Analyses of the Effects of Global Change on
Human Health and Welfare and Human Systems
Final Report, Synthesis and Assessment Product 4.6
U.S. Climate Change Science Program
And the Subcommittee on Global Change Research
Convening Lead Author
Janet L. Gamble, Ph.D., U.S. Environmental Protection Agency
Lead Authors 1
Kristie L. Ebi, Ph.D., ESS LLC.
Anne E. Grambsch, U.S. Environmental Protection Agency
Frances G. Sussman, Ph.D., Environmental Economics Consulting
Thomas J. Wilbanks, Ph.D., Oak Ridge National Laboratory
1 Contributing authors are acknowledged in individual chapters.
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SAP 4.6 Analysis of the Effects of Global Change on Human Health and Welfare and Human Systems
FEDERAL EXECUTIVE TEAM
Acting Director, Climate Change Science Program:
Director, Climate Change Science Program Office:
Lead Agency Principal Representative to CCSP,
National Program Director for the Global Change
Research Program, U.S. Environmental Protection Agency:
Product Lead, Global Change Research
Program, U.S. Environmental Protection Agency:
Chair, Synthesis and Assessment Product Advisory Group
Associate Director, National Center for Environmental
Assessment, U.S. Environmental Protection Agency:
Synthesis and Assessment Product Coordinator,
Climate Change Science Program Office:
Special Advisor, National Oceanic and Atmospheric
Administration
William J. Brennan
Peter A. Schultz
Joel D. Scheraga
Janet L. Gamble
Michael W. Slimak
Fabien J.G. Laurier
Chad McNutt
EDITORIAL AND PRODUCTION TEAM
Editor, U.S. Environmental Protection Agency:
Technical Editor, ICF International:
Technical Editor, ICF International:
Reference Coordinator, ICF International:
Reference Coordinator, ICF International:
Reference Coordinator, ICF International:
Logistical and Technical Support, ICF International:
Janet Gamble
Melinda Harris
Toby Krasney
Paul Stewart
Dylan Harrison-Atlas
Sarah Shapiro
Lauren Smith
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SAP 4.6 Analysis of the Effects of Global Change on Human Health and Welfare and Human Systems
Disclaimer: This document, part of the Synthesis and Assessment Products described in the U.S. Climate Change Science
Program (CCSP) Strategic Plan, was prepared in accordance with Section 515 of the Treasury and General Government
Appropriations Act for Fiscal Year 2001 (Public Law 106-554) and the information quality act guidelines issued by the
U.S. Environmental Protection Agency pursuant to Section 515. The CCSP Interagency Committee relies on U.S.
Environmental Protection Agency certifications regarding compliance with Section 515 and Agency guidelines as the basis
for determining that this product conforms with Section 515. For purposes of compliance with Section 515, this CCSP
Synthesis and Assessment Product is an "interpreted product" as that term is used in U.S. Environmental Protection
Agency guidelines and is classified as "highly influential". This document does not express any regulatory policies of the
United States or any of its agencies, or provides recommendations for regulatory action.
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SAP 4.6 Analysis of the Effects of Global Change on Human Health and Welfare and Human Systems
LETTER TO MEMBERS OF CONGRESS / TRANSMITTAL LETTER
LEFT BLANK INTENTIONALLY
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SAP 4.6 Analysis of the Effects of Global Change on Human Health and Welfare and Human Systems
AUTHORS TEAM FOR THIS REPORT
Executive Summary
Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Convening Lead Author: Janet L. Gamble, U.S. EPA
Lead Authors: Kristie L. Ebi, ESS LLC.; Frances G. Sussman,
Environmental Economics Consulting; Thomas J. Wilbanks, Oak
Ridge National Laboratory
Contributing Authors: Colleen Reid, ASPH Fellow; John V.
Thomas, U.S. EPA; Christopher P. Weaver, U.S. EPA; Melinda
Harris, ICF International; Randy Freed, ICF International
Convening Lead Author: Janet L. Gamble, U.S. EPA
Lead Authors: Kristie L. Ebi, ESS LLC.; Anne Grambsch, U.S.
EPA; Frances G. Sussman, Environmental Economics Consulting;
Thomas J. Wilbanks, Oak Ridge National Laboratory
Contributing Authors: Colleen E. Reid, ASPH Fellow; Katharine
Hayhoe, Texas Tech University; John V. Thomas, U.S. EPA;
Christopher P. Weaver, U.S. EPA
Lead Author: Kristie L. Ebi, ESS LLC.
Contributing Authors: John Balbus, Environmental Defense;
Patrick L. Kinney, Columbia University; Erin Lipp, University of
Georgia; David Mills, Stratus Consulting; Marie S. O'Neill,
University of Michigan; Mark Wilson, University of Michigan
Lead Author: Thomas J. Wilbanks, Oak Ridge National
Laboratory
Contributing Authors: Paul Kirshen, Tufts University; Dale
Quattrochi, NASA/Marshall Space Flight Center; Patricia Romero-
Lankao, NCAR; Cynthia Rosenzweig, NASA/Goddard; Matthias
Ruth, University of Maryland; William Solecki, Hunter College;
Joel Tarr, Carnegie Mellon University
Contributors: Peter Larsen, University of Alaska-Anchorage;
Brian Stone, Georgia Tech
Lead Author: Frances G. Sussman, Environmental Economics
Consulting
Contributing Authors: Maureen L. Cropper, University of
Maryland at College Park; Hector Galbraith, Galbraith
Environmental Sciences LLC.; David Godschalk, University of
North Carolina at Chapel Hill; John Loomis, Colorado State
University; George Luber, Centers for Disease Control and
Prevention; Michael McGeehin, Centers for Disease Control and
Prevention; James E. Neumann, Industrial Economics, Inc.; W.
Douglass Shaw, Texas A&M University; Arnold Vedlitz, Texas
A&M University; Sammy Zahran, Colorado State University
Convening Lead Author: Janet L. Gamble, U.S. EPA
Lead Authors: Kristie L. Ebi, ESS LLC.; Frances G. Sussman,
Environmental Economics Consulting; Thomas J. Wilbanks, Oak
Ridge National Laboratory
Contributing Authors: Colleen E. Reid, ASPH Fellow; John V.
Thomas, U.S. EPA; Christopher P. Weaver, U.S. EPA
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SAP 4.6 Analysis of the Effects of Global Change on Human Health and Welfare and Human Systems
ACKNOWLEDGMENTS
This report has been peer reviewed in draft form by individuals identified for their diverse
perspectives and technical expertise. The expert review and selection of reviewers followed the
OMB's Information Quality Bulletin for Peer Review. The purpose of this independent review
is to provide candid and critical comments that will assist the Climate Change Science Program
in making this published report as sound as possible and to ensure that the report meets
institutional standards. The peer review comments, draft manuscript and response to the peer
review comments are publicly available at: www.climatescience.gov/Library/sap/sap4-
6/default.php.
Environmental Protection Agency Internal Reviewers
We wish to thank the following individuals from the U.S. Environmental Protection Agency for
their review of the first, and in some case later, draft(s) of the report. Reviewers from within
EPA, included:
Lisa Conner Adam Daigneault Benjamin De Angelo
Barbara Glenn Doug Grano Matthew Heberling
Ju-Chin Huang Stephen Newbold Jason Samenow
Sara Terry
National Center for Environmental Assessment, Global Change Research Program
We extend our thanks to our colleagues in the Global Change Research Program who contributed
thoughtful insights, reviewed numerous drafts, and helped with the production of the report.
John Thomas Christopher Weaver
Federal Agency Reviewers
Likewise, we thank the reviewers from within the federal "family." Reviewers from across the
federal agencies provided their comments during the public comment period.
Brigid DeCoursey Department of Transportation
Mary Gant National Institutes of Environmental Health Sciences / NIH
Indur M. Goklany Department of Interior
Charlotte Ski dm ore Office of Management and Budget
Samuel P. Williamson Office of the Federal Coordinator for Meteorology
Public Reviewers
We also extend our thanks to the reviewers who provided their comments during the public
comment period, included individuals from the public.
William Fang Edison Electric Institute
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SAP 4.6 Analysis of the Effects of Global Change on Human Health and Welfare and Human Systems
Katherine Farrell
Hans Martin Fuessel
Eric Holdsworth
John Kinsman
Kim Knowlton
Sabrina McCormick
J. Alan Roberson
Gina Solomon
AACDH
PICIR
Edison Electric Institute
Edison Electric Institute
Natural Resources Defense Council
Michigan State University
American Water Works Association
Natural Resources Defense Council
Human Impacts of Climate Change Advisory Committee (HICCAC)
Finally, we are indebted to the thoughtful review provided by a Federal Advisory Committee
convened by the U.S. Environmental Protection Agency to provide an independent expert review
of the SAP 4.6. The panel (the Human Impacts of Climate Change Advisory Committee) met in
October 2007 to discuss their findings and recommendations for the report. Following extensive
revisions to the report, the HICCAC reconvened by teleconference in January 2008 to review the
authors' response to comments. The panel's review of the report has contributed to a markedly
improved document.
Chair Tom Dietz Michigan State University
Co-chair Barbara Entwi sie University of North Carolina
Members Howard Frumkin Centers for Disease Control and Prevention
Thanks are also in order to Joanna Foellmer, the Designated Federal Official from within the
National Center for Environmental Assessment (NCEA) who organized and managed the
HICCAC.
ICF International
We thank our colleagues at ICF International for their support—logistical and technical—in
preparing the report. We wish to extend special thanks to Melinda Harris and Randy Freed.
It has been an honor and a pleasure to work with all of the people named above as well as the
many colleagues we have encountered in the process of preparing this report. We hope that this
document will be a positive step forward in our efforts to assess the impacts of climate change on
human systems and to evaluate opportunities for adaptation.
Peter Gleick Pacific Institute
Jonathan Patz University of Wisconsin
Roger Pul warty NO A A
Eugene Rosa Washington State University
Susan Stonich University of California at Santa Barbara
Summary
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SAP 4.6 Analysis of the Effects of Global Change on Human Health and Welfare and Human Systems
RECOMMENDED CITATIONS
Note: The page numbers included below are
specific to the pre-layout draft of the report.
These page numbers will change in the final
printed version.
For the Report as a Whole:
CCSP, 2008: Analyses of the effects of global
change on human health and welfare and
human systems. A Report by the U.S. Climate
Change Science Program and the
Subcommittee on Global Change Research.
[Gamble, J.L. (ed.), K.L. Ebi, F.G. Sussman,
T.J. Wilbanks, (Authors)]. U.S.
Environmental Protection Agency,
Washington, DC, USA.
For Executive Summary:
Gamble, J.L., K.L. Ebi, F.G. Sussman, T.J.
Wilbanks, C. Reid, J.V. Thomas, C.P.
Weaver, M. Harris, and R. Freed, 2008:
Executive Summary. In: Analyses of the
effects of global change on human health and
welfare and human systems. A Report by the
U.S. Climate Change Science Program and the
Subcommittee on Global Change Research.
[Gamble, J.L. (ed.), K.L. Ebi, F.G. Sussman,
T.J. Wilbanks, (Authors)]. U.S.
Environmental Protection Agency,
Washington, DC, USA, p. ES-1 to ES-14.
For Chapter 1:
Gamble, J.L., K.L. Ebi, A. Grambsch, F.G.
Sussman, T.J. Wilbanks, C.E. Reid, K.
Hayhoe, J.V. Thomas, and C.P. Weaver, 2008:
Introduction. In: Analyses of the effects of
global change on human health and welfare
and human systems. A Report by the U.S.
Climate Change Science Program and the
Subcommittee on Global Change Research.
[Gamble, J.L. (ed.), K.L. Ebi, F.G. Sussman,
T.J. Wilbanks, (Authors)]. U.S.
Environmental Protection Agency,
Washington, DC, USA, p. 1-1 to 1-41.
For Chapter 2:
Ebi, K.L., J. Balbus, P.L. Kinney, E. Lipp, D.
Mills, M.S. O'Neill, and M. Wilson, 2008:
Effects of Global Change on Human Health.
In: Analyses of the effects of global change on
human health and welfare and human systems.
A Report by the U.S. Climate Change Science
Program and the Subcommittee on Global
Change Research. [Gamble, J.L. (ed.), K.L.
Ebi, F.G. Sussman, T.J. Wilbanks, (Authors)].
U.S. Environmental Protection Agency,
Washington, DC, USA, p. 2-1 to 2-78.
For Chapter 3:
Wilbanks, T.J., P. Kirshen, D. Quattrochi, P.
Romero-Lankao, C. Rosenzweig, M. Ruth, W.
Solecki, and J. Tarr, 2008: Effects of Global
Change on Human Settlements. In: Analyses
of the effects of global change on human
health and welfare and human systems. A
Report by the U.S. Climate Change Science
Program and the Subcommittee on Global
Change Research. [Gamble, J.L. (ed.), K.L.
Ebi, F.G. Sussman, T.J. Wilbanks, (Authors)].
U.S. Environmental Protection Agency,
Washington, DC, USA, p. 3-1 to 3-31.
For Chapter 4:
Sussman, F.G., M.L. Cropper, H. Galbraith,
D. Godschalk, J. Loomis, G. Luber, M.
McGeehin, J.E. Neumann, W.D. Shaw, A.
Vedlitz, and S. Zahran, 2008: Effects of
Global Change on Human Welfare. In:
Analyses of the effects of global change on
human health and welfare and human systems.
A Report by the U.S. Climate Change Science
Program and the Subcommittee on Global
Change Research. [Gamble, J.L. (ed.), K.L.
Ebi, F.G. Sussman, T.J. Wilbanks, (Authors)].
U.S. Environmental Protection Agency,
Washington, DC, USA, p. 4-1 to 4-74.
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SAP 4.6 Analysis of the Effects of Global Change on Human Health and Welfare and Human Systems
For Chapter 5: Gamble, J.L., K.L. Ebi, F.G.
Sussman, T.J. Wilbanks, C. Reid, J.V.
Thomas, and C.P. Weaver, 2008: Common
Themes and Research Recommendations. In:
Analyses of the effects of global change on
human health and welfare and human systems.
A Report by the U.S. Climate Change Science
Program and the Subcommittee on Global
Change Research. [Gamble, J.L. (ed.), K.L.
Ebi, F.G. Sussman, T.J. Wilbanks, (Authors)].
U.S. Environmental Protection Agency,
Washington, DC, USA, p. 5-1 to 5-11.
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SAP 4.6 Analysis of the Effects of Global Change on Human Health and Welfare and Human Systems
TABLE OF CONTENTS
Executive Summary
Abstract ES-3
ES.l Climate Change and Vulnerability ES-3
ES.2 Climate Change and Human Health ES-5
ES.3 Climate Change and Human Settlements ES-7
ES.4 Climate Change and Human Welfare ES-9
ES.5 Tables ES-11
1. Introduction
1.1 Scope and Approach of the SAP 4.6 1-3
1.2 Climate Change in the United States: Context for an Assessment of Impacts on Human
Systems 1-7
1.2.1 Rising temperatures 1-8
1.2.2 Trends in precipitation 1-9
1.2.3 Rising sea levels and erosion of coastal zones 1-10
1.2.4 Changes in Extreme Conditions 1-11
1.3 Population Trends and Migration Patterns: A Context for Assessing Climate-related Impacts
1-14
1.3.1 Trends in total U.S. Population 1-14
1.3.2 Migration patterns 1-15
1.4 Complex Linkages: The Role of Non-climate Factors 1-17
1.4.1 Economic status 1-18
1.4.2 Technology 1-18
1.4.3 Infrastructure 1-19
1.4.4 Human and Social Capital and Behaviors 1-20
1.4.5 Institutions 1-20
1.4.6 Interacting effects 1-21
1.5 Reporting Uncertainty in SAP 4.6 1-22
1.6 References 1-24
1.7 Tables 1-36
1.8 Figures 1-37
2. Human Health
2.1 Introduction 2-3
2.2 Observed Climate-Sensitive Health Outcomes in the United States 2-4
2.2.1 Thermal Extremes: Heat Waves 2-4
2.2.2 Thermal Extremes: Cold Waves 2-6
2.2.3 Extreme Events: Hurricanes, Floods, and Wildfires 2-6
2.2.4 Indirect Health Impacts of Climate Change 2-8
2.3 Projected Health Impacts of Climate Change in the United States 2-15
2.3.1 Heat-Related Mortality 2-15
2.3.2 Hurricanes, Floods, Wildfires and Health Impacts 2-17
2.3.3 Vectorborne and Zoonotic Diseases 2-18
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SAP 4.6 Analysis of the Effects of Global Change on Human Health and Welfare and Human Systems
2.3.4 Water- and Foodborne Diseases 2-18
2.3.5 Air Quality Morbidity and Mortality 2-19
2.4 Vulnerable Regions and Subpopulations 2-22
2.4.1 Vulnerable Regions 2-23
2.4.2 Specific Subpopulations at Risk 2-23
2.5 Adaptation 2-26
2.5.1 Actors and Their Roles and Responsibilities for Adaptation 2-27
2.5.2 Adaptation Measures to Manage Climate Change-Related Health Risks 2-29
2.6 Conclusions 2-29
2.7 Expanding the Knowledge Base 2-30
2.8 References 2-32
2.9 Boxes 2-57
2.10 Tables 2-61
2.11 Figures 2-72
3. Human Settlements
3.1 Introduction 3-3
3.1.1 Purpose 3-3
3.1.2 Background 3-3
3.1.3 Current State of Knowledge 3-4
3.2 Climate Change Impacts and the Vulnerabilities of Human Settlements 3-4
3.2.1 Determinants of Vulnerability 3-4
3.2.2 Impacts of Climate Change on Human Settlements 3-5
3.2.3 The Interaction of Climate Impacts with Non-Climate Factors 3-7
3.2.4 Realizing Opportunities from Climate Change in the United States 3-9
3.2.5 Examples of Impacts on Metropolitan Areas in the United States 3-10
3.3 Opportunities for Adaptation of Human Settlements to Climate Change 3-10
3.3.1 Perspectives on Adaptation by Settlements 3-11
3.3.2 Major Categories of Adaptation Strategies 3-12
3.3.3 Examples of Current Adaptation Strategies 3-13
3.3.4 Strategies to Enhance Adaptive Capacity 3-14
3.4 Conclusions 3-14
3.5 Expanding the Knowledge Base 3-15
3.6 References 3-17
3.7 Boxes 3-24
3.8 Tables 3-29
3.9 Figures 3-31
4. Human Welfare
4.1 Introduction 4-3
4.2 Human Welfare, Well-being, and Quality of Life 4-4
4.2.1 Individual Measures of Well-being 4-5
4.2.2 The Social Indicators Approach 4-6
4.2.3 A Closer Look at Communities 4-10
4.2.4 Vulnerable Populations, Communities, and Adaptation 4-12
4.3 An Economic Approach to Human Welfare 4-13
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SAP 4.6 Analysis of the Effects of Global Change on Human Health and Welfare and Human Systems
4.3.1 Economic Valuation 4-15
4.3.2 Impacts Assessment and Monetary Valuation 4-16
4.3.3 Human Health 4-17
4.3.4 Ecosystems 4-22
4.3.5 Recreational Activities and Opportunities 4-28
4.3.6 Amenity Value of Climate 4-35
4.4 Conclusions 4-38
4.5 Expanding the Knowledge Base 4-39
4.6 References 4-41
4.7 Appendix 1 4-57
4.8 Boxes 4-64
4.9 Tables 4-66
4.10 Figures 4-72
5. Research
5.1 Synthesis and Assessment Product 4.6: Advances in the Science 5-3
5.1.1 Complex Linkages and a Cascading Chain of Impacts Across Global Changes 5-3
5.1.2 Changes in Climate Extremes and Climate Averages 5-4
5.1.3 Vulnerable Populations and Vulnerable Locations 5-5
5.1.4 The Cost of and Capacity for Adaptation 5-6
5.1.5 An Integrative Framework 5-6
5.2 Expanding the Knowledge Base 5-7
5.2.1 Human Health Research Gaps 5-9
5.2.2 Human Settlements Research Gaps 5-10
5.2.3 Human Welfare Research Gaps 5-10
6. Glossary and Acronyms
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Synthesis and Assessment Product 4.6
Analyses of the Effects of Global Change on Human
Health and Welfare and Human Systems
Executive Summary
Convening Lead Author: Janet L. Gamble, U.S. Environmental Protection Agency
Lead Authors: Kristie L. Ebi, ESS, LLC; Frances G. Sussman, Environmental Economics Consulting;
Thomas J. Wilbanks, Oak Ridge National Laboratory
Contributing Authors: Colleen Reid, ASPH Fellow; John V. Thomas, U.S. Environmental Protection
Agency; Christopher P. Weaver, U.S. Environmental Protection Agency; Melinda Harris, ICF International;
Randy Freed, ICF International
ES-1
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SAP 4.6 Executive Summary
Table of Contents
Abstract 3
ES.l Climate Change and Vulnerability 3
ES.2 Climate Change and Human Health 5
ES.3 Climate Change and Human Settlements 7
ES.4 Climate Change and Human Welfare 9
ES.5 Tables 11
ES-2
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Abstract
Climate change, interacting with changes in land use and demographics, will affect
important human dimensions in the United States, especially those related to human
health, settlements and welfare. The challenges presented by population growth, an aging
population, migration patterns, and urban and coastal development will be affected by
changes in temperature, precipitation, and extreme climate-related events. In the future,
with continued global warming, heat waves and heavy downpours are very likely to
further increase in frequency and intensity. Cold days and cold nights are very likely to
become much less frequent over North America. Substantial areas of North America are
likely to have more frequent droughts of greater severity. Hurricane wind speeds, rainfall
intensity, and storm surge levels are likely to increase. Other changes include measurable
sea-level rise and increases in the occurrence of coastal and riverine flooding. The United
States is certainly capable of adapting to the collective impacts of climate change.
However, there will still be certain individuals and locations where the adaptive capacity
is less and these individuals and their communities will be disproportionally impacted by
climate change.
This report - the Synthesis and Assessment Product 4.6 (SAP 4.6) - focuses on impacts
of global climate change, especially impacts on three broad dimensions of the human
condition: human health, human settlements, and human welfare. The SAP 4.6 has been
prepared by a team of experts from academia, government, and the private sector in
response to the mandate of the U.S. Climate Change Science Program's Strategic Plan
(2003). The assessment examines potential impacts of climate change on human society,
opportunities for adaptation, and associated recommendations for addressing data gaps
and near- and long-term research goals.
ES. I Climate Change and Vulnerability
Climate variability and change challenge even the world's most advanced societies. At a
very basic level, climate affects the costs of providing comfort in our homes and work
places. A favorable climate can provide inputs for a good life: adequate fresh water
supplies; products from the ranch, the farm, the forests, the rivers and the coasts; pleasure
derived from tourist destinations and from nature, biodiversity, and outdoor recreation.
Climate not only supports the provision of many goods and services, but also affects the
spread of some diseases and the prevalence of other health problems. It is also associated
with threats from extreme events and natural disasters such as tropical storms, riverine
and coastal flooding, wildfires, droughts, wind, hail, ice, heat, and cold.
This report examines the impacts on human society of global change, especially those
associated with climate change. The impact assessments in this report do not rely on
specific emissions or climate change scenarios but, instead, rely on the existing scientific
literature with respect to our understanding of climate change and its impacts on human
health, settlements and human well-being in the United States. Because climate change
forecasts are generally not specific enough for the scale of local decision-making, this
report adopts a vulnerability perspective in assessing impacts on human society.
ES-3
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SAP 4.6 Executive Summary
A vulnerability approach focuses on estimating risks or opportunities associated with
possible impacts of climate change, rather than on estimating (quantitatively) the impacts
themselves which would require far more detailed information about future conditions.
Vulnerabilities are shaped not only by existing exposures, sensitivities, and adaptive
capacities but also by responses to risks. For example, Boston is generally more
vulnerable to heat waves than Dallas because there are fewer air-conditioned homes in
Boston than in Dallas. At the same time, human responses (e.g., the elderly not using air-
conditioning) also are an important determinant of impacts. This leads to our conclusion
that climate change will result in regional differences in impacts in the United States not
only due to a regional pattern of changes in climate but the regional nature of our
communities in adapting to these changes.
In the United States, we are observing the evidence of long-term changes in temperature
and precipitation consistent with global warming. Changes in average conditions are
being realized through rising temperatures, changes in annual and seasonal precipitation,
and rising sea levels. Observations also indicate there are changes in extreme conditions,
such as an increased frequency of heavy rainfall (with some increase in flooding), more
heat waves, fewer very cold days, and an increase in areas affected by drought. There
have been large fluctuations in the number of hurricanes from year to year which make it
difficult to discern trends. Evidence suggests that the intensity of Atlantic hurricanes and
tropical storms has increased over the past few decades. However, changes in frequency
are currently too uncertain for confident projection.
Changes in the size of the population, including especially sensitive sub-populations, and
their geographic distribution across the landscape need to be accounted for when
assessing climate variability and change impacts. According to the Census Bureau's
middle series projection, the US population will increase to some 570 million people.
Moreover, the elderly population is increasing rapidly and many health assessments
identify them as more vulnerable than younger age groups to a range of health impacts
associated with climate change. Although numbers produced by population projections
are important, nearly all trends point to more Americans living in areas that may be
especially vulnerable to the effects of climate change. For example, many rapidly
growing places in the Mountain West may also experience decreased snow pack during
winter and earlier spring melting, leading to lower stream flows, particularly during the
high-demand period of summer. Similarly, coastal areas are projected to continue to
increase in population, with associated increases in population density, over the next
several decades.
Climate is only one of a number of global changes that affect human well-being. These
non-climate processes and stresses interact with climate change, determining the overall
severity of climate impacts. Socioeconomic factors that can influence exposures,
vulnerability and impacts include population, economic status, technology, infrastructure,
human capital and social context and behaviors, and institutions. Trends in these factors
alter anticipated impacts from climate because they fundamentally shape the nature and
scope of human vulnerability. Understanding the impacts of climate change and
ES-4
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SAP 4.6 Executive Summary
variability on the quality of life in the United States therefore implies knowledge of how
these factors vary by location, time, and socioeconomic group.
Climate change will seldom be the sole or primary factor determining a population's or a
location's well-being. Ongoing adaptation also can significantly influence climate
impacts. For example, emergency warning systems have generally reduced deaths and
death rates from extreme events, while greater access to insurance and broader,
government-funded safety nets for people struck by natural disasters have ameliorated the
hardships they face. While this assessment focuses on how climate change could affect
the future health, well-being, and settlements in the United States, the extent of any
impacts will depend on an array of non-climate factors and adaptive measures. Finally,
the effects of climate change very often spread from directly impacted areas and sectors
to other areas and sectors through extensive and complex linkages. In summary, the
importance of climate change depends on the directness of the climate impact coupled
with demographic, social, economic, institutional, and political factors, including, the
degree of preparedness.
Consistent with all of the Synthesis and Assessment Products being prepared by the
CCSP, this report includes statements regarding uncertainty. Each chapter author team
assigned likelihood judgments that reflect their assessment of the current consensus of the
science and the quality and amount of evidence. The likelihood terminology and the
corresponding values that are used in this report are consistent with the latest IPCC
Fourth Assessment and are further explained in Chapter 1 of this report. As the focus of
this report is on impacts, it is important to note that these likelihood statements refer to
the statement of the impact, not statements related to underlying climatic changes.
Table ES.l provides examples of climate change impacts that are identified in the
chapters for human health, settlements, and human welfare and includes potential
adaptation strategies. The list of impacts is not comprehensive, but rather includes those
that the available evidence suggests may occur. It is important to note that not all effects
have been equally well-studied. The effects identified for welfare, in particular, should
be taken as examples of effects about which we have some knowledge, rather than a
complete listing of all welfare effects.
ES.2 Climate Change and Human Health
The United States is a highly developed country with a wide range of climates. While
there may be fewer cases of illness and death associated with climate change in the
United States than in the developing world, we nevertheless anticipate increased costs to
human health and well being. Greater wealth and a more developed public health system
and infrastructure (e.g., water treatment plants, sewers, and drinking water systems;
roads, rails and bridges; flood control structures) will continue to enhance our capacity to
respond to climate change. Similarly, governments' capacities for disaster planning and
emergency response are key assets that should allow the United States to adapt to many
of the health effects associated with climate change.
ES-5
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SAP 4.6 Executive Summary
It is very likely that heat-related morbidity and mortality will increase over the
coming decades. According to the U.S. Census, the U.S. population is aging; the percent
of the population over age 65 is projected to be 13% by 2010 and 20% by 2030 (over 50
million people). Older adults, very young children, and persons with compromised
immune systems are vulnerable to temperature extremes. This suggests that temperature-
related morbidity and mortality are likely to increase. Similarly, heat-related mortality
affects poor and minority populations disproportionately, in part due to lack of air
conditioning. The concentration of poverty in inner city neighborhoods leads to
disproportionate adverse effects associated with urban heat islands.
There is considerable speculation concerning the balance of climate change-related
decreases in winter mortality compared with increases in summer mortality. Net changes
in mortality are difficult to estimate because, in part, much depends on complexities in
the relationship between mortality and the changes associated with global change. Few
studies have attempted to link the epidemiological findings to climate scenarios for the
United States, and studies that have done so have focused on the effects of changes in
average temperature, with results dependent on climate scenarios and assumptions of
future adaptation. Moreover, many factors contribute to winter mortality, making highly
uncertain how climate change could affect mortality. No projections have been published
for the U.S. that incorporate critical factors, such as the influence of influenza outbreaks.
The impacts of higher temperatures in urban areas and likely associated increases
in tropospheric ozone concentrations can contribute to or exacerbate cardiovascular
and pulmonary illness if current regulatory standards are not attained. In addition,
stagnant air masses related to climate change are likely to degrade air quality in some
densely populated areas. It is important to recognize that the United States has a well-
developed and successful national regulatory program for ozone, PM2.5, and other criteria
pollutants. That is, the influence of climate change on air quality will play out against a
backdrop of ongoing regulatory control that will shift the baseline concentrations of air
pollutants. Studies to date have typically held air pollutant emissions constant over future
decades (i.e., have examined the sensitivity of ozone concentrations to climate change rather
than projecting actual future ozone concentrations). Physical features of communities,
including housing quality and green space, social programs that affect access to health
care, aspects of population composition (level of education, racial/ethnic composition),
and social and cultural factors are all likely to affect vulnerability to air quality.
Hurricanes, extreme precipitation resulting in floods, and wildfires also have the
potential to affect public health through direct and indirect health risks. SAP3.3
indicates that there is evidence for a human contribution to increased sea surface
temperatures in the tropical Atlantic and there is a strong correlation to Atlantic tropical
storm frequency, duration, and intensity. However, a confident assessment will require
further studies. The health risks associated with such extreme events are thus likely to
increase with the size of the population and the degree to which it is physically, mentally,
or financially constrained in its ability to prepare for and respond to extreme weather
events. For example, coastal evacuations prompted by imminent hurricane landfall are
only moderately successful. Many of those who are advised to flee to higher ground stay
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SAP 4.6 Executive Summary
behind in inadequate shelter. Surveys find that the public is either not aware of the
appropriate preventive actions or incorrectly assesses the extent of their personal risk.
There will likely be an increase in the spread of several food and water-borne
pathogens among susceptible populations depending on the pathogens' survival,
persistence, habitat range and transmission under changing climate and
environmental conditions. While the United States has successful programs to protect
water quality under the Safe Drinking Water Act and the Clean Water Act, some
contamination pathways and routes of exposure do not fall under regulatory programs
(e.g., dermal absorption from floodwaters, swimming in lakes and ponds with elevated
pathogen levels, etc.).The primary climate-related factors that affect these pathogens
include temperature, precipitation, extreme weather events, and shifts in their ecological
regimes. Consistent with our understanding of climate change on human health, the
impact of climate on food and water-borne pathogens will seldom be the only factor
determining the burden of human injuries, illness, and death.
Health burdens related to climate change will vary by region. For the continental
United States, the northern latitudes are likely to experience the largest increases in
average temperatures; they will also bear the brunt of increases in ground-level ozone and
other airborne pollutants. Because Midwestern and Northeastern cities are generally not
as well adapted to the heat as Southern cities, their populations are likely to be
disproportionately affected by heat related illnesses as heat waves increase in frequency,
severity, and duration. The range of many vectors is likely to extend northward and to
higher elevations. For some vectors, such as rodents associated with Hantavirus, ranges
are likely to expand, as the precipitation patterns under a warmer climate enhance the
vegetation that controls the rodent population. Forest fires with their associated
decrements to air quality and pulmonary effects are likely to increase in frequency,
severity, distribution, and duration in the Southeast, the Intermountain West and the
West. Table ES.2 summarizes regional vulnerabilities to a range of climate impacts.
Finally, climate change is very likely to accentuate the disparities already evident in
the American health care system. Many of the expected health effects are likely to fall
disproportionately on the poor, the elderly, the disabled, and the uninsured. The most
important adaptation to ameliorate health effects from climate change is to support and
maintain the United States' public health infrastructure.
ES.3 Climate Change and Human Settlements
Effects of climate change on human settlements are likely to vary considerably
according to location-specific vulnerabilities, with the most vulnerable areas likely
to include Alaska with increased permafrost melt, flood-risk coastal zones and river
basins, and arid areas with associated water scarcity. The main climate impacts have
to do with changes in the intensity, frequency and location of extreme weather events
and, in some cases, water availability rather than temperature change.
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SAP 4.6 Executive Summary
Changes in precipitation patterns will affect water supplies nationwide, with
precipitation varying across regions and over time. Likely reductions in snowmelt,
river flows, and groundwater levels, along with increases in saline intrusion into
coastal rivers and groundwater will reduce fresh water supplies. All things held
constant, population growth will increase the demand for drinking water even as changes
in precipitation will change the availability of water supplies. Moreover, storms, floods,
and other severe weather events are likely to affect infrastructure such as sanitation,
transportation, supply lines for food and energy, and communication. Some of the
nation's most expensive infrastructure, such as exposed structures like bridges and utility
networks, are especially vulnerable. In many cases, water supply networks and stressed
reservoir capacity interact with growing populations (especially in coastal cities and in
the Mountain and Pacific West). The complex interactions of land use, population
growth and dynamics of settlement patterns further challenge supplies of water for
municipal, industrial, and agricultural uses. In the Pacific Northwest the electricity base
dominated by hydropower is directly dependent upon the water flows from snowmelt.
Reduced hydropower would mean the need for supplemental electricity sources, resulting
in a wide variety of negative ripple effects to the economy and to human welfare.
Similarly, along the West Coast, communities are likely to experience greater demands
on water supplies even as regional precipitation declines and average snow packs
decrease.
Communities in risk-prone regions, such as coastal zones, have reason to be
concerned about potential increases in severe weather events. The combined effects
of severe storms and sea-level rise in coastal areas or increased risks of fire in more arid
areas are examples of how climate change may increase the magnitude of challenges
already facing risk-prone regions. Vulnerabilities may be especially pronounced for
rapidly-growing and/or larger metropolitan areas, where the potential magnitude of both
impacts and coping requirements are likely to be very large. On the other hand, such
regions have greater opportunity to adapt infrastructure and to make decisions that limit
vulnerability.
Warming is virtually certain to increase energy demand in U.S. cities for cooling in
buildings while it reduces demands for heating in buildings (see SAP 4.5 Effects of
Climate Change on Energy Production and Use in the United States). Demands for
cooling during warm periods could jeopardize the reliability of service in some regions
by exceeding the supply capacity, especially during periods of unusually high
temperatures. Higher temperatures also affect costs of living and business operation by
increasing costs of climate control in buildings
Climate change has the potential not only to affect communities directly but also
indirectly through impacts on other areas linked to their economies. Regional
economies that depend on sectors highly sensitive to climate such as agriculture, forestry,
water resources, or recreation and tourism could be affected either positively or
negatively by climate change. Climate change can add to stress on social and political
structures by increasing management and budget requirements for public services such as
public health care, disaster risk reduction, and even public safety. As sources of stress
grow and combine, the resilience of social and political structures are expected to be
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SAP 4.6 Executive Summary
challenged, especially in locales with relatively limited social and political capital.
