Managing the Risks of Extreme Events and Disasters to Advance ...

SPECIAL REPORT OF THE INTERGOVERNMENTAL PANEL

ON CLIMATE CHANGE

MANAGING THE RISKS OF EXTREME EVENTS AND DISASTERS TO ADVANCE

CLIMATE CHANGE ADAPTATION

Managing the Risks of Extreme Eventsand Disasters to Advance

Climate Change Adaptation

Special Report of the

Intergovernmental Panel on Climate Change

Extreme weather and climate events, interacting with exposed and vulnerable human and natural systems, can lead to disasters. ThisSpecial Report explores the challenge of understanding and managing the risks of climate extremes to advance climate change adaptation.Weather- and climate-related disasters have social as well as physical dimensions. As a result, changes in the frequency and severity ofthe physical events affect disaster risk, but so do the spatially diverse and temporally dynamic patterns of exposure and vulnerability.Some types of extreme weather and climate events have increased in frequency or magnitude, but populations and assets at risk havealso increased, with consequences for disaster risk. Opportunities for managing risks of weather- and climate-related disasters exist orcan be developed at any scale, local to international. Some strategies for effectively managing risks and adapting to climate changeinvolve adjustments to current activities. Others require transformation or fundamental change.

The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for the assessment of climate change, includingthe physical science of climate; impacts, adaptation, and vulnerability; and mitigation of climate change. The IPCC was established by theUnited Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) to provide the world with acomprehensive assessment of the current state of knowledge of climate change and its potential environmental and socioeconomicimpacts.

Managing the Risks of Extreme Eventsand Disasters to Advance

Climate Change Adaptation

Special Report of the

Intergovernmental Panel on Climate Change

Edited by

Christopher B. FieldCo-Chair Working Group II

Carnegie Institutionfor Science

Vicente BarrosCo-Chair Working Group II

CIMA / Universidad deBuenos Aires

Thomas F. StockerCo-Chair Working Group I

University of Bern

Qin DaheCo-Chair Working Group I

China MeteorologicalAdministration

David Jon Dokken

Gian-Kasper Plattner

Kristie L. Ebi

Simon K. Allen

Michael D. Mastrandrea

Melinda Tignor

Katharine J. Mach

Pauline M. Midgley

CAMBRIDGE UNIVERSITY PRESSCambridge, New York, Melbourne, Madrid, Cape Town,Singapore, So Paulo, Delhi, Tokyo, Mexico City

Cambridge University Press32 Avenue of the Americas, New York, NY 10013-2473, USA

www.cambridge.orgInformation on this title: www.cambridge.org/9781107607804

Intergovernmental Panel on Climate Change 2012

This publication is in copyright. Subject to statutory exceptionand to the provisions of relevant collective licensing agreements,no reproduction of any part may take place without the writtenpermission of Cambridge University Press.

First published 2012

Printed in the United States of America

A catalog record for this publication is available from the British Library.

ISBN 978-1-107-02506-6 HardbackISBN 978-1-107-60780-4 Paperback

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Use the following reference to cite the entire volume:IPCC, 2012: Managing the Risks of Extreme Events and Disasters to Advance Climate

Change Adaptation. A Special Report of Working Groups I and II of theIntergovernmental Panel on Climate Change [Field, C.B., V. Barros, T.F. Stocker,D. Qin, D.J. Dokken, K.L. Ebi, M.D. Mastrandrea, K.J. Mach, G.-K. Plattner, S.K. Allen,M. Tignor, and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, UK,and New York, NY, USA, 582 pp.

v

Section I Foreword ............................................................................................................................................................vi

Preface ...............................................................................................................................................................vii

Section II Summary for Policymakers ...............................................................................................................................3

Section III Chapter 1 Climate Change: New Dimensions in Disaster Risk, Exposure, Vulnerability, and Resilience .......25

Chapter 2 Determinants of Risk: Exposure and Vulnerability ........................................................................65

Chapter 3 Changes in Climate Extremes and their Impacts on the Natural Physical Environment ............109

Chapter 4 Changes in Impacts of Climate Extremes: Human Systems and Ecosystems .............................231

Chapter 5 Managing the Risks from Climate Extremes at the Local Level .................................................291

Chapter 6 National Systems for Managing the Risks from Climate Extremes and Disasters......................339

Chapter 7 Managing the Risks: International Level and Integration across Scales.....................................393

Chapter 8 Toward a Sustainable and Resilient Future.................................................................................437

Chapter 9 Case Studies ................................................................................................................................487

Section IV Annex I Authors and Expert Reviewers ....................................................................................................545

Annex II Glossary of Terms ........................................................................................................................555

Annex III Acronyms.....................................................................................................................................565

Annex IV List of Major IPCC Reports ..........................................................................................................569

Index ................................................................................................................................................................573

Contents

I Foreword and Preface

viii

This Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation(SREX) has been jointly coordinated by Working Groups I (WGI) and II (WGII) of the Intergovernmental Panel onClimate Change (IPCC). The report focuses on the relationship between climate change and extreme weather andclimate events, the impacts of such events, and the strategies to manage the associated risks.

The IPCC was jointly established in 1988 by the World Meteorological Organization (WMO) and the United NationsEnvironment Programme (UNEP), in particular to assess in a comprehensive, objective, and transparent manner all therelevant scientific, technical, and socioeconomic information to contribute in understanding the scientific basis of riskof human-induced climate change, the potential impacts, and the adaptation and mitigation options. Beginning in1990, the IPCC has produced a series of Assessment Reports, Special Reports, Technical Papers, methodologies, andother key documents which have since become the standard references for policymakers and scientists.

This Special Report, in particular, contributes to frame the challenge of dealing with extreme weather and climateevents as an issue in decisionmaking under uncertainty, analyzing response in the context of risk management. Thereport consists of nine chapters, covering risk management; observed and projected changes in extreme weather andclimate events; exposure and vulnerability to as well as losses resulting from such events; adaptation options from thelocal to the international scale; the role of sustainable development in modulating risks; and insights from specificcase studies.

Success in developing this report depended foremost on the knowledge, integrity, enthusiasm, and collaboration ofhundreds of experts worldwide, representing a very wide range of disciplines. We would like to express our gratitudeto all the Coordinating Lead Authors, Lead Authors, Contributing Authors, Review Editors, and Expert and GovernmentReviewers who devoted considerable expertise, time, and effort to produce this report. We are extremely grateful fortheir commitment to the IPCC process and we would also like to thank the staff of the WGI and WGII TechnicalSupport Units and the IPCC Secretariat, for their unrestricted commitment to the development of such an ambitiousand highly significant IPCC Special Report.

We are also very grateful to the governments which supported their scientists participation in this task, as well as toall those that contributed to the IPCC Trust Fund, thereby facilitating the essential participation of experts from thedeveloping world. We would also like to express our appreciation, in particular, to the governments of Australia,Panama, Switzerland, and Vietnam for hosting the drafting sessions in their respective countries, as well as to thegovernment of Uganda for hosting in Kampala the First Joint Session of Working Groups I and II which approved thereport. Our thanks are also due to the governments of Switzerland and the United States of America for funding theTechnical Support Units for WGI and WGII, respectively. We also wish to acknowledge the collaboration of thegovernment of Norway which also provided critical support for meetings and outreach and the United NationsInternational Strategy for Disaster Reduction (ISDR), in the preparation of the original report proposal.

We would especially wish to thank the IPCC Chairman, Dr. Rajendra Pachauri, for his direction and guidance of theIPCC process, as well as the Co-Chairs of Working Groups II and I, Professors Vicente Barros, Christopher Field, QinDahe, and Thomas Stocker, for their leadership throughout the development of this Special Report.

Foreword

Foreword

M. JarraudSecretary-GeneralWorld Meteorological Organization

A. SteinerExecutive DirectorUnited Nations Environment Programme

ix

Preface

This volume, Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation, is a SpecialReport of the Intergovernmental Panel on Climate Change (IPCC). The report is a collaborative effort of Working Group I(WGI) and Working Group II (WGII). The IPCC leadership team for this report also has responsibility for the IPCC FifthAssessment Report (AR5), scheduled for completion in 2013 and 2014.

