u 30.6, Boxes 15-1, 22-2, 25-9, 26-2, j shing; Fisheries co-management; Assisted species migration & dispersal; Ecological Controlling overfi d & CC-EA corridors; Seed banks , gene banks, & other conservation; Community-based natural resource ex situ a l management. a n o 3.5-6, 8.3, 9.3, 11.7, 11.9, 22.4, 29.6, i : Social safety nets & social protection; Food banks & distribution of food surplus; Municipal Services t a Box 13-2 services including water & sanitation; Vaccination programs; Essential public health services; Enhanced m n r emergency medical services. o o i f t s 8.3-4, 9.4, 10.7, 11.7, 13.3, 15.4, 17.5, Economic options : Financial incentives; Insurance; Catastrophe bonds; Payments for ecosystem n a a t 22.4, 26.7, 27.6, 29.6, Box 25-7 services; Pricing water to encourage universal provision and careful use; Microfi nance; Disaster r p t contingency funds; Cash transfers; Public-private partnerships. a & d l a A 4.4, 8.3, 9.3, 10.5, 10.7, 15.2, 15.4, Laws & regulations : Land zoning laws; Building standards & practices; Easements; Water regulations t n 17.5, 22.4, 23.4, 23.7, 24.4, 25.4, 26.3, & agreements; Laws to support disaster risk reduction; Laws to encourage insurance purchasing; e 27.3, 30.6, Table 25-2, Box CC-CR m ned property rights & land tenure security; Protected areas; Fishing quotas; Patent pools & Defi Institutional e r technology transfer. c n i 2.4, 3.6, 4.4, 5.5, 6.4, 7.5, 8.3, 11.7, National & government policies & programs : National & regional adaptation plans including g n 15.2-5, 22.4, 23.7, 25.4, 25.8, 26.8-9, cation; Urban upgrading mainstreaming; Sub-national & local adaptation plans; Economic diversifi i d 27.3-4, 29.6, Boxes 25-1, 25-2, & 25-9, programs; Municipal water management programs; Disaster planning & preparedness; Integrated u l Tables 9-2 & 17-1 water resource management; Integrated coastal zone management; Ecosystem-based management; c n i Community-based adaptation. 8.3-4, 9.4, 11.7, 12.3, 15.2-4, 22.4, Educational options : Awareness raising & integrating into education; Gender equity in education; Tables 15-1 & 25-2 25.4, 28.4, 29.6, , traditional, & local knowledge; Participatory action research & Extension services; Sharing indigenous social learning; Knowledge-sharing & learning platforms. 2.4, 5.5, 8.3-4, 9.4, 11.7, 15.2-4, 22.4, : Hazard & vulnerability mapping; Early warning & response systems; Informational options 23.5, 24.4, 25.8, 26.6, 26.8, 27.3, 28.2, Systematic monitoring & remote sensing; Climate services; Use of indigenous climate observations; Social 28.5, 30.6, Table 25-2, Box 26-3 Participatory scenario development; Integrated assessments. 5.5, 7.5, 9.4, 12.4, 22.3-4, 23.4, 23.7, Behavioral options : Household preparation & evacuation planning; Migration; Soil & water 25.7, 26.5, 27.3, 29.6, Table SM24-7, cation; Changed cropping, livestock, & conservation; Storm drain clearance; Livelihood diversifi Box 25-5 aquaculture practices; Reliance on social networks. n o i 8.3, 17.3, 20.5, Box 25-5 : Social & technical innovations, behavioral shifts, or institutional & managerial changes that Practical t produce substantial shifts in outcomes. a m r Table 14-1 14.2-3, 20.5, 25.4, 30.7, : Political, social, cultural, & ecological decisions & actions consistent with reducing Political Spheres of change o f vulnerability & risk & supporting adaptation, mitigation, & sustainable development. s n 14.2-3, 20.5, 25.4, Table 14-1 : Individual & collective assumptions, beliefs, values, & worldviews infl uencing climate-change Personal a r responses. T 27

29 Summary for Policymakers bout projected impacts; different perceptions of risks; competing values; absence of key adaptation leaders and advocates; and limited tools a to monitor adaptation effectiveness. Another constraint includes insufficient research, monitoring, and observation and the finance to maintain them. Underestimating the complexity of adaptation as a social process can create unrealistic expectations about achieving intended adaptation 73 outcomes. S P M Poor planning, overemphasizing short-term outcomes, or failing to sufficiently anticipate consequences can result in maladaptation Maladaptation can increase the vulnerability or exposure of the target group in the future, or the m e d i u m e v i d e n c e , h i g h a g r e e m e n ( ). t vulnerability of other people, places, or sectors. Some near-term responses to increasing risks related to climate change may also limit future 74 choices. For example, enhanced protection of exposed