Finally, population growth and economic development is occurring in those areas
that are likely to be vulnerable to the effects of climate change. Approximately half
of the U.S. population, 160 million people, will live in one of 673 coastal counties by
2008. Coastal areas - particularly those on gently-sloping coasts and zones with gradual
land subsidence - will be at risk for sea level rise, especially related to severe storms and
storm surges.
ES.4 Climate Change and Human Welfare
The terms human welfare, quality of life, and well-being are often used
interchangeably, and by a number of disciplines as diverse as psychology,
economics, health science, geography, urban planning, and sociology. There is a
shared understanding that all three terms refer to aspects of individual and group life that
improve living conditions and reduce chances of injury, stress, and loss.
Human well-being is typically defined and measured as a multi-dimensional
concept. Taxonomies of place-specific well-being or quality of life typically converge on
six dimensions: 1) economic conditions, 2) natural resources and amenities, 3) human
health, 4) public and private infrastructure, including transportation systems, 5)
government and public safety and 6) social and cultural resources. Climate change will
likely have impacts across all of these dimensions - both positive and negative. In
addition, the positive and negative effects of climate change will affect broader
communities, as networks of households, businesses, physical structures, and institutions
are located together across space and time.
Quantifying impacts of climate change on human well-being requires linking effects
in quality of life to the projected1 physical effects of climate change and the
consequent effects on human and natural systems. Economic analyses provide a
means of quantifying and, in some cases, placing dollar values on welfare effects. Even
in cases where welfare effects have been quantified, it is difficult to compare and
aggregate a range of effects across a number of sectors.
This report examines four types of effects on economic welfare: those on
ecosystems, human health, recreation, and amenities associated with climate. Many
of the goods and services affected by climate are not traded in markets; as a result, they
can be difficult to value." For example, ecologists have already identified a number of
ecological impacts of climate change, including the shifting, break up, and loss of certain
ecological communities; plant and animal extinctions and a loss in biodiversity; shifting
ranges of plant and animal populations; and changes in ecosystem processes, such as
1 A climate projection is the calculated response of the climate system to emissions or concentration
scenarios of greenhouse gases and aerosols, or radiative forcing scenarios, often based on simulations by
climate models. Climate projections are distinguished from climate predictions, in that the former critically
depend on the c m i s s i o n s/co ncc n t ra t i o n/radi a I i i >e forcing scenario used, and therefore on highly uncertain
assumptions of future socio-economic and technological development.
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SAP 4.6 Executive Summary
nutrient cycling and decomposition. While ecosystems provide a variety of services to
humans, including food and fiber, regulating air and water quality, support services such
as photosynthesis, and cultural services such as recreation and aesthetic or spiritual
values, these typically are not traded in markets.
Little research has been done linking these ecological changes to changes in services,
and still less has been done to quantify, or place dollar values on, these changes.
Ecosystem impacts also extend beyond the obvious direct effects within the natural
environment to indirect effects on human systems. For instance, nearly 90% of
Americans take part in outdoor recreation. The length of season of some of these
activities, such as hiking, boating, or golfing, may be favorably affected by slightly
increased temperatures. However, snow and ice sport seasons are likely to be shortened,
resulting in lost recreation opportunities. The net effect is unclear as decrements
associated with snow-based recreation may be more than outweighed by increases in
other outdoor activities.
An agenda for understanding the impacts of climate change on human welfare may
require taking steps both to develop a framework for addressing welfare, and to
address the data and methodological gaps inherent in the estimation and
quantification of effects. To that end, the study of climate change on human welfare is
still developing, and, to our knowledge, no study has made a systematic survey of the full
range of welfare impacts associated with climate change, much less attempted to quantify
them.
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SAP 4.6 Executive Summary
ES.5 Tables
Table ES. I Examples of Possible Impacts (present to 2050) of Climate Variability and Change
on Human Health, Settlements, and Welfare in the United States and Potential Adaptation
Strategies)
Focus Area
Climate Event
Examples of Possible
Impacts
Likelihood of
Impact Given
Climate Event
Occurs1
Potential Adaptation
Strategies
HUMAN HEALTH
Extreme temperatures
More heat waves and
higher maximum
temperatures
Fewer cold waves and
higher minimum
temperatures
Heat stress/stroke or
hyperthermia
Uncertain impacts on
mortality2
Very likely in
Midwest and
northeast urban
centers
Early watch and
warning systems and
installation of cooling
systems in residential
and commercial
buildings,
Changes in precipitation,
especially extreme
precipitation
Contaminated water and
food supplies with
associated
gastrointestinal illnesses,
including salmonella and
giardia
Likely in areas
with out-dated
or over-
subscribed water
treatment plants
Improve
infrastructure to
guard against
combined sewer
overflow; public
health response to
include "boil water"
advisories
Hurricane and storm
surge
Injuries from flying debris
and drowning / exposure
to contaminated flood
waters and to mold and
mildew / exposure to
carbon monoxide
poisoning from portable
generators
Likely in coastal
zones of the
southeast
Atlantic and the
Gulf Coast
Increase knowledge
and awareness of
vulnerability to
climate change (e.g.,
maps showing areas
vulnerable to storm
surges); public health
advisories in
immediate aftermath
of storm; coordinate
storm relief efforts
to insure that people
receive necessary
information for
safeguarding their
health
Temperature-related
effects on ozone3
Ozone concentrations
more likely to increase
than decrease; possible
contribution to
cardiovascular and
pulmonary illnesses,
including exacerbation of
asthma and chronic
obstructive pulmonary
disorder (COPD) if
current regulatory
standards are not
attained
Likely in urban
centers in the
mid-Atlantic and
the northeast
Public warning via air
quality action days;
encourage public
transit, walking and
bicycling to decrease
emissions
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SAP 4.6 Executive Summary
Focus Area
Climate Event
Examples of Possible
Impacts
Likelihood of
Impact Given
Climate Event
Occurs1
Potential Adaptation
Strategies
Wildfires
Degraded air quality,
contributing to asthma
and COPD aggravated
Likely in
California, the
Intermountain
West, the
southwest and
the southeast
Public health air
quality advisories
HUMAN SETTLEMENTS
Extreme temperatures
More heat waves and
higher maximum
temperatures
Fewer cold waves and
higher minimum
temperatures
Increased net energy
demand and expand
capacity for peak cooling
Reduced cold-related
stresses and costs
Very likely
Expand capacity for
cooling through
public utilities; invest
in alternative energy
sources
Drought
Strain on municipal and
agricultural water
supplies
Very likely in
intermountain
west, desert
southwest, and
southeast
Reallocate water
among current users;
develop water
markets to
encourage more
efficient allocation;
identify new sources
through expansion of
reservoirs;
encourage
conservation of
water for personal
and public use;
develop drought
resistant crops,
Hurricane and storm
surge
Disruption of
infrastructure, including
levee systems, river
channels, bridges, and
highway systems;
disruption of residential
neighborhoods
Very likely in
southeast
Atlantic Coast
and Gulf Coast
Increase knowledge
and awareness of
climate impacts (e.g.,
maps showing areas
vulnerable to storm
surges); harden
coastal zones or
retreat or relocate;
insure against
catastrophic loss due
to flooding and high
winds
Wildfires
Disruption of
communities and
property destruction
Very likely in
intermountain
west, desert
southwest, and
southeast
Clear vegetation
away from buildings;
issue emergency
evacuation orders,
prescribed burns,
thinning of
combustible matter
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SAP 4.6 Executive Summary
Focus Area
Climate Event
Examples of Possible
Impacts
Likelihood of
Impact Given
Climate Event
Occurs1
Potential Adaptation
Strategies
Late snow fall and early
snow melt
Disruption of water
supplies for municipal and
agricultural use
Very likely in
intermountain
west
Build reservoirs;
conserve water
supplies; divert
supply from
agricultural to
municipal use; modify
operation of existing
infrastructure to
account for changes
in hydrology; develop
drought resistant
crops, water prices
at replacement cost,
enable trading by
working with states
to develop property
rights
HUMAN WELFARE
Extreme temperatures
More heat waves and
higher maximum
temperatures
Discomfort; limit some
outdoor activities /
recreation
Very likely in
more northern
latitudes of the
United States
and in Alaska
Public health
watch/warning
advisories
Fewer cold waves and
higher minimum
temperatures
Limit some snow- and
cold-related recreational
opportunities; substantial
economic disruption to
recreation industry
Very likely in
intermountain
west, Northern
New England and
the Upper Great
Lakes
Engage in alternative
recreation activities
Late autumn snow fall and
early spring snow melt
Limit some snow-related
recreational
opportunities; substantial
economic disruption to
recreation industry
Very likely in
intermountain
west, Northern
New England and
the Upper Great
Lakes
Engage in alternative
recreation activities
Extreme precipitation
events
Local flooding and
contamination of water
supplies
Very likely
nationwide
Issue flood advisories
/ warnings
Hurricane and coastal
storms
At-risk properties
experience flood and
wind damage; individuals
experience disruption to
daily life
Very likely in
coastal zone of
the Gulf Coast
and the southern
Atlantic
Relocate dwellings
and business, and
reinforce structures
and infrastructure to
reduce disruptions
1 Based on impacts identified in the published, peer-reviewed literature and expert opinion. Does not include an
evaluation of likelihood of the climate event. May include some adaptation (e.g., in the baseline estimate) but generally
does not account for additional changes or developments in adaptive capacity.
2 Many factors contribute to winter mortality, making highly uncertain how climate change could affect mortality. No
projections have been published for the United States that incorporates critical factors, such as the influence of
influenza outbreaks.
3 If areas remain in compliance with National Ambient Air Quality Standards, people will not be exposed to unhealthy
air (;.e., cardiovascular and pulmonary illnesses will not occur). More stringent emissions controls may be required to
remain in compliance although this is uncertain and additional study is needed.
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SAP 4.6 Executive Summary
Table ES.2 Summary of Regional Vulnerabilities to Climate-Related Impacts1
United States
Census Regions
Climate-Related Impacts
Early
Snowmelt
Degraded
Air Quality
Urban Heat
Island
Wildfires
Heat
Waves
Drought
Tropical
Storms
Extreme
Rainfall
with
Flooding
Sea Level
Rise
New England
ME VT NH MA Rl CT
•
•
•
•
•
•
•
Middle Atlantic
NY PA NJ
•
•
•
•
•
•
•
•
East North Central
Wl Ml IL IN OH
•
•
•
•
•
•
West North Central
ND MN SD IANE KS MO
•
•
•
•
•
South Atlantic
VW VA MD MC SC GA FL DC
•
•
•
•
•
•
•
•
East South Central
KY TN MS AL
•
•
•
•
West South Central
TX OK AR LA
•
•
•
•
•
•
•
•
Mountain
MT ID WY NV UT CO AZ NM
•
•
•
•
•
•
Pacific
AK CAWAOR HI
•
•
•
•
•
•
•
•
•
1 Based on impacts identified in the published, peer-reviewed literature and expert opinion.
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Synthesis and Assessment Product 4.6
Chapter I: Introduction
Convening Lead Author: Janet L. Gamble, U.S. Environmental Protection Agency
Lead Authors: Kristie L. Ebi, ESS, LLC; Anne Grambsch, U.S. Environmental Protection Agency; Frances
G. Sussman, Environmental Economics Consulting; Thomas J. Wilbanks, Oak Ridge National Laboratory
Contributing Authors: Colleen E. Reid, ASPH Fellow; Katharine Hayhoe, Texas Tech University; John
V. Thomas, U.S. Environmental Protection Agency; Christopher P. Weaver, U.S. Environmental Protection
Agency
-------
SAP 4.6 Chapter 1: Introduction
Table of Contents
Table of Contents 2
1.1 Scope and Approach of the SAP 4.6 3
1.2 Climate Change in the United States: Context for an Assessment of Impacts on Human Systems 7
1.2.1 Rising Temperatures 8
1.2.2 Trends in Precipitation 9
1.2.3 Rising Sea Levels and Erosion of Coastal Zones 10
1.2.4 Changes in Extreme Conditions 11
1.3 Population Trends and Migration Patterns: A Context for Assessing Climate-related Impacts 14
1.3.1 Trends in Total U.S. Population 14
1.3.2 Migration Patterns 15
1.4. Complex Linkages: The Role of Non-climate Factors 17
1.4.1 Economic Status 18
1.4.2 Technology 18
1.4.3 Infrastructure 19
1.4.4 Human and Social Capital and Behaviors 20
1.4.5 Institutions 20
1.4.6 Interacting Effects 21
1.5 Reporting Uncertainty in SAP 4.6 22
1.6 References 24
1.7 Tables 36
1.8 Figures 37
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SAP 4.6 Chapter 1: Introduction
I. I Scope and Approach of the SAP 4.6
The Global Change Research Act of 1990 (Public Law 101-606) calls for the periodic
assessment of the impacts of global environmental change for the United States. In 2001,
a series of sector and regional assessments were conducted by the U.S. Global Change
Research Program as part of the First National Assessment of the Potential Consequences
of Climate Variability and Change on the United States. Subsequently, the U.S. Climate
Change Science Program developed a Strategic Plan (CCSP, 2003) calling for the
preparation of 21 synthesis and assessment products (SAPs) to inform policy making and
adaptive management across a range of climate-sensitive issues. Synthesis and
Assessment Product 4.6 examines the effects of global change on human systems. This
product addresses Goal 4 of the five strategic goals set forth in the CCSP Strategic Plan
to "understand the sensitivity and adaptability of different natural and managed
ecosystems and human systems to climate and related global changes" (CCSP, 2003).
The "global changes" assessed in this report include: climate variability and change,
evolving patterns of land use within the United States, and changes in the nation's
population.
While the mandate for the preparation of this report calls for evaluating the impacts of
global change, the emphasis is on those impacts associated with climate change.
Collectively, global changes are human problems, not simply problems for the natural or
the physical world. Hence, this SAP examines the vulnerability of human health and
socioeconomic systems to climate change across three foci, including: human health,
human settlements and human welfare. The three topics are fundamentally linked but
unique dimensions of global change.
Human health is one of the most basic and direct measures of human welfare. Following
past assessments of climate change impacts on human health, SAP 4.6 focuses on human
morbidity and mortality associated with extreme weather, vector-, water- and food-borne
diseases, and changes in air quality in the United States. However, it should be noted that
climate change in other parts of the world could impact human health in the United
States, (e.g., by affecting migration into the U.S., the safety of food imported into the
U.S., etc.). Adaptation is a key component to evaluating human health vulnerabilities,
including consideration of public health interventions (including prevention, response,
and treatment strategies) that could be revised, supplemented, or implemented to protect
human health and how much adaptation could be achieved.
Settlements are where people live. Humans live in a wide variety of settlements in the
United States, ranging from small villages and towns with a handful of people to
metropolitan regions with millions of inhabitants. In particular, SAP 4.6 focuses on urban
and highly-developed population centers in the United States. Because of their high
population density, urban areas multiply human health risks, and this is compounded by
their relatively high proportions of the very old, the very young, and the poor. In addition,
the components of infrastructure that support settlements, such as energy, water supply,
transportation, and waste disposal, have varying degrees of vulnerability to climate
change.
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SAP 4.6 Chapter 1: Introduction
Welfare is an economic term used to describe the state of well-being of humans on an
individual or collective basis. Human welfare is an elusive concept, and there is no
single, commonly accepted definition or approach to thinking about welfare. There is,
however, a shared understanding that increases in human welfare are associated with
improvements in individual and communal conditions in areas such as political power,
individual freedoms, economic power, social contacts, health and opportunities for
leisure and recreation, along with reductions in injury, stress, and loss. The physical
environment, with climate as one aspect, is among many factors that can affect human
welfare via economic, physical, psychological, and social pathways that influence
individual perceptions of quality of life. Some core aspects of quality of life are
expressed directly in markets (e.g., income, consumption, personal wealth, etc.). The
focus in SAP 4.6 is on non-market effects, although, these aspects of human welfare are
often difficult to measure and value (Mendelsohn et al., 1999; EPA, 2000).
The other Synthesis and Assessment Products related to CCSP's Goal 4 include reports
on climate impacts on sea level rise (SAP 4.1), ecosystem changes (SAP 4.2), agricultural
production (SAP 4.3), adaptive options for climate sensitive ecosystems (SAP 4.4),
energy use (SAP 4.5) and transportation system impacts along the Gulf Coast (SAP 4.7).
Collectively, these reports provide an overview of climate change impacts and
adaptations related to a range of human conditions in the United States.
The audience for this report includes research scientists, public health practitioners,
resource managers, urban planners, transportation planners, elected officials and other
policy makers, and concerned citizens. A recent National Research Council analysis of
global change assessments argues that the best assessments have an audience asking for
them, and a broad range of stakeholders (U.S. National Research Council, 2007). This
report clearly identifies the pertinent audience and what decisions it will inform.
Chapters 2-4 describe the impacts of climate change on human systems and outline
opportunities for adaptation. SAP 4.6 addresses the questions of how and where climate
change may impact U.S. socio-economic systems. The challenge for this project is to
derive an assessment of risks associated with health, welfare, and settlements and to
develop timely adaptive strategies to address a range of vulnerabilities. Risk assessments
evaluate impacts of climate change across an array of characteristics, including: the
magnitude of risk (both baseline and incremental risks), the distribution of risks across
populations (including minimally-impacted individuals as compared to maximally-
exposed individuals), and the availability, difficulty, irreversibility, and cost of adaptation
strategies. While the state of science limits the ability to conduct formal, quantitative risk
assessments, it is possible to develop information that is useful for formulating adaptation
strategies. Primary goals for adaptation to climate variability and change include:
1. To avoid maladaptive responses;
2. To establish protocols to detect and measure risks and to manage risks proactively
when possible;
3. To leverage technical and institutional capacity;
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SAP 4.6 Chapter 1: Introduction
4. To reduce current vulnerabilities to climate change;
5. To develop adaptive capacity to address new climate risks that exceed
conventional adaptive responses; and,
6. To recognize and respond to impacts which play out across time. (Scheraga and
Grambsch, 1998; WHO, 2003; IPCC, 2007b)
The issue of co-benefits is central in the consideration of adaptation to climate change.
Many potential adaptive strategies have co-benefits. Along with helping human
populations cope with climate change, adaptive strategies produce additional benefits.
For example:
¦ Creating and implementing early warning systems and emergency response plans
for heat waves can also improve those services for other emergency responses
while improving all-hazards preparedness; (Glantz, 2004)
¦ Improving the infrastructure and capacity of combined sewer systems to avoid
overflows due to changes in precipitation patterns also has the added benefit of
decreasing contaminant flows that cause beach closings and impact the local
ecology; (Rose etal., 2001)
¦ A key adaptation technique for settlements in coastal zones is to promote
maintenance or reconstruction of coastal wetlands ecosystems, which has the
added benefit of creation or protection of coastal habitats (Rose etal., 2001); and,
¦ Promotion of green building practices has added health and welfare benefits as
improving natural light in office space and schools has been shown to increase
productivity and mental health (Edwards and Torcellini, 2002).
Chapter 2 assesses the potential impacts of climate change on human health in the United
States. Timely knowledge of human health impacts may support our public health
infrastructure in devising and implementing strategies to prevent, compensate, or respond
to these effects. For each of the health endpoints, the assessment addresses a number of
topics, including:
¦ Reviewing evidence of the current burden associated with the identified health
outcome;
¦ Characterizing the human health impacts of current climate variability and
projected climate change (to the extent that the current literature allows);
¦ Discussing adaptation opportunities and support for effective decision making;
and,
¦ Outlining key knowledge gaps.
Each topic chapter includes research published from 2001 through early 2007 in the
United States, or in Canada, Europe, and Australia, where results may provide insights
for U.S. populations. As such, the health chapter serves as an update to the Health Sector
Assessment conducted as part of the First National Assessment in 2001.
Chapter 3 focuses on the climate change impacts and adaptations associated with human
settlements in the United States. The IPCC Third and Fourth Assessment Reports (IPCC,
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SAP 4.6 Chapter 1: Introduction
2001; IPCC, 2007c) conclude that settlements are among the human systems that are the
most sensitive to climate change. For example, if there are changes in climate extremes
there could be serious consequences for human settlements that are vulnerable to
droughts and wildfires, coastal and river floods, sea level rise and storm surge, heat
waves, land slides, and windstorms. However, specific changes in these conditions in
specific places cannot yet be projected with great confidence. Chapter 3 focuses on the
interactions between settlement characteristics, climate and other global stressors, with a
particular focus on urban areas and other densely-developed population centers in the
United States.
The scale and complexity of these built environments, transportation networks, energy
and resource demands, and the interdependence of these systems and their populaces,
suggests that urban areas are especially vulnerable to multiplying impacts in response to
externally imposed environmental stresses. The collective vulnerability of American
urban centers may also be determined by the disproportionate share of urban growth in
areas like the Inter-Mountain West or the Gulf Coast. The focus of Chapter 3 is on high
density or rapidly-growing settlements and the potential for changes over time in the
vulnerabilities associated with place-based characteristics (such as their climate regime,
elevation, and proximity to coasts and rivers) and spatial characteristics (such as whether
development patterns are sprawling or compact).
Chapter 4 focuses on the impacts of climate change on human welfare. To examine the
impacts of climate change on human welfare, this chapter reports on two relevant bodies
of literature: approaches to welfare that rely on both qualitative assessment and
quantitative measures, and economic approaches that monetize, or place money values,
on quantitative impacts.
Finally, Chapter 5 revisits the research recommendations and data gaps of previous
assessment activities and describes the progress to date and the opportunities going
forward. In addition, Chapter 5 reviews the overarching themes derived from Chapters 2-
4.
The remainder of this chapter is designed to provide the reader with an overview of the
current state of knowledge regarding:
1. Changes in climate in the United States;
2. Population trends, migration patterns, and the distribution of people across
settlements;
3. Non-climate stressors and their interactions with climate change to realize
complex impacts; and,
4. A discussion of the handling of uncertainty in reporting scientific results.
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1.2 Climate Change in the United States: Context for an
Assessment of Impacts on Human Systems
In the following chapters, the authors examine the impacts on human society of global
change, especially those associated with climate change. The impact assessments in
Chapters 2-4 do not rely on specific emissions or climate change scenarios but, instead,
rely on the existing scientific literature with respect to our understanding of climate
change and its impacts on human health, settlements and human well-being in the United
States. This report does not make quantitative projections of specific impacts in specific
locations based on specific projections of climate drivers of these impacts. Instead the
report adopts a vulnerability perspective.
A vulnerability approach focuses on estimating risks or opportunities associated with
possible impacts of climate change, rather than on estimating quantitatively the impacts
themselves which would require far more detailed information about future conditions.
Vulnerabilities are shaped not only by existing exposures, sensitivities, and adaptive
capacities but also by responses to risks. In addition, climate change is not the only
change confronting human societies: from a vulnerability perspective projected changes
in populations, the economy, technology, institutions, infrastructure, and human and
social capital are among the factors that also affect vulnerability to climate change. The
report reviews historical trends and variability to point to vulnerabilities and then, where
possible, determines the likely direction and range of potential climate-related impacts.
In the United States, we are observing the evidence of long-term changes in temperature
and precipitation consistent with global warming. Changes in average conditions are
being realized through rising temperatures, changes in annual and seasonal precipitation,
and rising sea levels. Observations also indicate there are changes in extreme conditions,
such as an increased frequency of heavy rainfall (with some increase in flooding), more
heat waves, fewer very cold days, and an increase in areas affected by drought.
Frequencies of tropical storms and hurricanes vary considerably from year to year and
there are limitations in the quality of the data which make it difficult to discern trends,
but evidence suggests some increases in their intensity and duration since the 1970s
(Christensen et al., 2007).
The following sections provide a brief introduction to climate change as a context for the
following chapters on impacts and adaptation. SAP4.6 did not itself evaluate climate
change projections as they were not used quantitatively in this assessment. The
Intergovernmental Panel on Climate Change provides a comprehensive evaluation of
climate change science. In their Summary for Policy Makers (IPCC, 2007a) reports the
following observed changes in global climate:
¦ "Warming of the climate system is unequivocal, as is now evident from
observations of increases in global average air and ocean temperature, widespread
melting of snow and ice, and rising global average sea level."
¦ "Eleven of the last twelve years rank among the 12 warmest years in the
instrumental record of global surface temperatures (since 1850)."
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SAP 4.6 Chapter 1: Introduction
¦ "Average temperature of the global ocean has increased to depths of at least 3000
m and that the ocean has been absorbing more than 80% of the heat added to the
climate system. Such warming causes sea water to expand, contributing to sea
level rise."
¦ "Mountain glaciers and snow cover have declined on average in both
hemispheres."
¦ "The frequency of heavy precipitation events has increased over most land areas,
consistent with warming and observed increases of atmospheric water vapor."
¦ "Widespread changes in extreme temperatures have been observed over the last
50 years... Hot days, hot nights, and heat waves have become more frequent."
¦ "There is observational evidence for an increase of intense tropical cyclone
activity in the North Atlantic since about 1970." (IPCC, 2007a)
Note that these changes are for the entire globe: changes in the United States may be
similar or differ from these global changes. The following sections examine U.S. climate
trends and historical records related to temperature, precipitation, sea level rise, and
changes in hurricanes and other catastrophic events. Information is also drawn from the
North American Chapter of the IPCC Fourth Assessment Report and the Climate Change
Science Programs Synthesis and Assessment Product 3.3: Weather and Climate Extremes
in a Changing Climate. Taken together, this discussion provides a context from which to
assess impacts of climate change on human health, human welfare, and human
settlements.
1.2.1 Rising Temperatures
Climate change is already affecting the United States. According to long-term station-
based observational records such as the Historical Climatology Network (Karl et al.,
1990; Easterling et al., 1999; Williams el a!., 2007), temperatures across the continental
United States have been rising at a rate of 0.1 °F per decade since the early 1900s.
Increases in average annual temperatures over the last century now exceed 1°F (Figure
1.1a). The degree of warming has varied by region across the United States, with the
West and Alaska experiencing the greatest degree of warming (U.S. Environmental
Protection Agency, 2007). These changes in temperature have led to an increase in the
number of frost-free days, with the greatest increases occurring in the West and
Southwest (Tebaldi et al., 2006). The Intergovernmental Panel on Climate Change, in its
most recent assessment report concluded that "Warming of the climate system is
unequivocal..." (IPCC, 2007a).
Figure I.I Observed trends in annual average (a) temperature (°F) and (b) precipitation
(inches) across the continental United States from 1896 to 2006 (Source: NCDC, 2007)
The current generation of global climate models, run with IPCC SRES scenarios of future
greenhouse gas emissions, simulate future changes in the earth's climate system that are
greater in magnitude and scope than those already observed. According to the IPCC, by
the end of the 21st century, annual surface temperature increases are projected to range
from 2-3°C near the coasts in the conterminous United States to more than 5°C in
northern Alaska. Nationally, annual warming in the United States is projected to exceed
2°C, with projected increases in summertime temperatures ranging between 3 and 5°C
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(greatest in the Southwest). The largest warming is projected to reach 10°C for winter
temperatures in the northernmost parts of Alaska. (IPCC, 2007c). For additional
information about the modeling results, see the IPCC Fourth Assessment Working Group
I Report, especially Chapter 11: Regional Climate Projections (Christensen et al., 2007)
1.2.2 Trends in Precipitation
Shifting precipitation patterns have also been observed. Over the last century, annual
precipitation across the continental United States has been increasing by an average of
0.18 inches per decade (Figure 1.1b). Broken down by season, winter precipitation
around the coastal areas, including the West, Gulf, and Atlantic coasts, has been
increasing by up to 30% while precipitation in the central part of the country (the
Midwest and the Great Plains) has been decreasing by up to 20%. Large-scale spatial
patterns in summer precipitation trends are more difficult to identify, as much of summer
rainfall comes in the form of small-scale convective precipitation. However, it appears
that there have been increases of 20-80% in summer rainfall over California and the
Pacific Northwest, and decreases on the order of 20-40% across much of the south. The
IPCC reports that rainfall is arriving in more intense events. (IPCC, 2007a).
El Nino events (a periodic warming of the tropical Pacific Ocean between South America
and the International Date Line) are associated with increased precipitation and severe
storms in some regions, such as the southeast United States and the Great Basin region of
the western United States. El Nino events have also been characterized by warmer
temperatures and decreased precipitation in other areas, such as western Canada, the
Pacific Northwest and parts of Alaska. Historically, El Nino events occur about every 3
to 7 years and alternate with the opposite phases of below-average temperatures in the
eastern tropical Pacific (La Nina). Since 1976-1977, there has been a tendency toward
more prolonged and stronger El Ninos (IPCC, 2007a). However, recent analyses of
climate simulations indicate no consistent trends in future El Nino amplitude or
frequency (Meehl et al., 2007)
Global model simulations summarized in the North American Chapter of the IPCC AR4,
show moderate increases in precipitation (10% or less) over much of the United States
over the next 100 years, except for the southwest. However, projected increases in these
simulations are partially offset by increases in evaporation, resulting in greater drying in
the central part of the United States. Projections for the central, eastern and western
regions of the United States show similar seasonal characteristics {i.e., winter increases,
summer decreases), although there is greater consensus for winter increases in the north
and summer decreases in the south. However, uncertainty around the projected changes is
large (IPCC, 2007b).
1.2.2.1 Changes in Snow Melt and Glacial Retreat
Warmer temperatures are melting mountain glaciers and more winter precipitation in
northern states is falling as rain instead of snow. (Huntington et al., 2004). Snow pack is
also melting faster, affecting stream flow in rivers. Over the last fifty years, changes in
the timing of snow melt has shifted the schedule of snow-fed stream flow in the western
part of the country by 1-4 weeks earlier in the year (Stewart et al., 2005). The seasonal
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"center of stream flow volume" {i.e., the date at which half of the expected winter-spring
stream flow has occurred) also appears to be advancing by on average one day per decade
for streams in the Northeast (Huntington et al., 2003).
This trend is projected to continue, with more precipitation falling as rain rather than
snow, and snow season length and snow depth are generally projected to decrease in most
of the country. Such changes tend to favor increased risk of winter flooding and lower
summer soil moisture and streamflows (IPCC, 2007a).
1.2.3 Rising Sea Levels and Erosion of Coastal Zones
Sea levels are rising and the IPCC concluded with high confidence that the rate of sea
level rise increased from the 19th to the 20th centuries (IPCC, 2007a). The causes for
observed sea-level rise over the past century include thermal expansion of seawater as it
warms and changes in land ice {e.g., melting of glaciers and snow caps). Over the 20th
century, sea level was rising at a rate of about 0.7 inches per decade (1.7 mm/yr ± 0.5
mm). For the period 1993 to 2003, the rate was nearly twice as fast, at 1.2 inches per
decade (3.1 mm/yr ± 0.7 mm). However, there is considerably decadal variability in the
tide gauge record so that it is unknown whether the higher rate in 1993 to 2003 is due to
decadal variability or an increase in the longer-term trend. (Bindoff et al., 2007). In the
past century, global sea level rose 5-8 inches.
Spatially sea-level change varies considerably: in some regions, rates are up to several
times the global mean rise, while in other regions sea level is falling. For example, for the
mid-Atlantic coast {i.e., from New York to North Carolina), the "effective" or relative
sea-level rise rates have exceeded the global rate due to a combination of land subsidence
and global sea level rise. In this region, relative sea-level rise rates ranged between 3 to 4
mm per year (~lft per century) over the 20th century. In other cases, local sea-level rise
is less than the global average because the land is still rising (rebounding) from when ice
sheets covered the area, depressing the Earth's crust. Local sea levels can actually be
falling in some cases (for example, the Pacific Northwest coast) if the land is rising more
than the sea is falling (for additional details about sea level rise and its effects on US
coasts please see Synthesis and Assessment Product 4.1 Coastal elevations and sensitivity
to sea level rise).
Rising global temperatures are projected to accelerate the rate of sea-level rise by further
expanding ocean water, melting mountain glaciers, and increasing the rate at which
Greenland and Antarctic ice sheets melt or discharge ice into the oceans. Estimates of
sea-level rise for a global temperature increase between 1.1 and 6.4°C (the IPCC estimate
of likely temperature increases by 2100) are about 7 to 23 inches (0.18m to 0.59m),
excluding the contribution from accelerated ice discharges from the Greenland and
Antarctica ice sheets. Extrapolating the recent acceleration of ice discharges from the
polar ice sheets would imply an additional contribution up to 8 inches (20cm). If melting
of these ice caps increases, larger values of sea-level rise cannot be excluded (IPCC,
2007a).
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1.2.4 Changes in Extreme Conditions
The climatic changes described above are often referred to as changes in "average"
conditions. Most observations of temperature will tend to be close to the average: days
with very hot temperatures happen infrequently. Similarly, only rarely will there be days
with extremely heavy precipitation. Climate change could result in a shift of the entire
distribution of a meteorological variable so that a relatively small shift in the mean could
be accompanied by a relatively large change in the number of relatively rare (according
to today's perspective) events. For example, with an increase in average temperatures, it
would be expected there would be an increase in the number of very hot days and a
decrease in the number of very cold days. Other, relatively rare, extreme events of
concern for human health, welfare and settlements include hurricanes, floods and
droughts.
In general, it is difficult to attribute any individual extreme event to a changing climate.
Because extreme events occur infrequently, there is typically limited information to
characterize these events and their trends. In addition, extreme events usually require
several conditions to exist for the event to occur, so that linking a particular extreme
event to a single, specific cause is problematic. For some extreme events, such as
extremely hot/cold days or rainfall extremes, there is more of an observational basis for
analyzing trends, increasing our understanding and ability to project future changes.
Finally, there are many different aspects to extremes. Frequency is perhaps the most often
discussed but changes in other aspects of extremes such as intensity (e.g., warmer hot
days), time of occurrence (e.g., earlier snowmelt), duration (e.g., longer droughts), spatial
extent and location are also important when determining impacts on human systems.
Synthesis and Assessment Product 3.3 Weather and Climate Extremes in a Changing
Climate (CCSP, 2008) has a much more detailed discussion of climate extremes that are
only very briefly described here. The interested reader is referred to that report for
additional details.
1.2.4.1 Heat and Cold Waves
Extreme temperatures (e.g., temperatures in the upper 90th or 95th percentile of the
distribution) often change in parallel with average temperatures. Since 1950, there are
more 3-day warm spells (exceeding the 90th percentile) when averaged over all of North
America (Peterson et al., 2008). While the number of heat waves has increased, the heat
waves of the 1930s remain the most severe in the U.S. historical record. Mirroring this
shift toward more hot days is a decrease in unusually cold days during the last few
decades. There has been a corresponding decrease in frost days and a lengthening of the
frost-free season over the past century. The number of frost days decreased by four days
per year in the United States during the 1948-1999 period, with the largest decreases, as
many as 13 days per year, occurring in the western United States (Easterling, 2002). For
the United States, the average length of the frost-free season over the 20th century
increased by almost two weeks (Kunkel et al., 2004).
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Recent studies have found that there is an increased likelihood of more intense, longer-
lasting and more frequent heat waves (Meehl and Tebaldi, 2004, Schar el al., 2004, Clark
et al., 2006). As the climate warms, the number of frost days is expected to decrease
(Cubasch et al., 2001) particularly along the northwest coast of North America (Meehl et
al., 2004). SAP 4.6, using a range of greenhouse gas emission scenarios and model
simulations, found that hot days, hot nights and heat waves are very likely to become
more frequent, that cold days and cold nights are very likely to become much less
frequent, and that the number of days with frost is very likely to decrease (CCSP, 2008).
Growing season length is related to frost days, which is projected to increase in a warmer
climate in most areas (Tebaldi et al., 2006).
1.2.4.2 Heavy Precipitation Events
Over the 20th century, periods of heavy downpours became more frequent and more
intense and accounted for a larger percentage of total precipitation (Karl and Knight,
1997; Groisman et al., 1999, 2001, 2004, 2005; Kunkel et al., 1999; Easterling et al.,
2000; Kunkel, 2003). These heavy rainfall events have increased in frequency by as
much as 100% across much of the Midwest and Northeast over the last century (Kunkel
et al., 1999). These findings are consistent with observed warming and associated
increases in atmospheric water vapor.