The Special Report brings together scientific communities with expertise in three very different aspects of managingrisks of extreme weather and climate events. For this report, specialists in disaster recovery, disaster risk management,and disaster risk reduction, a community mostly new to the IPCC, joined forces with experts in the areas of the physicalscience basis of climate change (WGI) and climate change impacts, adaptation, and vulnerability (WGII). Over thecourse of the two-plus years invested in assessing information and writing the report, scientists from these threecommunities forged shared goals and products.

Extreme weather and climate events have figured prominently in past IPCC assessments. Extremes can contribute todisasters, but disaster risk is influenced by more than just the physical hazards. Disaster risk emerges from the interactionof weather or climate events, the physical contributors to disaster risk, with exposure and vulnerability, the contributorsto risk from the human side. The combination of severe consequences, rarity, and human as well as physical determinantsmakes disasters difficult to study. Only over the last few years has the science of these events, their impacts, andoptions for dealing with them become mature enough to support a comprehensive assessment. This report provides acareful assessment of scientific, technical, and socioeconomic knowledge as of May 2011, the cut-off date for literatureincluded.

The Special Report introduced some important innovations to the IPCC. One was the integration, in a single SpecialReport, of skills and perspectives across the disciplines covered by WGI, WGII, and the disaster risk management com-munity. A second important innovation was the reports emphasis on adaptation and disaster risk management. Athird innovation was a plan for an ambitious outreach effort. Underlying these innovations and all aspects of thereport is a strong commitment to assessing science in a way that is relevant to policy but not policy prescriptive.

The Process

The Special Report represents the combined efforts of hundreds of leading experts. The Government of Norway andthe United Nations International Strategy for Disaster Reduction submitted a proposal for the report to the IPCC inSeptember 2008. This was followed by a scoping meeting to develop a candidate outline in March 2009. Followingapproval of the outline in April 2009, governments and observer organizations nominated experts for the author team.The team approved by the WGI and WGII Bureaux consisted of 87 Coordinating Lead Authors and Lead Authors, plus19 Review Editors. In addition, 140 Contributing Authors submitted draft text and information to the author teams. Thedrafts of the report were circulated twice for formal review, first to experts and second to both experts and governments,resulting in 18,784 review comments. Author teams responded to every comment and, where scientifically appropriate,modified drafts in response to comments, with Review Editors monitoring the process. The revised report was presentedfor consideration at the First Joint Session of WGI and WGII, from 14 to 17 November 2011. At the joint session,delegates from over 100 countries evaluated and approved, by consensus, the Summary for Policymakers on aline-by-line basis and accepted the full report.

Structure of the Special Report

This report contains a Summary for Policymakers (SPM) plus nine chapters. References in the SPM point to thesupporting sections of the technical chapters that provide a traceable account of every major finding. The first twochapters set the stage for the report. Chapter 1 frames the issue of extreme weather and climate events as a challenge

Preface

x

in understanding and managing risk. It characterizes risk as emerging from the overlap of a triggering physical eventwith exposure of people and assets and their vulnerability. Chapter 2 explores the determinants of exposure andvulnerability in detail, concluding that every disaster has social as well as physical dimensions. Chapter 3, the majorcontribution of WGI, is an assessment of the scientific literature on observed and projected changes in extreme weatherand climate events, and their attribution to causes where possible. Chapter 4 assesses observed and projectedimpacts, considering patterns by sector as well as region. Chapters 5 through 7 assess experience and theory inadaptation to extremes and disasters, focusing on issues and opportunities at the local scale (Chapter 5), the nationalscale (Chapter 6), and the international scale (Chapter 7). Chapter 8 assesses the interactions among sustainabledevelopment, vulnerability reduction, and disaster risk, considering both opportunities and constraints, as well as thekinds of transformations relevant to overcoming the constraints. Chapter 9 develops a series of case studies thatillustrate the role of real life complexity but also document examples of important progress in managing risk.

Acknowledgements

We wish to express our sincere appreciation to all the Coordinating Lead Authors, Lead Authors, Contributing Authors,Review Editors, and Expert and Government Reviewers. Without their expertise, commitment, and integrity, as well asvast investments of time, a report of this quality could never have been completed. We would also like to thank themembers of the WGI and WGII Bureaux for their assistance, wisdom, and good sense throughout the preparation ofthe report.

We would particularly like to thank the remarkable staffs of the Technical Support Units of WGI and WGII for theirprofessionalism, creativity, and dedication. In WGI, thanks go to Gian-Kasper Plattner, Simon Allen, Pauline Midgley,Melinda Tignor, Vincent Bex, Judith Boschung, and Alexander Nauels. In WGII, which led the logistics and overallcoordination, thanks go to Dave Dokken, Kristie Ebi, Michael Mastrandrea, Katharine Mach, Sandy MacCracken, RobGenova, Yuka Estrada, Eric Kissel, Patricia Mastrandrea, Monalisa Chatterjee, and Kyle Terran. Their tireless and verycapable efforts to coordinate the Special Report ensured a final product of high scientific quality, while maintaining anatmosphere of collegiality and respect.

We would also like to thank the staff of the IPCC Secretariat: Renate Christ, Gaetano Leone, Mary Jean Burer, SophieSchlingemann, Judith Ewa, Jesbin Baidya, Joelle Fernandez, Annie Courtin, Laura Biagioni, and Amy Smith Aasdam.Thanks are also due to Francis Hayes (WMO), Tim Nuthall (European Climate Foundation), and Nick Nutall (UNEP).

Our sincere thanks go to the hosts and organizers of the scoping meeting, the four lead author meetings, and theapproval session. We gratefully acknowledge the support from the host countries: Norway, Panama, Vietnam,Switzerland, Australia, and Uganda. It is a pleasure to extend special thanks to the government of Norway, whichprovided untiring support throughout the Special Report process.

Preface

Vicente Barros and Christopher B. FieldIPCC WGII Co-Chairs

Qin Dahe and Thomas F. StockerIPCC WGI Co-Chairs

II Summary for Policymakers

3

Drafting Authors:Simon K. Allen (Switzerland), Vicente Barros (Argentina), Ian Burton (Canada),Diarmid Campbell-Lendrum (UK), Omar-Dario Cardona (Colombia), Susan L. Cutter (USA),O. Pauline Dube (Botswana), Kristie L. Ebi (USA), Christopher B. Field (USA),John W. Handmer (Australia), Padma N. Lal (Australia), Allan Lavell (Costa Rica),Katharine J. Mach (USA), Michael D. Mastrandrea (USA), Gordon A. McBean (Canada),Reinhard Mechler (Germany), Tom Mitchell (UK), Neville Nicholls (Australia),Karen L. OBrien (Norway), Taikan Oki (Japan), Michael Oppenheimer (USA), Mark Pelling(UK), Gian-Kasper Plattner (Switzerland), Roger S. Pulwarty (USA), Sonia I. Seneviratne(Switzerland), Thomas F. Stocker (Switzerland), Maarten K. van Aalst (Netherlands),Carolina S. Vera (Argentina), Thomas J. Wilbanks (USA)

This Summary for Policymakers should be cited as:

IPCC, 2012: Summary for Policymakers. In: Managing the Risks of Extreme Events and Disasters to Advance

Climate Change Adaptation [Field, C.B., V. Barros, T.F. Stocker, D. Qin, D.J. Dokken, K.L. Ebi, M.D. Mastrandrea,

K.J. Mach, G.-K. Plattner, S.K. Allen, M. Tignor, and P.M. Midgley (eds.)]. A Special Report of Working Groups

I and II of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK, and

New York, NY, USA, pp. 3-21.

SPM Summaryfor Policymakers

4

A.

Summary for Policymakers

Context

This Summary for Policymakers presents key findings from the Special Report on Managing the Risks of ExtremeEvents and Disasters to Advance Climate Change Adaptation (SREX). The SREX approaches the topic by assessing thescientific literature on issues that range from the relationship between climate change and extreme weather andclimate events (climate extremes) to the implications of these events for society and sustainable development. Theassessment concerns the interaction of climatic, environmental, and human factors that can lead to impacts anddisasters, options for managing the risks posed by impacts and disasters, and the important role that non-climaticfactors play in determining impacts. Box SPM.1 defines concepts central to the SREX.