assets can lock in dependence on further protection measures. Limited evidence indicates a gap between global adaptation needs and the funds available for adaptation ( m e d i u m c o n f i d e n c e ). There is a need for a better assessment of global adaptation costs, funding, and investment. Studies estimating the global cost of adaptation 75 are characterized by shortcomings in data, methods, and coverage ( high confidence ). Significant co-benefits, synergies, and trade-offs exist between mitigation and adaptation and among different adaptation Increasing efforts to mitigate and adapt to climate responses; interactions occur both within and across regions ( v e r y h i g h c o n f i d e n c e ). change imply an increasing complexity of interactions, particularly at the intersections among water, energy, land use, and biodiversity, but tools to understand and manage these interactions remain limited. Examples of actions with co-benefits include (i) improved energy efficiency and cleaner energy sources, leading to reduced emissions of health-damaging climate-altering air pollutants; (ii) reduced energy and water consumption in urban areas through greening cities and recycling water; (iii) sustainable agriculture and forestry; and (iv) protection of 76 ecosystems for carbon storage and other ecosystem services. C-2. Climate-resilient Pathways and Transformation Climate-resilient pathways are sustainable-development trajectories that combine adaptation and mitigation to reduce climate change and its 77 impacts. They include iterative processes to ensure that effective risk management can be implemented and sustained. See Figure SPM.9. Prospects for climate-resilient pathways for sustainable development are related fundamentally to what the world accomplishes Since mitigation reduces the rate as well as the magnitude of warming, it also i g h c with climate-change mitigation ( n f i d e n c e ). h o increases the time available for adaptation to a particular level of climate change, potentially by several decades. Delaying mitigation actions 78 may reduce options for climate-resilient pathways in the future. Greater rates and magnitude of climate change increase the likelihood of exceeding adaptation limits ( h i g h c o n f i d e n c e ). Limits to adaptation occur when adaptive actions to avoid intolerable risks for an actor’s objectives or for the needs of a system are not possible or are not currently available. Value-based judgments of what constitutes an intolerable risk may differ. Limits to adaptation emerge from the interaction among climate change and biophysical and/or socioeconomic constraints. Opportunities to take advantage of positive synergies between adaptation and mitigation may decrease with time, particularly if limits to adaptation are exceeded. In some parts of the world, 79 insufficient responses to emerging impacts are already eroding the basis for sustainable development. 73 3.6, 4.4, 5.5, 8.4, 9.4, 13.2-3, 14.2, 14.5, 15.2-3, 15.5, 16.2-3, 16.5, 17.2-3, 22.4, 23.7, 24.5, 25.4, 25.10, 26.8-9, 30.6, Table 16-3, Boxes 16-1 and 16-3 74 5.5, 8.4, 14.6, 15.5, 16.3, 17.2-3, 20.2, 22.4, 24.4, 25.10, 26.8, Table 14-4, Box 25-1 75 14.2, 17.4, Tables 17-2 and 17-3 76 2.4-5, 3.7, 4.2, 4.4, 5.4-5, 8.4, 9.3, 11.9, 13.3, 17.2, 19.3-4, 20.2-5, 21.4, 22.6, 23.8, 24.6, 25.6-7, 25.9, 26.8-9, 27.3, 29.6-8, Boxes 25-2, 25-9, 25-10, 30.6-7, CC-WE, and CC-RF 77 2.5, 20.3-4 78 1.1, 19.7, 20.2-3, 20.6, Figure 1-5 79 1.1, 11.8, 13.4, 16.2-7, 17.2, 20.2-3, 20.5-6, 25.10, 26.5, Boxes 16-1, 16-3, and 16-4 28

30 Summary for Policymakers ransformations in economic, social, technological, and political decisions and actions can enable climate-resilient pathways ( h i g h T Specific examples are presented in Table SPM.1. Strategies and actions can be pursued now that will move towards climate- n o e f i d e n c ). c resilient pathways for sustainable development, while at the same time helping to improve livelihoods, social and economic well-being, and responsible environmental management. At the national level, transformation is considered most effective when it reflects a country’s own S M P visions and approaches to achieving sustainable development in accordance with its national circumstances and priorities. Transformations to 8 0 sustainability are considered to benefit from iterative learning, deliberative processes, and innovation. (C) Possible futures (B) Op portunity space (A) Our world High resilience Low risk Multiple stressors including (E) Clim ate-resilient