The intensity of precipitation events is projected to increase, particularly in high latitude
areas that experience increases in mean precipitation (Meehl et al., 2007). In areas where
mean precipitation decreases (most subtropical and mid-latitude regions), precipitation
intensity is projected to increase but there would be longer periods between rainfall
events. Precipitation extremes increase more than does the mean in most tropical and
mid- and high-latitude areas. Some studies project widespread increases in extreme
precipitation (Christensen et al., 2007), with greater risks of not only flooding from
intense precipitation, but also droughts from greater temporal variability in precipitation.
SAP 3.3 concluded that, over most regions, future precipitation is likely to be less
frequent but more intense, and precipitation extremes are very likely to increase (CCSP,
2008).
1.2.4.3 Changes in Flooding
Heavy rainfall clearly can lead to flooding, but assessing whether observed changes in
precipitation have lead to similar trends in flooding is difficult for a number of reasons. In
particular, there are many human influences on streamflow (e.g., dams, land-use changes,
etc.) that confound climatic influences. In some cases, researchers using the same data
came to opposite assessments about trends in high streamflows (Lins and Slack, 1999,
2005; Groisman etal, 2001, 2004). Short duration extreme precipitation events can lead
to localized flash flooding, but for large river basins, significant flooding will not occur
from these types of episodes alone; excessive precipitation must be sustained for weeks
to months for flooding to occur.
1.2.4.4 Changes in Droughts
An extended period with little precipitation is the main cause of drought, but the intensity
of a drought can be exacerbated by high temperatures and winds, a lack of cloudiness/low
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humidity which result in high evaporation rates. Droughts occur on a range of geographic
scales and can vary in their duration, in some cases lasting years. The 1930s and the
1950s experienced the most widespread and severe drought conditions (Andreadis et al.,
2005), although the early 2000s also saw severe droughts in some areas, especially in the
western United States (Piechota et al., 2004).
Based on observations averaged over the United States, there is no clear overall national
trend in droughts (CCSP, 2008). Over the past century, the area affected by severe and
extreme drought in the United States each year averaged about 14%: by comparison, in
1934 the area affected by drought was as high as 65% (CCSP, 2008). In recent years, the
drought-affected area ranged between 35 and 40% (CCSP, 2008). These trends at the
national level however mask important differences in drought conditions at regional
scales: one area may be very dry while another is wet. For example, in the Southwest and
parts of the interior of the West increased temperatures have led to rising drought trends
(Groisman etal., 2004; Andreadis and Lettenmaier, 2006). In the Southwest, the 1950s
were the driest period, though droughts in the past 10 years are approaching the 1950s
drought (CCSP, 2008). There are also recent regional tendencies toward more severe
droughts in parts of Alaska (CCSP, 2008).
Several generations of global climate models, including the most recent find an increase
in summer drying in the mid latitudes in a future, warmer climate (Meehl et al., 2007).
This tendency for drying of the mid-continental areas during summer indicates a greater
risk of droughts in those regions (CCSP, 2008). Analyses using several coupled global
circulation models project an increased frequency of droughts lasting a month or longer
in the Northeast (Hayhoe et al., 2007) and greatly reduced annual water availability over
the Southwest (Milly etal, 2005). SAP 3.3 concluded that droughts are likely to become
more frequent and severe in some regions of the country as higher air temperatures
increase the potential for evaporation.
1.2.4.5 Changes in Hurricanes
Assessing changes in hurricanes is difficult: There have been large fluctuations in the
number of hurricanes from year to year and from decade to decade. Furthermore, it is
only since the 1960s that reliable data can be assembled for assessing trends. In general,
there is increasing uncertainty in the data record the further back in time one goes but
significant increases in tropical cyclone frequency are likely since 1900 (CCSP, 2008).
However, the existing data and an adjusted record of tropical storms indicate no
significant linear trends beginning from the mid- to late 1800s to 2005 (CCSP, 2008).
Moreover, SAP 3.3 concluded that there is no evidence for a long-term increase in North
American mainland land-falling hurricanes.
Evidence suggests that the intensity of Atlantic hurricanes and tropical storms has
increased over the past few decades. SAP3.3 indicates that there is evidence for a human
contribution to increased sea surface temperatures in the tropical Atlantic and there is a
strong correlation to Atlantic tropical storm frequency, duration, and intensity. However,
a confident assessment will require further studies. An increase in extreme wave heights
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in the Atlantic since the 1970s has been observed: consistent with more frequent and
intense hurricanes (CCSP, 2008).
For North Atlantic hurricanes, SAP3.3 concludes that it is likely that wind speeds and
core rainfall rates will increase (Henderson-Sellers et al., 1998; Knutson and Tuleya,
2004, 2008; Emanuel, 2005). However, SAP3.3 concluded that "frequency changes are
currently too uncertain for confident projection" (CCSP, 2008). SAP3.3 also found that
the spatial distribution of hurricanes will likely change. Storm surge is likely to increase
due to projected sea level rise, though the degree to which these will increase has not
been adequately studied (CCSP, 2008).
1.3 Population Trends and Migration Patterns: A Context for
Assessing Climate-related Impacts
Assessments of climate-related risk must account for the size of the population, including
especially sensitive sub-populations, and their geographic distribution across the
landscape. The following discussion provides a basis for assessing the interactions of
global change within the larger context of demographic trends. In particular, the social
characteristics of a populace may interact with its spatial distribution to produce a non-
linear risk. In such instances, risk assessments are shaped by questions such as:
¦ Which counties, states, and regions will grow most rapidly?
¦ How many people will live in at-risk areas, such as coastal zones, flood plains,
and arid areas?
¦ What share of retirees will migrate and where will they move?
1.3.1 Trends in Total U.S. Population
The US population numbered some 280 million individuals in 2000.1 In 1900, the US
population numbered about 76 million people; fifty years later the population had roughly
doubled to 151 million people.
Population projections are estimates of the population at future dates. They are based on
assumptions about future births, deaths, international migration, and domestic migration
and represent plausible scenarios of future population.
In 2000 the IPCC published a set of emission scenarios for use in the Third Assessment
Report (Nakicenovic el al., 2000). The SRES scenarios were constructed to explore
future developments in the global environment with special reference to the production of
greenhouse gases and aerosol precursor emissions. The SRES team defined four narrative
storylines labeled Al, A2, B1 and B2, describing the relationships between the forces
driving greenhouse gas and aerosol emissions and their evolution during the 21st century
for large world regions and globally. Each storyline represents different demographic,
social, economic, technological, and environmental developments that diverge in
increasingly irreversible ways. (Nakicenovic et al., 2000)
1 Information on historical US population data and current population estimates and projections can be
found at http://www.census.gov/.
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The US Census Bureau periodically releases projections for the resident population of the
United States based on Census data. The cohort-component methodology2 is used in
these projections. Alternative assumptions of fertility, life expectancy, and net
immigration yield low, middle and high projections.
Figure 1.2 displays the SRES and Census population projections3 for the US. The Census
projections span a greater range than the SRES scenarios: by 2100 the low series
projection of 282 million is below the current population while the high projection is
about 1.2 billion, or about four times the current population. The Census middle series
projection is relatively close to the SRES A2 scenario (570 million vs. 628 million in
2100), while the SRES Al/Bl and B2 scenarios fall below the Census middle projection.
Figure 1.2 US Population Projections 2000-2100
1.3.1.1 Aging of the Population
The US population has not simply increased by 300% over the past century, it has also
shifted in its demographic structure. For example, in 1900 less than 4% of the US
population was 65 years or older; currently about 12% of Americans are 65 or older (He
et al., 2005). By 2050, the US population aged 65 and older is projected to be about 86
million, or about 21% of the total population. Nearly 5% of the projected population in
2050, over 20 million people, will be 85 years or older (He et al., 2005). Figure 1.3
displays the projected age distribution for the total resident population of the United
States by sex for the middle projection series.
Figure 1.3 Population Pyramids of the US 2000 and 2050 (Interim Projections based on
2000 Census)
The projected increase in the elderly population is an important variable in projections of
the effects of climate change. The elderly are identified in many health assessments as
more vulnerable than younger age groups to a range of health outcomes associated with
climate change, including injury resulting from weather extremes such as heatwaves,
storms and floods (WHO, 2003; IPCC, 2007b; NAST, 2001). Aging also can be expected
to be accompanied by multiple, chronic illnesses that may result in increased
vulnerability to infectious disease (NAST, 2001). Chapter two in this report also
identifies the elderly as a vulnerable subpopulation.
1.3.2 Migration Patterns
Although numbers produced by population projections are important, the striking
relationship between potential future settlement patterns and the areas that may
experience significant impacts of climate change is the critical insight. In particular,
nearly all trends point to more Americans living in areas that may be especially
vulnerable to the effects of climate change (see Figure 1.4). For example, many rapidly
2 See Census web-site for additional details on the projection methodology.
3 The Census projections are based on the 1990 Census. Preliminary projections based on the 2000 Census
for 2000-2050 are available.
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growing places in the Mountain West may also experience decreased snow pack during
winter and earlier spring melting, leading to lower stream flows, particularly during the
high-demand period of summer.
The continued growth of arid states in the West is therefore a critical crossroads for
human settlements and climate change. These states are expected to account for one-third
of all U.S. population growth over the next 25 years (US Census Bureau, 2005). The
combined effects of growing demand for water due to a growing population and changes
in water supplies associated with climatic change pose important challenges for these
states. For example, a study commissioned by the California Energy Commission
estimated that the Sierra Mountain snow pack could be reduced by 12% to 47% by 2050
(Cayan et al., 2006). At the same time, state projections anticipate an additional 20
million Californians by that date (California Department of Finance, 2007).
Figure 1.4: U.S. Population and Growth Trends with evidence of more pronounced
growth projected along the coasts, in urban centers, and in cities in the South and West
(NAST, 2001)
Growth in coastal population has kept pace with population growth in other parts of the
country, but given the small land area of the coasts, the density of coastal communities
has been increasing (Crossett et al., 2004). Over 50% of the US population now lives in
the coastal zone, and coastal areas are projected to continue to increase in population,
with associated increases in population density, over the next several decades. The
overlay of this migration pattern with climate change projections has several
implications. Perhaps the most obvious is the increased exposure of people and property
to the effects of sea level rise and hurricanes (Kunkel etal., 1999). With rapidly growing
communities near coastlines, property damages would be expected to increase even
without any changes in storm frequency or intensity (Changnon et al., 2003).
1.3.2.1 How Climate Impacts Migration Patterns
It is often said that Americans are a nation of movers and data collected for both the 1990
and 2000 Census support this notion. While roughly half of the U.S. population had lived
in the same house for the previous five years, nearly 10% had recently moved from out of
state.4 In other words, during the five year period preceding each Census, over 20
million Americans had moved across state lines and half of those moved to different
regions.
Although many forces shape domestic migration, climate is a key element of perceived
quality of life. In turn, quality of life can be an important factor driving the relocation
decisions of households and businesses. The popularity of the Places Rated Almanac and
other publications ranking cities' livability illustrates the concept's importance.
Additionally, many of the indicators in these reports are based directly on climatic
conditions (average winter and summer temperature, precipitation, days of sunshine,
humidity, etc.).
4 http://www.census.gov/Press-Release/www/2002/sumfile3 .html
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A range of studies have attempted to quantify how natural amenities, including a
favorable climate, affect migration. While the methods vary5 the conclusions are similar.
In general:
¦ People move for a variety of reasons other than climate, such as: proximity to
family and friends, employment opportunities, lower cost of living, and aesthetics,
¦ Areas with natural amenities that are close to urban centers have attracted the
largest numbers of in-migrants (Serow, 2001);
¦ Climate's impact on migration varies by income with lower income groups also
moving to colder areas in which their wages are likely to compare more favorably
to the cost of living (Rebhun and Raveh, 2006);
¦ For retirees, weather is a far more important rationale cited for moving out of an
area than moving to an area (AARP, 2006); and,
¦ Population growth in rural counties is strongly related to a more favorable climate
and other key natural amenities (McGranahan, 1999). In addition, new
information technologies may make it possible for some urban dwellers to move
to and work from rural regions.
1.4. Complex Linkages: The Role of Non-climate Factors
Climate is only one of a number of global changes that affect human well-being. These
non-climate processes and stresses interact with climate change, determining the overall
severity of climate impacts. Moreover, climate change impacts can spread from directly
impacted areas and sectors to other areas and sectors through extensive and complex
linkages (IPCC, 2007b). Evaluating future climate change impacts therefore require
assumptions, explicit and implicit, about how future socioeconomic conditions will
develop. The IPCC (1994) recommends the use of socioeconomic scenarios in impacts
assessments to capture in a consistent way these factors.
Socioeconomic scenarios have tended to focus on variables such as population and
measures of economic activity (e.g., Gross Domestic Product) that can be quantified
using well-established models or methods (for examples of economic models which have
been used for long run projections, see Nakicenovic et al., 2000; NAST 2001; Yohe et
al., 2007). While useful as a starting point, some key socioeconomic factors may not
allow this type of quantification: they could however be incorporated through a
qualitative, "storyline" approach and thus yield a more fully developed socioeconomic
scenario. The UNEP country study program guidance (Tol, 1998) notes the role of formal
modeling in filling in (but not defining) socioeconomic scenarios but also emphasizes the
role of expert judgment in blending disparate elements into coherent and plausible
scenarios. Generally socioeconomic scenarios have been developed in situations where it
is not possible to assign levels of probability to any particular future state of the world
and therefore it usually is not appropriate to make confidence statements with respect to a
specific socioeconomic scenario (Moss and Schneider, 2000).
5 Study methodologies include: aggregate studies of population changes alongside regional characteristics,
explanatory models developed from individual migration data and individual surveys.
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SAP 4.6 Chapter 1: Introduction
Socioeconomic scenarios include non-environmental factors that influence exposures,
vulnerability and impacts. Factors that may be incorporated into a scenario include:
¦ Population (e.g., demographics, immigration, domestic migration patterns);
¦ Economic status (income, prices);
¦ Technology (e.g., pesticides, vaccines, transportation modes, wireless
communications);
¦ Infrastructure (e.g., water treatment plants, sewers, and drinking water systems;
public health systems; roads, rails and bridges; flood control structures);
¦ Human capital and social context and behaviors (e.g., skills and knowledge, social
networks, lifestyles, diet); and,
¦ Institutions (legislative, social, managerial).
These factors are important both for characterizing potential effects of a changing climate
on human health, settlements and welfare and for evaluating the ability of the US to adapt
to climate change.
1.4.1 Economic Status
The US is a developed economy with GDP approaching $14 trillion and per capita
income of $38,611 in 2007 (US BEA, 2008). The US economy has large private and
public sectors, with strong emphasis on market mechanisms and private ownership
(Christensen etal., 2007). A nation's economic status clearly is important for
determining vulnerability to climate change: wealthy nations have the economic
resources to invest in adaptive measures and bear the costs of impacts and adaptation
thereby reducing their vulnerability (WHO, 2003; IPCC, 2001). With the aging of the
population (described in Section 1.3.1.1) however, the costs of health care are likely to
rise over the coming decades (Christensen et al., 2007). Moreover, if the trend toward
globalization continues through the 21st century, markets, primary factors of production,
ownership of assets, and policies and governance will become more international in
outlook (Stiglitz, 2002). Unfortunately, there has been little research to understand how
these economic trends interact with climate change to affect vulnerability (i.e., whether
they facilitate or hinder adaptation to climate change in the US).
1.4.2 Technology
The past half-century has seen stunning levels of technological advancement in the
United States which has done much to improve American standards of living. The
availability and access to technology at varying levels, in key sectors such as energy,
agriculture, water, transportation and health is a key component to understanding
vulnerability to climate change. Many technological changes, both large and small, have
reduced American's vulnerability to climate change (NAST, 2001). Improved roads and
automobiles, better weather and climate forecasting systems, computers and wireless
communication, new drugs and vaccines, better building materials, more efficient energy
production - the list is very long indeed- have contributed to America's material well
being while reducing vulnerability to climate. Many of the adaptive strategies that are
currently deployed that protect human beings from climate involve technology (e.g.,
warning systems, air conditioning and heating, pollution controls, building design, storm
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SAP 4.6 Chapter 1: Introduction
shelters, vector control, water treatment and sanitation) (WHO, 2003). Continued
advances in technology in the 21st century can increase substantially our ability to cope
with climate change (IPCC, 2007a; USGCRP, 2001).
However, it will be important to assess risks from proposed technological adaptations to
avoid or mitigate adverse effects (i.e., maladaptation) (Patz, 1996; Klein and Tol, 1997).
For example, if new pesticides are used to control disease vectors their effects on human
populations, insect predators, and insect resistance to pesticides need to be considered
(Scheraga and Grambsch, 1998; Gubler etal., 2001).
In addition, technological change can interact in complex ways with other socioeconomic
factors (e.g., migration patterns) and affect vulnerability to climate change. For example,
advances in transportation technology - electric streetcars, freight trucks, personal
automobiles, and the interstate highway system - have fueled the decentralization of
urban regions (Hanson and Giuliano 2004; Garreau 1991; Lang 2003). More recently, the
rapid development of new information technologies, such as the internet, have made
previously remote locations more accessible for work, recreation, or retirement. Whether
these developments increase or decrease vulnerability is unknown, but they do indicate
the need for socioeconomic scenarios to better characterize the complex linkages between
climate and non-climate factors in order evaluate vulnerability.
1.4.3 Infrastructure
Communities have reduced, and can further reduce, their vulnerability to adverse climate
effects through investments in infrastructure. For example, water resources in the US
have been modified and intensively managed over the years, partly in response to climate
variability (Cohan and Miller, 2001). These investments range from small, privately
constructed impoundments, water diversions and levees to major projects constructed by
federal and state governments. Public health infrastructures, such as sanitation facilities,
waste water treatment, and laboratory buildings reduce climate change health risks
(Grambsch and Menne, 2003). Coastal communities have developed an array of systems
to manage erosion and protect against flooding (see SAP 4.1 for an extensive discussion).
More generally infrastructure such as roads, rails and bridges, water supply systems and
drainage, mass transit and buildings can reduce vulnerability (Grambsch and Menne,
2003).
However, infrastructure can increase vulnerability if its presence encourages people to
locate in more vulnerable areas. For example, increasing the density of people in coastal
metropolitan areas, dependent on extensive fixed infrastructure, can increase
vulnerability to extreme events such as floods, storm surges and heat waves (NAST,
2001). In assessments of severe storms, measures of property damage are consistently
higher and loss of life lower in the US when compared with less-developed countries
(Cohan and Miller, 2001), reflecting both the high level of development in coastal zones
and the effectiveness of warnings and emergency preparedness (Pielke and Pielke, 1997).
Fixed infrastructure itself has the potential to be adversely impacted by climate change,
which can increase vulnerability to climate change. For example, flooding can
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overwhelm sanitation infrastructure and lead to water-related illnesses (Grambsch and
Menne, 2003). Much of the transportation infrastructure in the Gulf Coast has been
constructed on land at elevations below 16.4 ft: storm surge, therefore poses risks of
immediate flooding of infrastructure and damage caused by the force of floodwaters (see
SAP 4.7 for additional information on the vulnerability of Gulf Coast transportation
infrastructure to climate change). Damage to transportation infrastructure can make it
more difficult to assist affected populations (Grambsch and Menne, 2003).
1.4.4 Human and Social Capital and Behaviors
While these factors are extremely difficult to quantify, much less project into the future,
they are widely perceived to be important in determining vulnerability in a number of
different ways. In general, countries with higher levels of "human capital" or knowledge
are considered to be less vulnerable to climate change. Effective adaptation will require
individuals skilled at recognizing, reporting and responding to climate change effects.
Moreover, a number of the adaptive measures described in the literature require
knowledgeable, trained and skilled personnel to implement them. For example, skilled
public health managers, who understand surveillance and diagnostic information, will be
needed to mobilize appropriate responses. People trained in the operation, quality control
and maintenance of laboratories, communications equipment, and sanitation, wastewater,
and water supply systems are also key (Grambsch and Menne, 2003). Researchers and
scientists spanning a broad range of disciplines will be needed to provide a sound basis
for adaptive responses.
In addition to a countries' human capital {i.e., the knowledge, experience and expertise of
its citizens) the relationships, exchange of resources and knowledge, and the levels of
trust and conflicts between individuals {i.e., "social capital") are also important for
understanding future vulnerability to climate change (Adger, 2003; Lehtonen, 2004;
Pelling and High, 2005). Social networks can play an important role in coping and
recovery from extreme weather events (Adger, 2003). For example, individuals who were
socially isolated were found to be a greater risk of dying from extreme heat (Semenza et
al., 1996), as well as people living in neighborhoods without public gathering places and
active street life (Klinenberg, 2002).
Individual behaviors and responses to changing conditions also determine vulnerability.
For example, fitness, body composition, and level of activity are among the factors that
determine the impact extremely hot weather will have on the human body (see Chapter 2
for additional information). Whether this trend continues or not could have important
implications for determining vulnerability to climate change. Individual responses and
actions to reduce their exposures to extreme heat can also substantially ameliorate
adverse health impacts (McGeehin and Mirabelli, 2001). Successfully motivating
individuals to respond appropriately can therefore decrease vulnerability and reduce
health impacts — a key goal of public health efforts (McGeehin and Mirabelli, 2001).
1.4.5 Institutions
The ability to respond to climate change and reduce vulnerability is influenced by social
institutions as well as the social factors noted above. Institutions are viewed broadly in
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SAP 4.6 Chapter 1: Introduction
the climate change context and include a wide diversity of things such as regulations,
rules and norms that guide behavior. Examples include past development and land use
patterns, existing environmental and coastal laws; building codes, and legal rights.
Institutions also can determine a decision-maker's access to information and the ways in
which the information can be used (Moser et al, 2007).
Well-functioning institutions are essential to a modern society and provide a mechanism
for stability in otherwise volatile environments (Moser et al., 2007). Future options for
responding to future climate impacts are thus shaped by our past and present institutions
and how they evolve over time. In addition, the complex interaction of issues expected
with climate change may require new arrangements and collaborations between
institutions to address risks effectively, thereby enhancing adaptive capacity (Grambsch
and Menne, 2003). A number of institutional changes have been identified that improve
adaptive capacity and reduce vulnerability (see Chapter 3 for additional details). While
the importance of institutions is clear, there are few scenarios which incorporate an
explicit representation of them.
1.4.6 Interacting Effects
The same social and economic systems that bear the stress of climate change also bear
the stress of non-climate factors, including: air and water pollution, the influx of
immigrants, and an aging and over-burdened infrastructure in rapidly-growing
metropolitan centers and coastal zones. While non-climate stressors are currently more
pronounced than climate impacts, one cannot assume that this trend will persist.
Understanding the impacts of climate change and variability on health and quality of life
assumes knowledge of how these dynamics might vary by location and across time and
socioeconomic group. The effects of climate change often spread from directly affected
areas and sectors to other areas and sectors through complex linkages. The relative
importance of climate change depends on the directness of each climate impact and on
demographic, social, economic, institutional, and political factors, including, the degree
of emergency preparedness.
Consider the damage left by Hurricanes Katrina and Rita in 2005. Damage was measured
not only in terms of lives and property lost, but also in terms of the devastating impacts
on infrastructure, neighborhoods, businesses, schools, and hospitals as well as in the
disruption to families and friends in established communities, with lost lives and lost
livelihoods, challenges to psychological well-being, and exacerbation of chronic
illnesses. While the aftermath of a single hurricane is not the measure of climate change,
such an event demonstrates the disruptive power of climate impacts and the resulting
tangle of climate and non-climate stressors that complicate efforts to respond and to
adapt. Certainly, the impacts following these hurricanes reveal that socioeconomic factors
and failures in human systems may be as damaging as the storms themselves.
Another trend of significance for climate change is the suburbanization of poverty. A
recent study noted that by 2005 the number of low income households living in suburban
communities had for the first time surpassed the number living in central cities (Berube
and Kneebone, 2006). Although the poverty rate in cities was still double the suburban
rate, there were 1 million more people living in poverty in America's suburbs. Many of
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SAP 4.6 Chapter 1: Introduction
these people live in older inner-ring suburbs developed in the 1950's and 60's. The
climate adaptation challenge for these places is captured succinctly by a recent study:
"Neither fully urban nor completely suburban, America's older, inner-ring, "first" suburbs
have a unique set of challenges—such as concentrations of elderly and immigrant
populations as well as outmoded housing and commercial buildings—very different from
those of the center city and fast growing newer places. Yet first suburbs exist in a policy
blind spot with little in the way of state or federal tools to help them adapt to their new
realities" (Puentes and Warren, 2006).
1.5 Reporting Uncertainty in SAP 4.6
Uncertainty can be traced to a variety of sources: (1) a misspecification of the cause(s),
such as the omission of a causal factor resulting in spurious correlations; (2)
mischaracterization of the effect(s), such as a model that predicts cooling rather than
warming; (3) absence of or imprecise measurement or calibration (such as devices that
fail to detect minute causal agents); (4) fundamental stochastic (chance) processes; (5)
ambiguity over the temporal ordering of cause and effect; (6) time delays in cause and
effect; and, (7) complexity where cause and effect between certain factors are
camouflaged by a context with multiple causes and effects, feedback loops, and
considerable noise.
A new perspective on the treatment of uncertainty has emerged from the IPCC Third and
Fourth Assessment processes6. This new perspective suggests that uncertainties about
projections of climate changes, impacts, and responses include two fundamentally
different dimensions. One dimension recognizes that most processes and systems being
observed are characterized by inherent variability in outcomes: the more variable the
process or system, the greater the uncertainty associated with any attempt to project an
outcome. A second dimension recognizes limitations in our knowledge about processes
and systems.
This report is a summary of the state of the science on the impacts of climate change on
human health, human settlements and human welfare. With this focus, the assessment of
uncertainty in this report is based on the literature and the author team's expert judgment.
The considerations in determining confidence include the degree of belief within the
scientific community that available understanding, models, and analyses are accurate,
expressed by the degree of consensus in the available evidence and its interpretation. This
can be thought of using two different dimensions related to consensus. Figure 1.5
represents the qualitatively defined levels of understanding. It considers both the amount
of evidence available in support of findings and the degree of consensus among experts
on its interpretation.
6 SAP4.6 follows the Guidance Notes for Lead Authors of the IPCC Fourth Assessment Report on
Addressing Uncertainties, produced by the IPCC in July 2005. See http://www.ipcc.ch/pdf/supporting-
material/uncertainty-guidance-note.pdf for more details.
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SAP 4.6 Chapter 1: Introduction
Figure 1.5 Considerations in determining confidence
In this report, each chapter author team assigned likelihood judgments that reflect their
assessments of the current consensus of the science and the quality and amount of
evidence. This represents their expert judgment that the given likelihood impact
statement is likely to be true given a specified climatic change. The likelihood
terminology and corresponding values used in this report are shown in Table 1.1. As the
focus of this report is on impacts, it is important to note that these likelihood statements
refer to the impact, not the underlying climatic changes, i.e., the report does not address
whether the specific climatic change is likely to occur. Nor do the authors attempt an
assessment that takes into account a probabilistic accounting of both the likelihood of the
climatic change and the impact. The terms defined in Table 1.1 are intended to be used in
a relative sense to summarize judgments of the scientific understanding relevant to an
issue, or to express uncertainty in a finding where there is no basis for making more
quantitative statements.
The application of this approach to likelihood estimates demonstrates some variability
across each of the three core chapters (Chapters 2-4). This variability in reporting
uncertainty is based on the degree of richness of their respective knowledge bases. A
relatively more extensive and specific application of likelihood and state of the
knowledge estimates is possible for health impacts, only a more general approach is
warranted for conclusions about human settlements, and uncertainty statements about
human welfare conclusions are necessarily the least explicit.
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SAP 4.6 Chapter 1: Introduction
1.7 Tables
Table I.I Description of likelihood: probabilistic assessment of outcome having occurred or
occurring in the future based on quantitative analysis or elicitation of expert views.
Likelihood Terminology
Likelihood of the occurrence / outcome
Virtually certain
> 99% probability
Very likely
> 90% probability
Likely
> 66% probability
About as likely as not
33 - 66% probability
Unlikely
< 33% probability
Very unlikely
< 10% probability
Exceptionally unlikely
< 1% probability
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SAP 4.6 Chapter 1: Introduction
1.8 Figures
Figure I.I Observed trends in annual average (a) temperature (°F) and (b) precipitation
(inches) across the continental United States from 1896 to 2006 (Source: NCDC, 2007)
55.5
5? 55.0
54.5
3 54.0
I- 52.5
O) „„
51.5
Source: NCDC, 2007
< 50.5
1896
1916
1936
1956
1976
1996
34
¦5 33
32
31
30
29
28
O) 27
26
25
Source: NCDC, 2007
24
1896
1916
1936
1956
1976
1996
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SAP 4.6 Chapter 1: Introduction
Figure 1.2 US Population Projections 2000-2100
1000
¦Census 1990 low
Census 1990 mid
Census 1990 high
SRES A1, B1
-SRES A2
SRES B2
2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100
Data sources: Census Population Projections http://www.census.gov/population/www/proiections/natsum-
Tl.htinl
SRES Population Projections: http://sres.ciesin.columbia.edu/tgcia/
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SAP 4.6 Chapter 1: Introduction
Figure 1.3 Population Pyramids of the US 2000 and 2050 (Interim Projections based on 2000
Census)
80-84
75-79
70-74
65-69
60-64
55-59
50-54
45-49
40-44
35-39
30-34
25-29
20-24
15-19
10-14
Male
I Female
Data source: Census Population Projections http://www.census.gov/ipc/www/usinterimproi/
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SAP 4.6 Chapter 1: Introduction
Figure 1.4: U.S. Population arid Growth Trends with evidence of more pronounced growth
projected along the coasts, in urban centers, and in cities in the South and West (NAST, 2001).
Projected change in county pop-
ulation (percent), 1970 to 2030
>+250% (highest +3,877%)
n+50% to +250%
+5% to+50%
I I -5% to +5%
H-20% to-5%
¦40% to-20%
¦I <-40% (lowest -60%)
US Population and Growth Trends
Change in county population, 1970-2030
Each block on the map illustrates one county in the US. The height of
each block is proportional to that county's population density in the year
2000, so the volume of the block is proportional to the county's total pop-
ulation. The color of each block shows the county's projected change in
population between 1970 and 2030, with shades of orange denoting
increases and blue denoting decreases. The patterns of recent population
change, with growth concentrated along the coasts, in cities, and in the
South and West, are projected to continue.
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SAP 4.6 Chapter 1: Introduction
Figure 1.5 Considerations in determining confidence.
Level of
agreement
(on a
particular
finding)
Source: IPCC Guidance Notes on risk and uncertainty (2005)
High agreement,
limited evidence
High agreement,
medium evidence
High agreement,
much evidence
Medium agreement,
limited evidence
Medium agreement,
medium evidence
Medium agreement,
much evidence
Low agreement,
limited evidence
Low agreement,
medium evidence
Low agreement,
much evidence
>
Amount of evidence (number and quality of independent sources)
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Synthesis and Assessment Product 4.6
Chapter 2: Effects of Global Change on Human Health
Lead Author; Kristie L. Ebi, ESS, LLC
Contributing Authors: John Balbus, Environmental Defense; Patrick L. Kinney, Columbia University;
Erin Lipp, University of Georgia; David Mills, Stratus Consulting; Marie S. O'Neill, University of Michigan;
Mark Wilson, University of Michigan
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SAP 4.6 Chapter 2: Human Health
Table of Contents
2.1 Introduction 3
2.2 Observed Climate-Sensitive Health Outcomes in the United States 4
2.2.1 Thermal Extremes: Heat Waves 4
2.2.2 Thermal Extremes: Cold Waves 6
2.2.3 Extreme Events: Hurricanes, Floods, and Wildfires 6
2.2.4 Indirect Health Impacts of Climate Change 8
2.3 Projected Health Impacts of Climate Change in the United States 15
2.3.1 Heat-Related Mortality 15
2.3.2 Hurricanes, Floods, Wildfires and Health Impacts 17
2.3.3 Vectorborne and Zoonotic Diseases 18
2.3.4 Water- and Foodborne Diseases 18
2.3.5 Air Quality Morbidity and Mortality 19
2.4 Vulnerable Regions and Subpopulations 22
2.4.1 Vulnerable Regions 23
2.4.2 Specific Subpopulations at Risk 23
2.5 Adaptation 26
2.5.1 Actors and Their Roles and Responsibilities for Adaptation 27
2.5.2 Adaptation Measures to Manage Climate Change-Related Health Risks 29
2.6 Conclusions 29
2.7 Expanding the Knowledge Base 30
2.8 References 32
2.9 Boxes 57
2.10 Tables 61
2.11 Figures 72
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SAP 4.6 Chapter 2: Human Health
2.1 Introduction
Climate change can affect health directly and indirectly. Directly, extreme weather events
(floods, droughts, windstorms, fires, and heatwaves) can affect the health of Americans
and cause significant economic impacts. Indirectly, climate change can alter or disrupt
natural systems, making it possible for vector, water-, and foodborne diseases to spread
or emerge in areas where they had been limited or not existed, or for such diseases to
disappear by making areas less hospitable to the vector or pathogen (NRC, 2001).
Climate also can affect the incidence of diseases associated with air pollutants and
aeroallergens.1 (Bernard etal., 2001) The cause-and-effect chain from climate change to
changing patterns of health outcomes is often complex and includes factors such as initial
health status, financial resources, effectiveness of public health programs, and access to
medical care. Therefore, the severity of future impacts will be determined by changes in
climate as well as by concurrent changes in nonclimatic factors and by adaptations
implemented to reduce negative impacts.
A comprehensive assessment of the potential impacts of climate change on human health
in the United States was published in 2000. This First National Assessment was
undertaken by the U.S. Global Change Research Program. The Health Sector Assessment
examined potential impacts and identified research and data gaps to be addressed in
future research; results appeared in a special issue of Environmental Health Perspectives
(May 2001). The Health Sector Assessment's conclusions on the potential health impacts
of climate change in the United States included:
¦ Populations in Northeastern and Midwestern U.S. cities are likely to experience
the greatest number of illnesses and deaths in response to changes in summer
temperatures (McGeehin and Mirabelli, 2001).
¦ The health impacts of extreme weather events hinge on the vulnerabilities and
recovery capabilities of the natural environment and the local population
(Greenough et al., 2001).
¦ If the climate becomes warmer and more variable, air quality is likely to be
affected (Bernard et al., 2001). However, uncertainties in climate models make
the direction and degree of change speculative (Bernard and Ebi, 2001).
¦ Federal and state laws and regulatory programs protect much of the U.S.
population from waterborne disease. However, if climate variability increases,
current and future deficiencies in areas such as watershed protection,
infrastructure, and storm drainage systems will probably increase the risk of
contamination events (Rose et al., 2000).
¦ It is unlikely that vector- and rodent-borne diseases will cause major epidemics in
the United States if the public health infrastructure is maintained and improved
(Gubleretal., 2001).
¦ Multiple uncertainties preclude any definitive statement on the direction of
potential future change for each of the health outcomes assessed (Patz et al.,
2000).
1 Any of various airborne substances, such as pollen or spores, that can cause an allergic response.
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SAP 4.6 Chapter 2: Human Health
The assessment further concluded that much of the U.S. population is protected against
adverse health outcomes associated with weather and/or climate by existing public health
and medical care systems, although certain populations are at increased risk.
This chapter of Synthesis Assessment Product 4.6 updates the Health Sector Assessment.
It also examines adaptation strategies that have been or are expected to be developed by
the public health community in response to the challenges and opportunities posed by
climate change. The first section of this chapter focuses on climate-related impacts on
human morbidity and mortality from extreme weather, vector-, water- and foodborne
diseases, and changes in air quality. For each health endpoint, the assessment addresses
the potential impacts, populations that are particularly vulnerable, and research and data
gaps that, if bridged, would allow significant advances in future assessments of the health
impacts of global change. The assessment includes research published from 2001 through
early 2007 in the United States or in Canada, Europe, and Australia, where results may
provide insights for U.S. populations.
This chapter summarizes the current burden of climate-sensitive health determinants and
outcomes for the United States, before assessing the potential health impacts of climate
change. Two types of studies are assessed. Studies that increase our understanding of the
associations between weather variables and health outcomes raise possible concerns
about the impacts of a changing climate. A few studies project the burden of health
outcomes using scenarios of socioeconomic and climate change.