The character and severity of impacts from climate extremes depend not only on the extremes themselves but also onexposure and vulnerability. In this report, adverse impacts are considered disasters when they produce widespreaddamage and cause severe alterations in the normal functioning of communities or societies. Climate extremes,exposure, and vulnerability are influenced by a wide range of factors, including anthropogenic climate change, naturalclimate variability, and socioeconomic development (Figure SPM.1). Disaster risk management and adaptation toclimate change focus on reducing exposure and vulnerability and increasing resilience to the potential adverse impactsof climate extremes, even though risks cannot fully be eliminated (Figure SPM.2). Although mitigation of climatechange is not the focus of this report, adaptation and mitigation can complement each other and together cansignificantly reduce the risks of climate change. [SYR AR4, 5.3]

Figure SPM.1 | Illustration of the core concepts of SREX. The report assesses how exposure and vulnerability to weather and climate events determine impacts and the likelihoodof disasters (disaster risk). It evaluates the influence of natural climate variability and anthropogenic climate change on climate extremes and other weather and climate eventsthat can contribute to disasters, as well as the exposure and vulnerability of human society and natural ecosystems. It also considers the role of development in trends in exposureand vulnerability, implications for disaster risk, and interactions between disasters and development. The report examines how disaster risk management and adaptation to climatechange can reduce exposure and vulnerability to weather and climate events and thus reduce disaster risk, as well as increase resilience to the risks that cannot be eliminated.Other important processes are largely outside the scope of this report, including the influence of development on greenhouse gas emissions and anthropogenic climate change,and the potential for mitigation of anthropogenic climate change. [1.1.2, Figure 1-1]

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Box SPM.1 | Definitions Central to SREX

Core concepts defined in the SREX glossary1 and used throughout the report include:

Climate Change: A change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the meanand/or the variability of its properties and that persists for an extended period, typically decades or longer. Climate change may be dueto natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or inland use.2

Climate Extreme (extreme weather or climate event): The occurrence of a value of a weather or climate variable above (or below)a threshold value near the upper (or lower) ends of the range of observed values of the variable. For simplicity, both extreme weatherevents and extreme climate events are referred to collectively as climate extremes. The full definition is provided in Section 3.1.2.

Exposure: The presence of people; livelihoods; environmental services and resources; infrastructure; or economic, social, or culturalassets in places that could be adversely affected.

Vulnerability: The propensity or predisposition to be adversely affected.

Disaster: Severe alterations in the normal functioning of a community or a society due to hazardous physical events interacting withvulnerable social conditions, leading to widespread adverse human, material, economic, or environmental effects that require immediateemergency response to satisfy critical human needs and that may require external support for recovery.

Disaster Risk: The likelihood over a specified time period of severe alterations in the normal functioning of a community or a societydue to hazardous physical events interacting with vulnerable social conditions, leading to widespread adverse human, material,economic, or environmental effects that require immediate emergency response to satisfy critical human needs and that may requireexternal support for recovery.

Disaster Risk Management: Processes for designing, implementing, and evaluating strategies, policies, and measures to improve theunderstanding of disaster risk, foster disaster risk reduction and transfer, and promote continuous improvement in disaster preparedness,response, and recovery practices, with the explicit purpose of increasing human security, well-being, quality of life, resilience, andsustainable development.

Adaptation: In human systems, the process of adjustment to actual or expected climate and its effects, in order to moderate harm orexploit beneficial opportunities. In natural systems, the process of adjustment to actual climate and its effects; human intervention mayfacilitate adjustment to expected climate.

Resilience: The ability of a system and its component parts to anticipate, absorb, accommodate, or recover from the effects of ahazardous event in a timely and efficient manner, including through ensuring the preservation, restoration, or improvement of itsessential basic structures and functions.

Transformation: The altering of fundamental attributes of a system (including value systems; regulatory, legislative, or bureaucraticregimes; financial institutions; and technological or biological systems).

____________

1 Reflecting the diversity of the communities involved in this assessment and progress in science, several of the definitions used in this Special Report differ in breadth orfocus from those used in the Fourth Assessment Report and other IPCC reports.

2 This definition differs from that in the United Nations Framework Convention on Climate Change (UNFCCC), where climate change is defined as: a change of climatewhich is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variabilityobserved over comparable time periods. The UNFCCC thus makes a distinction between climate change attributable to human activities altering the atmosphericcomposition, and climate variability attributable to natural causes.

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This report integrates perspectives from several historically distinct research communities studying climate science,climate impacts, adaptation to climate change, and disaster risk management. Each community brings differentviewpoints, vocabularies, approaches, and goals, and all provide important insights into the status of the knowledgebase and its gaps. Many of the key assessment findings come from the interfaces among these communities. Theseinterfaces are also illustrated in Table SPM.1. To accurately convey the degree of certainty in key findings, the reportrelies on the consistent use of calibrated uncertainty language, introduced in Box SPM.2. The basis for substantiveparagraphs in this Summary for Policymakers can be found in the chapter sections specified in square brackets.

Exposure and vulnerability are key determinants of disaster risk and of impacts when risk is realized.[1.1.2, 1.2.3, 1.3, 2.2.1, 2.3, 2.5] For example, a tropical cyclone can have very different impacts depending on whereand when it makes landfall. [2.5.1, 3.1, 4.4.6] Similarly, a heat wave can have very different impacts on differentpopulations depending on their vulnerability. [Box 4-4, 9.2.1] Extreme impacts on human, ecological, or physicalsystems can result from individual extreme weather or climate events. Extreme impacts can also result from non-extreme events where exposure and vulnerability are high [2.2.1, 2.3, 2.5] or from a compounding of events or theirimpacts. [1.1.2, 1.2.3, 3.1.3] For example, drought, coupled with extreme heat and low humidity, can increase the riskof wildfire. [Box 4-1, 9.2.2]

Extreme and non-extreme weather or climate events affect vulnerability to future extreme events by modifyingresilience, coping capacity, and adaptive capacity. [2.4.3] In particular, the cumulative effects of disasters at local

Figure SPM.2 | Adaptation and disaster risk management approaches for reducing and managing disaster risk in a changing climate. This report assesses a wide range ofcomplementary adaptation and disaster risk management approaches that can reduce the risks of climate extremes and disasters and increase resilience to remaining risks as theychange over time. These approaches can be overlapping and can be pursued simultaneously. [6.5, Figure 6-3, 8.6]

7

B.

or sub-national levels can substantially affectlivelihood options and resources and the capacityof societies and communities to prepare for andrespond to future disasters. [2.2, 2.7]

A changing climate leads to changes in thefrequency, intensity, spatial extent, duration,and timing of extreme weather and climateevents, and can result in unprecedentedextreme weather and climate events. Changesin extremes can be linked to changes in the mean,variance, or shape of probability distributions, or allof these (Figure SPM.3). Some climate extremes (e.g.,droughts) may be the result of an accumulation ofweather or climate events that are not extremewhen considered independently. Many extremeweather and climate events continue to be theresult of natural climate variability. Natural variabilitywill be an important factor in shaping futureextremes in addition to the effect of anthropogenicchanges in climate. [3.1]

Observations ofExposure, Vulnerability,Climate Extremes,Impacts, and DisasterLosses

The impacts of climate extremes and the potentialfor disasters result from the climate extremesthemselves and from the exposure and vulnerabilityof human and natural systems. Observed changesin climate extremes reflect the influence ofanthropogenic climate change in addition to naturalclimate variability, with changes in exposure andvulnerability influenced by both climatic and non-climatic factors.