pathways climate change oints (D) Decision p ressors Biophysical st Resilience space Social st ressors (F) Pathways that lower r esilience resilience h risk Low Hig Figure SPM.9 | pinge on resilience from many directions, Opportunity space and climate-resilient pathways. (A) Our world [Sections A-1 and B-1] is threatened by multiple stressors that im represented here simply as biophysical and social stressors. Stressors include climate change, climate variability, land-use change, degradation of ecosystems, poverty and inequality, and cultural factors. (B) Opportunity space [Sections A-2, A-3, B-2, C-1, and C-2] refers to decision points and pathways that lead to a range of (C) possible futures [Sections C and B-3] with differing levels of resilience and risk. (D) Decision points result in actions or failures-to-act throughout the opportunity space, and together they constitute the process of managing or failing to manage risks related to climate change. (E) Climate-resilient pathways (in green) within the opportunity space lead to a more resilien t world through adaptive learning, increasing scientific knowledge, effective adaptation and mitigation measures, and other choices that reduce risks. (F) Pathways that lower resilience (in red) can involve insufficient mitigation, maladaptation, failure to learn and use knowledge, and other actions that lower resilience; and they can be irreversible in terms of possible futures. 80 1.1, 2.1, 2.5, 8.4, 14.1, 14.3, 16.2-7, 20.5, 22.4, 25.4, 25.10, Figure 1-5, Boxes 16-1, 16-4, and TS.8 29

31 Summary for Policymakers SUPPLEMENTARY MATERIAL Table SPM.A1 | Observed impacts attributed to climate change reported in the scientifi c literature since the AR4. These impacts have been attributed to climate change with , with the relative contribution of climate change to the observed change indicated (major or minor), for natural and human systems dence high confi , or medium , low , very low across eight major world regions over the past several decades . [Tables 18-5, 18-6, 18-7, 18-8, and 18-9] Absence from the table of additional impacts attributed to climate change does not imply that such impacts have not occurred. S M P Africa , major contribution from climate change) high confi etreat of tropical highland glaciers in East Africa ( dence R • , Snow & Ice , major contribution from climate change) • West African rivers ( low confi dence Reduced discharge in Rivers & Lak es, high confi dence , major contribution from climate change) cation increases in the Great Lakes and Lake Kariba ( ake surface warming and water column stratifi • L Floods & Drought ncreased soil moisture drought in the Sahel since 1970, partially wetter conditions since 1990 ( medium confi dence , major contribution from climate change) I • Tables 18-5, 18-6, and 22-3] [22.2-3, dence medium confi , major contribution from climate change) ree density decreases in western Sahel and semi-arid Morocco, beyond changes due to land use ( T • Terrestrial Range shifts of several southern plants and animals dence , beyond changes due to land use ( , major contribution from climate change) • medium confi Ecosystems res on Mt. Kilimanjaro ( , major contribution from climate change) dence low confi ncreases in wildfi • I [22.3, Tables 18-7 and 22-3] high confi dence , major contribution from climate change) ecline in coral reefs in tropical African waters , beyond decline due to human impacts ( • D Coastal Erosion [Table 18-8] & Marine Ecosystems • dence Adaptive responses to changing rainfall by South African farmers , beyond changes due to economic conditions ( very low confi , major contribution from climate Food Production change) & Livelihoods , major contribution from climate change) ecline in fruit-bearing trees in Sahel ( low confi dence D • • , minor contribution from Malaria increases in Kenyan highlands , beyond changes due to vaccination, drug resistance, demography, and livelihoods ( dence low confi limate change) c , minor contribution from dence • Reduced fi sheries productivity of Great Lakes and Lake Kariba, beyond changes due to fi sheries management and land use ( low confi limate change) c Table 18-9] [7.2, 11.5, 13.2, 22.3, Europe Retreat of Alpine , Scandinavian, and Icelandic glaciers ( high confi dence , major contribution from climate change) • Snow & Ice , • Increase in rock slope failures in western Alps ( medium confi dence , major contribution from climate change) Rivers & Lak es, oods ( dence Changed occurrence of extreme river discharges and fl , minor contribution from climate change) • very low confi & Drought Floods [18.3, 23.2-3, Tables 18-5 and 18-6; WGI AR5 4.3] Earlier greening, leaf emergence dence , major contribution from climate change) high confi , and fruiting in temperate and boreal trees ( • Terrestrial Increased colonization of alien plant species in Europe dence , beyond a baseline of some invasion ( , major contribution from climate change) • medium confi Ecosystems dence • Earlier arrival of migratory birds in Europe since 1970 ( medium confi , major contribution from climate change) dence , major contribution from climate change) low confi Upward shift in tree-line in Europe • , beyond changes due to land use ( high confi dence Increasing burnt forest areas during recent decades in Portugal and Greece • , major contribution from climate , beyond some increase due to land use ( change) Tables 18-7 and 23-6] [4.3, 18.3, , major contribution from climate • Northward distributional shifts of zooplankton, fi shes, seabirds, and benthic invertebrates in northeast Atlantic ( high confi dence Coastal Erosion change) & Marine , major contribution from climate change) dence medium confi sh species across European seas ( • Northward and depth shift in distribution of many fi Ecosystems dence , major contribution from climate change) • Plankton phenology changes in northeast Atlantic ( medium confi • Spread of warm water species into the Mediterranean, beyond changes due to invasive species and human impacts ( medium confi dence , major contribution from climate change) [6.3, 23.6, 30.5, Tables 6-2 and 18-8, Boxes 6-1 and CC-MB] , major contribution low confi • Shift from cold-related mortality to heat-related mortality in England and Wales, beyond changes due to exposure and health care ( dence Food Production from climate change) & Livelihoods Impacts on livelihoods of Sámi people in northern Europe dence medium confi , beyond effects of economic and sociopolitical changes ( • , major contribution from climate change) Stagnation of wheat yields in some countries in recent decades , despite improved technology ( • , minor contribution from climate change) dence medium confi medium confi dence , minor contribution from climate Positive yield impacts for some crops mainly in northern Europe, beyond increase due to improved technology ( • change) , minor contribution from climate change) dence medium confi Spread of bluetongue virus in sheep and of ticks across parts of Europe ( • [18.4, 23.4-5, Table 18-9, Figure 7-2] Continued next page 30

32 Summary for Policymakers able SPM.A1 (continued) T sia A dence high confi ermafrost degradation in Siberia, Central Asia, and Tibetan Plateau ( , major contribution from climate change) • P , now & Ice S • , major contribution from climate change) dence Shrinking mountain glaciers across most of Asia ( medium confi es, ivers & Lak R , minor contribution from climate change) dence • Changed water availability in many Chinese rivers , beyond changes due to land use ( low confi & Drought Floods • Increased fl ow in several rivers due to shrinking glaciers ( high confi dence , major contribution from climate change) • Earlier timing of maximum spring fl ood in Russian rivers ( medium confi dence , major contribution from climate change) educed soil moisture in north-central and northeast China (1950 – 2006) ( medium confi dence , major contribution from climate change) • R S M P Surface water degradation in parts of Asia, beyond changes due to land use ( medium confi , minor contribution from climate change) • dence [24.3-4, 28.2, Tables 18-5, 18-6, and SM24-4, Box 3-1; WGI AR5 4.3, 10.5] • medium confi dence , major contribution from Changes in plant phenology and growth in many parts of Asia (earlier greening), particularly in the north and east ( Terrestrial limate change) c Ecosystems Distribution shifts of many plant and animal species upwards in elevation or polewards medium confi dence , major contribution from • , particularly in the north of Asia ( climate change) , major contribution from climate change) • Invasion of Siberian larch forests by pine and spruce during recent decades ( low confi dence , major contribution from climate change) dence high confi Advance of shrubs into the Siberian tundra ( • 4.3, 24.4, 28.2, Table 18-7, Figure 4-4] [ , major contribution from climate change) • Decline in coral reefs in tropical Asian waters , beyond decline due to human impacts ( high confi dence Coastal Erosion c, and of a predatory fi sh in the Sea of Japan ( medium confi dence , major contribution Northward range extension of corals in the East China Sea and western Pacifi • & Marine from climate change) cosystems E dence , major contribution from climate change) low confi c, beyond fl uctuations due to fi sheries ( • Shift from sardines to anchovies in the western North Pacifi dence , major contribution from climate change) • Increased coastal erosion in Arctic Asia ( low confi Tables 6-2 and 18-8] [6.3, 24.4, 30.5, mpacts on livelihoods of indigenous groups in Arctic Russia, beyond economic and sociopolitical changes ( low confi dence , major contribution from climate change) I • Food Production • medium confi dence , minor contribution from climate change) Negative impacts on aggregate wheat yields in South Asia, beyond increase due to improved technology ( & Livelihoods low confi dence Negative impacts on aggregate wheat and maize yields in China, beyond increase due to improved technology ( , minor contribution from climate change) • Increases in a water-borne disease in Israel ( dence , minor contribution from climate change) low confi • Tables 18-4 and 18-9, Figure 7-2] [7.2, 13.2, 18.4, 28.2, Australasia Signifi • cant decline in late-season snow depth at 3 of 4 alpine sites in Australia (1957– 2002) ( medium confi dence , major contribution from climate change) Snow & Ice , dence medium confi • Substantial reduction in ice and glacier ice volume in New Zealand ( , major contribution from climate change) es, Rivers & Lak • Intensifi cation of hydrological drought due to regional warming in southeast Australia ( low confi dence , minor contribution from climate change) & Drought Floods ow in river systems in southwestern Australia (since the mid-1970s) ( , major contribution from climate change) dence Reduced infl high confi • [25.5, Tables 18-5, 18-6, and 25-1; WGI AR5 4.3] • Changes in genetics , growth, distribution, and phenology of many species, in particular birds, butterfl ies, and plants in Australia, beyond fl uctuations due to variable Terrestrial , land use, pollution, and invasive species ( high confi dence , major contribution from climate change) local climates Ecosystems Expansion of some wetlands and contraction of adjacent woodlands in southeast Australia ( , major contribution from climate change) dence low confi • • Expansion of monsoon rainforest at expense of savannah and grasslands in northern Australia ( medium confi dence , major contribution from climate change) Waikato River, New Zealand ( low confi dence , major contribution from climate change) • Migration of glass eels advanced by several weeks in [Tables 18-7 and 25-3] • Southward shifts in the distribution of marine species near Australia, beyond changes due to short-term environmental fl uctuations, fi shing, and pollution ( medium Coastal Erosion confi dence , major contribution from climate change) & Marine • dence , major contribution from climate change) Change in timing of migration of seabirds in Australia ( low confi Ecosystems , beyond effects from pollution and physical disturbance ( Increased coral bleaching in Great Barrier Reef and western Australian reefs , major high confi • dence contribution from climate change) , beyond effects from pollution ( Changed coral disease patterns at Great Barrier Reef dence , major contribution from climate change) • medium confi [6.3, 25.6, Tables 18-8 and 25-3] • Advanced timing of wine-grape maturation in recent decades , beyond advance due to improved management ( medium confi dence , major contribution from climate Food Production change) & Livelihoods . summer human mortality in Australia, beyond changes due to exposure and health care ( low confi dence , major contribution from climate change) Shift in winter vs • cation of agricultural activities in Australia, beyond changes due to policy, markets, and short-term climate variability ( dence , minor Relocation or diversifi • low confi contribution from climate change) Tables 18-9 and 25-3, Box 25-5] [11.4, 18.4, 25.7-8, North America • Shrinkage of glaciers across western and northern North America ( high confi dence , major contribution from climate change) , Snow & Ice dence high confi Decreasing amount of water in spring snowpack in western North America (1960 • , major contribution from climate change) – 2002) ( es, Rivers & Lak • Shift to earlier peak fl ow in snow dominated rivers in western North America ( high confi dence , major contribution from climate change) & Drought Floods Increased runoff in the midwestern and