It is important to note that the assessment focuses on how climate change could affect the
future health of Americans. However, the net impact of any changes will depend on many
other factors, including demographics; population and regional vulnerabilities; the future
social, economic, and cultural context; availability of resources and technological
options; built and natural environments; public health infrastructure; and the availability
and quality of health and social services.
The chapter then turns to adaptation to the potential health impacts of environmental
change in the United States. It also considers public health interventions (including
prevention, response, and treatment strategies) that could be revised, supplemented, or
implemented to protect human health in response to the challenges and opportunities
posed by global change; and how much adaptation could achieve.
2.2 Observed Climate-Sensitive Health Outcomes in the United
States
2.2.1 Thermal Extremes: Heat Waves
Excess deaths occur during heatwaves, on days with higher-than-average temperatures,
and in places where summer temperatures vary more or where extreme heat is rare (Braga
et al., 2001). Figure 2.1 illustrates that the relation between temperature and mortality is
nonlinear, typically J- or U-shaped, and that increases in mortality occur even below
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temperatures considered to be extremely hot. This figure was created using log-linear
regression to analyze 22 years of data on daily mortality and outdoor temperature in
eleven U.S. cities (Curriero el al., 2002). Exposure to excessive natural heat caused a
reported 4,780 deaths during the period 1979 to 2002, and an additional 1,203 deaths had
hyperthermia reported as a contributing factor (CDC, 2005). These numbers are
underestimates of the total mortality associated with heatwaves because the person filling
out the death certificate may not always list heat as a cause. Furthermore, heat can
exacerbate chronic health conditions, and several analyses have reported associations
with cause-specific mortality, including cardiovascular, renal, and respiratory diseases;
diabetes; nervous system disorders; and other causes not specifically described as heat-
related (Conti et al., 2007; Fouillet el al., 2006; Medina-Ramon el al., 2006). Among the
most well-documented heatwaves in the United States are those that occurred in 1980 (St.
Louis and Kansas City, Missouri), 1995 (Chicago, Illinois), and 1999 (Cincinnati, Ohio;
Philadelphia, Pennsylvania; and Chicago, Illinois). The highest death rates in these
heatwaves occurred in people over 65 years of age.
Less information exists on temperature-related morbidity, and those studies that have
examined hospital admissions and temperature have not seen consistent effects, either by
cause or by demonstrated coherence with mortality effects where both deaths and
hospitalizations were examined simultaneously (Kovats et al., 2004; Michelozzi el al.,
2006; Schwartz et al., 2004; Semenza etal., 1999).
Age, fitness, body composition, and level of activity are important determinants of how
the human body responds to exposure to thermal extremes (DeGroot el al., 2006;
Havenith etal., 1995; Havenith et al., 1998; Havenith, 2001). Groups particularly
vulnerable to heat-related mortality include the elderly, very young, city-dwellers, those
with less education, people on medications such as diuretics, the socially isolated, the
mentally ill, those lacking access to air conditioning, and outdoor laborers (Diaz et al.,
2002; Klinenberg, 2002; McGeehin and Mirabelli, 2001; Semenza et al., 1996; Whitman
et al., 1997; Basu etal., 2005; Gouveia et al., 2003; Greenberg et al., 1983; O'Neill etal.,
2003; Schwartz, 2005; Jones et al., 1982; Kovats et al., 2004; Schwartz et al., 2004;
Semenza etal., 1999; Watkins etal., 2001). A sociological analysis of the 1995 Chicago
heatwave found that people living in neighborhoods without public gathering places and
active street life were at higher risk, highlighting the important role that community and
societal characteristics can play in determining vulnerability (Klinenberg, 2002).
Figure 2.1 Temperature-mortality relative risk functions for I I U.S. cities, 1973-1994.
Northern cities: Boston, Massachusetts; Chicago, Illinois; New York, New York;
Philadelphia, Pennsylvania; Baltimore, Maryland; and Washington, DC. Southern cities:
Charlotte, North Carolina; Atlanta, Georgia; Jacksonville, Florida; Tampa, Florida; and
Miami, Florida. Relative risk is defined as the risk of an event such as mortality relative
to exposure, such that the relative risk is a ratio of the probability of the event
occurring in the exposed group versus the probability of occurrence in the control
(non-exposed) group.
Urban heat islands may increase heat-related health impacts by raising air temperatures in
cities 2-10°F over the surrounding suburban and rural areas due to absorption of heat by
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dark paved surfaces and buildings, lack of vegetation and trees, heat emitted from
buildings, vehicles, and air conditioners, and reduced air flow around buildings (EPA,
2005; Pinho and Orgaz, 2000; Vose et al., 2004; Xu and Chen, 2004). However, in some
regions, urban areas may not experience greater heat-related mortality than in rural areas
(Sheridan and Dolney, 2003); few comparisons of this nature have been published.
The health impacts of high temperatures and high air pollution can interact, with the
extent of interaction varying by location (Bates, 2005; Goodman et al., 2004; Goodman
et al., 2004; Keatinge and Donaldson, 2001; O'Neill et al., 2005; Ren et al., 2006).
2.2.2 Thermal Extremes: Cold Waves
From 1979 to 2002, an average of 689 reported deaths per year (range 417-1,021),
totaling 16,555 over the period, were attributed to exposure to excessive cold
temperatures (Fallico etal., 2005). Cold also contributes to deaths caused by respiratory
and cardiovascular diseases, so the overall mortality burden is likely underestimated.
Factors associated with increased vulnerability to cold include black race (Fallico et al.,
2005); living in Alaska, New Mexico, North Dakota, and Montana, or living in milder
states that experience rapid temperature changes (North and South Carolina) and western
states with greater ranges in nighttime temperatures (e.g., Arizona) (Fallico etal, 2005);
having less education (O'Neill et al., 2003); being female or having pre-existing
respiratory illness (Wilkinson et al., 2004); lack of protective clothing (Donaldson et al.,
2001); income inequality, fuel poverty, and low residential thermal standards (Healy,
2003); and living in nursing homes (Hajat etal., 2007).
Because climate change is projected to reduce the severity and length of the winter
season (IPCC, 2007a), there is considerable speculation concerning the balance of
climate change-related decreases in winter mortality compared with increases in summer
mortality. Net changes in mortality are difficult to estimate because, in part, much
depends on complexities in the relationship between mortality and the changes associated
with global change. Few studies have attempted to link the epidemiological findings to
climate scenarios for the United States, and studies that have done so have focused on the
effects of changes in average temperature, with results dependent on climate scenarios
and assumptions of future adaptation. Moreover, many factors contribute to winter
mortality, making highly uncertain how climate change could affect mortality. No
projections have been published for the United States that incorporate critical factors,
such as the influence of influenza outbreaks.
2.2.3 Extreme Events: Hurricanes, Floods, and Wildfires
The United States experiences a wide range of extreme weather events, including
hurricanes, floods, tornadoes, blizzards, windstorms, and drought. Other extreme events,
such as wildfires, are strongly influenced by meteorological conditions. Direct morbidity
and mortality due to an event increase with the intensity and duration of the event, and
can decrease with advance warning and preparation. Health also can be affected
indirectly. Examples include carbon monoxide poisonings from portable electric
generator use following hurricanes (CDC, 2006b) and an increase in gastroenteritis cases
among hurricane evacuees (CDC, 2005a). The mental health impacts (e.g., post traumatic
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stress disorder, depression) of these events are likely to be especially important, but are
difficult to assess (Middleton et ah., 2002; Russoniello et ah., 2002; Verger et ah., 2003;
North et ah, 2004; Fried et ah., 2005; Weisler et ah, 2006). However, failure to fully
account for direct and indirect health impacts may result in inadequate preparation for
and response to future extreme weather events.
Figure 2.2 shows the annual number of deaths attributable to hurricanes in the United
States from the 1900 Galveston storm, (NOAA, 2006), records for the years 1940-2004
(NOAA, 2005a), and a summary of a subset of the 2005 hurricanes (NOAA, 2007). The
data shown are dominated by the 1900 Galveston storm and a subset of 2005 hurricanes,
particularly Katrina and Rita, which together accounted for 1,833 of the 2,002 lives lost
to hurricanes in 2005 (NOAA, 2007b). While Katrina was a Category 3 hurricane and its
path was forecast well in advance, there was a secondary failure of the levee system. This
illustrates that multiple factors contribute to making a disaster and that adaptation
measures may not fully avert adverse consequences.
From 1940 through 2005 roughly 4,300 lives were lost in the United States to hurricanes.
The impact of the 2005 hurricane season is especially notable as it doubled the estimate
of the average number of lives lost to hurricanes in the United States over the previous 65
years.
Figure 2.2 Annual Deaths Attributed to Hurricanes in the United States, 1900 and
1940-2005
Figure 2.3 shows the annual number of deaths attributed to flooding in the United States
from 1940-2005 (NOAA, 2007a). Over this period roughly 7,000 lives were lost.
Figure 2.3 Annual Deaths Attributed to Flooding in the United States, 1940-2005
A wildfire's health risk is largely a function of the population in the affected area and the
speed and intensity with which the wildfire moves through those areas. Wildfires can
increase eye and respiratory illnesses due to fire-related air pollution. Climate conditions
affect wildfire incidence and severity in the West (Westerling et ah, 2003; Gedalof et ah,
2005; Sibold and Veblen, 2006). Between 1987-2003 and 1970-1986, there was a nearly
fourfold increase in the incidence of large Western wildfires {i.e., fires that burned at
least 400 hectares) (Westerling et ah, 2006). The key driver of this increase was an
average increase in springtime temperature of 0.87°C that affected spring snowmelt,
subsequent potential for evapotranspiration, loss of soil moisture, and drying of fuels
(Running, 2006; Westerling et ah, 2006). Data providing a time-series summary of deaths
similar to the data in Figures 2.2 and 2.3 was not identified.
There is a rich body of literature detailing the mental health impacts of extreme weather
events. Anxiety and depression, the most common mental health disorders, can be
directly attributable to the experience of the event {i.e., being flooded) or indirectly
during the recovery process {e.g., Gerrity and Flynn, 1997). These psychological effects
tend to be much longer lasting and can be worse than the physical effects experienced
during an event and its immediate aftermath.
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Extreme events are often multi-strike stressors, with stress associated with the event
itself; the disruption and problems of the recovery period; and the worry or anxiety about
the risk of recurrence of the event (Tapsell et al, 2002). During the recovery period,
mental health problems can arise from the problems associated with geographic
displacement, damage to the home or loss of familiar possessions, and stress involved
with the process of repairing. The full impact often is not appreciated until after people's
homes have been put back in order. For instance, in the aftermath of Hurricane Katrina in
2005, mental health services in New Orleans were challenged by an increased incidence
of serious mental illness, including anxiety, major depression, and post-traumatic stress
disorder (PTSD). Shortly after Katrina, a Centers for Disease Control and Prevention poll
found that nearly half of all survey respondents indicated a need for mental health care,
yet less than 2% were receiving professional attention (Weisler et al., 2006).
2.2.4 Indirect Health Impacts of Climate Change
The observation that most vector-, water- or foodborne and/or animal-associated diseases
exhibit a distinct seasonal pattern suggests a priori that weather and/or climate influence
their distribution and incidence. The following sections differentiate between zoonotic
and water- and foodborne diseases, although many water- and foodborne diseases are
zoonotic.
2.2.4.1 Vectorborne and Zoonotic (VBZ) Diseases
Transmission of infectious agents by blood-feeding arthropods (particular insect or tick
species) and/or by non-human vertebrates (certain rodents, canids, and other mammals)
has changed significantly in the United States during the past century. Diseases such as
rabies and cholera have become less widespread and diseases such as typhus, malaria,
yellow fever, and dengue fever have largely disappeared, primarily because of
environmental modification and/or socioeconomic development (Philip and Bozeboom,
1973; Beneson, 1995; Reiter, 1996). While increasing average temperatures may allow
the permissive range for Aedes aegypti, the mosquito vector of dengue virus, to move
further north in the US, it is unlikely that more cases of dengue fever will be observed
because most people are protected while living indoors due to quality housing. Indeed, a
recent epidemic of dengue in southern Texas and northern Mexico produced many cases
among the relatively poor Mexicans, and very few cases among Texans (Reiter et al.,
1999). At the same time, other diseases reported their distribution either because of
suitable environmental conditions (including climate) or enhanced detection (examples
include Lyme disease, ehrlichioses, and Hantavirus pulmonary syndrome) or were
introduced and are expanding their range due to appropriate climatic and ecosystem
conditions (West Nile Virus; e.g., Reisen et al., 2006). Still others are associated with
non-human vertebrates that have complex associations with climate variability and
human disease (e.g., plague, influenza). The burden of VBZ diseases in the United States
is not negligible and may grow in the future because the forces underlying VBZ disease
risk simultaneously involve weather/climate, ecosystem change, social and behavioral
factors, and larger political-economic forces that are part of globalization. In addition,
introduction of pathogens from other regions of the world is a very real threat.
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Few original research articles on climate and VBZ diseases have been published in the
United States and in other developed temperate countries since the First National
Assessment. Overall, these studies provide evidence that climate affects the abundance
and distributions of vectors that may carry West Nile virus, Western Equine encephalitis,
Eastern Equine encephalitis, Bluetongue virus, and Lyme disease. Climate also may
affect disease risk, but sometimes in counter-intuitive ways that do not necessarily
translate to increased disease incidence (Wegbreit and Reisen, 2000; Subak, 2003;
McCabe and Bunnell, 2004; DeGaetano, 2005; Purse et al., 2005; Kunkel et al., 2006;
Ostfeld et al., 2006; Shone et al., 2006). Changes in other factors such as hosts, habitats,
and human behavior are also important.
2.2.4.2 Waterborne and Foodborne Diseases
Water and foodborne diseases continue to cause significant morbidity in the United
States. In 2002, there were 1,330 food-related disease outbreaks (Lynch et al., 2006), 34
outbreaks from recreational water (2004), and 30 outbreaks from drinking water (2004)
(Dziuban et al., 2006; Liang et al., 2006). For outbreaks of foodborne disease with
known etiology, bacteria {Salmonella) accounted for 55% and viruses accounted for 33%
(Lynch et al., 2006). Viral associated outbreaks rose from 16% in 1998 to 42% in 2002,
primarily due to increases in norovirus (Lynch etal., 2006). In recreational water,
bacteria accounted for 32% of outbreaks, parasites (primarily Cryptosporidium) for 24%,
and viruses 10% (Dziuban etal., 2006). Similarly in drinking water outbreaks of known
etiology, bacteria were the most commonly identified agent (29%, primarily
Campylobacter), followed by parasites and viruses (each identified 5% of the time) (2003
- 2004; Liang et al., 2006). Gastroenteritis continues to be the primary disease associated
with food and water exposure. In 2003 and 2004, gastroenteritis was noted in 48% and
68%) of reported recreational and drinking water outbreaks, respectively (Dziuban et al.,
2006; Liang et al., 2006).
Water- and foodborne disease remain highly underreported (e.g., Mead etal, 1999). Few
people seek medical attention and of those that do, few cases are diagnosed (many
pathogens are difficult to detect and identify in stool samples) or reported. Using a
combination of underreporting estimates, passive and active surveillance data, and
hospital discharge data, Mead etal. (1999) estimated that over 210 million cases of
gastroenteritis occur annually in the United States, including over 900,000
hospitalizations and over 6,000 deaths. More recently, Herikstad et al. (2002) estimated
as many as 375 million episodes of diarrhea occur annually in the United States, based on
a self-reporting study. These numbers far exceed previous estimates. Of the total
estimated annual cases, just over 39 million can be attributed to a specific pathogen and
approximately 14 million are transmitted by food (Mead etal., 1999). While bacteria
continue to cause the majority of documented foodborne and waterborne outbreaks
(Lynch et al., 2006; Liang et al., 2006), the majority of sporadic (non outbreak) cases of
disease are caused by viruses (67%; primarily noroviruses), followed by bacteria (30%,
primarily Campylobacter and Salmonella) and parasites (3%, primarily Giardia and
Cryptosporidium). While the outcome of many gastrointestinal diseases is mild and self
limiting, they can be fatal or significantly decrease fitness in vulnerable populations,
including young children, the immunocompromised, and the elderly. Children ages 1-4
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and older adults (>80 years) each make up more than 25% of hospitalizations involving
gastroenteritis, but older adults contributed to 85% of the associated deaths (Gangarosa et
ah, 1992). As the U.S. population ages, the economic and public health burden of
diarrheal disease will increase proportionally without appropriate interventions.
Most pathogens of concern for food- and waterborne exposure are enteric and transmitted
by the fecal-oral route. Climate may affect the pathogen directly by influencing its
growth, survival, persistence, transmission, or virulence. In addition, there may be
important interactions between land-use practices and climate variability. For example,
incidence of foodborne disease associated with fresh produce is growing (FDA, 2001;
Powell and Chapman, 2007). Storm events and flooding may result in the contamination
of food crops (especially produce such as leafy greens and tomatoes) with feces from
nearby livestock or feral animals. Therefore, changing climate or environments may alter
the transmission of pathogens or affect the ecology and/or habitat of zoonotic reservoirs
(NAS, 2001)
Studies in North America (United States and Canada) (Fleury et ah, 2006; Naumova et
ah, 2006), Australia (D'Souza et ah, 2004), and several countries across Europe (Kovats
et ah, 2004a) report striking similarities in correlations between peak ambient
temperatures (controlled for season) and peak in clinical cases of salmonellosis. Over this
broad geographic range, yearly peaks in salmonellosis cases occur within 1 to 6 weeks of
the highest reported ambient temperatures. Mechanisms suggested include replication in
food products at various stages of processing (D' Souza et ah, 2004; Naumova et ah,
2006) and changes in eating habits during warm summer months {i.e., outdoor eating)
(Fleury et ah, 2006). Additionally, because Salmonella are well adapted to both host
conditions and the environment, they can grow readily even under low nutrient
conditions at warm temperatures {e.g., in water and associated with fruits and vegetables)
(Zhuang et ah, 1995; Mouslim et ah, 2002). Evidence supports the notion that increasing
global temperatures will likely increase rates of salmonellosis; however, additional
research is needed to determine the critical drivers behind this trend {i.e., intrinsic
properties of the pathogen or extrinsic factors related to human behavior).
The possible effects of increasing temperatures on Campylobacter infection rates and
patterns cannot be reliably projected. The apparent seasonality of campylobacteriosis
incidence is more variable than salmonellosis and temperature models are less consistent
in their ability to account for the observed infection patterns. In the northeastern United
States, Canada, and the U.K., Camplyobacter infection peaks coincide with high annual
daily or weekly temperatures (Louis et ah, 2005; Fleury et ah, 2006; Naumova et ah,
2006). However, in several other European countries, campylobacteriosis rates peak
earlier, before high annual temperatures, and in those cases temperature accounts for only
4% of the interannual variability (Kovats, et ah, 2005). Pathogenic species of
Campylobacter cannot replicate in the environment and will not persist long under non-
microaerophilic conditions, suggesting that high ambient temperatures would not
contribute to increased replication in water or in food products.
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Leptospirosis is a re-emerging disease in the United States and, given its wide case
distribution, high number of pathogenic strains and wide array of hosts, it is often cited as
one of the most widespread zoonotic disease in the world (Meites et ah, 2004; WHO,
1999). While it has not been a reportable disease nationally since 1995, several states
continue to collect passive surveillance data and cases continue to be reported (Katz et
ah, 2002; Meites et ah, 2004). Because increased disease rates are linked to warm
temperatures, epidemiological evidence suggest that climate change may increase the
number of cases.
Pathogenic species of Vibrio (primarily V. vulnificus) account for 20% of sporadic
shellfish-related illnesses and over 95% of deaths (Lipp and Rose 1997; Morris, 2003).
While the overall incidence of illness from Vibrio infections remains low, the rate of
infection increased 41% since 1996 (Vugia et ah, 2006). Vibrio species are more
frequently associated with warm climates (e.g., Janda et ah, 1988; Lipp et ah, 2002).
Coincident with proliferation in the environment, human cases also occur during warm
temperatures. In the US, the highest case rates occur in the summer months (Dziuban et
ah, 2006). Given the close association between temperature, the pathogen, and disease,
increasing temperatures may increase the geographic range and disease burdens of Vibrio
pathogens (e.g., Lipp et ah, 2002). For example, increasing prevalence and diversity of
Vibrio species has been noted in northern Atlantic waters of the United States coincident
with warm water (Thompson et ah, 2004). Additionally, although most cases of V.
vulnificus infection are attributed to Gulf Coast states, this species recently has been
isolated from northern waters in the United States (Pfeffer et ah, 2003; Randa et ah,
2004).
The most striking example of an increased range in pathogen distribution and incidence
was documented in 2004, when an outbreak of shellfish-associated V. parahaemolyticus
was reported from Prince William Sound in Alaska (McLaughlin et ah, 2005). V.
parahaemolyticus had never been isolated from Alaskan shellfish before and it was
thought that Alaskan waters were too cold to support the species (McLaughlin et ah,
2005). In the period preceding the July 2004 outbreak, water temperatures in the
harvesting area consistently exceeded 15° C and the mean daily water temperatures were
significantly higher than in the prior six years (McLaughlin et al., 2005). This outbreak
extended the northern range of oysters known to contain V. parahaemolyticus and cause
illness by 1,000 km. Given the well-documented association between increasing sea
surface temperatures and proliferation of many Vibrio species, evidence suggests that
increasing global temperatures will lead to an increased burden of disease associated with
certain Vibrio species in the United States, especially V. vulnificus and V.
parahaemolyticus.
Protozoan parasites, particularly Cryptosporidium and Giardia, contribute significantly to
waterborne and to a lesser extent foodborne disease burdens in the United States. Both
parasites are zoonotic and form environmentally resistant infective stages, with only 10-
12 oocysts or cysts required to cause disease. In 1998, 1.2 cases of cryptosporidiosis per
100,000 people were reported in the United States (Dietz and Roberts, 2000); the
immunocompromised are at particularly high risk (Casman et ah, 2001; King and Monis,
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2006). Between 2003 and 2004, of the 30 reported outbreaks of gastroenteritis from
recreational water, 78.6% were due to Cryptosporidium and 14.3% were due to Giardia
(Dzuiban etal., 2006). Giardia has historically been the most commonly diagnosed
parasite in the United States; between 1992 and 1997 there were 9.5 cases per 100,000
people (Furness etal., 2000). Both Cryptosporidium and Giardia case reports peak in late
summer and early fall, particularly among younger age groups (Dietz and Roberts, 2000;
Furness et al., 2000). For both parasites, peak rates of reported infection in Massachusetts
occurred approximately one month after the annual temperature peak (Naumova et al.,
2006). The lagged association between peak annual temperatures and peaks in reported
cases in late summer has been attributed to increased exposure during the summer
bathing season, especially in the younger age groups, and to a slight lag in reporting
(Dietz and Roberts, 2000; Furness etal., 2000; Casman etal., 2001). With increasing
global temperatures, an increase in recreational use of water can be reasonably expected
and could lead to increased exposure among certain groups, especially children.
Naegleria fowleri is a free-living amboeboflagellate found in lakes and ponds at warm
temperatures, either naturally or in thermally polluted bodies of water. While relatively
rare, infections are almost always fatal (Lee et al., 2002). N. fowleri can be detected in
environmental waters at rates up to 50% (Wellings et al., 1977) at water temperatures
above 25°C (Cabanes et al., 2001). Cases are consistently reported in the United States;
between 1999 and 2000, four cases (all fatal) were reported. While N. fowleri continues
to be a rare disease, it remains more common in the United States than elsewhere in the
world (Marciano-Cabral etal., 2003). Given its association with warm water, elevated
temperatures could increase this pathogen's range.
Epidemiologically significant viruses for food and water exposure include enteroviruses,
rotaviruses, hepatitis A virus, and norovirus. Viruses account for 67% of foodborne
disease, and the vast majority of these are due to norovirus (Mead et al., 1999). Rotavirus
accounts for a much smaller fraction of viral foodborne disease (Mead et al., 1999), but is
a significant cause of diarrheal disease among infants and young children (Charles etal.,
2006). Enteroviruses are not reportable and therefore incidence rates are poorly reflected
in surveillance summaries (Khetsuriani et al., 2006). With the exception of hepatitis A
(Naumova et al., 2006), enteric viral infection patterns follow consistent year to year
trends. Enteroviruses are characterized by peaks in cases in the early to late summer
(Khetsuriani etal., 2006), while rotavirus and norovirus infections typically peak in the
winter (Cook et al., 1990; Lynch et al., 2006). No studies have been able to identify a
clear role for temperature in viral infection patterns.
An analysis of waterborne outbreaks associated with drinking water in the United States
between 1948 and 1994 found that 51% of outbreaks occurred following a daily
precipitation event in the 90th percentile and 68% occurred when precipitation levels
reached the 80th percentile (Curriero et al., 2001) (Figure 2.4). Similarly, Thomas et al.,
(2006) found that the risk of waterborne disease doubled when rainfall amounts surpassed
the 93rd percentile. Rose et al., (2000) found that the relationship between rainfall and
disease was stronger for surface water outbreaks, but the association was significant for
both surface and groundwater sources. In 2000, groundwater used for drinking water in
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Walkerton, Ontario was contaminated with E. coli 0157:H7 and Campylobacter during
rains that surpassed the 60-year event mark for the region and the 100-year event mark in
local areas (Auld et al., 2004). In combination with preceding record high temperatures,
2,300 people in a community of 4,800 residents became ill (Hrudey et al., 2003; Auld et
al., 2004).
Figure 2.4 Drinking Waterborne Disease Outbreaks and 90%-ile Precipitation Events
(a two month lag precedes outbreaks); 1948 - 1994.
Floodwaters may increase the likelihood of contaminated drinking water and lead to
incidental exposure to standing floodwaters. In 1999, Hurricane Floyd hit North Carolina
and resulted in severe flooding of much of the eastern portion of the state, including
extensive hog farming operations. Residents in the affected areas experienced over twice
the rate of gastrointestinal illness following the flood (Setzer and Domino, 2004).
Following the severe floods of 2001 in the Midwest, contact with floodwater was shown
to increase the rate and risk of gastrointestinal illness, especially among children (Wade
et al., 2004); however, consumption of tap water was not a risk factor as drinking water
continued to meet all regulatory standards (Wade et al., 2004).
2.2.4.3 Influenza
Influenza may be considered a zoonosis in that pigs, ducks, etc. serve as non-human hosts
to the influenza viruses (e.g., H3N2, H1N1) that normally infect humans (not H5N1). A
number of recent studies evaluated the influence of weather and climate variability on the
timing and intensity of the annual influenza season in the United States and Europe.
Results indicated that cold winters alone do not predict pneumonia and influenza (P&I)-
related winter deaths, even though cold spells may serve as a short-term trigger (Dushoff
et al., 2005), and that regional differences in P&I mortality burden may be attributed to
climate patterns and to the dominant circulating virus subtype (Greene et al., 2006).
Studies in France and the United States demonstrated that the magnitude of seasonal
transmission (whether measured as mortality or morbidity) during winter seasons is
significantly higher during years with cold El Nino Southern Oscillation (ENSO)
conditions than during warm ENSO years (Flahault et al., 2004; Viboud et al., 2004),
whereas a study in California concluded that higher temperatures and El Nino years
increased hospital admissions for viral pneumonia (Ebi et al., 2001). In an attempt to
better understand the spatio-temporal patterns of ENSO and influenza, Choi etal., (2006)
used stochastic models (mathematical models that take into account the presence of
randomness) to analyze California county-specific influenza mortality, and produced
maps that showed different risks during the warm and cool phases. In general, these
studies of influenza further support the importance of climate drivers at a global and
regional scale, but have not advanced our understanding of underlying mechanisms.
2.2.4.4 Valley Fever
Valley fever (Coccidioidomycosis) is an infectious disease caused by inhalation of the
spores of a soil-inhabiting fungus that thrives during wet periods following droughts. The
disease is of public health importance in the desert southwest. In the early 1990s,
California experienced an epidemic of Valley Fever following five years of drought
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(Kolivras and Comrie, 2003). Its incidence varies seasonally and annually, which may be
partly due to climatic variations (Kolivras and Comrie, 2003; Zender and Talamantes,
2006). If so, then climate change could affect its incidence and geographic range.
2.2.4.5 Morbidity and Mortality Due to Changes in Air Quality
Millions of Americans continue to live in areas that do not meet the health-based
National Ambient Air Quality Standards (NAAQS) for ozone and fine particulate matter
(PM2.5). Both ozone and PM2.5 have well-documented health effects, and levels of these
two pollutants have the potential to be influenced by climate change in a variety of ways.
Ground-level ozone is formed mainly by reactions that occur in polluted air in the
presence of sunlight. Nitrogen oxides (emitted mainly by burning of fuels) and volatile
organic compounds (emitted both by burning of fuels and by evaporation from vegetation
and stored fuels, solvents, and other chemicals) are the key precursor pollutants for ozone
formation. Ozone formation increases with greater sunlight and higher temperatures; it
reaches peak concentrations during the warm half of the year, and then mostly in the late
afternoon and early evening. Cloud cover and mixing height are two additional
meteorological factors that influence ozone concentrations. It has been firmly established
that breathing ozone results in short-term, reversible decreases in lung function
(Folinsbee et al., 1988) as well as inflammation deep in the lungs (Devlin et al., 1991). In
addition, epidemiology studies of people living in polluted areas have suggested that
ozone may increase the risk of asthma-related hospital visits (Schwartz, 1995), premature
mortality (Kinney and Ozkaynak, 1991; Bell et al., 2004), and possibly the development
of asthma (McConnell et al., 2002). Vulnerability to ozone health effects is greater for
persons who spend time outdoors during episode periods, especially with physical
exertion, because this results in a higher cumulative dose to the lung. Thus, children,
outdoor laborers, and athletes may be at greater risk than people who spend more time
indoors and who are less active. At a given lung dose, little has been firmly established
about vulnerability as a function of age, race, and/or existing health status. However,
because their lungs are inflamed, asthmatics are potentially more vulnerable than non-
asthmatics.
PM2.5 is a far more complex pollutant than ozone, consisting of all airborne solid or
liquid particles that share the property of being less than 2.5 micrometers in aerodynamic
diameter. 2 All such particles are included, regardless of their size, composition, and
biological reactivity. PM2.5 has complex origins, including primary particles directly
emitted from sources and secondary particles that form via atmospheric reactions of
precursor gases. Most of the particles captured as PM2.5 arise from burning of fuels,
including primary particles such as diesel soot and secondary particles such as sulfates
and nitrates. Epidemiologic studies have demonstrated associations between both short-
term and long-term average ambient concentrations and a variety of adverse health
outcomes including respiratory symptoms such as coughing and difficulty breathing,
2 Aerodynamic diameter is defined in a complex way to adjust for variations in shape and density of
various particles, and is based on the physical diameter of a water droplet that would settle to the ground at
the same rate as the particle in question. For a spherical water particle, the aerodynamic and physical
diameters are identical.
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decreased lung function, aggravated asthma, development of chronic bronchitis, heart
attack, and arrhythmias (Dockery el al., 1993; Samet el al., 2000; Pope el al., 1995, 2002,
2004; Pope and Dockery, 2006; Dominici et al, 2006; Laden et al., 2006). Associations
have also been reported for increased school absences, hospital admissions, emergency
room visits, and premature mortality. Susceptible individuals include people with existing
heart and lung disease, and diabetics, children, and older adults. Because the mortality
risks of PM2.5 appear to be mediated through narrowing of arteries and resultant heart
impacts (Kiinzli el al., 2005), persons or populations with high blood pressure and/or pre-
existing heart conditions may be at increased risk. In a study of mortality in relation to
long-term PM2.5 concentrations in 50 U.S. cities, individuals without a high school
education demonstrated higher concentration/response functions that those with more
education (Pope et al., 2002). This result suggests that low education was a proxy for
increased likelihood of engaging in outdoor labor with an associated increase in exposure
to ambient air.
Using a coupled climate-air pollution three-dimensional model, Jacobson (2008)
compared the health effects of pre-industrial vs. present day atmospheric concentrations
of CO2. The results suggest that increasing concentrations of CO2 increased tropospheric
ozone and PM2.5, which increased mortality by about 1.1% per degree temperature
increase over the baseline rate; Jacobson estimated that about 40% of the increase was
due to ozone and the rest to particulate matter. The estimated mortality increase was
higher in locations with poorer air quality.
2.2.4.6 Aeroallergens and Allergenic Diseases
Climate change has caused an earlier onset of the spring pollen season for several species
in North America (Casassa et al., 2007). Although data are limited, it is reasonable to
infer that allergenic diseases caused by pollen, such as allergic rhinitis, also have
experienced concomitant changes in seasonality (Emberlin et al., 2002; Burr et al., 2003).
Several laboratory studies suggest that increasing CO2 concentrations and temperatures
could increase ragweed pollen production and prolong the ragweed pollen season (Wan el
al., 2002; Wayne et al., 2002; Singer et al., 2005; Ziska et al., 2005; Rogers etal., 2006)
and increase some plant metabolites that can affect human health (Ziska et al., 2005;
Mohan et al., 2006). Although there are suggestions that the abundance of a few species
of airborne pollens has increased due to climate change, it is unclear whether the
allergenic content of these pollen types has changed (Huynen and Menne, 2003; Beggs
and Bambrick, 2005). The introduction of new invasive species associated with climatic
and other changes, such as ragweed and poison ivy, may increase current health risks.
There are no projections of the possible impacts of climate change on allergenic diseases.
2.3 Projected Health Impacts of Climate Change in the United
States
2.3.1 Heat-Related Mortality
Determinants of how climate change could alter heat-related mortality include actual
changes in the mean and variance of future temperatures; factors affecting temperature
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variability at the local scale; demographic and health characteristics of the population;
and policies that affect the social and economic structure of communities, including
urban design, energy policy, water use, and transportation planning. Barring an
unexpected and catastrophic economic decline, residential and industrial development
will increase over the coming decades, which could increase urban heat islands in the
absence of urban design and new technologies to reduce heat loads.
The U.S. population is aging; the percent of the population over age 65 is projected to be
13% by 2010 and 20% by 2030 (over 50 million people) (Day, 1996). Older adults are
physiologically and socially vulnerable (Khosla and Guntupalli, 1999; Klinenberg, 2002)
to hot weather and heatwaves, suggesting that heat-related mortality could increase.
Evidence that diabetics are at greater risk of heat-related mortality (Schwartz 2005),
along with the increasing prevalence of obesity and diabetes (Seidell, 2000; Visscher and
Seidell, 2001), suggests that reduced fitness and higher-fat body composition may
contribute to increased mortality.
Table 2.1 summarizes projections of temperature-related mortality either in the United
States or in temperate countries whose experience is relevant to the United States (Dessai,
2003) (Woodruff et al., 2005) (Knowlton et al., 2007) (CLIMB, 2004; Hayhoe et al.,
2004). Similar studies are underway in Europe (Kosatsky et al., 2006; Lachowsky and
Kovats, 2006). All studies used downscaled projections of future temperature
distributions in the geographic region of interest. The studies used different approaches to
incorporate likely future adaptation, addressing such issues as increased availability of air
conditioning, heatwave early warning systems, demographic changes, and enhanced
services such as cooling shelters and physiological adaptation.
Time-series studies also can shed light on potential future mortality during temperature
extremes. Heat-related mortality has declined over the past decades (Davis et al., 2002;
Davis et al., 2003a; Davis et al., 2003b). A similar trend, for cold and heat-related
mortality, was observed in London over the last century (Carson et al., 2006). The
authors speculate that these declines are due to increasing prevalence of air-conditioning
(in the United States), improved health care, and other factors. These results do not
necessarily mean that future increases in heat-related mortality may not occur in the
United States, as some have claimed (Davis et al., 2004), because the percentage of the
population with access to air conditioning is high in most regions (thus with limited
possibilities for increasing access). Further, population level declines may obscure
persistent mortality impacts in vulnerable groups.
In summary, given the projections of increases in the frequency, intensity, and duration of
heatwaves and projected demographic changes, the at-risk population will increase
(highly likely). The extent to which mortality increases will depend on the effective
implementation of a range of adaptation options, including heatwave early warning
systems, urban design to reduce heat loads, and enhanced services during heatwaves.
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2.3.2 Hurricanes, Floods, Wildfires and Health Impacts
No studies have projected the future health burdens of extreme weather events. There is
concern that climate change could increase the frequency and/or severity of extreme
events, including hurricanes, floods, and wildfires.