Exposure and Vulnerability

Exposure and vulnerability are dynamic, varying across temporal and spatial scales, and depend oneconomic, social, geographic, demographic, cultural, institutional, governance, and environmental factors(high confidence). [2.2, 2.3, 2.5] Individuals and communities are differentially exposed and vulnerable based oninequalities expressed through levels of wealth and education, disability, and health status, as well as gender, age,class, and other social and cultural characteristics. [2.5]

Settlement patterns, urbanization, and changes in socioeconomic conditions have all influenced observedtrends in exposure and vulnerability to climate extremes (high confidence). [4.2, 4.3.5] For example, coastal


Without climate changeWith climate change

extreme cold extreme hotcold hot

Prob

abili

ty o

f Occ

urre

nce

Prob

abili

ty o

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Prob

abili

ty o

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less extreme cold

weather

moreextreme cold

weather

less cold

weather

near constant extreme cold

weather

near constant cold

weathermore

extreme hot weather

more extreme hot

weather

more extreme hot

weather

more cold

weather

more hot

weather

more hot

weather

more hot

weather

a)

b)

c)

Shifted Mean

Increased Variability

Changed Symmetry

Mean: without and with weather change

Figure SPM.3 | The effect of changes in temperature distribution onextremes. Different changes in temperature distributions between present andfuture climate and their effects on extreme values of the distributions:(a) effects of a simple shift of the entire distribution toward a warmer climate;(b) effects of an increase in temperature variability with no shift in the mean;(c) effects of an altered shape of the distribution, in this example a change inasymmetry toward the hotter part of the distribution. [Figure 1-2, 1.2.2]

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settlements, including in small islands and megadeltas, and mountain settlements are exposed and vulnerable toclimate extremes in both developed and developing countries, but with differences among regions and countries.[4.3.5, 4.4.3, 4.4.6, 4.4.9, 4.4.10] Rapid urbanization and the growth of megacities, especially in developing countries,have led to the emergence of highly vulnerable urban communities, particularly through informal settlements andinadequate land management (high agreement, robust evidence). [5.5.1] See also Case Studies 9.2.8 and 9.2.9.Vulnerable populations also include refugees, internally displaced people, and those living in marginal areas. [4.2, 4.3.5]

Climate Extremes and Impacts

There is evidence from observations gathered since 1950 of change in some extremes. Confidence inobserved changes in extremes depends on the quality and quantity of data and the availability of studiesanalyzing these data, which vary across regions and for different extremes. Assigning low confidence inobserved changes in a specific extreme on regional or global scales neither implies nor excludes thepossibility of changes in this extreme. Extreme events are rare, which means there are few data available to makeassessments regarding changes in their frequency or intensity. The more rare the event the more difficult it is to identifylong-term changes. Global-scale trends in a specific extreme may be either more reliable (e.g., for temperatureextremes) or less reliable (e.g., for droughts) than some regional-scale trends, depending on the geographical uniformityof the trends in the specific extreme. The following paragraphs provide further details for specific climate extremesfrom observations since 1950. [3.1.5, 3.1.6, 3.2.1]

It is very likely that there has been an overall decrease in the number of cold days and nights,3 and an overall increasein the number of warm days and nights,3 at the global scale, that is, for most land areas with sufficient data. It is likelythat these changes have also occurred at the continental scale in North America, Europe, and Australia. There is mediumconfidence in a warming trend in daily temperature extremes in much of Asia. Confidence in observed trends in dailytemperature extremes in Africa and South America generally varies from low to medium depending on the region. Inmany (but not all) regions over the globe with sufficient data, there is medium confidence that the length or numberof warm spells or heat waves3 has increased. [3.3.1, Table 3-2]

There have been statistically significant trends in the number of heavy precipitation events in some regions. It is likelythat more of these regions have experienced increases than decreases, although there are strong regional andsubregional variations in these trends. [3.3.2]

There is low confidence in any observed long-term (i.e., 40 years or more) increases in tropical cyclone activity (i.e.,intensity, frequency, duration), after accounting for past changes in observing capabilities. It is likely that there has beena poleward shift in the main Northern and Southern Hemisphere extratropical storm tracks. There is low confidence inobserved trends in small spatial-scale phenomena such as tornadoes and hail because of data inhomogeneities andinadequacies in monitoring systems. [3.3.2, 3.3.3, 3.4.4, 3.4.5]

There is medium confidence that some regions of the world have experienced more intense and longer droughts, inparticular in southern Europe and West Africa, but in some regions droughts have become less frequent, less intense,or shorter, for example, in central North America and northwestern Australia. [3.5.1]

There is limited to medium evidence available to assess climate-driven observed changes in the magnitude andfrequency of floods at regional scales because the available instrumental records of floods at gauge stations arelimited in space and time, and because of confounding effects of changes in land use and engineering. Furthermore,there is low agreement in this evidence, and thus overall low confidence at the global scale regarding even the sign ofthese changes. [3.5.2]

____________

3 See SREX Glossary for definition of these terms: cold days / cold nights, warm days / warm nights, and warm spell heat wave.

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It is likely that there has been an increase in extreme coastal high water related to increases in mean sea level.[3.5.3]

There is evidence that some extremes have changed as a result of anthropogenic influences, includingincreases in atmospheric concentrations of greenhouse gases. It is likely that anthropogenic influences have ledto warming of extreme daily minimum and maximum temperatures at the global scale. There is medium confidencethat anthropogenic influences have contributed to intensification of extreme precipitation at the global scale. It islikely that there has been an anthropogenic influence on increasing extreme coastal high water due to an increase inmean sea level. The uncertainties in the historical tropical cyclone records, the incomplete understanding of the physicalmechanisms linking tropical cyclone metrics to climate change, and the degree of tropical cyclone variability provideonly low confidence for the attribution of any detectable changes in tropical cyclone activity to anthropogenicinfluences. Attribution of single extreme events to anthropogenic climate change is challenging. [3.2.2, 3.3.1, 3.3.2,3.4.4, 3.5.3, Table 3-1]

Disaster Losses

Economic losses from weather- and climate-related disasters have increased, but with large spatial andinterannual variability (high confidence, based on high agreement, medium evidence). Global weather- andclimate-related disaster losses reported over the last few decades reflect mainly monetized direct damages to assets,and are unequally distributed. Estimates of annual losses have ranged since 1980 from a few US$ billion to above200 billion (in 2010 dollars), with the highest value for 2005 (the year of Hurricane Katrina). Loss estimates are lower-bound estimates because many impacts, such as loss of human lives, cultural heritage, and ecosystem services, aredifficult to value and monetize, and thus they are poorly reflected in estimates of losses. Impacts on the informal orundocumented economy as well as indirect economic effects can be very important in some areas and sectors, but aregenerally not counted in reported estimates of losses. [4.5.1, 4.5.3, 4.5.4]

Economic, including insured, disaster losses associated with weather, climate, and geophysical events4 arehigher in developed countries. Fatality rates and economic losses expressed as a proportion of grossdomestic product (GDP) are higher in developing countries (high confidence). During the period from 1970 to2008, over 95% of deaths from natural disasters occurred in developing countries. Middle-income countries with rapidlyexpanding asset bases have borne the largest burden. During the period from 2001 to 2006, losses amounted to about1% of GDP for middle-income countries, while this ratio has been about 0.3% of GDP for low-income countries andless than 0.1% of GDP for high-income countries, based on limited evidence. In small exposed countries, particularlysmall island developing states, losses expressed as a percentage of GDP have been particularly high, exceeding 1% inmany cases and 8% in the most extreme cases, averaged over both disaster and non-disaster years for the period from1970 to 2010. [4.5.2, 4.5.4]

Increasing exposure of people and economic assets has been the major cause of long-term increases ineconomic losses from weather- and climate-related disasters (high confidence). Long-term trends in economicdisaster losses adjusted for wealth and population increases have not been attributed to climate change,but a role for climate change has not been excluded (high agreement, medium evidence). These conclusionsare subject to a number of limitations in studies to date. Vulnerability is a key factor in disaster losses, yet it is not wellaccounted for. Other limitations are: (i) data availability, as most data are available for standard economic sectors indeveloped countries; and (ii) type of hazards studied, as most studies focus on cyclones, where confidence in observedtrends and attribution of changes to human influence is low. The second conclusion is subject to additional limitations:(iii) the processes used to adjust loss data over time, and (iv) record length. [4.5.3]

____________

4 Economic losses and fatalities described in this paragraph pertain to all disasters associated with weather, climate, and geophysical events.

10

C.


Disaster Risk Management and Adaptation to ClimateChange: Past Experience with Climate Extremes

Past experience with climate extremes contributes to understanding of effective disaster risk management andadaptation approaches to manage risks.