northeastern US ( medium confi dence , minor contribution from climate change) • [Tables 18-5 and 18-6; WGI AR5 2.6, 4.3] • medium confi dence , major contribution from climate change) Phenology changes and species distribution shifts upward in elevation and northward across multiple taxa ( Terrestrial Increased wildfi medium confi dence , major contribution from climate change) • re frequency in subarctic conifer forests and tundra ( Ecosystems Regional increases in tree mortality and insect infestations in forests ( low confi , minor contribution from climate change) • dence re activity, fi re frequency and duration, and burnt area in forests of the western US and boreal forests in Canada, beyond changes due to land use Increase in wildfi • re management ( medium confi dence , minor contribution from climate change) and fi Table 18-7, Box 26-2] [26.4, 28.2, , major contribution from climate change) high confi Northward distributional shifts of northwest Atlantic fi sh species ( • dence Coastal Erosion • Changes in musselbeds along the west coast of US ( high confi dence , major contribution from climate change) & Marine • c ( high confi dence , major contribution from climate change) Changed migration and survival of salmon in northeast Pacifi Ecosystems Increased coastal erosion in Alaska and Canada ( medium confi dence , major contribution from climate change) • Tables 6-2 and 18-8] [18.3, 30.5, , major contribution • Impacts on livelihoods of indigenous groups in the Canadian Arctic, beyond effects of economic and sociopolitical changes ( medium confi dence Food Production from climate change) & Livelihoods [18.4, 28.2, Tables 18-4 and 18-9] Continued next page 31

33 Summary for Policymakers Table SPM.A1 (continued) Central and South America hrinkage of Andean glaciers ( high confi dence , major contribution from climate change) • S Snow & Ice , medium confi ows in Amazon River ( hanges in extreme fl , major contribution from climate change) dence C • es, Rivers & Lak , major contribution from climate change) dence • Changing discharge patterns in rivers in the western Andes ( medium confi Floods & Drought , major contribution from climate change) dence ncreased streamfl ow in sub-basins of the La Plata River, beyond increase due to land-use change ( high confi I • [27.3, Tables 18-5, 18-6, and 27-3; WGI AR5 4.3] S P M , minor contribution from climate change) ncreased tree mortality and forest fi re in the Amazon ( low confi dence I • Terrestrial • Rainforest degradation and recession in the Amazon, beyond reference trends in deforestation and land degradation ( low confi dence , minor contribution from climate Ecosystems hange) c Table 18-7] 4.3, 18.3, 27.2-3, [ • Increased coral bleaching in western Caribbean, beyond effects from pollution and physical disturbance ( high confi dence , major contribution from climate change) Coastal Erosion , minor contribution from climate change) angrove degradation on north coast of South America, beyond degradation due to pollution and land use ( low confi dence • M & Marine [27.3, Table 18-8] Ecosystems • More vulnerable livelihood trajectories for indigenous Aymara farmers in Bolivia due to water shortage , beyond effects of increasing social and economic stress Food Production medium confi dence , major contribution from climate change) ( & Livelihoods medium confi Increase in agricultural yields and expansion of agricultural areas in southeastern South America, beyond increase due to improved technology ( , • dence major contribution from climate change) 13.1, 27.3, Table 18-9] [ Polar Regions dence high confi , major contribution from climate change) Decreasing Arctic sea ice cover in summer ( • , Snow & Ice , major contribution from climate change) • Reduction in ice volume in Arctic glaciers ( high confi dence es, Rivers & Lak ecreasing snow cover extent across the Arctic ( medium confi dence , major contribution from climate change) • D & Drought Floods Widespread permafrost degradation, especially in the southern Arctic ( dence , major contribution from climate change) high confi • , major contribution from climate change) ce mass loss along coastal Antarctica ( medium confi dence I • Increased river discharge for large circumpolar rivers (1997–2007) ( low confi dence , major contribution from climate change) • Increased winter minimum river fl ow in most of the Arctic ( medium confi dence , major contribution from climate change) • ncreased lake water temperatures 1985–2009 and prolonged ice-free seasons ( medium