Theoretically, climate change could increase the frequency and severity of hurricanes by
warming tropical seas where hurricanes first emerge and gain most of their energy
(Pielke etal., 2005; Trenberth, 2005; Halverson, 2006). Controversy over whether
hurricane intensity increased over recent decades stem less from the conceptual
arguments than from the limitations of available hurricane incidence data (Halverson,
2006; Landsea, 2005; Pielke et al., 2005; Trenberth, 2005). Even if climate change
increases the frequency and severity of hurricanes, it will be difficult to definitively
identify this trend for some time because of the relatively short and highly variable
historical data available as a baseline for comparison. Adding to the uncertainty, some
research has projected that climate change could produce future conditions that might
hinder the development of Atlantic hurricanes despite the warming of tropical seas
(NO A A, 2007c).
Evidence suggests that the intensity of Atlantic hurricanes and tropical storms has
increased over the past few decades. SAP3.3 indicates that there is evidence for a human
contribution to increased sea surface temperatures in the tropical Atlantic and there is a
strong correlation to Atlantic tropical storm frequency, duration, and intensity. However,
a confident assessment will require further studies. An increase in extreme wave heights
in the Atlantic since the 1970s has been observed: consistent with more frequent and
intense hurricanes (CCSP, 2008).
For North Atlantic hurricanes, SAP3.3 concludes that it is likely that wind speeds and
core rainfall rates will increase (Henderson-Sellers etal., 1998; Knutson and Tuleya,
2004, 2008; Emanuel, 2005). However, SAP3.3 concluded that "frequency changes are
currently too uncertain for confident projection" (CCSP, 2008). SAP3.3 also found that
the spatial distribution of hurricanes will likely change. Storm surge is likely to increase
due to projected sea level rise, though the degree to which these will increase has not
been adequately studied (CCSP, 2008).
Theoretical arguments for increases in extreme precipitation and flooding are based on
the principles of the hydrological cycle where increasing average temperature will
intensify evaporation and subsequently increase precipitation (Bronstert, 2003; Kunkel,
2003, Senior et al., 2002). Looking at the available data for evidence of a climate change
signal, evidence suggests that the number of extreme precipitation events in the United
States has increased (Balling Jr. and Cerveny, 2003; Groisman et al., 2004; Kunkel,
2003). However, these results are not as consistent when evaluated by season or region
(Groisman et al., 2004).
Projections of changes in the future incidence of extreme-precipitation and flooding rely
on the results from general circulation models (GCMs). These models project increases in
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mean precipitation with a disproportionate increase in the frequency of extreme
precipitation events (Senior etal., 2002). Kim (2003) used a regional climate model to
project that a doubling in CO2 concentrations in roughly 70 years could increase the
number of days with at least 0.5 mm of precipitation by roughly 33% across the study's
defined elevation gradients in the western United States. Furthermore, the IPCC
concluded that it is very likely (>90% certainty) that trends in extreme precipitation will
continue in the 21st century (IPCC, 2007a).
Studies modeling future wildfire incidence in the western United States using GCM
outputs project increasingly severe wildfires, measured both in terms of energy released
and the number of fires that avoid initial containment in areas that GCMs project will be
increasingly dry (Brown etal., 2004; Fried etal., 2004). In general, these results suggest
much of the western United States could face an increasing wildfire risk from climate
change. The apparent exception could be the Pacific Northwest, including northern
California, where GCMs generally project a wetter future.
Factors independent of the impacts of and responses to climate change will affect
vulnerability to extreme events, including population growth, continued urban sprawl,
population shifts to coastal areas, and differences in the degree of community preparation
for extreme events (U.S. Census Bureau, 2004).
All else equal, the anticipated demographic changes will increase the size of the U.S.
population at risk for future extreme weather events (very likely). This raises the potential
for increasing total numbers of adverse health impacts from these events, even if the rate
these impacts are experienced decreases (where the rate reflects the number of impacts
per some standard population size among those actually experiencing the events).
2.3.3 Vectorborne and Zoonotic Diseases
Modeling the possible impacts of climate change on VBZ diseases is complex, and few
studies have made projections for diseases of concern in the United States. Studies
suggest that temperature influences the distributions of Ixodes spp. ticks that transmit
pathogens causing Lyme disease in the United States (Brownstein et al., 2003) and
Canada (Ogden et al., 2006), and tick-borne encephalitis in Sweden (Lindgren et al.,
2000). Higher minimum temperatures were generally favorable to the potential of
expanding tick distributions and greater local abundance of these vectors. However,
changing patterns of tick-borne encephalitis (TBE) in Europe are not consistently related
to changing climate (Randolph, 2004a). Climate change is projected to decrease the
geographic range of TBE in areas of lower latitude and elevation as transmission expands
northward (Randolph and Rogers, 2000).
2.3.4 Water- and Foodborne Diseases
Several important pathogens that are commonly transmitted by food or water may be
susceptible to changes in replication, survival, persistence, habitat range, and
transmission under changing climatic and environmental conditions (Table 2.2). Many of
these agents show seasonal infection patterns (indicating potential underlying
environmental or weather control), are capable of survival or growth in the environment,
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or are capable of waterborne transport. Factors that may affect these pathogens include
changes in temperature, precipitation, extreme weather events (i.e., storms), and
ecological shifts. While the US has successful programs to protect water quality under
the Safe Drinking Water Act and the Clean Water Act, some contamination pathways and
routes of exposure do not fall under regulatory programs (e.g., dermal absorption from
floodwaters, swimming in lakes and ponds with elevated pathogen levels, etc.).
2.3.5 Air Quality Morbidity and Mortality
The sources and conditions that give rise to elevated ozone and PM2.5 in outdoor air in
the United States have been and will continue to be affected by global environmental
changes related to land use, economic development, and climate change. Conversions of
farmland and forests into housing developments and the infrastructure of schools and
businesses that support them change the spatial patterns and absolute amounts of
emissions from fuel combustion related to transportation, space heating, energy
production, and other activities. Resulting vegetation patterns affect biogenic volatile
organic compound (VOC) emissions that influence ozone production. Conversion of land
from natural to man-made also changes the degree to which surfaces absorb solar energy
(mostly in the form of light) and later re-radiate that energy as heat, which contributes to
urban heat islands. In addition to their potential for increasing heat-related health effects,
heat islands also can influence local production and dispersion of air pollutants like ozone
and PM2.5.
It is important to recognize that U.S. Environmental Protection Agency administers a
well-developed and successful national regulatory program for ozone, PM2.5, and other
criteria pollutants. Although many areas of the US remain out of compliance with the
ozone and PM2.5 standards, there is evidence for gradual improvements in recent years,
and this progress can be expected to continue with more stringent emissions controls
going forward in time. Thus, the influence of climate change on air quality will play out
against a backdrop of ongoing regulatory control of both ozone and PM2.5 that will shift
the baseline concentrations of these two important air pollutants. On the other hand, most
of the studies that have examined potential future climate impacts on air quality reviewed
below have tried to isolate the climate effect by holding precursor emissions constant
over future decades. Thus, the focus has been on examining the sensitivity of ozone
concentrations to alternative future climates rather than on attempting to predict actual
future ozone concentrations.
The influence of meteorology on air quality is substantial and well-established (EPRI,
2005), raising the possibility that changes in climate could alter patterns of air pollution
concentrations. Temperature and cloud cover affect the chemical reactions that lead to
ozone and secondary particle formation. Winds, vertical mixing, and rainfall patterns
influence the movement and dispersion of anthropogenic pollutant emissions in the
atmosphere, with generally improved air quality at higher winds, mixing heights, and
rainfall. The most severe U.S. air pollution episodes occur with atmospheric conditions
that limit both vertical and horizontal dispersion over multi-day periods. Methods used to
study the influence of climatic factors on air quality range from statistical analyses of
empirical relationships to integrated modeling of future air quality resulting from climate
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change. To date, most studies have been limited to climatic effects on ozone. Additional
research is needed on the impacts of climate change on anthropogenic particulate matter
concentrations.
Leung and Gustafson (2005) used regional climate simulations for temperature, solar
radiation, precipitation, and stagnation/ventilation, and projected worse air quality in
Texas and better air quality in the Midwest in 2045-2055 compared with 1995-2005. Aw
and Kleeman (2003) simulated an episode of high air pollution in southern California in
1996 with observed meteorology and then with higher temperatures. Ozone
concentrations increased up to 16% with higher temperatures, while the PM2.5 response
was more variable due to opposing forces of increased secondary particle formation and
more evaporative losses from nitrate particles. Bell and Ellis (2004) showed greater
sensitivity of ozone concentrations in the Mid-Atlantic to changes in biogenic than to
changes in anthropogenic emissions. Ozone's sensitivity to changing temperatures,
absolute humidity, biogenic VOC emissions, and pollution boundary conditions on a
fine-scale (4 km grid resolution) varied in different regions of California (Steiner et al.,
2006).
Several studies explored the impacts of climate change alone on future ozone projections.
In a coarse-scale analysis of pollution over the continental United States, Mickley et al.,
(2004) used the GISS (NASA Goddard Institute for Space Studies) 4x5° model to project
that, due to climate change alone (Alb emission scenario), air pollution could increase in
the upper Midwest due to decreases between 2000 and 2052 in the frequency of Canadian
frontal passages that clear away stagnating air pollution episodes. The 2.8x2.8° Mozart
global chemistry/climate model was used to explore global background and urban ozone
changes over the 21st century in response to climate change, with ozone precursor
emissions kept constant at 1990s levels (Murazaki and Hess, 2006). While global
background decreased slightly, the urban concentrations due to U.S. emissions increased.
As part of the New York Climate and Health Study, Hogrefe and colleagues conducted
local-scale analyses of air pollution impacts of future climate changes using integrated
modeling (Hogrefe et al., 2004a,b,c; 2005a,b) to examine the impacts of climate and land
use changes on heat- and ozone-related health impacts in the NYC metropolitan area
(Knowlton et al., 2004; Kinney et al., 2006; Bell et al., 2007; Civerolo et al., 2006). The
GISS 4x5° was used to simulate hourly meteorological data from the 1990s through the
2080s based on the A2 and B2 SRES scenarios. The A2 scenario assumes roughly double
the C02 emissions of B2. The global climate outputs were downscaled to a 36 km grid
over the eastern United States using the MM5 regional climate model. The MM5 results
were used in turn as inputs to the CMAQ regional-scale air quality model. Five summers
(June, July, and August) in each of four decades (1990s, 2020s, 2050s, and 2080s) were
simulated at the 36 km scale. Pollution precursor emissions over the eastern United States
were based on U.S. EPA estimates at the county level for 1996. Compared with
observations from ozone monitoring stations, initial projections were consistent with
ozone spatial and temporal patterns over the eastern United States in the 1990s (Hogrefe
et al., 2004a). Average daily maximum 8-hour concentrations were projected to increase
by 2.7, 4.2, and 5.0 ppb in the 2020s, 2050s, and 2080s, respectively due to climate
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change (Figure 2.5) (Hogrefe et al., 2004b). The influence of climate on mean ozone
values was similar in magnitude to the influence of rising global background by the
2050s, but climate had a much greater impact on extreme values than did the global
background. When biogenic VOC emissions were allowed to increase in response to
warming, an additional increase in ozone concentrations was projected that was similar in
magnitude to that of climate alone (Hogrefe etal., 2004b). Climate change shifted the
distribution of ozone concentrations towards higher values, with larger relative increases
in future decades (Figure 6).
Figure 2.5 (a) Summertime Average Daily Maximum 8-hour Ozone Concentrations
(ppb) for the 1990s and Changes for the (b) 2020s relative to the 1990s, (c) 2050s
relative to the 1990s, and (d) 2080s relative to the 1990s. All are based on the A2
Scenario relative to the 1990s. Five consecutive summer seasons were simulated in each
decade.
Figure 2.6 Frequency Distributions of Summertime Daily Maximum 8-hr Ozone
Concentrations over the eastern United States in the 1990s, 2020s, and 2050s based on
the A2 Scenario.
Projections in Germany also found larger climate impacts on extreme ozone values
(Forkel and Knoche, 2006). Using the IS92a business-as-usual scenario, the ECHAM4
GCM projected changes for the 2030s compared with the 1990s; the output was
downscaled to a 20 km grid using a modification of the MM5 regional model, which was
in-turn linked to the RADM2 ozone chemistry model. Both biogenic VOC emissions and
soil NO emissions were projected to increase as temperatures rose. Daily maximum
ozone concentrations increased by between 2 and 6 ppb (6-10%) across the study region.
The number of cases where daily maximum ozone exceeded 90 ppb increased by nearly
four-fold, from 99 to 384.
Using the NYCHP integrated model, PM2.5 concentrations are projected to increase with
climate change, with the effects differing by component species, with sulfates and
primary PM increasing markedly and with organic and nitrated components decreasing,
mainly due to movement of these volatile species from the particulate to the gaseous
phase (Hogrefe et al., 2005b; 2006).
Hogrefe et al., (2005b) noted that "the simulated changes in pollutant concentrations
stemming from climate change are the result of a complex interaction between changes in
transport, mixing, and chemistry that cannot be parameterized by spatially uniform linear
regression relationships." Additional uncertainties include how population vulnerability,
mix of pollutants, housing characteristics, and activity patterns may differ in the future.
For example, in a warmer world, more people may stay indoors with air conditioners in
the summer when ozone levels are highest, decreasing personal exposures (albeit with
potential increases in pollution emissions from power plants). Baseline mortality rates
may change due to medical advances, changes in other risk factors such as smoking and
diet, and aging of the population.
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The New York Climate and Health Project examined the marginal sensitivity of health to
changes in climate to project the potential health impacts of ozone in the eastern United
States (Knowlton et al, 2004; Bell etal., 2007). Knowlton and colleagues computed
absolute and percentage increases in ozone-related daily summer-season deaths in the
NYC metropolitan region in the 2050s as compared with the 1990s using a downscaled
GCM/RCM/air quality model (Knowlton et al, 2004; Kinney et al., 2006). The
availability of county-scale ozone projections made it possible to compare impacts in the
urban core with those in outlying areas. Increases in ozone-related mortality due to
climate change ranged from 0.4 to 7.0% across 31 counties. Bell and colleagues
expanded the analysis to 50 eastern cities and examined both mortality and hospital
admissions (Bell etal, 2007). Average ozone concentrations were projected to increase
by 4.4 ppb (7.4%) in the 2050s; the range was 0.8% to 13.7%. In addition, ozone red alert
days could increase by 68%. Changes in health impacts were of corresponding
magnitude.
Based on the new research findings published since the previous assessment, the
following summary statements can be made:
¦ There is an established but incomplete level of knowledge suggesting that both
ozone and fine particle concentrations may be affected by climate change.
¦ A substantial body of new evidence on ozone supports the interpretation that
ozone concentrations would be more likely to increase than decrease in the United
States as a result of climate change, holding precursor emissions constant.
¦ Too few data yet exist for PM to draw firm conclusions about the direction or
magnitude of climate impacts
2.4 Vulnerable Regions and Subpopulations
In adapting the IPCC's definitions3 to public health, "vulnerability" can be defined as the
summation of all risk and protective factors that ultimately determine whether an
individual or subpopulation experiences adverse health outcomes, and "sensitivity" can
be defined as an individual's or subpopulation's increased responsiveness, primarily for
biological reasons, to a given exposure. Thus, specific subpopulations may experience
heightened vulnerability for climate-related health effects for a wide variety of reasons.
Biological sensitivity may be related to the developmental stage, presence of pre-existing
chronic medical conditions (such as the sensitivity of people with chronic heart
conditions to heat-related illness), acquired factors (such as immunity), and genetic
factors (such as metabolic enzyme subtypes that play a role in sensitivity to air pollution
effects). Socioeconomic factors also play a critical role in altering vulnerability and
sensitivity to environmentally-mediated factors. They may alter the likelihood of
exposure to harmful agents, interact with biological factors that mediate risk (such as
nutritional status), and/or lead to differences in the ability to adapt or respond to
exposures or early phases of illness and injury. For public health planning, it is critical to
3IPCC Second Assessment. Climate Change 1995. Available at http://www.ipcc.ch/pub/sa(E).pdf.
Accessed 11-12-07.
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recognize populations that may experience synergistic effects of multiple risk factors for
health problems related to climate change and to other temporal trends.
2.4.1 Vulnerable Regions
Populations living in certain regions of the United States may experience altered risks for
specific climate-sensitive health outcomes due to their regions' baseline climate,
abundance of natural resources such as fertile soil and fresh water supplies, elevation,
dependence on private wells for drinking water, or vulnerability to coastal surges or
riverine flooding. Some regions' populations may in fact experience multiple climate-
sensitive health problems simultaneously. One approach to identifying such areas is to
map regions currently experiencing increased rates of climate-sensitive health outcomes
or other indicators of increased climate risk, as illustrated in Figure 2.7a-2.7d.
Residents of low-lying coastal regions, which are common locations for hurricane
landfalls and flooding, are particularly vulnerable to the health impacts of climate change.
Those who live in the Gulf Coast region, for example, are likely to experience increased
human health burdens due to the constellation of more intense storms, greater sea level
rise, coastal erosion, and damage to freshwater resources and infrastructure. Other coastal
areas may also experience the combination of sea level rise chronically threatening water
supplies and periodic infrastructure damage from more intense storms. Populations in the
Southwest and Great Lakes regions may experience increased strain on water resources
and availability due to climate change. More intense heat waves and heat-related illnesses
may take place in regions where extreme heat events already occur, such as interior
continental zones of the United States. High-density urban populations will experience
heightened health risks, in part due to the heat-island effect. In addition, increased
demand for electricity during summers may lead to greater air pollution levels (IPCC,
2007b).
Figure 2.7 a-d U.S. maps indicating counties with existing vulnerability to climate
sensitive health outcomes: (a) location of hurricane landfalls; (b) extreme heat events,
defined by CDC as temperatures 10 or more degrees above the average high
temperature for the region and lasting for several weeks; (c) percentage of population
over age 65; (d) West Nile Virus cases reported in 2004. Historical disease activity,
especially in the case of WNV, is not necessarily predictive of future vulnerability.
2.4.2 Specific Subpopulations at Risk
Vulnerable subpopulations may be categorized according to specific health endpoints.
(Table 2.3). While this is typically the way the scientific literature reports risk factors for
adverse health effects, this section discusses vulnerability for a variety of climate-
sensitive health endpoints one subpopulation at a time.
2.4.2.1 Children
Children's small body mass to surface area ratio and other factors make them more
vulnerable to heat-related morbidity and mortality (AAP, 2000), while their increased
breathing rates relative to body size, time spent outdoors, and developing respiratory
tracts heighten their sensitivity to harm from ozone air pollution (AAP, 2004). In
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addition, children's relatively naive immune systems increase the risk of serious
consequences from water and foodborne diseases; specific developmental factors make
them more vulnerable to complications from specific severe infections like E Coli
0157:H7.
Children's lack of immunity also plays a role in higher risk of mortality from malaria
(CDC, 2004b). Conversely, maternal antibodies to dengue in infants convey increased
risk of developing dengue hemorrhagic syndromes. A second peak of greater risk of
complications from dengue appears in children between the ages of 3 and 5 (Guzman and
Khouri, 2002).
Children may also be more vulnerable to psychological complications of extreme weather
events related to climate change. Following two floods in Europe in the 1990s, children
demonstrated moderate to severe stress symptoms (Becht etal., 1998; cited in Hajat el
ah, 2003) and long-term PTSD, depression, and dissatisfaction with ongoing life
(Bokszanin, 2000; cited in Hajat et ah, 2003).
2.4.2.2 Older Adults
Health effects associated with climate change pose significant risks for the elderly, who
often have frail health and limited mobility. Older adults are more sensitive to
temperature extremes, particularly heat (Semenza et ah, 1996; Medina-Ramon el ah,
2006); individuals 65 years of age and older comprised 72% of the heat-related deaths in
the 1995 Chicago heatwave (Whitman et ah, 1997). The elderly are also more likely to
have preexisting medical conditions, including cardiovascular and respiratory illnesses,
which may put them at greater risk of exacerbated illness by climate-related events or
conditions. For example, a 2004 rapid needs assessment of older adults in Florida found
that Hurricane Charley exacerbated preexisting, physician-diagnosed medical conditions
in 24-32% of elderly households (CDC, 2004a). Also, effects of ambient particulate
matter on daily mortality tend to be greatest in older age groups (Schwartz, 1995).
2.4.2.3 Impoverished Populations
Even in the United States, the greatest health burdens related to climate change are likely
to fall on those with the lowest socioeconomic status (O'Neill et ah, 2003a). Most
affected are individuals with inadequate shelter or resources to find alternative shelter in
the event their community is disrupted. While quantitative methods to assess the increase
in risk related to these social and economic factors are not well-developed, qualitative
insights can be gained by examining risk factors for mortality and morbidity from recent
weather-related extreme events such as the 1995 heatwave in Chicago and Hurricane
Katrina in 2005 (Box 2.1).
Studies of heatwaves identify poor housing conditions, including lack of access to air
conditioning and living spaces with fewer rooms, as significant risk factors for heat-
related mortality (Kalkstein, 1993; Semeza el al., 1996). Higher heat-related mortality
has been associated with socioeconomic indicators, such as lacking a high school
education and living in poverty (Curriero et ah, 2002). Financial stress plays a role, as
one study of the 1995 Chicago heatwave found that concern about the affordability of
utility bills influenced individuals to limit air conditioning use (Klinenberg, 2002). The
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risk for exposure and sensitivity to air pollution is also elevated among groups in a lower
socioeconomic position (O'Neill et al., 2003a).
Air conditioning is an important short-term method for protecting health, but is not a
sustainable long-term adaptation technology because the electricity use is often
associated with greenhouse gas emissions and during heatwaves can overload the grid
and contribute to outages (O'Neill, 2003c). Furthermore, the elderly with limited budgets
and racial minorities are less likely to have access to air conditioning or to use it during
hot weather (O'Neill et al., 2005b, Sheridan, 2006). Incentives for and availability of
high-efficiency, low energy-demand residential cooling systems, especially among
disadvantaged populations, can advance health equity and minimize some of the negative
aspects of air conditioning.
Another area of concern for impoverished populations is the impact that climate change
may have on food systems and food supply. In the United States, food insecurity is a
prevalent health risk among the poor, particularly poor children (Cook et al., 2007). On a
global scale, studies suggest that climate change is likely to contribute to food insecurity
by reducing crop yield, most significantly at lower latitudes, due to shortened growing
periods and decreases in water availability (Parry et al., 2005). In the United States,
changes in the price of food would likely contribute to food insecurity to a greater degree
than overall scarcity.
The tragic loss of life that occurred after Hurricane Katrina underscores the increased
vulnerability of special populations and demonstrates that, in the wake of extreme
weather events, particularly those that disrupt medical infrastructure and require large-
scale evacuation, treating individuals with chronic diseases is of critical concern (Ford et
al., 2006).
2.4.2.4 People with Chronic Conditions and Mobility and Cognitive Constraints
People with chronic medical conditions have an especially heightened vulnerability for
the health impacts of climate change. Extreme heat poses a great risk for individuals with
diabetes (Schwartz, 2005), and extreme cold has an increased effect on individuals with
chronic obstructive pulmonary disease (Schwartz, 2005). People with mobility and
cognitive constraints may be at particular risk during heatwaves and other extreme
weather events (EPA, 2006). As noted above, those with chronic medical conditions are
also at risk of worsened status as the result of climate-related stressors and limited access
to medical care during extreme events.
2.4.2.5 Occupational Groups
Certain occupational groups, primarily by virtue of spending their working hours
outdoors, are at greater risk of climate-related health outcomes. Outdoor workers in rural
or suburban areas, such as electricity and pipeline utility workers, are at increased risk of
infection with Lyme Disease, although evidence is lacking for greater risk of clinical
illness (Schwartz and Goldstein, 1990; Piacentino and Schwartz, 2002). They and other
outdoor workers have increased exposures to ozone air pollution and heat stress,
especially if work tasks involve heavy exertion.
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2.4.2.6 Recent Migrants and Immigrants
Residential mobility, migration, and immigration may increase vulnerability. For
example, new residents in an area may not be acclimated to the weather patterns, have
lower awareness of risks posed by local vectorborne diseases, and have fewer social
networks to provide support during an extreme weather event. U.S. immigrants returning
to their countries of origin to visit friends and relatives have also been shown to suffer
increased risks of severe travel-associated diseases (Bacaner etal., 2004, Angell and
Cetron, 2005). This vulnerability may become more significant if such diseases, which
include malaria, viral hepatitis, and typhoid fever, become more prevalent in immigrants'
countries of origin because of climate change.
2.5 Adaptation
Realistically assessing the potential health effects of climate change must include
consideration of the capacity to manage new and changing climatic conditions.
Individuals, communities, governments, and other organizations currently engage in a
wide range of actions to identify and prevent adverse health outcomes associated with
weather and climate. Although these actions have been largely successful, recent extreme
events and outbreaks of vectorborne diseases highlight areas for improvement
(Confalonieri et al., 2007). Climate change is likely to further challenge the ability of
current programs and activities to control climate-sensitive health determinants and
outcomes. Preventing additional morbidity and mortality requires consideration of all
upstream drivers of adverse health outcomes, including developing and deploying
adaptation policies and measures that consider the full range of health risks that are likely
to arise with climate change.
In public health, prevention is the term analogous to adaptation, acknowledging that
adaptation implies a set of continuous or evolving practices and not just upfront
investments. Public health prevention is classified as primary, secondary, or tertiary.
Primary prevention aims to prevent the onset of disease in an otherwise unaffected
population (such as regulations to reduce harmful exposures to ozone). Secondary
prevention entails preventive action in response to early evidence of health effects
(including strengthening disease surveillance programs to provide early intelligence on
the emergence or re-emergence of health risks at specific locations, and responding
effectively to disease outbreaks, such as West Nile virus). Tertiary prevention consists of
measures (often treatment) to reduce long-term impairment and disability and to
minimize suffering caused by existing disease. In general, primary prevention is more
effective and less expensive than secondary and tertiary prevention. For every health
outcome, there are multiple possible primary, secondary, and tertiary preventions.
The degree to which programs and measures will need to be modified to address the
additional pressures due to climate change will depend on factors such as the current
burden of climate-sensitive health outcomes, the effectiveness of current interventions,
projections of where, when, and how quickly the health burdens could change with
changes in climate and climate variability (which depends on the rate and magnitude of
climate change), the feasibility of implementing additional cost-effective interventions,
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other stressors that could increase or decrease resilience to impacts, and the social,
economic, and political context within which interventions are implemented (Ebi et al.,
2006a). Failure to invest in adaptation may leave communities poorly prepared and
increase the probability of severe adverse consequences (Haines et al., 2006a,b).
Adaptation to climate change is basically a risk management issue. Adaptation and
mitigation are the primary responses to manage current and projected risks. Mitigation
and adaptation are not mutually exclusive; co-benefits to human health can result
concurrently with implementation of mitigation and adaptation actions. A dialogue is
needed on prioritizing the costs of mitigation actions designed to limit future climate
change and the potential costs of continually trying to adapt to its impacts. This dialogue
should explicitly recognize that there is no guarantee that future changes in climate will
not present a threshold that poses technological or physical limits to which adaptation is
not possible.
Adaptation policies and measures should address both projected risks and the regions and
populations that currently are not well adapted to climate-related health risks. Because
the degree and rate of climate change is projected to increase over time, adaptation will
be a continual process of designing and implementing policies and programs to prevent
adverse impacts from changing exposures and vulnerabilities (Ebi et al., 2006). Clearly,
the extent to which effective proactive adaptations are developed and deployed will be a
key determinant of future morbidity and mortality attributable to climate change.
Regional vulnerabilities to the health impacts of climate change are influenced by
physical, social, demographic, economic, and other factors. Adaptation activities take
place within the context of slowly changing factors that are specific to a region or
population, including specific population and regional vulnerabilities, social and cultural
factors, the built and natural environment, the status of the public health infrastructure,
and health and social services. Because these factors vary across geographic and temporal
scales, adaptation policies and measures generally are more successful when focused on a
specific population and location. Additional important factors include the degree of risk
perceived, the human and financial resources available for adaptation, the available
technological options, and the political will to undertake adaptation.
2.5.1 Actors and Their Roles and Responsibilities for Adaptation
Responsibility for the prevention of climate-sensitive health risks rests with individuals,
community and state governments, national agencies, and others. The roles and
responsibilities vary by health outcome. For example, individuals are responsible for
taking appropriate action on days with declared poor air quality, with health care
providers and others responsible for providing the relevant information, and government
agencies providing the regulatory framework. Community governments play a central
role in preparedness and response for extreme events because of their jurisdiction over
police, fire, and emergency medical services. Early warning systems for extreme events
such as heat waves (Box 2.2) and outbreaks of infectious diseases may be developed at
the community or state level. The federal government funds research and development to
increase the range of decision support planning and response tools. Medical and nursing
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schools are responsible for ensuring that health professionals are trained in the
identification and treatment of climate-sensitive diseases. The Red Cross and other
nongovernmental organizations (NGOs) often play critical roles in disaster response.
Additional research and development are needed to ensure that surveillance systems
account for and anticipate the potential effects of climate change. Ensuring that
surveillance systems account for and anticipate the potential effects of climate change
will be beneficial. For example, surveillance systems in locations where changes in
weather and climate may foster the spread of climate-sensitive pathogens and vectors into
new regions would help advance our understanding of the associations between disease
patterns and environmental variables. This knowledge could be used to develop early
warning systems that warn of outbreaks before most cases have occurred. Increased
understanding is needed of how to design these systems where there is limited knowledge
of the interactions of climate, ecosystems, and infectious diseases (NAS, 2001).
There are no inventories in the United States of the various actors taking action to cope
with climate change-related health impacts. However, the growing numbers of city and
state actions on climate change show increasing awareness of the potential risks. As of 1
November 2007, more than 700 cities have signed the U.S. Mayors Climate Protection
Agreement (http://www.seattle.gov/mayor/climate/cpaText.htm); although this agreement
focuses on mitigation through increased energy efficiency, one strategy, planting trees,
can both sequester CO2 and reduce urban heat islands. The New England Governors and
Eastern Canadian Premiers developed a Climate Change Action Plan because of concerns
about public health associated with degradation in air quality, public health risks, the
magnitude and frequency of extreme climatic phenomena and availability of water.
(NEG/ECP, 2001). One action item focuses on the reduction and/or adaptation of
negative social, economic, and environmental impacts. Activities being undertaken
include a long-term phenology study, and studies on temperature increases and related
potential impacts.
Strategies, policies, and measures implemented by community and state governments,
federal agencies, NGOs, and other actors can change the context for adaptation by
conducting research to assess vulnerability and to identify technological options available
for adaptation, implementing programs and activities to reduce vulnerability, and shifting
human and financial resources to address the health impacts of climate change. State and
federal governments also can provide guidance for vulnerability assessments that
consider a range of plausible future scenarios. The results of these assessments can be
used to identify priority health risks (over time), particularly vulnerable populations and
regions, effectiveness of current adaptation activities, and modifications to current
activities or new activities to implement to address current and future climate change-
related risks.
Table 2.4 summarizes the other roles and responsibilities of various actors for adapting to
climate change. Note that viewing adaptation from a public health perspective results in
similar activities being classified as primary rather than secondary prevention under
different health outcomes. It is not possible to prevent the occurrence of a heatwave, so
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primary prevention focuses on actions such as developing and enforcing appropriate
infrastructure standards, while secondary prevention focuses on implementing early
warning systems and other activities. For vectorborne diseases, primary prevention refers
to preventing exposure to infected vectors; in this case, early warning systems can be
considered primary prevention. For most vectorborne diseases, there are few options for
preventing disease onset once an individual has been bitten.
A key activity not included in this framework is research on the associations between
weather / climate and various health outcomes, taking into consideration other drivers of
those outcomes (e.g., taking a systems-based approach), and projecting how those risks
may change with changing weather patterns. Increased understanding of the human
health risks posed by climate change is needed for the design of effective, efficient, and
timely adaptation options.
2.5.2 Adaptation Measures to Manage Climate Change-Related Health Risks
Determining where populations are not effectively coping with current climate variability
and extremes facilitates identification of the additional interventions that are needed now.
However, given uncertainties in climate change projections, identifying current
adaptation deficits is not sufficient to protect against projected health risks. Adaptation
measures can be categorized into legislative policies, decision support tools, technology
development, surveillance and monitoring of health data, infrastructure development, and
other. Table 2.5 lists some adaptation measures for health impacts from heatwaves,
extreme weather events, vectorborne diseases, waterborne diseases, and air quality. These
measures are generic because the local context, including vulnerabilities and adaptive
capacity, need to be considered in the design of programs and activities to be
implemented.
An additional category of measures includes public education and outreach to provide
information to the general public and specific vulnerable groups on climate risks to which
they may be exposed and appropriate actions to take. Messages need to be specific to the
region and group; for example, warnings to senior citizens of an impending heatwave
should focus on keeping cool and drinking lots of water. Box 2.3 provides tips for dealing
with extreme heatwaves developed by U.S. EPA with assistance from federal, state, local,
and academic partners (U.S. EPA, 2006).
2.6 Conclusions
The conclusions from this assessment are consistent with those of the First National
Assessment: climate change poses a risk for U.S. populations, with uncertainties limiting
quantitative projections of the number of increased injuries, illnesses, and deaths
attributable to climate change. However, the strength and consistency of projections for
climatic changes for some exposures of concern to human health suggest that
implementation of adaptation actions should commence now (Confalonieri etal., 2007).
Further, trends in factors that affect vulnerability, such as a larger and older U.S.
population, will increase overall vulnerability to health risks. At the same time, the
capacity of the U.S to implement effective and timely adaptation measures is assumed to
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remain high throughout this century, thus reducing the likelihood of severe health
impacts if appropriate programs and activities are implemented. However, the nature of
the risks posed by climate change means that some adverse health outcomes may not be
avoidable, even with attempts at adaptation. Severe health impacts will not be evenly
distributed across populations and regions, but will be concentrated in the most
vulnerable groups.
Proactive policies and measures should be identified that improve the context for
adaptation, reduce exposures related to climate variability and change, prevent the onset
of climate-sensitive health outcomes, and increase treatment options. Future community,
state, and national assessments of the health impacts of climate variability and change
should identify gaps in adaptive capacity, including where barriers and constraints to
implementation, such as governance mechanisms, need to be addressed.
Because of regional variability in the types of health stressors attributable to climate
change and their associated responses, it is difficult to summarize adaptation at the
national level. Planning for adaptation is hindered by the fact that downscaled climate
projections, as well as other climate information and tools, are generally not available to
local governments. Such data and tools are essential for sectors potentially affected by
climate change to assess their vulnerability and possible adaptation options, catalogue,
evaluate, and disseminate adaptation measures. Explicit consideration of climate change
is needed in the many programs and research activities within federal, state, and local
agencies that are relevant to adaptation to ensure that they have maximum effectiveness
and timeliness in reducing future vulnerability. In addition, collaboration and
coordination are needed across agencies and sectors to ensure protection of the American
population to the current and projected impacts of climate change.
2.7 Expanding the Knowledge Base
Few research and data gaps have been filled since the First National Assessment. An
important shift in perspective that occurred since the First National Assessment is a
greater appreciation of the complex pathways and relationships through which weather
and climate affect health, and the understanding that many social and behavioral factors
will influence disease risks and patterns (NRC, 2001). Several research gaps identified in
the First National Assessment have been partially filled by studies that address the
differential effects of temperature extremes by community, demographic, and biological
characteristics; that improve our understanding of exposure-response relationships for
extreme heat; and that project the public health burden posed by climate-related changes
in heatwaves and air quality. Despite these advances, the body of literature remains small,
limiting quantitative projections of future impacts.
Improving our understanding of the linkages between climate change and health in the
United States, may require a wide range of activities along the following lines:
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Improve characterization of exposure-response relationships, particularly at
regional and local levels, including identifying thresholds and particularly
vulnerable groups.
Collect data on the early effects of changing weather patterns on climate-sensitive
health outcomes.