The severity of the impacts of climate extremes depends strongly on the level of the exposure andvulnerability to these extremes (high confidence). [2.1.1, 2.3, 2.5]

Trends in exposure and vulnerability are major drivers of changes in disaster risk (high confidence). [2.5]Understanding the multi-faceted nature of both exposure and vulnerability is a prerequisite for determining howweather and climate events contribute to the occurrence of disasters, and for designing and implementing effectiveadaptation and disaster risk management strategies. [2.2, 2.6] Vulnerability reduction is a core common element ofadaptation and disaster risk management. [2.2, 2.3]

Development practice, policy, and outcomes are critical to shaping disaster risk, which may be increasedby shortcomings in development (high confidence). [1.1.2, 1.1.3] High exposure and vulnerability are generallythe outcome of skewed development processes such as those associated with environmental degradation, rapid andunplanned urbanization in hazardous areas, failures of governance, and the scarcity of livelihood options for the poor.[2.2.2, 2.5] Increasing global interconnectivity and the mutual interdependence of economic and ecological systemscan have sometimes contrasting effects, reducing or amplifying vulnerability and disaster risk. [7.2.1] Countries moreeffectively manage disaster risk if they include considerations of disaster risk in national development and sector plansand if they adopt climate change adaptation strategies, translating these plans and strategies into actions targetingvulnerable areas and groups. [6.2, 6.5.2]

Data on disasters and disaster risk reduction are lacking at the local level, which can constrain improvementsin local vulnerability reduction (high agreement, medium evidence). [5.7] There are few examples of nationaldisaster risk management systems and associated risk management measures explicitly integrating knowledge of anduncertainties in projected changes in exposure, vulnerability, and climate extremes. [6.6.2, 6.6.4]

Inequalities influence local coping and adaptive capacity, and pose disaster risk management and adaptationchallenges from the local to national levels (high agreement, robust evidence). These inequalities reflectsocioeconomic, demographic, and health-related differences and differences in governance, access to livelihoods,entitlements, and other factors. [5.5.1, 6.2] Inequalities also exist across countries: developed countries are often betterequipped financially and institutionally to adopt explicit measures to effectively respond and adapt to projectedchanges in exposure, vulnerability, and climate extremes than are developing countries. Nonetheless, all countries facechallenges in assessing, understanding, and responding to such projected changes. [6.3.2, 6.6]

Humanitarian relief is often required when disaster risk reduction measures are absent or inadequate(high agreement, robust evidence). [5.2.1] Smaller or economically less-diversified countries face particularchallenges in providing the public goods associated with disaster risk management, in absorbing the losses caused byclimate extremes and disasters, and in providing relief and reconstruction assistance. [6.4.3]

Post-disaster recovery and reconstruction provide an opportunity for reducing weather- and climate-relateddisaster risk and for improving adaptive capacity (high agreement, robust evidence). An emphasis on rapidlyrebuilding houses, reconstructing infrastructure, and rehabilitating livelihoods often leads to recovering in ways thatrecreate or even increase existing vulnerabilities, and that preclude longer-term planning and policy changes forenhancing resilience and sustainable development. [5.2.3] See also assessment in Sections 8.4.1 and 8.5.2.

Risk sharing and transfer mechanisms at local, national, regional, and global scales can increase resilienceto climate extremes (medium confidence). Mechanisms include informal and traditional risk sharing mechanisms,

11

micro-insurance, insurance, reinsurance, and national, regional, and global risk pools. [5.6.3, 6.4.3, 6.5.3, 7.4] Thesemechanisms are linked to disaster risk reduction and climate change adaptation by providing means to finance relief,recovery of livelihoods, and reconstruction; reducing vulnerability; and providing knowledge and incentives for reducingrisk. [5.5.2, 6.2.2] Under certain conditions, however, such mechanisms can provide disincentives for reducing disasterrisk. [5.6.3, 6.5.3, 7.4.4] Uptake of formal risk sharing and transfer mechanisms is unequally distributed across regionsand hazards. [6.5.3] See also Case Study 9.2.13.

Attention to the temporal and spatial dynamics of exposure and vulnerability is particularly importantgiven that the design and implementation of adaptation and disaster risk management strategies andpolicies can reduce risk in the short term, but may increase exposure and vulnerability over the longerterm (high agreement, medium evidence). For instance, dike systems can reduce flood exposure by offeringimmediate protection, but also encourage settlement patterns that may increase risk in the long term. [2.4.2, 2.5.4,2.6.2] See also assessment in Sections 1.4.3, 5.3.2, and 8.3.1.

National systems are at the core of countries capacity to meet the challenges of observed and projectedtrends in exposure, vulnerability, and weather and climate extremes (high agreement, robust evidence).Effective national systems comprise multiple actors from national and sub-national governments, the private sector,research bodies, and civil society including community-based organizations, playing differential but complementaryroles to manage risk, according to their accepted functions and capacities. [6.2]

Closer integration of disaster risk management and climate change adaptation, along with the incorporationof both into local, sub-national, national, and international development policies and practices, could providebenefits at all scales (high agreement, medium evidence). [5.4, 5.5, 5.6, 6.3.1, 6.3.2, 6.4.2, 6.6, 7.4] Addressingsocial welfare, quality of life, infrastructure, and livelihoods, and incorporating a multi-hazards approach into planningand action for disasters in the short term, facilitates adaptation to climate extremes in the longer term, as is increasinglyrecognized internationally. [5.4, 5.5, 5.6, 7.3] Strategies and policies are more effective when they acknowledge multiplestressors, different prioritized values, and competing policy goals. [8.2, 8.3, 8.7]

Future Climate Extremes, Impacts, and Disaster Losses

Future changes in exposure, vulnerability, and climate extremes resulting from natural climate variability, anthropogenicclimate change, and socioeconomic development can alter the impacts of climate extremes on natural and humansystems and the potential for disasters.

Climate Extremes and Impacts

Confidence in projecting changes in the direction and magnitude of climate extremes depends on manyfactors, including the type of extreme, the region and season, the amount and quality of observationaldata, the level of understanding of the underlying processes, and the reliability of their simulation inmodels. Projected changes in climate extremes under different emissions scenarios5 generally do not strongly divergein the coming two to three decades, but these signals are relatively small compared to natural climate variability overthis time frame. Even the sign of projected changes in some climate extremes over this time frame is uncertain. Forprojected changes by the end of the 21st century, either model uncertainty or uncertainties associated with emissionsscenarios used becomes dominant, depending on the extreme. Low-probability, high-impact changes associated with


D.

____________

5 Emissions scenarios for radiatively important substances result from pathways of socioeconomic and technological development. This report usesa subset (B1, A1B, A2) of the 40 scenarios extending to the year 2100 that are described in the IPCC Special Report on Emissions Scenarios(SRES) and that did not include additional climate initiatives. These scenarios have been widely used in climate change projections andencompass a substantial range of carbon dioxide equivalent concentrations, but not the entire range of the scenarios included in the SRES.

12


218

247

17

3

6

26

22

9

15

5

1

10

23

25

14

4

11

16

1319

8

2112

20

Full model range

Central 50%intermodel range

Med

ian

B1A

1BA

2Sc

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ios:20

466

520

810

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Return period (Years)

Decr

ease

in re

turn

per

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impl

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ore

frequ

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tem

pera

ture

eve

nts (

see

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Legen

d

2046

65

2081

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1251020

22

Alas

ka/N

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a - 1

2046

65

2081

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1251020E. C

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eenl

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l. - 2

2046

65

2081

00

1251020

W. N

orth

Am

erica

- 3

2046

65

2081

00

1251020

C. N

orth

Am

erica

- 4

2046

65

2081

00

1251020

E. N

orth

Am

erica

- 5

2046

65

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00

1251020Cen

tral A

mer

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exico

- 6

2046

65

2081

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Amaz

on -

7

2046

65

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N.E.

Bra

zil -

8

2046

65

2081

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1251020W. C

oast

Sou

th A

mer

ica -

9

2046

65

2081

00

1251020

S.E.