confi dence , major contribution from climate change) I • • high confi dence , major Disappearance of thermokarst lakes due to permafrost degradation in the low Arctic. New lakes created in areas of formerly frozen peat ( contribution from climate change) [28.2, Tables 18-5 and 18-6; WGI AR5 4.2-4, 4.6, 10.5] dence , major contribution from climate change) • Increased shrub cover in tundra in North America and Eurasia ( high confi Terrestrial • medium confi dence , major contribution from climate change) Advance of Arctic tree-line in latitude and altitude ( Ecosystems , due to snowbed reduction and/or tundra shrub encroachment ( dence Changed breeding area and population size of subarctic birds , major contribution • medium confi from climate change) • high confi dence , major contribution from climate change) Loss of snow-bed ecosystems and tussock tundra ( Impacts on tundra animals from increased ice layers in snow pack, following rain-on-snow events ( medium confi dence , major contribution from climate change) • Increased plant species ranges in the • dence , major contribution from climate change) West Antarctic Peninsula and nearby islands over the past 50 years ( high confi Increased phytoplankton productivity in Signy Island lake waters ( dence , major contribution from climate change) • high confi [28.2, Table 18-7] , major contribution from climate change) dence • Increased coastal erosion across Arctic ( medium confi Coastal Erosion Negative effects on non-migratory Arctic species ( high confi dence , major contribution from climate change) • & Marine Decreased reproductive success in Arctic seabirds ( medium confi dence , major contribution from climate change) • Ecosystems Decline in Southern Ocean seals and seabirds ( dence , major contribution from climate change) • medium confi Reduced thickness of foraminiferal shells in southern oceans , due to ocean acidifi cation ( medium confi dence , major contribution from climate change) • Reduced krill density in Scotia Sea ( dence • , major contribution from climate change) medium confi Table 18-8] [6.3, 18.3, 28.2-3, , major contribution from climate • Impact on livelihoods of Arctic indigenous peoples dence medium confi , beyond effects of economic and sociopolitical changes ( Food Production change) & Livelihoods • Increased shipping traffi c across the Bering Strait ( medium confi dence , major contribution from climate change) [18.4, 28.2, Tables 18-4 and 18-9, Figure 28-4] Small Islands Increased water scarcity in Jamaica, beyond increase due to water use ( , minor contribution from climate change) dence • very low confi Snow & Ice , [Table 18-6] Rivers & Lak es, & Drought Floods dence • Tropical bird population changes in Mauritius ( , major contribution from climate change) medium confi Terrestrial • Decline of an endemic plant in Hawai’i ( medium confi dence , major contribution from climate change) Ecosystems Upward trend in tree-lines and associated fauna on high-elevation islands ( low confi dence , minor contribution from climate change) • [29.3, Table 18-7] , major contribution from dence high confi • Increased coral bleaching near many tropical small islands , beyond effects of degradation due to fi shing and pollution ( Coastal Erosion climate change) & Marine • Degradation of mangroves , wetlands, and seagrass around small islands, beyond degradation due to other disturbances ( very low confi dence , minor contribution from Ecosystems climate change) • Increased fl ooding and erosion, beyond erosion due to human activities, natural erosion, and accretion ( low confi dence , minor contribution from climate change) • Degradation of groundwater and freshwater ecosystems due to saline intrusion, beyond degradation due to pollution and groundwater pumping ( low confi dence , minor contribution from climate change) Table 18-8] [29.3, low sheries due to direct effects and effects of increased coral reef bleaching, beyond degradation due to overfi shing and pollution ( • Increased degradation of coastal fi Food Production confi dence , minor contribution from climate change) & Livelihoods [18.3-4, 29.3, 30.6, Table 18-9, Box CC-CR] 32

34 INTERGOVERNMENTAL PANEL ON climate change WG II WORKING GROUP II CONTRIBUTION TO THE FIFTH ASSESSMENT REPORT OF THE INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE

Related documents

when rising seas hit home full report

when rising seas hit home full report

When Rising Seas Hit Home Hard Choices Ahead for Hundreds of US Coastal Communities

More info »