Collect and enhance long-term surveillance data on health issues of potential
concern, including vectorborne and zoonotic diseases, air quality, pollen and mold
counts, reporting of food- and waterborne diseases, morbidity due to temperature
extremes, and mental health impacts from extreme weather events.
Develop quantitative models of possible health impacts of climate change that can
be used to explore the consequences of a range of socioeconomic and climate
scenarios.
Increase understanding of the processes of adaptation, including social and
behavioral dimensions, as well as the costs and benefits of interventions.
Evaluate the implementation of adaptation measures. For example, evaluation of
heatwave warning systems, especially as they become implemented on a wider
scale (NOAA, 2005), is needed to understand how to motivate appropriate
behavior.
Understand local and regional scale vulnerability and adaptive capacity to
characterize the potential risks and the time horizon over which climate risks
might arise; these assessments should include stakeholders to ensure their needs
are identified and addressed in subsequent research and adaptation activities.
Improve comprehensive estimates of the co-benefits of adaptation and mitigation
policies in order to clarify trade-offs and synergies.
Improve collaboration across the multiple agencies and organizations with
responsibility and research related to climate change-related health impacts, such
as weather forecasting, air and water quality regulations, vector control programs,
and disaster preparation and response.
Anticipate infrastructure requirements that will be needed to protect against
extreme events such as heatwaves, and food- and waterborne diseases, or to alter
urban design to decrease heat islands, and to maintain drinking and wastewater
treatment standards and source water and watershed protection.
Develop downscaled climate projections at the local and regional scale in order to
conduct the types of vulnerability and adaptation assessments that will enable
adequate response to climate change and to determine the potential for
interactions between climate and other risk factors, including societal,
environmental, and economic. The growing concern over impacts from extreme
events demonstrates the importance of climate models that allow for stochastic
generation of possible future events, to assess not only how disease and pathogen
population dynamics might respond, but also to assess whether levels of
preparedness are likely to be adequate.
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2.9 Boxes
Box 2.1 Vulnerable Populations and Hurricane Katrina
In 2005, Hurricane Katrina caused more than 1,500 deaths along the Gulf Coast, and
many of these victims were members of vulnerable subpopulations, such as hospital and
nursing-home patients, older adults who required care within their homes, and individuals
with disabilities (U.S. CHSGA, 2006). The hurricane was complicated by a catastrophic
failure of the levee system that was intended to shield those areas in New Orleans that lie
at or below sea level. According to the Louisiana Department of Health and Hospitals,
more than 45% of the state's identified victims were 75 years of age or older; 69% were
above age 60 (LDHH, 2006). In Mississippi, 67% of the victims whose deaths were
directly, indirectly, or possibly related to Katrina were 55 years of age or older (MSDH,
2005).
At hurricane evacuation centers in Louisiana, Mississippi, Arkansas, and Texas, chronic
illness was the most commonly reported health problem, accounting for 33% or 4,786 of
14,531 visits (CDC, 2006a). Six of the fifteen deaths indirectly related to the hurricane
and its immediate aftermath in Alabama were associated with preexisting cardiovascular
disease (CDC, 2006c), and the storm disrupted an estimated 100,000 diabetic evacuees
across the region from obtaining appropriate care and medication (Cefalu etal., 2006).
One study suggested that the hurricane had a negative effect on reproductive outcomes
among pregnant women and infants, who experienced exposure to environmental toxins,
limited access to safe food and water, psychological stress, and disrupted health care
(Callaghan el al., 2007). Other vulnerable individuals included those without personal
means of transportation and poor residents in Louisiana and Mississippi who were unable
to evacuate in time (U.S. CHSGA, 2006).
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Box 2.2 Heatwave Early Warning Systems
Projections for increases in the frequency, intensity and duration of heatwaves suggests
more cities need heatwave early warning systems, including forecasts coupled with
effective response options, to warn the public about the risks during such events (Meehl
and Tebaldi 2004). Prevention programs designed to reduce the toll of hot weather on the
public have been instituted in several cities, and guidance has been developed to further
aid communities seeking to plan such interventions, including buddy systems, cooling
centers, and community preparedness (EPA 2006b). Although these systems appear to
reduce the toll of hot weather (Ebi et al., 2004; Ebi and Schmier 2005; Weisskopf et al.,
2002), and enhanced preparedness following events such as the 1995 heatwaves in
Chicago and elsewhere, a survey of individuals 65 or older in four North American cities
(Dayton, OH; Philadelphia, PA; Phoenix, AZ; and Toronto, Ontario, Canada) found that
the public was unaware of appropriate preventive actions to take during heatwaves
(Sheridan 2006). Although respondents were aware of the heat warnings, the majority did
not consider they were vulnerable to the heat, or did not consider hot weather to pose a
significant danger to their health. Only 46% modified their behavior on the heat advisory
days. Although many individuals surveyed had access to home air-conditioning, their use
of it was influenced by concerns about energy costs. Precautionary steps recommended
during hot weather, such as increasing intake of liquids, were taken by very few
respondents (Sheridan 2006). Some respondents reported using a fan indoors with
windows closed and no air-conditioning, a situation that can increase heat exposure and
be potentially deadly. Further, simultaneous heat warnings and ozone alerts were a source
of confusion, because recommendations not to drive conflicted with the suggestion to
seek cooler locations if the residence was too warm. Critical evaluation is needed of
heatwave early warning systems, including which components are effective and why
(Kovats and Ebi 2006; NO A A 2005).
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SAP 4.6 Chapter 2: Human Health
Box 2.3: Quick Tips for Responding to Excessive Heat waves
For the Public
Do
• Use air conditioners or spend time in air-conditioned locations such as malls and
libraries
• Use portable electric fans to exhaust hot air from rooms or draw in cooler air
• Take a cool bath or shower
• Minimize direct exposure to the sun
• Stay hydrated - regularly drink water or other nonalcoholic fluids
• Eat light, cool, easy-to-digest foods such as fruit or salads
• Wear loose fitting, light-colored clothes
• Check on older, sick, or frail people who may need help responding to the heat
• Know the symptoms of excessive heat exposure and the appropriate responses.
Don't
• Direct the flow of portable electric fans toward yourself when room temperature
is hotter than 90°F
• Leave children and pets alone in cars for any amount of time
• Drink alcohol to try to stay cool
• Eat heavy, hot, or hard-to-digest foods
• Wear heavy, dark clothing.
Useful Community Interventions
For Public Officials
Send a clear public message
• Communicate that EHEs [extreme heat event] are dangerous and conditions can
be life-threatening. In the event of conflicting environmental safety
recommendations, emphasize that health protection should be the first priority.
Inform the public of anticipated EHE conditions
• When will EHE conditions be dangerous?
• How long will EHE conditions last?
• How hot will it feel at specific times during the day (e.g., 8 a.m., 12 p.m., 4 p.m.,
8 p.m.)?
Assist those at greatest risk
• Assess locations with vulnerable populations, such as nursing homes and public
housing
• Staff additional emergency medical personnel to address the anticipated increase
in demand
• Shift/expand homeless intervention services to cover daytime hours
• Open cooling centers to offer relief for people without air conditioning and urge
the public to use them.
Provide access to additional sources of information
• Provide toll-free numbers and Web site addresses for heat exposure symptoms
and responses
• Open hotlines to report concerns about individuals who may be at risk
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SAP 4.6 Chapter 2: Human Health
• Coordinate broadcasts of EHE response information in newspapers and on
television and radio.
Source: U.S. EPA, 2006
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SAP 4.6 Chapter 2: Human Health
2.10 Tables
Table 2.1 Projections of Impacts of Climate Change on Heat-Related Mortality
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The impacts projected for Lisbon were more sensitive to the choice of regional climate model
than the method used to calculate excess deaths, and the author described the challenge of
extrapolating health effects at the high end of the temperature distribution, for which data are
sparse or nonexistent (Dessai 2003).
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SAP 4.6 Chapter 2: Human Health
Table 2.2. Possible Influence of Climate Change on Climate Susceptible Pathogens and/or Disease, Based on Observational
Models or Empirical Evidence
Pathogen
Climate Related
Driver
Possible Influence of Climate Change
Likelihood
of Change3
Basis for Assessment
References
Bacteria
Salmonella
Rising Temperature
Changes in
Precipitation
Shifts in Reservoir
Host Ranges
Increasing temperature associated with
increasing clinical cases
Precipitation and run-off associated with
increased likelihood of contamination of
surface waters used for recreation, drinking
or irrigation.
Shifts in habitat and range of reservoir hosts
may influence exposure routes and/or rate of
contact with humans
Likely
Likely
More likely
than not
Likelihood of climate event
is high and published
research supports disease
trend
Likelihood of climate event
is probable but more
research is needed to
confirm disease trend
Likelihood of climate event
is probable but there is
insufficient research on this
relationship
D'Souza et al., 2004;
Kovats et al., 2004a;
Fleury et al., 2006;
Naumova et al., 2006
Haley 2006;
Holley et al., 2006
Srikantiah et al., 2003
Campylobacter Rising Temperature
Increasing temperatures may expand typical More likely
peak season of clinical infection, or result in than not
earlier peak (commonly spring and summer)
Increasing temperatures may result in shorter About as
developmental times for flies, contributing to likely as not
increased transmission by this proposed
vector
Likelihood of climate event
is high and published
research supports disease
trend, but mechnisms are
not understood
Likelihood of climate event
and fly development trend is
high but additional research
is needed to confirm disease
association
Skelly & Weinstein,
2003; Louis et al.,
2005; Kovats et al.,
2005
Nichols, 2005
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SAP 4.6 Chapter 2: Human Health
Changes in
Increasing precipitation and run-off
More likely
Likelihood of climate event
Avid, etal., 2004;
Precipitation
associated with increased likelihood of
than not
is probable but more
Vereen etal., 2007
contamination of surface waters used for
research is needed to
recreation or drinking
confirm disease trend
Shifts in Reservoir
Shifts in habitat and range of reservoir hosts
More likely
Likelihood of climate event
Stanley et al., 1998;
Host Ranges or
(geographically or temporally) may influence
than not
is probable but there is
Lacey, 1993; Southern
Behavoir
exposure routes and/or rate of contact with
insufficient research on this
etal., 1990
humans
relationship
Vibrio species Rising Temperature
Increasing ambient temperatures associated
Very likely
Likelihood of climate event
Cook, 1994
with growth in pre-harvest and post-harvest
is high and evidence
shellfish (in absence of appropriate post-
supports growth trend in
harvest controls) and increasing disease
ambient waters; adaptive
(control) measures
(refrigeration) would reduce
this effect for post-harvest
oysters
Increasing temperature associated with
Extremely
Likelihood of climate event
Janda etal., 1988;
higher environmental prevalence and disease
likely
is high and evidence is
Lipp et al., 2002;
supports environmental
McLaughlin et al.,
growth trend
2005; Dziuban et al.,
2006
Increasing temperature associated with range
Very likely
Likelihood of climate event
McLaughlin et al.,
expansion
is high and evidence
2005
collected to date supports
trend; more data needed to
confirm
Changes in
Increasing precipitation and fresh water run
About as
Likelihood of climate event
Lipp etal., 2001b;
Precipitation
off leads to depressed estuarine salinities and
likely as not
is probable but additional
Louis et al., 2003
increase in some Vibrio species
research is needed to
confirm pathogen
distribution patterns
Sea Level Changes
Rising sea level and or storm surge increase
Likely
Likelihood of climate event
Lobitz et al., 2000
range and human exposure
is probable but confirmatory
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SAP 4.6 Chapter 2: Human Health
research is needed on
disease patterns
Leptospira
Rising Temperature
Increasing temperatures may increase range
of pathogen (temporally and geographically)
Likely
Likelihood of climate event
is high but additional
research is needed to
confirm pathogen
distribution patterns
Bharti et al., 2003;
Howell and Cole, 2006
Changes in
Increasing precipitation and run off precedes
Likely
Likelihood of climate event
Meites et al., 2004
Precipitation
outbreaks
in probable and research
supports this pattern
Viruses
Enteroviruses
Rising Temperature
Increasing temperature associated with
increased or expanded peak clinical season
(summer)
Unlikely
Likelihood of climate event
is high but no mechanistic
studies are available to
explain the underlying cause
of this seasonality.
Khetsuriani et al.,
2006
Increasing temperature associated with
About as
Likelihood of climate event
Gantzcr el al., 1998;
increased decay and inactivation of viruses in
likely as not
is high and research
Wetz et al., 2004
the environment
demonstrates decreased
persistence under increasing
temperatures but little data
are available to relate this
with disease
Changes in
Increasing precipitation associated with
Likely
Likelihood of climate is
Lipp et al., 2001a;
Precipitation
increased loading of viruses to water and
increased exposure or disease
probable and research
supports this pattern
Frost et al., 2002;
Fong et al., 2005
Norovirus
Rising Temperature
Increasing temperature leads to decreased
retention of virus in shellfish
Unlikely
Likelihood of climate event
is high and research
indicates seasonally high
shellfish loading in winter
but there is no evidence for
direct control of temperature
on seasonality of infection
Burkhardt and Calci,
2000
Increasing temperature associated with
Unlikely
Likelihood of climate event
Mounts etal., 2000
shorter peak clinical season (winter)
is high and research
indicates seasonal disease
peak in winter but there is
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SAP 4.6 Chapter 2: Human Health
Changes in
Precipitation
Increasing temperature associated with
increased decay and inactivation of viruses in
the environment
Increasing precipitation associated with
increased loading of viruses to crops and
fresh produce
Increasing precipitation associated with
increased loading of viruses to water and
increased exposure or disease
About as
likely as not
More likely
than not
Likely
no evidence for direct
control of temperature on
seasonality of infection
Likelihood of climate event
is high and research
demonstrates decreased
persistence under increasing
temperatures but little data
are available to relate this
with disease
Likelihood of climate event
is probable but there is
insufficient research on this
relationship
Likelihood of climate is
probable and research
supports this pattern
Griffin et al., 2003
Miossec et al., 2000
Goodman et al., 1982
Rotavirus
Rising Temperature
Increasing temperature associated with About as
increased decay and inactivation of viruses in likely as not
the environment
Dampening of winter seasonal peak in About as
temperate latitudes likely as not
Likelihood of climate event
is high and research
demonstrates decreased
persistence under increasing
temperatures but little data
are available to relate this
with disease
Likelihood of climate event
is high and research
indicates seasonal disease
peak in winter but there is
no evidence for direct
control of temperature on
seasonality of infection;
although tropical countries
do not exhibit a seasonal
peak
Rzezutka and Cook,
2004
Cooke/ al., 1990
Parasites
Naegleria
fowleri
Rising Temperature
Increasing temperature associated with More likely
expanded range and conversion to flagellated than not
Likelihood of climate event
is high but more research is
Cabanes et al., 2001
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SAP 4.6 Chapter 2: Human Health
form (infective)
needed to confirm disease
trend
Cryptosporidium Rising Temperature
Changes in
Precipitation
Expanding recreational (swimming) season About as
may increase likelihood of exposure and likely as not
disease
Increasing precipitation associated with Very likely
increased loading of parasite to water and
increased exposure and disease
Likelihood of climate event
is high but there is
insufficient research on this
relationship
Likelihood of climate event
is probable and research
supports this pattern but
adaptive measures (water
treatment and infrastructure)
would reduce this effect
Naumova el a!., 2006
Curriero el al., 2001;
Davies et al., 2004
Giardia
Rising Temperature
Changes in
Precipitation
Shifts in Reservoir
Host Ranges or
Behavoir
Expanding recreational (swimming) season About as
may increase likelihood of exposure and likely as not
disease
Increasing precipitation associated with Very likely
increased loading of parasite to water and
increased disease
Increasing temperature associated with About as
shifting range in reservoir species (carriers) likely as not
and expanded disease range
Likelihood of climate event
is high but there is
insufficient research on this
relationship
Likelihood of climate event
is probable and research
supports this pattern but
adaptive measures (water
treatment and infrastructure)
would reduce this effect
Likelihood of climate event
is probable but there is
insufficient research on this
relationship
Naumova el al., 2006
Kistcmann el al., 2002
Parkinson and Butler,
2005
a Likelihood was based on expert judgment of the strength of the research and the likelihood of the event. See Chapter 1 for a
discussion of likelihood (section 1.5).
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SAP 4.6 Chapter 2: Human Health
Table 2.3. Climate-Sensitive Health Outcomes and Particularly Vulnerable
Groups
Climate-Sensitive Health
Particularly Vulnerable Groups
Outcome
Heat-Related Illnesses and
Elderly, chronic medical conditions, infants and
Deaths
children, pregnant women, urban and rural poor,
outdoor workers
Diseases and Deaths Related
Children, pre-existing heart or lung disease, diabetes,
to Air Quality
athletes, outdoor workers
Illnesses and Deaths Due to
Poor, pregnant women, chronic medical conditions,
Extreme Weather Events
mobility and cognitive constraints
Water- and Foodborne Illness
Immunocompromised, elderly, infants; specific risks for
specific consequences (e.g., Campylobacter and
Guillain-Barre syndrome, E. coli 0157:H7)
Vectorborne Illnesses
A. Lyme Disease
Children, outdoor workers
B. Hantavirus
Rural poor, occupational groups
C. Dengue
Infants, elderly
D. Malaria
Children, immunocompromised, pregnant women,
genetic (e.g., G6PD status)
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SAP 4.6 Chapter 2: Human Health
Table 2.4: Actors and Their Roles and Responsibilities for Adaptation to Climate Change Health Risks
Actor
Reduce Exposures
Extreme Temperature and Weather Events
Individuals Stay informed about impending weather
events
Follow guidance for emergency
preparedness
Community, Provide scientific and technical
State, and guidance for building and infrastructure
National standards
Agencies Enforce building and infrastructure
standards, including identification of
restricted building zones where
necessary
NGOs and Other
Actors
Vectorborne and Zoonotic Diseases
Individuals Take appropriate actions to reduce
exposure to infected vectors, including
eliminating vector breeding sites around
residence
Prevent Onset of Adverse Health
Outcomes
Follow guidance for conduct during and
following an extreme weather event (such as
seeking cooling centers during a heatwave
or evacuation during a hurricane)
Develop scientific and technical guidance
and decisions support tools for development
of early warning systems and emergency
response plans, including appropriate
individual behavior
Implement early warning systems and
emergency response plans
Conduct tests of early warning systems and
response plans before events
Conduct education and outreach on
emergency preparedness
NGOs and other actors play critical roles in
emergency preparedness and disaster relief
Vaccinate for diseases to which one would
likely be exposed
Reduce Morbidity and Mortality
Seek treatment when needed
Ensure that emergency
preparedness plans include medical
services
Improve programs to monitor the
air, water, and soil for hazardous
exposures
Improve surveillance programs to
collect, analyze, and disseminate
data on the health consequences of
extreme events and heatwaves
Monitor and evaluate the
effectiveness of systems
Education and training of health
professionals on risks from
extreme weather events
Seek treatment when needed
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Community, Provide scientific and technical
State, and guidance and decision support tools for
National development of early warning systems
Agencies Conduct effective vector (and pathogen)
surveillance and control programs
(including consideration of land use
policies that affect vector distribution
and habitats)
Develop early warning systems for
disease outbreaks, such as West Nile
virus
Develop and disseminate information on
appropriate individual behavior to avoid
exposure to vectors
Waterborne and Foodborne Diseases
Individuals
Community,
State, and
National
Agencies
Follow proper food-handling guidelines
Follow guidelines on drinking water
from outdoor sources
Improve surveillance and control
programs for early detection of disease
outbreaks
Develop methods to ensure watershed
protection and safe water and food
handling (e.g., Clean Water Act)
Diseases Related to Air Quality
Individuals Follow advice on appropriate behavior
on high ozone days
SAP 4.6 Chapter 2: Human Health
Conduct research on vaccines and other
preventive measures
Conduct research and development on rapid
diagnostic tools
Provide vaccinations to those likely to be
exposed
Conduct research on treatment
options
Develop and disseminate
information on signs and
symptoms of disease to guide
individuals on when to seek
treatment
Seek treatment when needed
Sponsor research and development on rapid
diagnostic tools for food- and waterborne
pathogens
Sponsor research and development
on treatment options
Develop and disseminate
information on signs and
symptoms of disease to guide
individuals on when to seek
treatment
For individuals with certain respiratory Seek treatment when needed
diseases, follow medical advice during
periods of high air pollution
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Community, Develop and enforce regulations of
State, and pollutants (e.g., Clean Air Act)
National
Agencies
SAP 4.6 Chapter 2: Human Health
Develop decision support tools for early Conduct research on treatment
warning systems options
Conduct education and outreach on the risks
of exposure to air pollutants
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SAP 4.6 Chapter 2: Human Health
Table 2.5: Adaptation Measures to Reduce Climate Change-Related Health Risks
Decision
Support Tools
Technology
Development
Surveillance
and Monitoring
Infrastructure
Development
Other
Heatwaves
Enhance early
warning systems
Improve building
design to reduce heat
loads during summer
months
Alter health data
collection systems to
monitor for increased
morbidity and
mortality during a
heatwave
Improve urban design
to reduce urban heat
islands by planting
trees, increasing
green spaces, etc.
Conduct research on
effective approaches
to encourage
appropriate behavior
during a heatwave
Extreme Weather
Events
Enhance early warning
systems and
emergency response
plans
Vectorborne Diseases Waterborne Diseases
Alter health data
collection systems to
monitor for disease
outbreaks during and
after an extreme event
Design infrastructure
to withstand projected
extreme events
Conduct research on
effective approaches to
encourage appropriate
behavior during an
extreme event
Enhance early warning
systems based on
climate and
environmental data for
selected diseases
Develop vaccines for
West Nile virus and
other vectorborne
diseases
Develop more rapid
diagnostic tests
Enhance vector
surveillance and control
programs
Monitor disease
occurrence
Consider possible
impacts of infrastructure
development, such as
water storage tanks, on
vectorborne diseases
Develop early warning
systems based on climate
and environmental data for
conditions that may
increase selected diseases
Develop more rapid
diagnostic tests
Enhance surveillance and
monitoring programs for
waterborne diseases
Consider possible impacts
of placement of sources of
water- and foodborne
pathogens (e.g., cattle near
drinking water sources)
Air Quality
Enhance alert
systems for high
air pollution days
Enhance health
data collection
systems to
monitor for health
outcomes due to
air pollution
Improve public
transit systems to
reduce traffic
emissions
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SAP 4.6 Chapter 2: Human Health
2.1 I Figures
Figure 2.1. Temperature-mortality relative risk functions for II U.S. cities, 1973-1994.
Northern cities: Boston, Massachusetts; Chicago, Illinois; New York, New York; Philadelphia,
Pennsylvania; Baltimore, Maryland; and Washington, DC. Southern cities: Charlotte, North
Carolina; Atlanta, Georgia; Jacksonville, Florida; Tampa, Florida; and Miami, Florida. Relative risk
is defined as the risk of an event such as mortality relative to exposure, such that the relative
risk is a ratio of the probability of the event occurring in the exposed group versus the
probability of occurrence in the control (non-exposed) group.
(Curriero et al., 2002)
Northern Cities
0
20
40
60
SO
Tempffraturg ^degrees Fahrefihert)
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SAP 4.6 Chapter 2: Human Health
Figure 2.2. Annual Deaths Attributed to Hurricanes in the United States, 1900 and 1940-2005
10000
2005, Dennis, Katrina,
Rta, and Wilma 2,002
deaths 1
Galveston, 1900,
~8,000 deaths
1000
100
< •
A A A
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SAP 4.6 Chapter 2: Human Health
Figure 2.3. Annual Deaths Attributed to Flooding in the United States, 1940-2005
600
540
u>
| 480
o
o 420
U-
E 360
o
t 300
| 240
Q
| 180
| 120
<
60
0
1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Year
Source: NOAA, 2007a
t
t
~
f[ A*
I I I
m
i i i
:WA/^U
I I I I I I I
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SAP 4.6 Chapter 2: Human Health
Figure 2.4. Drinking Waterborne Disease Outbreaks and 90%-iie Precipitation Events (a two
month lag precedes outbreaks); 1948 - 1994.
• Watershed outbreak location
O Extreme precipitation
I~1 Hydrologic region boundary
l~l State boundary
Source: Curriero eta I., 2001
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SAP 4.6 Chapter 2: Human Health
Figure 2.5: (a) Summertime Average Daily Maximum 8-hour Ozone Concentrations (ppb) for
the 1990s and Changes for the (b) 2020s relative to the 1990s, (c) 2050s relative to the 1990s,
and (d) 2080s relative to the 1990s. All are based on the A2 Scenario relative to the 1990s. Five
consecutive summer seasons were simulated in each decade.
a) b)
Source: Hogrefe eta I., 2004a.
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SAP 4.6 Chapter 2: Human Health
Figure 2.6. Frequency Distributions of Summertime Daily Maximum 8-hr Ozone
Concentrations over the eastern United States in the 1990s, 2020s, and 2050s based on the A2
Scenario.
in
CM
>.
o
c
0)
D
er
0)
0)
>
ns
0)
tr
o
CM
LO
¥
10 30
~
1990s
B
2020s A2
¦
2050s A2
ll
50 70 90 110 130
Daily Maximum 8-hr Ozone Concentration (ppb)
Source: FromHogrefe etal., 2005a
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SAP 4.6 Chapter 2: Human Health
Figure 2.7.a-d. U.S. maps indicating counties with existing vulnerability to climate
sensitive health outcomes: (a) location of hurricane landfalls; (b) extreme heat events,
defined by CDC as temperatures 10 or more degrees above the average high temperature
for the region and lasting for several weeks; (c) percentage of population over age 65; (d)
West Nile Virus cases reported in 2004. Historical disease activity, especially in the case
of WNV, is not necessarily predictive of future vulnerability. Maps were generated using
NationalAtlas.gov™ Map Maker (2008).
Geographic Vulnerability of US Residents
to Selected Climate Related Health Impacts
Location of Hurricane Landfalls,
1995-2000
Locations of Extreme Heat Events,
1995-2000
Percentage of US Population 65
or older, 2000
West Nile Virus Cases, 2004
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Synthesis and Assessment Product 4.6
Chapter 3: Effects of Global Change on Human
Settlements
Lead Author; Thomas J. Wilbanks, Oak Ridge National Laboratory
Contributing Authors: Paul Kirshen, Tufts University; Dale Quattrochi, NASA/Marshall Space Flight
Center; Patricia Romero-Lankao, NCAR; Cynthia Rosenzweig, NASA/Goddard; Matthias Ruth, University
of Maryland; William Solecki, Hunter College; Joel Tarr, Carnegie Mellon University
Contributors: Peter Larsen, University of Alaska-Anchorage; Brian Stone, Georgia Tech
-------
SAP 4.6 Chapter 3: Human Settlements
Table of Contents
3.1 Introduction 3
3.1.1 Purpose 3
3.1.2 Background 3
3.1.3 Current State of Knowledge 4
3.2 Climate Change Impacts and the Vulnerabilities of Human Settlements 4
3.2.1 Determinants of Vulnerability 4
3.2.2 Impacts of Climate Change on Human Settlements 5
3.2.3. The Interaction of Climate Impacts with Non-Climate Factors 7
3.2.4 Realizing Opportunities from Climate Change in the United States 9
3.2.5 Examples of Impacts on Metropolitan Areas in the United States 10
3.3 Opportunities for Adaptation of Human Settlements to Climate Change 10
3.3.1. Perspectives on Adaptation by Settlements 11
3.3.2 Major Categories of Adaptation Strategies 12
3.3.3 Examples of Current Adaptation Strategies 13
3.3.4: Strategies to Enhance Adaptive Capacity 14
3.4. Conclusions 14
3.5 Expanding the Knowledge Base 15
3.6 References 17
3.7 Boxes 24
3.8 Tables 29
3.9 Figures 31
3-2
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SAP 4.6 Chapter 3: Human Settlements
3.1 Introduction
3.1.1 Purpose
Human settlements are where people live and work, including all population centers
ranging from small rural communities to densely developed metropolitan areas. This
chapter addresses climate change impacts, both positive and negative, on human
settlements in the United States. First, the chapter summarizes current knowledge about
the vulnerability of human settlements to climate change, in a context of concurrent
changes in other non-climate factors. Next, the chapter summarizes opportunities within
settlements for adaptation to climate change. Finally, the chapter provides an overview of
recommendations for expanding the current knowledge base with respect to climate
change and human settlements.
3.1.2 Background
Events such as Hurricane Katrina in 2005 and electric power outages during the hot
summer of 2006 have demonstrated how climate-related events can dramatically impact
U.S. settlements. Climate affects the costs of assuring comfort at home and work.
Climate affects inputs for a good life: water, products and services from agriculture and
forestry, pleasures and tourist potentials from nature, biodiversity, and outdoor recreation.
Climate also affects the presence and spread of diseases and other health problems, and it
is associated with threats from natural disasters, including floods, fires, droughts, wind,
hail, ice, and heat and cold waves.
Some U.S. settlements may find opportunities in climate change. Warmer winters are not
necessarily undesirable. Periods of change tend to reward forward-looking, effectively-
governed communities. Considering climate change effects may help to focus attention
on other important issues for the long-term sustainable development of settlements and
communities. Furthermore, planning for the future is an essential part of public policy
decision-making in urban areas.
Since infrastructure investments in urban areas are often both large and difficult to
reverse, climate considerations are increasingly perceived as one of a number of relevant
issues to consider when planning for the future (Ruth, 2006a). If U.S. settlements,
especially larger cities, respond effectively to climate change concerns, their actions
could have far-reaching implications for human well-being, because these areas are
where most of the U.S. population lives, large financial decisions are made, political
influence is often centered, and technological and social innovations take place.
Meanwhile, the pattern of human settlements in the United States is changing. In addition
to shifts of population from frost-belt to sun-belt settlements, patterns are changing in
other ways as well. For instance, what once appeared to be an inexorable spread of
households from urban centers to peripheries is showing renewal in many city centers as
metropolitan areas continue to expand across multiple jurisdictions (Solecki and
Leichenko, 2006). Modern information technologies are enabling people to perform what
were historically urban functions from relatively remote locations (Riebsame, 1997).
3-3
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SAP 4.6 Chapter 3: Human Settlements
3.1.3 Current State of Knowledge
The current knowledge base provides limited grounds for developing conclusions and
recommendations related to climate impacts on human settlements. In many cases, the
best that can be done is to sketch out the issue "landscape" that should be considered by
both policy-makers and the research community as a basis for further discussion, offering
illustrations from the relatively small research literature that is now available.
The fact is that little research has been done to date specifically on the effects of climate
change in U.S. cities and towns. Reasons appear to include (i) limitations in capacities to
project climate change impacts at the geographic scale of a metropolitan area (or smaller)
and (ii) the fact that none of the federal agencies currently active in climate science
research has a clear responsibility for settlement impact issues. Improvements in our
understanding of the impacts of and adaptation to climate change across different sectors
and geographic regions, differential vulnerabilities, and in designing interventions to
build resilience are all needed (NRC, 2007).
To some degree, gaps can be filled by referring to several comprehensive analyses that do
exist, to literature on effects of climate variation on settlements and their responses, to
research on climate change impacts on cities in other parts of the world, and to historical
analogs of responses of urban areas to significant environmental changes. A text box
entitled Historical Perspective of the U.S. Urban Responses to Environmental Change is
included as Box 3.1. This perspective examines how American cities have been affected
by environmental change over the past two centuries. But this is little more than a place
to start.
At the current state of knowledge, vulnerabilities to possible impacts are easier to project
than actual impacts because they estimate risks or opportunities associated with possible
consequences rather than estimating the consequences themselves, which requires far
more detailed information about future conditions. Vulnerabilities are shaped not only by
existing exposures, sensitivities, and adaptive capacities but also by the ability of
settlements to develop responses to risks.
3.2 Climate Change Impacts and the Vulnerabilities of Human
Settlements
This section examines possible impacts of climate change on settlements in the United
States including the determinants of vulnerability to such impacts and how those impacts
could affect settlement patterns and various systems related to those patterns.
3.2.1 Determinants of Vulnerability
It has been difficult to project impacts of climate change on human settlements in the
United States, in part because climate change forecasts are not specific enough for the
scale of decision-making (as for other relatively local-scale impact questions) but
moreover because climate change is not the only change being confronted by settlements.
More often, attention is paid to vulnerabilities to climate change, if those changes should
occur.
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Vulnerabilities to or opportunities from climate change are related to three factors, both
in absolute terms and in comparison to other elements (Clark et al., 2000):
1. Exposure to climate change. To what climate changes are settlements likely to be
exposed: Changes in temperature or precipitation? Changes in storm exposures
and/or intensities? Changes in sea level?
2. Sensitivity to climate change. If primary climate changes occur, how sensitive are
the activities and populations of a settlement to those changes? For instance, a
city dependent substantially on a regional agricultural or forestry economy, or to
the availability of abundant water resources, might be considered more sensitive
than a city whose economy is based mainly on an industrial sector less sensitive to
climate variation.
3. Adaptive capacity. Finally, if effects are experienced due to a combination of
exposure and sensitivity, how able is a settlement to handle those impacts without
disabling damages, perhaps even while realizing new opportunities?
3.2.2 Impacts of Climate Change on Human Settlements
Impacts of climate change on human settlements vary regionally (see Table 3.2 and
Vignettes below), and generally relate to some of the following issues:
1. Effects on health. It is well-established that higher temperatures in urban areas are
related to higher levels of ozone which cause respiratory and cardiovascular
problems. There is also some evidence that combined effects of heat stress and air
pollution may be greater than simple additive effects (Patz and Balbus, 2001).
Moreover, historical data show relationships between mortality and temperature
extremes (Rozenzweig and Solecki, 2001a). Other health concerns include
changes in exposure to water and food-borne diseases, vector-borne diseases,
concentrations of plant species associated with allergies, and exposures to
extreme weather events such as storms, floods, and fires (see Chapter 2).
2. Effects on water and other urban infrastructures. Changes in precipitation
patterns may lead to reductions in meltwater, river flows, groundwater levels, and
in coastal areas lead to saline intrusion in rivers and groundwater, affecting water
supply; and warming may increase water demands (Gleick et al., 2000; Kirshen,
2002; Ruth et al., 2007). Moreover, storms, floods, and other severe weather
events may affect other infrastructure, including sanitation systems,
transportation, supply lines for food and energy, and communication. Exposed
structures such as bridges and electricity transmission networks are especially
vulnerable. In many cases, infrastructures are interconnected; an impact on one
can also affect others (Kirshen, et al., 2007). An example is an interruption in
energy supply, which increases heat stress for vulnerable populations (Ruth et al.,
2006a). Many of the infrastructures in older cities are aging and are already under
stress from increasing demands.
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3. Effects on energy requirements. Warming is virtually certain to increase energy
demand in U.S. cities for cooling in buildings while it reduces demands for
heating in buildings (see SAP 4.5). Demands for cooling during warm periods
could jeopardize the reliability of service in some regions by exceeding the supply
capacity, especially during periods of unusually high temperatures (see Vignettes
in Boxes 3.2 and 3.3). Higher temperatures also affect costs of living and business
operation by increasing costs of climate control in buildings (Amato et al., 2005;
Ruth and Lin, 2006c; Kirshen et al., 2007).
4. Effects on the urban metabolism. An urban area is a living complex mega-
organism, associated with a host of inputs, transformations, and outputs: heat,
energy, materials, and others (Decker et al., 2000). An example is the Urban Heat
Index, which measures the degree to which built/paved areas are associated with
higher temperatures than surrounding rural areas (see Box 3.4: Climate Change
Impacts on the Urban Heat Island Effect (UHI)). Imbalances in the urban
metabolism can aggravate climate change impacts, such as roles of UHI in the
formation of smog in cities. The maps in this box demonstrate how the built
environment creates and retains heat in metropolitan settings.
5. Effects on economic competitiveness, opportunities, and risks. Climate change has
the potential not only to affect settlements directly but also to affect them through
impacts on other areas linked to their economies at regional, national, and
international scales (Rosenzweig and Solecki, 2006). In addition, it can affect a
settlement's economic base if it is sensitive to climate, as in areas where
settlements are based on agriculture, forestry, water resources, or tourism (IPCC,
2001b).
6. Effects on social and political structures. Climate change can add to stress on
social and political structures by increasing management and budget requirements
for public services such as public health care, disaster risk reduction, and even
public security. As sources of stress grow and combine, the resilience of social
and political structures that are already somewhat unstable is likely to suffer,
especially in areas with relatively limited resources (Sherbinin etal., 2006).