Sou

th A

mer

ica -

10

2046

65

2081

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31

2423

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1

2046

65

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C. E

urop

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2

2046

65

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1251020S. E

urop

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edite

rrane

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13

2046

65

2081

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Saha

ra -

14

2046

65

2081

00

1251020

W. A

frica

- 15

2046

65

2081

00

1251020

E. A

frica

- 16

2046

65

2081

00

1251020

S. A

frica

- 17

2046

65

2081

00

1251020N.

Asia

- 18

2046

65

2081

00

1251020E.

Asia

- 22

2046

65

2081

00

1251020Ti

beta

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atea

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1

2046

65

2081

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1251020C.

Asia

- 20

2046

65

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00

1251020W

. Asia

- 19

2046

65

2081

00

1251020S.

Asia

- 23

2046

65

2081

00

1251020S.

E. A

sia -

24

2046

65

2081

00

1251020N.

Aus

tralia

- 25

2046

65

2081

00

1251020S. A

ustra

lia/N

ew Z

eala

nd -

26

2046

65

2081

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1251020Glo

be (L

and

only

)

Figu

re S

PM.4

A |

Proj

ecte

d re

turn

per

iods

for t

he m

axim

um d

aily

tem

pera

ture

that

was

exc

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ave

rage

onc

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a 20

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in th

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0th

cent

ury

(198

120

00).

A de

crea

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plie

s m

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nts

(i.e.

, les

s tim

e be

twee

n ev

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on

aver

age)

. The

box

plo

ts s

how

resu

lts fo

r reg

iona

lly a

vera

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proj

ectio

ns fo

r tw

o tim

e ho

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46 to

206

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to th

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iffer

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RES

emiss

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sce

nario

s (B

1, A

1B, A

2) (s

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). Re

sults

are

bas

ed o

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glo

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limat

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s (G

CMs)

con

tribu

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to th

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Inte

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s is

indi

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d by

the

size

of th

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(in w

hich

50%

of t

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pro

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ions

are

con

tain

ed),

and

the

leng

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f the

whi

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dica

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the

max

imum

and

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proj

ectio

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s). S

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alue

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and

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The

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be i

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usin

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s. [3

.3.1

, Fig

ure

3-1,

Fig

ure

3-5]

13

the crossing of poorly understood climate thresholds cannot be excluded, given the transient and complex nature ofthe climate system. Assigning low confidence for projections of a specific extreme neither implies nor excludes thepossibility of changes in this extreme. The following assessments of the likelihood and/or confidence of projections aregenerally for the end of the 21st century and relative to the climate at the end of the 20th century. [3.1.5, 3.1.7, 3.2.3,Box 3-2]

Models project substantial warming in temperature extremes by the end of the 21st century. It is virtuallycertain that increases in the frequency and magnitude of warm daily temperature extremes and decreases in coldextremes will occur in the 21st century at the global scale. It is very likely that the length, frequency, and/or intensityof warm spells or heat waves will increase over most land areas. Based on the A1B and A2 emissions scenarios, a1-in-20 year hottest day is likely to become a 1-in-2 year event by the end of the 21st century in most regions, exceptin the high latitudes of the Northern Hemisphere, where it is likely to become a 1-in-5 year event (see Figure SPM.4A).Under the B1 scenario, a 1-in-20 year event would likely become a 1-in-5 year event (and a 1-in-10 year event inNorthern Hemisphere high latitudes). The 1-in-20 year extreme daily maximum temperature (i.e., a value that wasexceeded on average only once during the period 19812000) will likely increase by about 1C to 3C by the mid-21stcentury and by about 2C to 5C by the late 21st century, depending on the region and emissions scenario (based onthe B1, A1B, and A2 scenarios). [3.3.1, 3.1.6, Table 3-3, Figure 3-5]

It is likely that the frequency of heavy precipitation or the proportion of total rainfall from heavy falls willincrease in the 21st century over many areas of the globe. This is particularly the case in the high latitudes andtropical regions, and in winter in the northern mid-latitudes. Heavy rainfalls associated with tropical cyclones are likelyto increase with continued warming. There is medium confidence that, in some regions, increases in heavy precipitationwill occur despite projected decreases in total precipitation in those regions. Based on a range of emissions scenarios(B1, A1B, A2), a 1-in-20 year annual maximum daily precipitation amount is likely to become a 1-in-5 to 1-in-15 yearevent by the end of the 21st century in many regions, and in most regions the higher emissions scenarios (A1B and A2)lead to a stronger projected decrease in return period. See Figure SPM.4B. [3.3.2, 3.4.4, Table 3-3, Figure 3-7]

Average tropical cyclone maximum wind speed is likely to increase, although increases may not occur inall ocean basins. It is likely that the global frequency of tropical cyclones will either decrease or remainessentially unchanged. [3.4.4]

There is medium confidence that there will be a reduction in the number of extratropical cyclones averagedover each hemisphere. While there is low confidence in the detailed geographical projections of extratropicalcyclone activity, there is medium confidence in a projected poleward shift of extratropical storm tracks. There is lowconfidence in projections of small spatial-scale phenomena such as tornadoes and hail because competing physicalprocesses may affect future trends and because current climate models do not simulate such phenomena. [3.3.2, 3.3.3,3.4.5]

There is medium confidence that droughts will intensify in the 21st century in some seasons and areas, dueto reduced precipitation and/or increased evapotranspiration. This applies to regions including southern Europeand the Mediterranean region, central Europe, central North America, Central America and Mexico, northeast Brazil,and southern Africa. Elsewhere there is overall low confidence because of inconsistent projections of drought changes(dependent both on model and dryness index). Definitional issues, lack of observational data, and the inability of modelsto include all the factors that influence droughts preclude stronger confidence than medium in drought projections.See Figure SPM.5. [3.5.1, Table 3-3, Box 3-3]

Projected precipitation and temperature changes imply possible changes in floods, although overall thereis low confidence in projections of changes in fluvial floods. Confidence is low due to limited evidence andbecause the causes of regional changes are complex, although there are exceptions to this statement. There is mediumconfidence (based on physical reasoning) that projected increases in heavy rainfall would contribute to increases inlocal flooding in some catchments or regions. [3.5.2]


14


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Full model range

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Med

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B1A

1BA

2Sc

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Return period (Years)

2046

65

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35102050

Decr

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2046

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2046

65

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25

2046

65

2081

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2.4

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- 24

2046

65

2081

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S. A

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23

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2081

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19

2046

65

2081

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35102050

C. A

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20

2046

65

2081

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Tibe

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- 21

2046

65

2081

00

35102050

E. A

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22

2046

65

2081

00

35102050

N. A

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18

2046

65

2081

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S. A

frica

- 17

2046

65

2081

00

35102050

E. A

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2046

65

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65

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2046

65

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00

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1

2046

65

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Sou

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10

2046

65

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53

61

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Sou

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9

2046

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57

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8

2046

65

2081

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7

2046

65

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- 6

2046

65

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- 5

2046

65

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C. N

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Am

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- 4

2046

65

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W. N

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- 3

2046

65

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2046

65

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2.4

Alas

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Figu

re S

PM.4

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retu

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even

t tha

t was

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the

late

20t

h ce

ntur

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rage

onc

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a 20

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(198

120

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A de

crea

se in

retu

rn p

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d im

plie

s m

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frequ

ent

extre

me

prec

ipita

tion

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ts (i

.e.,

less

tim

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on

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. The

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ts s

how

resu

lts fo

r reg

iona

lly a

vera

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proj

ectio

ns fo

r tw

o tim

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46 to

206

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for t

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ased

on

14 G

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to th

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IP3.

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ong

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by th

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whi

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d th

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ngth

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(indi

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axim

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nd m

inim

um p

roje

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om a

ll m

odel

s). S

ee le

gend

for d

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alue

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for l

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.3.2

, Fig

ure

3-1,

Fig

ure

3-7]

15


It is very likely that mean sea level rise will contribute to upward trends in extreme coastal high waterlevels in the future. There is high confidence that locations currently experiencing adverse impacts such as coastalerosion and inundation will continue to do so in the future due to increasing sea levels, all other contributing factorsbeing equal. The very likely contribution of mean sea level rise to increased extreme coastal high water levels, coupledwith the likely increase in tropical cyclone maximum wind speed, is a specific issue for tropical small island states.[3.5.3, 3.5.5, Box 3-4]

There is high confidence that changes in heat waves, glacial retreat, and/or permafrost degradation willaffect high mountain phenomena such as slope instabilities, movements of mass, and glacial lake outburstfloods. There is also high confidence that changes in heavy precipitation will affect landslides in some regions. [3.5.6]

There is low confidence in projections of changes in large-scale patterns of natural climate variability.Confidence is low in projections of changes in monsoons (rainfall, circulation) because there is little consensus in climatemodels regarding the sign of future change in the monsoons. Model projections of changes in El NioSouthern

-0.6 -0.2 0.2 0.60

Standard DeviationStandard Deviation

-0.75 -0.25 0.25 0.7500.4-0.4 -0.50 0.50

2046 - 2065

Change in consecutive dry days (CDD)

2046 - 2065

Soil moisture anomalies (SMA)

2081 - 2100

2081 - 2100

Dryness+ Dryness +

Figure SPM.5 | Projected annual changes in dryness assessed from two indices. Left column: Change in annual maximum number of consecutive dry days (CDD: days withprecipitation

E.

16


Oscillation variability and the frequency of El Nio episodes are not consistent, and so there is low confidence inprojections of changes in this phenomenon. [3.4.1, 3.4.2, 3.4.3]

Human Impacts and Disaster Losses

Extreme events will have greater impacts on sectors with closer links to climate, such as water, agricultureand food security, forestry, health, and tourism. For example, while it is not currently possible to reliably projectspecific changes at the catchment scale, there is high confidence that changes in climate have the potential to seriouslyaffect water management systems. However, climate change is in many instances only one of the drivers of futurechanges, and is not necessarily the most important driver at the local scale. Climate-related extremes are also expectedto produce large impacts on infrastructure, although detailed analysis of potential and projected damages are limitedto a few countries, infrastructure types, and sectors. [4.3.2, 4.3.5]

In many regions, the main drivers of future increases in economic losses due to some climate extremes willbe socioeconomic in nature (medium confidence, based on medium agreement, limited evidence). Climateextremes are only one of the factors that affect risks, but few studies have specifically quantified the effects ofchanges in population, exposure of people and assets, and vulnerability as determinants of loss. However, the fewstudies available generally underline the important role of projected changes (increases) in population and capital atrisk. [4.5.4]

Increases in exposure will result in higher direct economic losses from tropical cyclones. Losses will alsodepend on future changes in tropical cyclone frequency and intensity (high confidence). Overall losses due toextratropical cyclones will also increase, with possible decreases or no change in some areas (medium confidence).Although future flood losses in many locations will increase in the absence of additional protection measures (highagreement, medium evidence), the size of the estimated change is highly variable, depending on location, climatescenarios used, and methods used to assess impacts on river flow and flood occurrence. [4.5.4]

Disasters associated with climate extremes influence population mobility and relocation, affecting host andorigin communities (medium agreement, medium evidence). If disasters occur more frequently and/or with greatermagnitude, some local areas will become increasingly marginal as places to live or in which to maintain livelihoods. Insuch cases, migration and displacement could become permanent and could introduce new pressures in areas ofrelocation. For locations such as atolls, in some cases it is possible that many residents will have to relocate. [5.2.2]

Managing Changing Risksof Climate Extremes and Disasters

Adaptation to climate change and disaster risk management provide a range of complementary approaches formanaging the risks of climate extremes and disasters (Figure SPM.2). Effectively applying and combining approachesmay benefit from considering the broader challenge of sustainable development.

Measures that provide benefits under current climate and a range of future climate change scenarios,called low-regrets measures, are available starting points for addressing projected trends in exposure,vulnerability, and climate extremes. They have the potential to offer benefits now and lay the foundationfor addressing projected changes (high agreement, medium evidence). Many of these low-regrets strategiesproduce co-benefits, help address other development goals, such as improvements in livelihoods, human well-being,and biodiversity conservation, and help minimize the scope for maladaptation. [6.3.1, Table 6-1]

Potential low-regrets measures include early warning systems; risk communication between decisionmakers and localcitizens; sustainable land management, including land use planning; and ecosystem management and restoration.

17

Other low-regrets measures include improvements to health surveillance, water supply, sanitation, and irrigation anddrainage systems; climate-proofing of infrastructure; development and enforcement of building codes; and bettereducation and awareness. [5.3.1, 5.3.3, 6.3.1, 6.5.1, 6.5.2] See also Case Studies 9.2.11 and 9.2.14, and assessment inSection 7.4.3.

Effective risk management generally involves a portfolio of actions to reduce and transfer risk and torespond to events and disasters, as opposed to a singular focus on any one action or type of action (highconfidence). [1.1.2, 1.1.4, 1.3.3] Such integrated approaches are more effective when they are informed by andcustomized to specific local circumstances (high agreement, robust evidence). [5.1] Successful strategies include acombination of hard infrastructure-based responses and soft solutions such as individual and institutional capacitybuilding and ecosystem-based responses. [6.5.2]

Multi-hazard risk management approaches provide opportunities to reduce complex and compound hazards(high agreement, robust evidence). Considering multiple types of hazards reduces the likelihood that risk reductionefforts targeting one type of hazard will increase exposure and vulnerability to other hazards, in the present andfuture. [8.2.5, 8.5.2, 8.7]

Opportunities exist to create synergies in international finance for disaster risk management and adaptationto climate change, but these have not yet been fully realized (high confidence). International funding fordisaster risk reduction remains relatively low as compared to the scale of spending on international humanitarianresponse. [7.4.2] Technology transfer and cooperation to advance disaster risk reduction and climate change adaptationare important. Coordination on technology transfer and cooperation between these two fields has been lacking, whichhas led to fragmented implementation. [7.4.3]

Stronger efforts at the international level do not necessarily lead to substantive and rapid results at thelocal level (high confidence). There is room for improved integration across scales from international to local. [7.6]

Integration of local knowledge with additional scientific and technical knowledge can improve disasterrisk reduction and climate change adaptation (high agreement, robust evidence). Local populations documenttheir experiences with the changing climate, particularly extreme weather events, in many different ways, and this self-generated knowledge can uncover existing capacity within the community and important current shortcomings. [5.4.4]Local participation supports community-based adaptation to benefit management of disaster risk and climateextremes. However, improvements in the availability of human and financial capital and of disaster risk and climateinformation customized for local stakeholders can enhance community-based adaptation (medium agreement, mediumevidence). [5.6]

Appropriate and timely risk communication is critical for effective adaptation and disaster risk management(high confidence). Explicit characterization of uncertainty and complexity strengthens risk communication. [2.6.3]Effective risk communication builds on exchanging, sharing, and integrating knowledge about climate-related risksamong all stakeholder groups. Among individual stakeholders and groups, perceptions of risk are driven by psychologicaland cultural factors, values, and beliefs. [1.1.4, 1.3.1, 1.4.2] See also assessment in Section 7.4.5.

An iterative process of monitoring, research, evaluation, learning, and innovation can reduce disaster riskand promote adaptive management in the context of climate extremes (high agreement, robust evidence).[8.6.3, 8.7] Adaptation efforts benefit from iterative risk management strategies because of the complexity, uncertainties,and long time frame associated with climate change (high confidence). [1.3.2] Addressing knowledge gaps throughenhanced observation and research can reduce uncertainty and help in designing effective adaptation and riskmanagement strategies. [3.2, 6.2.5, Table 6-3, 7.5, 8.6.3] See also assessment in Section 6.6.

Table SPM.1 presents examples of how observed and projected trends in exposure, vulnerability, andclimate extremes can inform risk management and adaptation strategies, policies, and measures. The


18


Tabl

e SP

M.1

|Ill

ustr

ativ

e ex

ampl

es o

f opt

ions

for r

isk

man

agem

ent a

nd a

dapt

atio

n in

the

cont

ext o

f cha

nges

in e

xpos

ure,

vul

nera

bilit

y, a

nd c

limat

e ex

trem

es. I

n ea

ch e

xam

ple,

info

rmat

ion

is c

hara

cter

ized

at t

hesc

ale

dire

ctly

rele

vant

to d

ecis

ionm

akin

g. O

bser

ved

and

proj

ecte

d ch

ange

s in

clim

ate

extr

emes

at g

loba

l and

regi

onal

sca

les

illus

trat

e th

at th

e di

rect

ion

of, m

agni

tude

of,

and/

or d

egre

e of

cer

tain

ty fo

r cha

nges

may

diffe

r acr

oss

scal

es.