7. Effects on vulnerable populations (see Chapter 1). Where climate change stresses
settlements, it is likely to be especially problematic for vulnerable parts of the
population: the poor, the elderly, those already in poor health, the disabled, those
living alone, those with limited rights and power (e.g., recent in-migrants with
limited English skills), and/or indigenous populations dependent on one or a few
resources. As one example, warmer temperatures in urban summers have a more
direct impact on populations who live and work without air-conditioning.
Implications for environmental justice are clear; see, for instance, Congressional
Black Caucus Foundation, 2004.
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8. Effects on vulnerable regions. Approximately half of the U.S. population, 160
million people, will live in one of 673 coastal counties by 2008 (Crossett et al.,
2004). Obviously, settlements in coastal areas - particularly on gently-sloping
coasts -should be concerned about sea level rise in the longer term, especially if
they are subject to severe storms and storm surges and/or if their regions are
showing gradual land subsidence (Neumann et al., 2000; Kirshen el al., 2004).
Settlements in risk-prone regions have reason to be concerned about severe
weather events, ranging from severe storms combined with sea-level rise in
coastal areas to increased risks of fire in drier arid areas. Vulnerabilities may be
especially great for rapidly-growing and/or larger metropolitan areas, where the
potential magnitude of both impacts and coping requirements could be very large
(IPCC, 2001b; Wilbanks etal., 2007b).
Different combinations of circumstances are likely to cause particular concerns for cities
and towns in the United States as they consider possible implications of climate change.
3.2.3. The Interaction of Climate Impacts with Non-Climate Factors.
In general, climate change effects on human settlements in the United States are
imbedded in a variety of complexities that make projections of quantitative impacts over
long periods of time very difficult. For instance, looking out over a period of many
decades, it seems likely that other kinds of change—such as technological, economic, and
institutional—will have more impact on the sustainability of most settlements rather than
climate change per se (Wilbanks, etal., 2007b). Climate change will interact with other
processes, driving forces, and stresses; and its significance, positive or negative, will
largely be determined by these interactions. It is therefore difficult to assess effects of
climate change without a reasonably clear picture of future scenarios for these other
processes.
In many cases, these interactions involve not only direct impacts such as warming or
more or less precipitation but, sometimes more important, second, third, or higher-order
impacts, as direct impacts cascade through urban systems and other settlement-
determined processes (e.g., warming which affects urban air pollution which affects
health which affects public service requirements which affect social harmony: Kirshen et
al., 2007). Some of these higher-order impacts, in turn, may feed back to create ripple
effects of their own. For example, a heat wave may trigger increased energy demands for
cooling, which may cause more air conditioners and power generators to be operated,
which could lead to higher urban heat island effects, inducing even higher cooling needs.
Besides this "multi-stress" perspective, it is highly likely that effects of climate change on
settlements are shaped by certain "thresholds," below which effects are incidental but
beyond where effects quickly become major when a limiting or inflection point is
reached. An example might be a city's capacity to cope with sustained heat stress
combined with a natural disaster. In general, these climate-related thresholds for human
settlements in the United States are not well-understood. For multi-stress assessments of
thresholds, changes in climate extremes are very often of more concern than changes in
climate averages. Besides extreme weather events, such as hurricanes or tornadoes, ice
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storms, winds, heat waves, drought, or fire, settlements may be affected by changes in
daily or seasonal high or low levels of temperature or precipitation, which have not
always been projected by climate change models.
Finally, human settlements may be affected by climate change mitigation_initiatives as
well as by climate change itself. Examples include effects on policies related to energy
sources and uses, environmental emissions, and land use. The most direct and short-term
effects would likely be on settlements in regions whose economies are closely related to
the production and consumption of large quantities of fossil fuels. Indirect and longer
term effects are less predictable.
As climate change affects settlements in the United States, impacts are realized at the
intersection of climate change with underlying forces. Most of the possible effects are
linked with changes in regional comparative advantage, with consequent migration of
population and economic activities (Ruth and Coelho, in press). Examples of these
complex interactions and issues include:
1. Regional risks and availability of insurance. It is possible that regions exposed to
risks from climate change will see movement of population and economic activity
to other locations. One reason is public perceptions of risk, but a more powerful
driving force may be the availability of insurance. The insurance sector is one of
the most adaptable of all economic sectors, and its exposure to costs from severe
storms and other extreme weather events is likely to lead it to withdraw (or to
make much more expensive) private insurance coverage from areas vulnerable to
climate change impacts (Wilbanks, et al., 2007b), which would encourage both
businesses and individual citizens to consider other locations over a period of
several decades.
2. Areas whose economies are linked with climate-sensitive resources or assets.
Settlements whose economic bases are related to such sectors as agriculture,
forestry, tourism, water availability, or other climate-related activities could be
affected either positively or negatively by climate change, depending partly on the
adaptability of those sectors {i.e., their ability to adapt to changes without shifting
to different locations).
3. Shifts in comparative living costs, risks, and amenities. Related to a range of
possible climate change effects - higher costs for space cooling in warmer areas,
higher costs of water availability in drier areas, more or less exposure to storm
impacts in some areas, and sea level rise - regions of the United States and their
associated settlements are likely to see gradual changes over the long term in their
relative attractiveness for a variety of human activities. One example, although its
likelihood is highly uncertain, would be a gradual migration of the "Sun Belt"
northward, as retirees and businesses attracted by environmental amenities find
that regions less exposed to very high temperatures and seasonal major storms are
more attractive as places to locate.
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4. Changes in regional comparative advantage related to shifts in energy resource
use. If climate mitigation policies result in shifts from coal and other fossil
resources toward non-fossil energy sources, or if climate changes affect the
prospects of renewable energy sources (especially hydropower), regional
economies related to the production and/or use of energy from these sources could
be affected, along with regional economies more closely linked with alternatives,
(citation: SAP 4.5)
5. Urban "footprints " on other areas. Resource requirements for urban areas
involve larger areas than their own bounded territories alone. Ecologists have
sought to estimate the land area required to supply the consumption of resources
and compensate for emissions and other wastes from urban areas (e.g., Folke el
al., 1997). By possibly affecting settlements, along with their resource capacities
for their inputs and destinations of their outputs, climate change could affect the
nature, size, and geographic distribution of these footprints.
Human settlements are foci for many economic, social, and governmental processes, and
historical experience has shown that catastrophes in cities can have significant economic,
financial, and political effects much more broadly. The case which has received the most
attention to date is insurance and finance (Wilbanks, et al., 2007b).
3.2.4 Realizing Opportunities from Climate Change in the United States
Climate change can have positive as well as negative implications for settlements.
Examples of potential positive effects include:
1. Reduced winter weather costs and stresses. Warmer temperatures in periods of
the year that are normally cold are not necessarily undesirable. They reduce cold-
related stresses and costs (e.g., costs of warming buildings and costs of clearing
ice and snow from roads and streets), particularly for cold-vulnerable populations.
They expand opportunities for warmer-weather recreational opportunities over
larger parts of the year, and they expand growing seasons for crops, parks, and
gardens.
2. Increased attention to long-term sustainability. One of the most positive aspects
of climate change can be that its capacity to stimulate a broader discussion of
what sustainability means for settlements (Wilbanks, 2003; Ruth, 2006). Even if
climate change itself may not be the most serious threat to sustainability,
considering climate change impacts in a multi-change, multi-stage context can
encourage and facilitate processes that lead to progress in dealing with other
sources of stress as well.
3. Improved competitiveness compared with settlements subject to more serious
adverse impacts. While some settlements may turn out to be "losers" due to
climate change impacts, others may be "winners," as changes in temperature or
precipitation result in added economic opportunities (see the following section), at
least if climate change is not severe. In addition for many settlements climate
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change can be an opportunity not only to compare their net impacts with others,
seeking advantages as a result, but to present a progressive image by taking
climate change (and related sustainability issues) seriously.
3.2.5 Examples of Impacts on Metropolitan Areas in the United States
Possible impacts of climate change on settlements in the United States are usually
assessed by projecting climate changes at a regional scale: temperature, precipitation,
severe weather events, and sea level rise (see Table 3.2 and Boxes 3.2 and 3.3). Ideally,
these regional projections are at a relatively detailed scale, and ideally they consider
seasonal as well as annual changes and changes in extremes as well as in averages; but
these conditions cannot always be met.
The most comprehensive assessments of possible climate change impacts on settlements
in the United States have been two studies of major metropolitan areas:
1. New York: This assessment concluded that impacts of climate change on this
metropolitan area are likely to be primarily negative over the long term, with
potentially significant costs increasing as the magnitude of climate change
increases, although there are substantial uncertainties. (Rosenzweig and Solecki,
2001a; Rosenzweig and Solecki, 2001b; Solecki and Rosenzweig, 2006).
2. Boston: This assessment concluded that long-term impacts of climate change are
likely to depend at least as much on behavioral and policy changes over this
period as on temperature and other climate changes (Kirshen et al., 2004;
Kirshen et al., 2006; Kirshen et al., 2007)
Other U.S. studies include Seattle (Hoo and Sumitani, 2005) and Los Angeles (Koteen et
al., 2001) (Table 3.1). Internationally, studies have included several major metropolitan
areas, such as London (London Climate Change Partnership, 2004) and Mexico City
(Molina etal., 2005) as well as possible impacts on smaller settlements (e.g., AIACC: see
www.aiaccproject.org). A relevant historical study of effects of an urban heat wave in the
United States is reported by Klinenberg (2003).
3.3 Opportunities for Adaptation of Human Settlements to
Climate Change
Settlements are important in considering prospects for adaptation to climate change, both
because they represent concentrations of people and because buildings and other
infrastructures offer ways to manage risk and monitor/control threats associated with
climate extremes and other non-climate stressors.
Where climate change presents risks of adverse impacts for U.S. settlements and their
populations, there are two basic options to respond to such concerns (a third is combining
the two). One response is to contribute to climate change mitigation strategies, i.e., by
taking actions to reduce their greenhouse gas emissions and by showing leadership in
encouraging others to support such actions (see Box 3.5: Roles of Settlements in Climate
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Change Mitigation). The second response is to consider strategies for adaptation, i.e.,
finding ways either to reduce sensitivity to projected changes or to increase the
settlement's coping capacities. Adaptation can rely mainly on anticipatory actions to
avoid damages and costs, such as "hardening" coastal structures to sea-level rise; or
adaptation can rely mainly on response potentials, such as emergency preparedness; or it
can include a mix of the two approaches. Research to date suggests that anticipatory
adaptation may be more cost-effective than reactive adaptation (Kirshen et al., 2004).
Adaptation strategies will be important to the well-being of U.S. settlements as climate
change evolves over the next century. As just one example, the New York climate impact
assessment (Rosenzweig and Solecki, 2001a) projects significant increases in heat-related
deaths based on historical relationships between heat stress and mortality, unchanged by
adaptation. The Boston CLIMB assessment (Kirshen et al., 2004) projects that, despite
similar projections of warming, heat-related deaths will decline over the coming century
because of adaptation. Whether or not adaptation to climate change occurs in U.S. cities
is therefore a potentially serious issue. The CLIMB assessment includes analyses
showing that in many cases adaptation actions taken now are better than adaptation
actions delayed until a later time (Kirshen et al., 2006).
3.3.1. Perspectives on Adaptation by Settlements
For decision-makers in U.S. settlements climate change is yet one more source of
possible risks that need to be addressed. Climate change is different as an issue because it
is relatively long-term in its implications, future impacts are uncertain, and public
awareness is growing from a relatively low level to a higher level of concern. Because
climate change is different in these ways, it is seldom attractive to consider allocating
massive amounts of funding or management attention to current climate change actions.
What generally makes more sense is to consider ways that actions which reduce
vulnerabilities to climate change impacts (or increase prospects for realizing benefits
from climate change impacts) are also desirable for other reasons as well: often referred
to as "co-benefits." Examples include actions that reduce vulnerabilities to current
climate variability regardless of long-term climate change, actions that add resilience to
water supply and other urban infrastructures that are already stressed, and actions that
make metropolitan areas more attractive for their citizens in terms of their overall quality
of life.
Cities and towns have used both "hard" approaches such as developing infrastructure and
"soft" approaches such as regulations to address impacts of climate variability. Examples
include water supply and waste water systems, drainage networks, buildings,
transportation systems, land use and zoning controls, water quality standards and
emission caps, and tax incentives. All of these are designed in part with climate and
environmental conditions in mind. The setting of regulations has always been a context of
benefit-cost analysis and political realities; and infrastructure is also designed in a
benefit-cost framework, subject to local design codes. The fact that both regulations and
infrastructures vary considerably across the United States reflects cultural, economic, and
environmental factors; and this suggests that mechanisms exist to respond to concerns
about climate change. Urban designers and managers deal routinely with uncertainties,
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because they must consider uncertain demographic and other socioeconomic changes;
thus, if climate change is properly institutionalized into the urban planning process, it can
be handled as yet another uncertainty.
3.3.2 Major Categories of Adaptation Strategies
Adaptation strategies for human settlements, large and small, include a wide range of
possibilities such as:
1. Changing the location of people or activities (within or between settlements) -
especially addressing the costs of sustaining built environments in vulnerable
areas: e.g., siting and land use policies and practices to shift from more vulnerable
areas to less, adding resilience to new construction in vulnerable areas, increased
awareness of changing hazards and associated risks, and assistance for the less-
advantaged (including actions by the private insurance sector as a likely driving
force).
2. Changing the spatial form of a settlement - managing growth and change over
decades without excluding critical functions (e.g., architectural innovations
improving the sustainability of structures, reducing transportation emissions by
reducing the length of journeys to work, seeking efficiencies in resource use
through integration of functions, and moving from brown spaces to green spaces).
Among the alternatives receiving the most attention are encouraging "green
buildings" (e.g., green roofs: Parris, 2007; see Rosenzweig etal., 2006a;
Rosenzweig et al., 2006b) and increasing "green spaces" within urban areas (e.g.,
Bonsignore, 2003).
3. Technological change to reduce sensitivity of physical and linkage infrastructures
- e.g., more efficient and affordable interior climate control, surface materials that
reduce heat island effects (Quattrochi et al., 2000), waste reduction and advanced
waste treatment, and better warning systems and controls. Physical design
changes for long-lived infrastructure may also be appropriate, such as building
water-treatment or storm-water runoff outflow structures based on projected sea
level rather than the historical level.
4. Institutional change to improve adaptive capacity, including assuring effective
governance, providing financial mechanisms for increasing resiliency, improving
structures for coordinating among multiple jurisdictions, targeting assistance
programs for especially impacted segments of the population, adopting
sustainable community development practices, and monitoring changes in
physical infrastructures at an early stage (Wilbanks et al., 2007a). Policy
instruments include zoning, building and design codes, terms for financing, and
early warning systems (Kirshen et al., 2005).
5. "No regrets" or low net cost policy initiatives that add resilience to the settlement
and its physical capital - e.g., in coastal areas changing building codes for new
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construction to require coping with projected amounts of sea-level rise over the
expected lifetimes of the structures.
The choice of strategies from among the options is likely to depend on co-benefits in
terms of other social, economic, and ecological driving forces; the availability of fiscal
and human resources; and political aspects of "who wins" and "who loses."
3.3.3 Examples of Current Adaptation Strategies
In most cases in the United States, settlements have been more active in climate change
mitigation than climate change adaptation (see Box 3.5), but there are some indications
that adaptation is growing as a subject of interest (Solecki and Rosenzweig, 2005; Ruth,
2006). Bottom-up grassroots activities currently under way in the United States are
considerable, and that number appears to be growing. For example, Boston has built a
new wastewater treatment plant at least one-half meter higher than currently necessary to
cope with sea level rise, and in a coastal flood protection plan for a site north of Boston
the U.S. Corps of Engineers incorporated sea-level rise into their analysis (Easterling el
al., 2004). California is considering climate change adaptation strategies as a part of its
more comprehensive attention to climate change policies (Franco, 2005). And, Alaska is
already pursuing ways to adapt to permafrost melting and other climate change effects.
Meanwhile, in some cases, settlements are taking actions for other reasons that add
resilience to climate change effects. An example is the promotion of water conservation,
which is reducing per capita water consumption in cities that could be subject to
increased water scarcity (City of New York, 2005).
It seems very likely that local governments will play an important role in climate change
responses in the United States Many adaptation options must be evaluated at a relatively
local scale in terms of their relative costs and benefits and their relationships with other
urban sustainability issues, and local governments are important as guardians of public
services, able to mobilize a wide range of stakeholders to contribute to broad community-
based initiatives (as in the case of the London Climate Change Partnership, 2004).
Because climate change impact concerns and adaptation potentials tend to cross
jurisdictional boundaries in highly fragmented metropolitan areas, local actions might
encourage cross-boundary interactions that would have value for other reasons as well.
While no U.S. communities have developed comprehensive programs to ameliorate the
effects of heat islands, some localities are recognizing the need to address these effects.
In Chicago, for example, several municipal buildings have been designed to
accommodate "green" rooftops. Atlanta has had a Cool Communities "grass roots" effort
to educate local and state officials and developers on strategies that can be used to
mitigate the UHI. This Cool Communities effort was instrumental in getting the State of
Georgia to adopt the first commercial building code in the country emphasizing the
benefits of cool roofing technology (Young, 2002; Estes, Jr. et al., 2003). The "Excessive
Heat Events Guidebook" developed by the Environmental Protection Agency in
collaboration with NOAA, CDC, and DHS provides information for municipal officials
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in the event of an excessive heat event:
http://www.epa.gov/hiri/about/heatguidebook.html.
3.3.4: Strategies to Enhance Adaptive Capacity
In most cases, the likelihood of effective adaptation is related to the capacity to adapt,
which in turn is related to such variables as knowledge and awareness, access to fiscal
and human resources, and good governance (IPCC, 2001b). Strategies for enhancing such
capacities in U.S. settlements are likely to include the development and use of local
expertise on climate change issues (AAG, 2003), attention to the emerging experience
with climate change effects and response strategies globally and in other U.S.
settlements, information sharing about adaptation potentials and constraints among
settlements and their components (likely aided by modern information technology), and
an emphasis on participatory decision-making, where local industries, institutions, and
community groups are drawn into discussions of possible responses.
3.4. Conclusions
Even from a current knowledge base that is very limited, it is possible to conclude several
things about effects of climate change on human settlements in the United States:
1. Climate change takes place in the context of a variety of factors driving an area's
development: it is likely to be a secondary factor in most places, with its
importance determined mainly by its interactions with other factors, except in the
case of major abrupt climate change (very likely).
2. Effects of climate change will vary considerably according to location-specific
vulnerabilities, and the most vulnerable areas are likely to be Alaska, coastal and
river basins susceptible to flooding, arid areas where water scarcity is a pressing
issue, and areas whose economic bases are climate-sensitive (very likely).
3. The main impact concerns, in areas other than Alaska, have to do with changes in
the intensity, frequency, and/or location of extreme weather events and, in some
cases, water availability rather than changes in temperature (very likely).
4. Over the time period covered by current climate change projections, the potential
for adaptation through technological and institutional development as well as
behavioral changes are considerable, especially where such developments meet
other sustainable development needs as well, especially considering the initiatives
already being shown at the local level across the United States (extremely likely).
5. While uncertainties are very large about specific impacts in specific time periods,
it is possible to talk with a higher level of confidence about vulnerabilities to
impacts for most settlements in most parts of the United States (virtually certain).
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3.5 Expanding the Knowledge Base
A number of sources, including NACC, 1998; Parson et al., 2003; Ruth, 2006; and Ruth
et al., 2004, have considered research pathways for improving the understanding of
effects of climate change on human settlements in the United States.
The following list suggests a number of research topics that would help expand the
knowledge base about the linkages between climate change and human settlements.
¦ Advance understanding of settlement vulnerabilities, impacts, and adaptive
responses in a variety of different local contexts around the country through case
studies. In addition to identifying vulnerable settlements, these studies should also
identify vulnerable populations (such as the urban poor and native populations on
rural and/or tribal lands) that have limited capacities for response to climate
change, within those settlements. Better understanding of climate change at the
community scale would provide a basis for adaptation research that addresses
social justice and environmental equity concerns.
¦ Develop better projections of climate change at the scale of U.S. metropolitan
areas or smaller, including scenarios projecting extremes and scenarios involving
abrupt changes.
¦ Improve abilities to associate projections of climate change in U.S. settlements
with changes in other driving forces related to impacts, such as changes in
metropolitan/urban patterns and technological change.
¦ Design practically implementable, socially acceptable strategies for shifting
human populations and activities away from vulnerable locations.
¦ Improve the understanding of vulnerabilities of urban inflows and outflows to
climate change impacts, as well as second and third-order impacts of climate
change in urban environments, including interaction effects among different
aspects of the urban system.
¦ Improve the understanding of the relationships between settlement patterns (both
regional and intra-urban) and resilience/adaptive capacity.
¦ Improve understanding of how urban decision-making is changing as populations
become more heterogeneous and decisions become more decentralized, especially
as this affects adaptive responses.
¦ Review current policies and practices related to climate change responses to help
inform community decision-makers and other stakeholders about potentials for
relatively small changes to make a large difference.
¦ Evaluate and document experiences with urban/settlement climate change
responses while involving decision-making, research and stakeholder
communities more actively in discussions of climate change impacts and response
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issues. Focus attention on the costs, benefits, and possible limits and potentials of
adaptation to climate change vulnerabilities in U.S. cities and smaller settlements.
¦ Improve tools and approaches for infrastructure planning and design to reduce
exposure and sensitivity to climate change effects while increasing adaptive
capacity.
¦ Enhance coordination within federal government agencies to improve
understanding about impacts, vulnerabilities and responses to climate change for
the nation's cities and smaller settlements. Connections with U.S. urban decision-
makers can enable integration of climate change considerations into what they do
with building codes, zoning, lending practices, etc. as mainstreamed urban
decision processes.
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SAP 4.6 Chapter 3: Human Settlements
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SAP 4.6 Chapter 3: Human Settlements
Hunter, J.R., 2006: Testimony before the Committee on Banking, Housing and Urban
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SAP 4.6 Chapter 3: Human Settlements
3.7 Boxes
Box 3.1: U.S. Urban Responses to Environmental Change:
A Historial Perspective
Over time, American cities have been affected by environmental change. City founders often showed an
important disregard with respect to siting of settlements, focusing on aspects of location such as
commercial or recreational opportunities rather than on risks such as flood potential, limited water, food or
fuel supplies, or the presence of health threats. Oftentimes settlers severely exploited their environments,
polluting ground water and adjacent water bodies, building in unsafe and fragile locations, changing
landforms, and filling in wetlands. Construction of the urban built environment involved vast alterations in
the landscape, as forests and vegetation and wildlife species were eliminated and replaced by highways,
suburbs, and commercial buildings. The building of wastewater and water supply systems had the effect of
altering regional hydrology and creating large vulnerabilities. In other cases settlers concluded that the
weather was changing for the good, that technology would solve problems or that new resources could be
discovered.
Technological fixes were pursued to seek ways to modify or control environmental change. Cities exposed
to flooding built levees and seawalls and channelized rivers. When urbanites depleted and polluted local
water supplies cities went outside their boundaries to seek new supplies: building reservoirs, aqueducts, and
creating protected watersheds. When urban consumption exhausted local fuel sources, cities adapted to new
fuels, embraced new technologies, or searched far beyond city boundaries for new supplies. Many of these
actions resulted in the extension of the urban ecological footprint, so that urban growth and development
affected not only the urban site but also increasingly the urban hinterland and beyond.
There are few examples of environmental disasters or climate change actually resulting in the abandonment
of an urban site. One case appears to be that of the Hohokam Indians of the Southwest, who built extensive
irrigation systems, farmed land, and built large and dense settlements over a period of approximately 1,500
years (Krech, 1999: 45-72). Yet, they abandoned their settlements and disappeared into history. The most
prominent explanation for their disappearance is an ecological one ~ that the Hohokam irrigation systems
suffered from salinization and water logging, eventually making them unusable. Other factors besides
ecological ones may have also entered into the demise of their civilization and abandonment of their cities,
but the ecological explanation appears to have the most supporters.
In the case of America in the 19th and 20th centuries, however, no city has been abandoned because of
environmental or climatic factors. Galveston, Texas suffered from a catastrophic tidal wave but still exists
as a human settlement, now protected by an extensive sea wall. Johnstown, Pennsylvania has undergone
major and destructive flooding since the late 19th century, but continues to survive as a small city. Los
Angeles and San Francisco are extremely vulnerable to earthquakes, but still continue to increase in
population. And, in coming years New Orleans almost certainly will experience a hurricane as or more
severe than Katrina, and yet rebuilding goes on, encouraged by the belief that technology will protect it in
the future. Whether or not ecological disaster or extreme risk will eventually convince Americans to
abandon some of their settlements, as the Hohokam did, has yet to be determined (Colten, 2005; Steinberg,
2006; Vale and Campanella, 2005).
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SAP 4.6 Chapter 3: Human Settlements
Box 3.2: Vignettes of Vulnerability -1
Alaskan Settlements
No other region in the United States is likely to be as profoundly changed by climate change as
Alaska, our nation's part of the polar region of Earth (ACIA, 2004). Because warming is more pronounced
closer to the poles, and because settlement and economic activities in Alaska have been shaped and often
constrained by Arctic conditions, in this region warming is especially likely to reshape patterns of human
settlement.
Human settlements in Alaska are already being exposed to impacts from global warming (ACIA,
2004), and these impacts are expected to increase. Many coastal communities see increasing exposure to
storms, with significant coastal erosion, and in some cases facilities are being forced either to relocate or to
face increasing risks and costs. Thawing ground is beginning to destabilize transportation, buildings, and
other facilities, posing needs for rebuilding, with ongoing warming adding to construction and maintenance
costs. And indigenous communities are facing major economic and cultural impacts. One recent estimate of
the value of Alaska's public infrastructure at risk from climate change set the value at tens of billions of
today's dollars by 2080, with the replacement of buildings, bridges, and other structures with long lifetimes
having the largest public costs (Larsen et al., 2007).
Besides impacts on built infrastructures designed for permafrost foundations and effects on
indigenous societies, many observers expect warming in Alaska to stimulate more active oil and gas
development (and perhaps other natural resource exploitation), and if thawing of Arctic ice permits the
opening of a year-round Northwest sea passage it is virtually certain that Alaska's coast will see a boom in
settlements and port facilities (ACIA, 2004).
Coastal Southeast Settlements
While there is currently no evidence for a long-term increase in North American mainland land-
falling hurricanes, concerns remain that certain aspects of hurricanes, such as wind speed and rainfall rates
may increase (CCSP, 2008). In addition, sea level rise is expected to increase storm surge levels (CCSP,
2008). Recent hurricanes striking the coast of the U.S. Southeast cannot be attributed clearly to climate
change, but they suggest a range of possible impacts. As an extreme case, consider the example of
Hurricane Katrina. In 2005, the city of New Orleans had a population of about half a million, located on the
delta of the Mississippi River along the U.S. Gulf Coast. Urban development throughout the 20th Century
has significantly increased land use and settlement in areas vulnerable to flooding, and a number of studies
had indicated growing vulnerabilities to storms and flooding. In late August 2005, Hurricane Katrina
moved onto the Louisiana and Mississippi coast with a storm surge, supplemented by waves, reaching up to
8.5 m above sea level. In New Orleans, the surge reached around 5m, overtopping and breaching sections
of the city's 4.5m defenses, flooding 70 to 80 % of New Orleans, with 55 % of the city's properties
inundated by more than 1.2 m and maximum flood depths up to 6 m. 1101 people died in Louisiana, nearly
all related to flooding, concentrated among the poor and elderly. Across the whole region, there were 1.75
million private insurance claims, costing in excess of $40 billion (Hartwig, 2006), while total economic
costs are projected to be significantly in excess of $100 billion. Katrina also exhausted the federally backed
National Flood Insurance Program (Hunter, 2006), which had to borrow $20.8 billion from the Government
to fund the Katrina residential flood claims. In New Orleans alone, while flooding of residential structures
caused $8-$10 billion in losses, $3-6 billion was uninsured. 34,000-35,000 of the flooded homes carried no
flood insurance, including many that were not in a designated flood risk zone (Hartwig, 2006). Six months
after Katrina, it was estimated that the population of New Orleans was 155,000, with the number projected
to rise to 272,000 by September 2008 - 56% of its pre-Katrina level (McCarthy et al., 2006).
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SAP 4.6 Chapter 3: Human Settlements
Box 3.3: Vignettes of Vulnerability - II
Arid Western Settlements
Human settlements in the arid West are affected by climate in a variety of ways, but perhaps most of all by
water scarcity and risks of fire. Clearly, access to water for urban populations is sensitive to climate,
although the region has developed a vast system of engineered water storage and transport facilities,
associated with a very complex set of water rights laws (NACC, 2001). It is very likely that climate change
will reduce winter snowfall in the West, reducing total runoff - increasing spring runoff while decreasing
summer water flows. Meanwhile, water demands for urban populations, agriculture, and power supply are
expected to increase, and conflicts over water rights are likely to increase. If total precipitation decreases or
becomes more variable, extending the kinds of drought that have affected much of the interior West in
recent years, water scarcity will be exacerbated, and increased water withdrawals from wells could affect
aquifer levels and pumping costs. Moreover, drying increases risks of fire, which have threatened urban
areas in California and other Western areas in recent years. The five-year average of acres burned in the
West is more than 5 million, and urban expansion is increasing the length of the urban-wild lands interface
(Morehouse et al., 2006). Drying would lengthen the fire season, and pest outbreaks such as the pine beetle
could affect the scale of fires.
Summer 2006 Heat Wave
In July and August 2006, a severe heat wave spread across the United States, with most parts of the country
recording temperatures well above the average for that time of the year. For example, temperatures in
California were extraordinarily high, setting records as high as 130°. As many as 225 deaths were reported
by press sources, many of them in major cities such as New York and Chicago. Electric power transformers
failed in several areas, such as St. Louis and Queens, New York, causing interruptions of electric power
supply, and some cities reported heat-related damages to water lines and roads. In many cities, citizens
without home air-conditioning sought shelter in public and office buildings, and city/county health
departments expressed particular concern for the elderly, the young, pregnant women, and individuals in
poor health. Although this heat wave cannot be attributed directly to climate change, it suggests a number
of issues for human settlements in the United States as they contemplate a prospect of temperature
extremes in the future that are higher and/or longer-lasting than historical experience.
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SAP 4.6 Chapter 3: Human Settlements
Box 3.4: Climate Change Impacts on The Urban Heat Island Effect (UHI)
(Lo and Quattrochi, 2003; Brazel and Quattrochi, 2006; Ridd, 2006; Stone, 2006)
Climate change impacts on the Urban Heat Island (UHI) effect will primarily depend upon the geographic
location of a specific city, its urban morphology (i.e., landscape and built-up characteristics), and areal
extent (i.e., overall spatial "footprint"). These factors will mitigate or exacerbate how the UHI phenomenon
(Figure 3.1) is affected by climate change, but overall, climate change is likely to impact the UHI effect in
the following ways:
• Exacerbation of the intensity and areal extent of the UHI as a result of warmer surface and air
temperatures along with the overall growth of urban areas around the world. Additionally, as urban
areas grow and expand, there is a propensity for lower albedos which forces a more intense UHI effect.
(There is also some indication that sustained or prolonged higher nighttime air temperatures over cities
that may result from warmer global temperatures will have a more significant impact on humans than
higher daytime temperatures.)
• As the UHI intensifies and increases, there could be a subsequent impact on deterioration of air quality,
particularly on ground level ozone caused by higher overall air temperatures and an increased
background effect produced by the UHI as an additive air temperature factor that helps to elevate
ground level ozone production. Additionally, particulate matter (PM2 5) could increase due to a number
of human induced and natural factors (e.g., more energy production to support higher usage of air
conditioning).
• The UHI has an impact on local meteorological conditions by forcing rainfall production either over,
or downwind, of cities. As the UHI effect intensifies, there will be a higher probability for urban-
induced rainfall production (dependent upon geographic location) with a subsequent increase in urban
runoff and flash flooding.
• Exacerbation and intensification of the UHI would have impacts on human health:
increased incidence of heat stress
impact on respiratory illnesses such as asthma due to increases in particulate matter
caused by deterioration in air quality as well as increased pollination production because
of earlier pollen production from vegetation in response to warmer overall temperatures
Figure 3.1. Example of urban surface temperatures and albedo for the Atlanta, Georgia Central Business
District (CBD) area derived from high spatial resolution (10m) aircraft thermal remote sensing data.
The image on the left illustrates daytime surface heating for urban surfaces across the CBD. White and red
colors indicate very warm surfaces (~40-50°C). Green relates to surfaces of moderately warm temperatures
(~25-30°C). Blue indicates cool surfaces (e.g., vegetation, shadows) (~15-20°C). Surface temperatures are
reflected in the albedo image on the right where warm surfaces are dark (i.e., low reflectivity) and cooler
surfaces are in red and green (i.e., higher reflectivity). The images exemplify how urban surface
characteristics influence temperature and albedo as drivers of the urban heat island effect (Quattrochi el al.,
2000).
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SAP 4.6 Chapter 3: Human Settlements
Box 3.5: Roles of Settlements in Climate Change Mitigation
Although U.S. government commitments to climate change mitigation policies at the
national level have emerged only recently, an increasing number of state and local authorities are
involved in strategies to mitigate greenhouse gas emissions (Selin and Vandeveer, 2005; Rabe,
2006; Selin, 2006). U.S. states and cities are joining such initiatives as ICLEI (ICLEI, 2006), the
U.S. Mayor Climate Protection Agreement, the Climate Change Action Plan, the Regional
Greenhouse Gas Initiative (RGGI) (Selin, 2006), and the Large Cities Climate Leadership
Group.1 These initiatives focus on emissions inventories; on such actions aimed at reducing GHG
emissions as switching to more energy efficient vehicles, using more efficient furnaces and
conditioning systems, and introducing renewable portfolio standards (RPS). These strategies,
which mandate an increase in the amount of electricity generated from renewable resources also
adapt to negative social, economic and environmental impacts; and on actions to promote public
awareness (see references in footnote 1).
Different drivers lie behind these mitigation efforts. Public and private entities have
begun to "perceive" such possible impacts of climate change as rising sea level, extreme shifts in
weather, and losses of key resources. They have realized that a reduction of GHG emissions
opens opportunities for longer economic development (e.g., investment in renewable energy:
Rabe, 2006). In addition, climate change can become a political priority if it is reframed in terms
of local issues (i.e., air quality, energy conservation) already on the policy agenda (Betsill, 2001;
Bulkeley and Betsill, 2003; Romero Lankao, 2007)
The promoters of these initiatives face challenges related partly to inertia (e.g., the time it
takes to replace energy facilities and equipment with a relatively long life of 5 to 50 years: Haites
el al., 2007). They can also face opposition from organizations who do not favor actions to reduce
GHG emissions, some of whom are prepared to bring legal challenges against state and local
initiatives (Rabe, 2006:17). But the number of bottom-up grassroots activities currently under
way in the United States is considerable, and that number appears to be growing.
1 ICLEI is the International Council for Local Environmental Initiatives. Local governments participating in
ICLEI's Cities for Climate Protection (CCP) Campaign commit to a) conduct an energy- and emissions-
inventory and forecast, b) establish an emissions target, c) develop and obtain approval for the Local
Action Plan, d) Implement policies and measures, and e) monitor and verily results (ICLEI, 2006: April 20
2006 www.iclei.org'). The Large Cities Climate Leadership Group is a group of cities committed to the
reduction of urban carbon emissions and adapting to climate change. It was founded following the World
Cities Leadership Climate Change Summit organized by the Mayor of London in October 2005. For more
information on the US Mayor Climate Protection Agreement see http://www.seattle.gov/mayor/climate/
3-28
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SAP 4.6 Chapter 3: Human Settlements
3.8 Tables
Table 3.1. Overview of Integrated Assessments of Climate Impacts and Adaptation in U.S.
Cities, "x" indicates that the reference addresses a category of interest.