The

exam

ples

wer

e se

lect

ed b

ased

on

avai

labi

lity

of e

vide

nce

in th

e un

derly

ing

chap

ters

, inc

ludi

ng o

n ex

posu

re, v

ulne

rabi

lity,

clim

ate

info

rmat

ion,

and

risk

man

agem

ent a

nd a

dapt

atio

n op

tions

. The

y ar

e in

tend

edto

refle

ct re

leva

nt ri

sk m

anag

emen

t the

mes

and

sca

les,

rath

er th

an to

pro

vide

com

preh

ensiv

e in

form

atio

n by

regi

on. T

he e

xam

ples

are

not

inte

nded

to re

flect

any

regi

onal

diff

eren

ces

in e

xpos

ure

and

vuln

erab

ility

, or i

nex

perie

nce

in ri

sk m

anag

emen

t.Th

e co

nfid

ence

in p

roje

cted

cha

nges

in c

limat

e ex

trem

es a

t loc

al s

cale

s is

ofte

n m

ore

limite

d th

an th

e co

nfid

ence

in p

roje

cted

regi

onal

and

glo

bal c

hang

es. T

his

limite

d co

nfid

ence

in c

hang

es p

lace

s a

focu

s on

low

-reg

rets

risk

man

agem

ent o

ptio

ns th

at a

im to

redu

ce e

xpos

ure

and

vuln

erab

ility

and

to in

crea

se re

silie

nce

and

prep

ared

ness

for r

isks

that

can

not b

e en

tirel

y el

imin

ated

. Hig

her-c

onfid

ence

pro

ject

ed c

hang

es in

clim

ate

extr

emes

, at a

sca

le re

leva

nt to

ada

ptat

ion

and

risk

man

agem

ent d

ecis

ions

, can

info

rm m

ore

targ

eted

adj

ustm

ents

in s

trat

egie

s, po

licie

s, an

d m

easu

res.

[3.1

.6, B

ox 3

-2, 6

.3.1

, 6.5

.2]

Obs

erve

d: L

ow c

onfid

ence

at g

loba

l sca

le

rega

rdin

g (c

limat

e-dr

iven

) obs

erve

d ch

ange

s in

the

mag

nitu

de a

nd fr

eque

ncy

of fl

oods

.

Proj

ecte

d: L

ow c

onfid

ence

in p

roje

ctio

ns o

f ch

ange

s in

flood

s bec

ause

of l

imite

d ev

iden

ce

and

beca

use

the

caus

es o

f reg

iona

l cha

nges

are

co

mpl

ex. H

owev

er, m

ediu

m c

onfid

ence

(bas

ed o

n ph

ysica

l rea

soni

ng) t

hat p

roje

cted

incr

ease

s in

heav

y pr

ecip

itatio

n w

ill c

ontri

bute

to

rain

-gen

erat

ed lo

cal fl

oodi

ng in

som

e ca

tchm

ents

or r

egio

ns.

[Tab

le 3

-1, 3

.5.2

]

Rapi

d ex

pans

ion

of p

oor p

eopl

e liv

ing

in in

form

al se

ttlem

ents

aro

und

Nairo

bi h

as le

d to

hou

ses o

f wea

k bu

ildin

g m

ater

ials

bein

g co

nstru

cted

im

med

iate

ly a

djac

ent t

o riv

ers a

nd to

bl

ocka

ge o

f nat

ural

dra

inag

e ar

eas,

incr

easin

g ex

posu

re a

nd v

ulne

rabi

lity.

[6.4

.2, B

ox 6

-2]

Obs

erve

d: L

ow c

onfid

ence

rega

rdin

g tre

nds i

n he

avy

prec

ipita

tion

in E

ast

Afric

a, b

ecau

se o

f ins

uffic

ient

evi

denc

e.

Proj

ecte

d: L

ikel

y in

crea

se in

hea

vy

prec

ipita

tion

indi

cato

rs in

Eas

t Afri

ca.

[Tab

le 3

-2, T

able

3-3

, 3.3

.2]

Lim

ited

abili

ty to

pro

vide

loca

l flas

h flo

od p

roje

ctio

ns.

[3.5

.2]

Low

-regr

ets o

ptio

ns th

at re

duce

exp

osur

e an

d vu

lner

abili

ty a

cros

s a ra

nge

of h

azar

d tre

nds:

St

reng

then

ing

build

ing

desig

n an

d re

gula

tion

Po

verty

redu

ctio

n sc

hem

es

Ci

ty-w

ide

drai

nage

and

sew

erag

e im

prov

emen

ts

The

Nairo

bi R

iver

s Reh

abili

tatio

n an

d Re

stor

atio

n Pr

ogra

mm

e in

clude

s ins

talla

tion

of ri

paria

n bu

ffers

, ca

nals,

and

dra

inag

e ch

anne

ls an

d cle

aran

ce o

f exi

stin

g ch

anne

ls; a

ttent

ion

to c

limat

e va

riabi

lity

and

chan

ge in

th

e lo

catio

n an

d de

sign

of w

aste

wat

er in

frast

ruct

ure;

and

en

viro

nmen

tal m

onito

ring

for fl

ood

early

war

ning

.

[6.3

, 6.4

.2, B

ox 6

-2, B

ox 6

-6]

Obs

erve

d: L

ikel

y in

crea

se in

ext

rem

e co

asta

l hi

gh w

ater

wor

ldw

ide

rela

ted

to in

crea

ses i

n m

ean

sea

leve

l.

Proj

ecte

d: V

ery

likel

y th

at m

ean

sea

leve

l rise

w

ill c

ontri

bute

to u

pwar

d tre

nds i

n ex

trem

e co

asta

l hig

h w

ater

leve

ls.

High

con

fiden

ce th

at lo

catio

ns c

urre

ntly

ex

perie

ncin

g co

asta

l ero

sion

and

inun

datio

n w

ill

cont

inue

to d

o so

due

to in

crea

sing

sea

leve

l, in

the

abse

nce

of c

hang

es in

oth

er c

ontri

butin

g fa

ctor

s. Li

kely

that

the

glob

al fr

eque

ncy

of tr

opica

l cy

clone

s will

eith

er d

ecre

ase

or re

mai

n es

sent

ially

unc

hang

ed.

Like

ly in

crea

se in

ave

rage

trop

ical c

yclo

ne

max

imum

win

d sp

eed,

alth

ough

incr

ease

s may

no

t occ

ur in

all

ocea

n ba

sins.

[Tab

le 3

-1, 3

.4.4

, 3.5

.3, 3

.5.5

]

Spar

se re

gion

al a

nd te

mpo

ral c

over

age

of te

rrest

rial-b

ased

obs

erva

tion

netw

orks

and

lim

ited

in si

tu o

cean

ob

serv

ing

netw

ork,

but

with

impr

oved

sa

telli

te-b

ased

obs

erva

tions

in re

cent

de

cade

s.

Whi

le c

hang

es in

stor

min

ess m

ay

cont

ribut

e to

cha

nges

in e

xtre

me

coas

tal

high

wat

er le

vels,

the

limite

d ge

ogra

phica

l cov

erag

e of

stud

ies t

o da

te

and

the

unce

rtain

ties a

ssoc

iate

d w

ith

stor

min

ess c

hang

es o

vera

ll m

ean

that

a

gene

ral a

sses

smen

t of t

he e

ffect

s of

stor

min

ess c

hang

es o

n st

orm

surg

e is

not p

ossib

le a

t thi

s tim

e.

[Box

3-4

, 3.5

.3]

Low

-regr

ets o

ptio

ns th

at re

duce

exp

osur

e an

d vu

lner

abili

ty a

cros

s a ra

nge

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