Bloomfield
Kooten
Rosenzweig
Kirshen
Hoo and
et aL, 1999
et aL, 2001
et aL, 2000
et aL, 2004
Sumitani, 2005
Location:
Greater Los
New York
Metropolitan
Metropolitan
Metropolitan
Angeles
New York
Boston
Seattle
Coverage:
Water supply
V
V
V
V
Water Quality
V
Water Demand
V
Sea-level Rise
V
V
V
V
Transportation
•/
•/
Communication
Energy
V
V
Public Health
Vector-borne Diseases
Food-borne Diseases
V
Temperature-related
V
Mortality
Temperature-related
V
V
Morbidity
Air-quality Related
Mortality
Air-quality Related
V
Morbidity
Other Health Issues
V
V
V
Ecosystems
Wetlands
Other Ecol.(Wildfires)
V
V
Urban Forests (Trees and
V
Vegetation)
Air Quality
V
V
Extent of:
Quantitative Analysis
Low
Medium
Medium
High
Low
Computer-based
None
Low
Low
High
None
Modeling
Scenario Analysis
None
None
Medium
High
Medium
Explicit Risk Analysis
None
None
None
Medium
None
Involvement of:
Local Planning Agencies
None
None
High
High
High
Local Government
None
None
High
High
High
Agencies
Private Industry
None
None
None
Low
None
Non-profits
None
None
Low
High
None
Citizens
None
None
None
Medium
None
Identification of:
Adaptation Options
X
X
X
X
X
Adaptation Cost
X
X
Extent of Integration
None
None
Low
Medium
Low
Across Systems
Attention to Differential
None
None
Low
Low
Low
Impacts (e.g., on
individual types of
businesses, populations)
3-29
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SAP 4.6 Chapter 3: Human Settlements
Table 3.2. Regional vulnerabilities of settlements to impacts of climate change in the United
States
REGIONAL VULNERABILITIES OF SETTLEMENTS TO
IMPACTS OF CLIMATE CHANGE
Region
Vulnerabilities
Major Uncertainties
Metro NE
Flooding, infrastructures, health,
water supply, sea-level rise
Storm behavior, precipitation
Larger NE
Changes in local landscapes,
tourism, water, energy needs
Ecosystem impacts
Mid-Atlantic
Multiple stresses; e.g.,
interactions between climate
change and aging infrastructures
Ecosystem impacts
Coastal SE
More intense storms,
sea-level rise, flooding, heat
stress
Storm behavior,
coastal land use, sea-level rise
Inland SE
Water shortages,
heat stress,
UH1, economic impacts
Precipitation change,
development paths
Upper Midwest
Lake and river levels, extreme
weather events, health
Precipitation change, storm
behavior
Inner Midwest
Extreme weather events, health
Storm behavior
Appalachians
Ecological change, reduced
demand for coal
Ecosystem impacts, energy
policy impacts
Great Plains
Water supply, extreme events,
stresses on communities
Precipitation changes, weather
extremes
Mountain West
Reduced snow, water shortages,
fire, tourism
Precipitation changes, effects
on winter snowpack
Arid Southwest
Water shortages, fire
Development paths,
precipitation changes
California
Water shortages, heat stress; sea
level rise
Temperature and precipitation
changes, infrastructure impacts
Northwest
Water shortages, ecosystem
stresses, coastal effects
Precipitation changes, sea-level
rise
Alaska
Effects of warming, vulnerable
populations
Warming, sea-level rise
Hawaii
Storms and other weather
extremes, freshwater supplies,
health, sea-level rise
Storm behavior, precipitation
change
3-30
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SAP 4.6 Chapter 3: Human Settlements
3.9 Figures
Figure 3.1. Example of urban surface temperatures and albedo for the Atlanta, Georgia Central
Business District (CBD) area derived from high spatial resolution (10m) aircraft thermal remote
sensing data.
(Quattrochi et a I., 2000)
. ¦ P * . "1*,* • k'il ~ fr]
* fed! >
-------
Synthesis and Assessment Product 4.6
Chapter 4: Effects of Global Change on Human Welfare
Lead Author; Frances G. Sussman, Environmental Economics Consulting
Contributing Authors: Maureen L. Cropper, University of Maryland at College Park; Hector
Galbraith, Galbraith Environmental Sciences LLC; David Godschalk, University of North Carolina at
Chapel Hill; John Loomis, Colorado State University; George Luber, Centers for Disease Control and
Prevention; Michael McGeehin, Centers for Disease Control and Prevention; James E. Neumann,
Industrial Economics, Incorporated; W. Douglass Shaw, Texas A&M University; Arnold Vedlitz, Texas
A&M University; Sammy Zahran, Colorado State University
-------
SAP 4.6 Chapter 4: Human Welfare
TABLE OF CONTENTS
4.1 Introduction 3
4.2 Human Welfare, Well-being, and Quality of Life 4
4.2.1 Individual Measures of Well-being 5
4.2.2 The Social Indicators Approach 6
4.2.3 A Closer Look at Communities 10
4.2.4 Vulnerable Populations, Communities, and Adaptation 12
4.3 An Economic Approach to Human Welfare 13
4.3.1 Economic Valuation 15
4.3.2 Impacts Assessment and Monetary Valuation 16
4.3.3 Human Health 17
4.3.4 Ecosystems 22
4.3.5 Recreational Activities and Opportunities 28
4.3.6 Amenity Value of Climate 35
4.4 Conclusions 38
4.5 Expanding the Knowledge Base 39
4.6 References 41
4.7 Appendix 1 57
4.8 Boxes 64
4.9 Tables 66
4.10 Figures 72
4-2
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SAP 4.6 Chapter 4: Human Welfare
4.1 Introduction
Human welfare is an elusive concept, and there is no single, commonly accepted definition or
approach to thinking about welfare. Yet there is a shared understanding that human welfare,
well-being, and quality of life (terms that are often used interchangeably) refer to aspects of
individual and group life that improve living conditions and reduce chances of injury, stress, and
loss. The physical environment is one factor, among many, that may improve or reduce human
well-being. Climate is one aspect of the physical environment, and can affect human well-being
via economic, physical, psychological, and social pathways that influence individual perceptions
of quality of life.
Climate change may result in lifestyle changes and adaptive behavior with both positive and
negative implications for well-being. For example, warmer temperatures may change the amount
of time that individuals are comfortable spending outdoors in work, recreation, or other
activities, and temperature combined with other climatic changes may alter (or induce) changes
in intra- and inter-country human migration patterns. More generally, studies of climate change
and the United States identify an assortment of impacts on human health, the productivity of
human and natural systems, and human settlements. Many of these impacts—ranging from
changes in livelihoods to changes in water quality and supply—are linked to some aspect of
human well-being.
Communities are an integral determinant of human well-being. Climate change that affects
public goods—such as damaged infrastructure or interruptions in public services—or disrupts the
production of goods and services, will affect economic performance including overall health,
poverty, employment, and other measures. These changes may have consequences, such as a lost
job or a more difficult commute, that affect individual well-being directly. In other cases,
individual well-being may be indirectly affected due to concern for the well-being of other
individuals, or for a lack of cohesion within the community. The sustainability or resilience of a
community {i.e., its ability to cope with climate change and other stressors over the long term)
may be reduced by climate change weakening the physical and social environment. In the
extreme, such changes may undermine the individual's sense of security or faith in government's
capacity to accommodate change.
Completely cataloging the effects of global change on human well-being or welfare would be an
immense undertaking. Despite its importance, no well-accepted structure for doing so has been
developed and applied. Moreover, little (if any) research focuses explicitly on the impact of
global change on human well-being, per se. The chapter seeks to make a review of this topic
manageable by focusing on several discrete issues:
¦ Alternative approaches to defining and studying human well-being
¦ Identifying human well-being and quality of life measures and indicators (qualitative and
quantitative)
¦ Describing economic welfare and monetary methods of assigning value to climate
change's potential impacts
¦ Providing examples of climate change impacts on selected categories of well-being and
reporting indicators of economic welfare for these categories
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SAP 4.6 Chapter 4: Human Welfare
Section 4.2, focuses on valuation and non-monetary metrics and draws on the literature to
provide insights into a possible foundation for future research into the effects of climate change
on human well-being. This section first discusses the literature defining human well-being. Next,
it presents an illustrative place-based-indicators approach (the typical approach of planners and
policy makers to evaluating quality of life in communities, cities, and countries). Approaches of
this type represent a commonly accepted way of thinking about well-being that is linked to
objective (and sometimes subjective) measures. While a place-based indicators approach has not
been applied to climate change, it has the potential to provide a framework for identifying
categories of human well-being that might be affected by climate change, and for making the
identification of measures or metrics of well-being a more concrete enterprise in the future. To
illustrate that potential, the section draws links between community welfare and some of the
negative impacts of climate change.
Economics has been at the forefront of efforts to quantify the welfare impacts of climate change.
Economists employ, however, a very specific definition of well-being—economic welfare—for
valuing goods and services or, in this case, climate impacts. This approach is commonly used to
support environmental policy decision making in many areas. Section 4.3 very briefly describes
the basis of this approach, and the techniques that economists use (focusing on those that have
been applied to estimate impacts of climate change). This section next summarizes the existing
economic estimates of the non-market impacts of climate change.1 An accompanying appendix
provides more information on the economic approach to valuing changes in welfare, and
highlights some of the challenges in applying valuation techniques to climate impacts.
The fourth section of the chapter summarizes some of the key points of the chapter and the
chapter concludes with a brief discussion of research gaps.
4.2 Human Welfare, Well-being, and Quality of Life
No single, widely accepted definition exists for the term human welfare, or for related terms such
as well-being and quality of life, and they are all often used interchangeably (Veenhoven, 1988,
1996, 2000; Ng, 2003; Rahman, 2007). Academic economists, epidemiologists, health scientists,
psychologists, sociologists, geographers, political scientists, and urban planners have all rendered
their own definitions and statistical indicators of life quality at both individual and community
levels.2 For purposes of clarity in this chapter, from this point forward we adopt the convention
of the Millenium Assessment (MA, 2005) and the Intergovernmental Panel on Climate Change
(IPCC, 2007b), which use "well-being" as an umbrella term—referring broadly to the extent to
which human conditions satisfy the range of constituents of well-being, including health, social
relations, material needs, security, and freedom of choice. "Quality of life" is here used
1 Because more concrete aspects of welfare, such as impacts on prices or income, may be covered by other synthesis
and assessment products (see, for example, discussions of dollar values in SAP 4.3, The Effects of Climate Change
on Agriculture, Land Resources, Water Resources, and Biodiversity, which is in draft form at the time this is being
written), this report focuses exclusively on the types of intangible amenities that directly impact quality of life, but
are not traded in markets, including health, recreation, ecosystems, and climate amenities.
2 For example, In sociological literature, the terms well-being and welfare are used interchangeably to refer to
objectively measurable life chances and experiences, and the term quality of life is used to describe subjective
assessments and experiences of individuals.
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SAP 4.6 Chapter 4: Human Welfare
synonymously with well-being, to reflect usage in a wide range of disciplines, including medical,
sociological, psychological, and urban planning literatures. The term "welfare" is generally used
herein to refer narrowly to economic measures of individual well-being, although it is also used
in the context of communities in a broader sense.
Despite differences in definitions, human well-being—in its broadest sense—is typically a multi-
dimensional concept, addressing the availability, distribution, and possession of economic assets,
and non-economic goods such as life expectancy, morbidity and mortality, literacy and
educational attainment, natural resources and ecosystem services, and participatory democracy.
These conceptualizations often also include social and community resources (sometimes referred
to as social capital in social scientific literature), such as the presence of voluntary associations,
arts, entertainment, and shared recreational amenities (see Putnam, 1993, 2000). The quantity of
community resources shared by a population is often called social capital.3 These components of
life quality are interrelated and correlate with subjective valuations of life satisfaction, happiness,
pleasure, and the operation of successful democratic political systems (Putnam, 2000).
The concepts of well-being, economic welfare, and quality of life play important roles not only
in academic research, but also in practical analysis and policy making. Quality of life measures
may be used, for example, to gauge progress in meeting policy or normative goals in particular
cities by planners; municipalities in New Zealand, England, Canada, and United States have
constructed their own metrics of quality of life to estimate the overall well-being and life chances
available to citizens. Similarly, health-related quality of life measures can indicate progress in
meeting goals. For example, the U.S. Medicare program uses metrics to track quality of life for
beneficiaries and to monitor and improve health care quality (HCFR, 2004). Moreover,
international agencies from the United Nations Human Development Programme (UNDP) to the
Milllenium Ecosystem Assessment on Ecosystems and Human Well-Being and highly regarded
periodicals like The Economist, have built composite measures of human and societal well-being
to compare and rank nations of the world.4
Life quality and human well-being are increasingly important objects of theoretical and empirical
research in diverse disciplines. Two analytic approaches characterize the research literature:
(1) studies that emphasize well-being as an individual attribute or possession; and (2) studies that
treat well-being as a social or economic phenomenon associated with a geographic place.
4.2.1 Individual Measures of Well-being
Approaches focusing on individuals are generally found in medical, health, cognitive, and
economic sciences, and it is to these we turn first, and then next to place-focused indicators.
3 The concept of social capital has been defined, in different ways, by Putnam (1993, 1995, 2000) and by Coleman
(1988, 1990, 1993). For Coleman, social capital is a store of community value that is embodied in social structures
and the relations between social actors, from which individuals can draw in the pursuit of private interest. Putnam's
definition is similar, but places a stronger emphasis on altruism and community resources.
4 See, for example, the discussion of the sources of Table 1 subsequently in this chapter, which include a number of
country-level quality of life assessments. The UNDP Human Development Index, a country by country ranking of
quality of life indicators, can be accessed at http://hdr.undp.org/en/statistics/.
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SAP 4.6 Chapter 4: Human Welfare
4.2.1.1 Health Focused Approaches
In medical science, quality of life is used as an outcome variable to evaluate the effectiveness of
medical, therapeutic, and/or policy interventions to promote population health. Quality of life is
an individual's physiological state constituted by body structure, function, and capability that
enable pursuit of stated and revealed preferences. In medical science, the concept of life quality
is synonymous with good health - a life free of disease, illness, physical, and/or cognitive
impairment (Raphael et al., 1996, 1999, 2001).
In addition to objective measures of physical and occupational function, disease absence, or
somatic sensation, life quality scientists measure an individual's perception of life satisfaction.
The scientific basis of such research is that pain and/or discomfort associated with a
physiological impairment are registered and experienced variably. Based on patient reports or
subjective valuations, psychologists and occupational therapists have developed valid and
reliable instruments to assess how mental, developmental, and physical disabilities interfere with
the performance and enjoyment of life activities (Bowling, 1997; Guyatt et al., 1993).
4.2.1.2 Economic and Psychological Approaches
Individual valuations of life quality also anchor economic and psychological investigations of
happiness and utility. In the new science of happiness, scholars use the tools of neuroscience,
experimental research, and modern statistics to discover and quantify the underlying
psychological and physiological sources of happiness (for reviews see Kahneman et al., 1999;
Frey and Stutzer, 2002; Kahneman and Krueger, 2006). Empirical studies show, for example,
that life satisfaction and happiness correlate predictably with marital status (married persons are
generally happier than single people), religiosity (persons that practice religion report lower
levels of stress and higher levels of life satisfaction), and individual willingness to donate time,
money and effort to charitable causes. Similarly, the scholarly literature notes interesting
statistical associations between features of climate (such as variations in sunlight, temperature,
and extreme weather events) and self-reported levels of happiness, utility, or life satisfaction.
Individual valuations of health, psychological, and emotional well-being are sometimes summed
across representative samples of a population or country to estimate correspondences between
life satisfaction and "hard" indicators of living standards such as income, life expectancy,
educational attainment, and environmental quality. Cross-national analyses generally find that
population happiness or life satisfaction increases with income levels and material standards of
living (Ng, 2003) and greater personal autonomy (Diener et al., 1995; Diener and Diener,
1995).5 In such studies, subjective valuations of life satisfaction are embedded in broader
conceptions of quality of life associated with the conditions of a geographic place, community,
region or country—the social indicators approach.
4.2.2 The Social Indicators Approach
In this second strand of research, what some refer to as the social indicators approach, scholars
assemble location-specific measures of social, economic, and environmental conditions, such as
5Some studies suggest that individual utility or happiness is not positively determined by some absolute quantity of
income, wealth, or items consumed, but rather how an individual perceives his or her lot in relation to others or to
conditions in their past. See, for example, Frank 1985.
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SAP 4.6 Chapter 4: Human Welfare
employment rates, consumption flows, the availability of affordable housing, rates of crime
victimization and public safety, public monies invested in education and transportation
infrastructure, and local access to environmental, cultural, and recreational amenities. These
place-specific variables are seen as exogenous sources of individual life quality. Scholars reason
that life quality is a bundle of conditions, amenities, and lifestyle options that shape stated and
revealed preferences. In technical terms, the social indicators approach treats quality of life as a
latent variable, jointly determined by several causal variables that can be measured with
reasonable accuracy.
The indicators approach has several advantages in the context of understanding the impacts of
climate change on human well-being. First, social indicators have considerable intuitive appeal,
and their widespread use has not only made it familiar to both researchers and the general public,
but has subjected them to considerable debate and discussion. Second, they offer considerable
breadth and flexibility in terms of categories of human well-being that can be included. Third,
for many of the indicators or dimensions of well-being, objective metrics exist for measurement.
In addition, while its strength is in providing indicators of progress on individual dimensions of
quality of life, the indicators approach has also been used to support aggregate or composite
measures, at least for purposes of ranking or measuring progress. Various techniques are also
available, or being developed, that aggregate or combine measures of well-being. These range
from pure data reduction procedures to stakeholder input models where variables are evaluated
on their level of social and economic importance. For example, Richard Florida (2002a) has
constructed a statistical index of technology, talent, and social tolerance variables to estimate the
human capital of cities in the United States. Given the analytical strengths of the social indicators
approach, it may be a good starting point for understanding the relationships between human
well-being and climate change.
4.2.2.1 A Taxonomy of Categories of Wellbeing
Taxonomies of place-specific well-being or quality of life typically converge on six categories or
dimensions: (1) economic conditions; (2) natural resources, environment, and amenities; (3)
human health; (4) public and private infrastructure; (5) government and public safety; and (6)
social and cultural resources. These categories represent broad aspects of personal and family
circumstances, social structures, government, environment, and the economy that influence well-
being. Table 4.1 illustrates these categories, which are listed in Column 1. The third column,
"components/indicators of welfare" provides examples of the way in which these categories are
often interpreted. These components represent what, in an ideal world, researchers would wish to
measure in order to determine how a specific society fares from the perspective of well-being.
The fourth column provides illustrative metrics, i.e., objective or quantifiable measures that are
often used by researchers as indicators of well-being for each category.6 Finally, the last column
provides some examples of climate impacts that may be linked to that category. This column
should not be viewed as an attempt to create a comprehensive list of impacts, or even to list
6 Sources that contributed to the development of Table 1 include: MA (2005); Sufian, 1993; Rahman, 2007, and
Lambiri, el al., 2007. Insights were also derived from quality of life studies of individual cities and countries,
including: http://www.bigcities.govt.nz/indicators.htm Quality of Life in New Zealand's Large Urban Areas',
http://www.asu.edu/copp/morrison/public/aofl99.htm What Matters in Greater Phoenix 1999 Edition: Indicators of
Our Quality of Life; and http://www.icci.org/statistics/qualitvoflife.aspx Tracking the Quality of Life in
Jacksonville.
4 -7
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SAP 4.6 Chapter 4: Human Welfare
impacts with equal weights, in terms of importance or likelihood of occurrence. Further, while
Table 4.1 focuses on negative impacts (as potentially more troubling for quality of life), there are
also opportunities or potential positive impacts that will result in some categories.
These categories of well-being or life quality are interrelated. For example, as economic or social
conditions in a society improve (e.g., as measured by GDP per capita and rates of adult literacy),
improvements occur in human health outcomes such as infant mortality, rates of morbidity, and
female life expectancy at birth. Thus, while the categories and corresponding metrics of well-
being presented in Table 4.1 are analytically separable, in reality they are highly interconnected.7
Economics as a source of quality of life refers to a mix of production, consumption, and
exchange activities that constitute the material well-being of a geographic place, community,
region or country. Standard components of economic well-being include income, wealth,
poverty, employment opportunities, and costs of living. Localities characterized by efficient and
equitable allocation of economic rewards and opportunities enable material security and
subjective happiness of residents (Florida, 2002a).
Natural resources, environment, and amenities as a source of well-being refers to natural
features, such as ecosystem services, species diversity, air and water quality, natural hazards and
risks, parks and recreational amenities, and resource supplies and reserves. Natural resources and
amenities directly and indirectly affect economic productivity, aesthetic and spiritual values, and
human health (Blomquist et al., 1988; Glaeser et al., 2001; Cheshire and Magrini, 2006).
Human health as a source of well-being includes features of a community, locality, region or
country that influence risks of mortality, morbidity, and the availability of health care services.
Good health is desirable in itself as a driver of life expectancy (and the quality of life during
those years), and is also critical to economic well-being by enabling labor force participation
(Raphael etal., 1996, 1999, 2001).
Public and private infrastructure sources of well-being include transportation, energy and
communication technologies that enable commerce, mobility, and social connectivity. These
technologies provide basic conditions for individual pursuits of well-being (Lambiri et al., 2007).
Government and public safety as a source of well-being are activities by elected representatives
and bureaucratic officials that secure and maximize the public services, rights, liberties, and
safety of citizens. Individuals derive happiness and utility from the employment, educational,
civil rights, public service, and security efforts of their governments (Suffian, 1993).
Finally, social and cultural resources as a source of well-being are conditions of life that
promote social harmony, family and friendship, and the availability of arts, entertainment, and
leisure activities that facilitate human happiness. The terms social and creative capital have
7 More recently, scholars (Costanza et al. 2007) and government agencies (like NOAA's Coastal Service Center)
have moved toward the global concept of capital to integrate indicators and assess community quality of life. The
term capital is divided into four types: economic; physical; ecological or natural; and socio-cultural. Various metrics
constitute these types of capital, and are understood to foster community resilience and human needs of subsistence,
reproduction, security, affection, understanding, participation, leisure, spirituality, creativity, identity, and freedom
See also Rothman, Amelung, and Poleme (2003).
4 -8
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SAP 4.6 Chapter 4: Human Welfare
become associated with these factors. Communities with greater levels of social and creative
capital are expected to have greater individual and community quality of life (Putnam, 2000;
Florida, 2002b).
In thinking about these indicators, it is important to keep two important contextual realities about
climate change and well-being at the forefront. First, while discussions of climate change usually
have a global resonance to them, the fact is that the effects of any specific changes in
temperature, rainfall, storm frequency/intensity and sea level rise will be felt at the local and
regional level by citizens and communities living and working in those vulnerable areas.
Therefore, not all populations will be placed under equal amounts of climate change-generated
stress. Some will experience greater impacts, will suffer greater damage, and will need more
remediation and better plans and resource allocations for adaptation and recovery efforts to
protect and restore quality of life (see, for example, Zahran et al., 2008; Liu, Vedlitz and Alston,
2008; Vedlitz et al., 2007).
Second, not all citizens in areas more vulnerable to climate change effects are equally at risk.
Some population groupings, within the same community, will be more vulnerable and at risk
than others. Those who are poorer, minorities, aged or infirmed, and children are at greater risk
than others to the stresses of climate change events (Lindell and Perry, 2004; Peacock, 2003).
Recognizing that not all citizens of a particular vulnerable area share the same level of risk is
something that planners and decision makers must take into account in projecting the likely
impacts of climate change events on their populations, and in dealing with recovery of those
populations (Murphy and Gardoni, 2008).
Finally, the situation is further complicated as climate stressors negatively affect disease
conditions in other nations with particularly vulnerable and mobile populations. Increased
communicable disease incidence in developing nations have the potential, through legal and
illegal tourism and immigration, to affect community welfare and individual well-being in the
United States.
4.2.2.2 Climate Change and Quality of Life Indicators
Social indicators are generally used to evaluate progress towards a goal: How is society doing?
Who is being affected? Tracking performance for these indicators using the types of metrics
or measures indicated in Table 4.1—could provide information to the public on how
communities and other entities are reacting to, and successfully adapting to (or failing to adapt
to), climate change. The indicators and metrics included in Table 4.1 are intended to be
illustrative of the types of indicators that might be used, rather than a comprehensive or
recommended set. In any category, multiple indicators could be used; and any one of the
indicators could have several measures. For example, exposure to natural hazards and risks could
be measured by the percentage of a locality's tax base located in a high hazard zone, the number
of people exposed to a natural hazard, the funding devoted to hazard mitigation, or the costs of
hazard insurance, among others. Similarly, some indicators are more amenable to objective
measurement; others are more difficult to measure, such as measures of social cohesion. The
point to be taken from Table 4.1 is that social indicators provide a diverse and potentially rich
perspective on human well-being.
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SAP 4.6 Chapter 4: Human Welfare
The taxonomy presented in Table 4.1—or a similar taxonomy—might also provide a basis for
analyses of the impacts of climate change on human well-being, providing a list of important
categories for research (the components or indicators of life quality), as well as appropriate
metrics (e.g., employment, mortality or morbidity, etc.). The social indicators approach, and the
specific taxonomy presented here, are only one of many that could be developed.8 At the least,
different conditions and stakeholder mixes may demand different emphases. All taxonomies,
however, face a common problem: how to interpret and use the diverse indicators, in order to
compare and contrast alternative adaptive or mitigating responses to climate change. For some
purposes, metrics have been developed that that aggregate across individuals or individual
categories of well-being and present a composite measure of well-being; or otherwise
operationalize related concepts, such as vulnerability (see, for example the discussion of Figure
4.1).
Figure 4.1 Geography of Climate Change Vulnerability at the County Scale
4.2.3 A Closer Look at Communities
Looking beyond well-being of individuals to the welfare (broadly speaking) of communities—
networks of households, businesses, physical structures, and institutions—provides a broader
perspective on the impacts of climate change. The categories and metrics in Table 4.1 are
appealing from an analytical perspective in part because they represent dimensions of well-being
that are clearly important to individuals, but that also have counterparts and can generally be
measured objectively at the community level. Thus, for example, the counterparts of individual
income or health status are, at the social level, per capita income or mortality/illness rates. The
concept of community welfare is linked to human communities, but is not confined to
communities in urban areas, or even in industrialized cultures. Human communities in remote
areas, or subsistence economies, face the same range of quality of life issues—from health to
spiritual values—although they may place different weights on different values; thus, the weights
placed on different components of welfare are not determined a priori, but depend on
community values and decision making.
Viewing social indicators and metrics through the lens of the community can be instructive in
several ways. First, communities are dynamic entities, with multiple pathways of interactions
among people, places, institutions, policies, structures, and enterprises. Thus, while the social
indicators described in Table 4.1 have metrics that can be measured independently of each other,
they are not determined independently within the complex reality of interdependent human
systems. Second, in part because of this interdependence, the aggregate welfare of a community
is more than a composite of its quality of life metrics; sustainability provides one means of
approaching a concept of aggregate welfare. Third, vulnerability and adaptation are typically
analyzed at the sectoral level: "what should agriculture, or the public health system, do to plan
for or adapt to climate change." The issue can also, however, be addressed at the level of the
community. Each of these issues is touched on below.
8 In addition to variants on the social indicators approach, other types of taxonomies are possible—for example a
taxonomy based on broad systems (atmospheric, aquatic, geologic, biological, and built environment), or on forms
of capital that make up the productive base of society (natural, manufactured, human, and social). Well-being can
also be viewed in terms of its endpoints: necessary material for a good life, health and bodily well-being, good social
relations, security, freedom and choice, and peace of mind and spiritual existence (Rothman, Amelung, and Poleme.,
2003).
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4.2.3.1 Community Welfare and Individual Well-being
Rapid onset extreme weather events, such as hurricanes or tornadoes, can do serious damage to
community infrastructure, public facilities and services, tax base, and overall community
reputation and quality of life, from which recovery may take years and never be complete (see
additional discussion in Chapter 3). More gradual changes in temperature and precipitation will
have both negative and positive effects. For example, as discussed elsewhere in this chapter,
warmer average temperatures increase risks from heat-related mortality in the summer, but
decrease risks from cold-related mortality in the winter, for susceptible populations. Effects such
as these will not, however, be confined to a few individual sectors, nor are the effects across all
sectors independent.
To illustrate the interdependence of impacts and, by extension, the analogous social indicators
and metrics, consider a natural resource that faces additional stresses from climate change: fish
populations in estuaries, such as the Chesapeake Bay, that are already stressed by air and water
pollution from industry, agriculture, and cities. In this case, while the direct effects of climate
will occur to the resource itself, indirect effects can alter welfare as measured by economic,
social, and human health indicators. Table 4.2 presents some of the possible pathways by which
resource changes could affect diverse categories of quality of life; the purpose of Table 4.2 is not
to assert that all these effects will occur or that they will be significant if they do occur as a result
of climate change, but rather to illustrate the linkages. These linkages underscore the importance
of understanding interdependencies within the community or, from another perspective, across
welfare indicators. Table 4.2 illustrates the general principle of complex linkages in which a
general equilibrium approach can be used to model climate change impacts.
4.2.3.2 Sustainability of Communities
Understanding how climate change and extreme events affect community welfare requires a
different conceptual framework than that for understanding individual level impacts, such as
quality of life.9 Communities are more than the sum of their parts; they have unique aggregate
identities shaped by dynamic social, economic, and environmental components. They also have
life cycles, waxing and waning in response to societal and environmental changes (Diamond,
2005; Fagan, 2001; Ponting, 1991; Tainter, 1988). Sustainability is a paramount community
goal, typically expressed in terms of sustainable development in order to express the ongoing
process of adaptation into the long-term future. "Climate change involves complex interactions
between climatic, environment, economic, political, institutional, social, and technological
processes. It cannot be addressed or comprehended in isolation from broader societal goals (such
as sustainable development)..." (Banuri and Weyant, 2001). Even for a country as developed as
the US, continuing growth and development creates both pressures on the natural and built
environments and opportunities for moving in sustainable directions.
While the term sustainability does not have a single, widely-accepted definition, a central
guideline is to balance economic, environmental, and social needs and values (Campbell, 1996;
9 Measures of quality of life provide a database of relevant individual characteristics at various points in time,
including economic conditions, natural resources and amenities, human health, public and private infrastructure,
government and public safety, and social and cultural resources. Sustainable development measures are similar, but
reflect more emphasis on long-term and reciprocal effects, as well as a concern for community-wide and equitable
outcomes.
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Berke et al., 2006), sometimes portrayed as a three-legged stool. It is distinguished from quality
of life by its dynamic linking of economic, environmental, and social components, and by its
future orientation (Campbell, 1996; Porter, 2000). Sustainability is seen as living on nature's
"interest," while protecting natural capital. Sustainability is a comprehensive social goal that
transcends individual sector or impact measurements, although it can include narrower
community welfare concepts such as the healthy city. Thinking about the impacts of climate
change on communities through the lens of sustainable development allows us to envision cross-
sector economic, environmental, and social dynamics.
4.2.4 Vulnerable Populations, Communities, and Adaptation
Responding to climate change at the community level requires understanding both vulnerability
and adaptive responses that the community can take. Vulnerability of a community depends on
its exposure to climate risk, how sensitive systems within that community are to climate
variability and change, and the adaptive capacity of the community {i.e., how it is able to respond
and protect its citizens from climate change). Different groups within the community will be
differentially vulnerable to climate changes, such as extreme events, and infrastructure and
community coping capacity will be more or less effective in invoking a resilient response to
climate change.
4.2.4.1 Vulnerable Populations
Categories of persons susceptible to environmental risks and hazards include racial and ethnic
groups (Bolin, 1986; Fothergill etal., 1999; Lindell and Perry, 2004; Cutter, 2006), and groups
defined by economic variables of wealth, income, and poverty (Peacock, 2003; Dash et al., 1997;
Fothergill and Peek, 2004). Overall, research indicates that minorities and the poor are
differentially harmed by disaster events. Economic disadvantage, lower human capital, limited
access to social and political resources, and residential choices are social and economic reasons
that contribute to observed differences in disaster vulnerability by race/ethnicity and economic
status. While the literature on climate change and vulnerable populations is relatively
underdeveloped, Chapter 2 on Human Health and Chapter 3 on Human Settlements each address
population vulnerabilities.
Economic, social and health effects are not neatly bounded by geographic or political regions,
and so the damage and stresses that occur in a specific locality are not limited in their effects to
only that community. As Hurricane Katrina made clear, impacts felt in one community ripple
throughout the region and nation. Persons made homeless in New Orleans resettled in Baton
Rouge, Lafayette and Houston, creating stresses on those communities. Vulnerable groups
migrate from stricken areas to more hospitable ones, taking their health, economic and
educational needs and problems with them across both national and state lines
4.2.4.2 Vulnerable Communities
While most analyses of vulnerability tend to be conducted at the regional scale, Zahran et al.
(2008) have brought the analysis closer to the community level by mapping the geography of
climate change vulnerability at the county scale. The study uses measures of both physical
vulnerability (expected temperature change, extreme weather events, and coastal proximity) and
adaptive capacity (as represented by economic, demographic, and civic participation variables
that constitute a locality's socioeconomic capacity to commit to costly climate change policy
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initiatives). Their map identifies the concentrations of highly vulnerable counties as lying along
the east and west coasts and Great Lakes, with medium vulnerability counties mostly inland in
the southeast, southwest, and northeast. (See Figure 4.1, in which darker areas represent higher
vulnerability).
Many possible dimensions can be used to identify and measure vulnerabilities to climate change
impacts and stressors. The one presented in Figure 4.1 illustrates that the concept of vulnerability
is a viable one and can be measured and applied to communities in a GIS context. It is not the
purpose of this chapter to focus in great detail on vulnerability measurement issues (for those
interested in other formulations of the vulnerability concept, see Dietz et al., In Press).
4.2.4.3 Adaptation
From the perspective of the community, the goal of successful adaptation to climate impacts—
particularly potentially adverse impacts—is to maintain the long-term sustainability and survival
of the community. Thus, a resilient community is capable of absorbing climate changes and the
shocks of extreme events without breakdowns in its economy, natural resource base, or social
systems (Godschalk, 2003). Given their control over shared resources, communities have the
capacity to adapt to climate change in larger and more coordinated ways than individuals, by
creating plans and strategies to increase resilience in the face of future shocks, while at the same
time ensuring that the negative impacts of climate change do not fall disproportionately on their
most vulnerable populations and demographic groups (Smit and Pilifosova, 2001).
Public policies and programs are in place in the United States to enhance the capacity of
communities to mitigate10 damage and loss from natural hazards and extreme events (Burby,
1998; Mileti, 1999; Godschalk, 2007). A considerable body of research looks at responses to
natural hazards, and recent research has shown that the benefits of natural hazard mitigation at
the national level outweigh its costs by a factor of four to one on average (Multihazard
Mitigation Council, 2005; Rose et al., 2007). Research also has been done on the social
vulnerability of communities to natural hazards (Cutter et al., 2003) and the economic resilience
of businesses to natural hazards (Tierney, 1997; Rose, 2004). However, there is scant research on
U.S. policies dealing with community adaptation to the broader impacts of climate change.
4.3 An Economic Approach to Human Welfare
Welfare, well-being, and quality of life are often viewed as multi-faceted concepts. In subjective
assessments of happiness or quality of life (see the discussion in Section 4.2), the individual
makes a net evaluation of his or her current state, taking into account (at least implicitly) and
balancing all the relevant facets or dimensions of that state of being. Constructing an overall
statement regarding welfare from a set of objective measures, however, requires a means of
weighting or ranking, or otherwise aggregating, these measures. The economic approach supplies
one—although not the only possible—approach to aggregation.11
10 In the natural hazards and disasters field, a single term—mitigation—refers both to adaptation to hazards and
mitigation of their stresses. (See the Disaster Mitigation Act of 2000, Public Law 106-390.)
11 In part because of the difficulty in compiling the information needed for aggregation of economic measures,
Jacoby (2004) proposes a portfolio approach to benefits estimation, focusing on a limited set of indicators of global
climate change, of regional impact, and one global monetary measure. The set of measures would not be the only
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Quantitative measures of welfare that use a common metric have two potential advantages. First,
the ability to compare welfare impacts across different welfare categories makes it possible to
identify and rank categories with regard to the magnitude or importance of effects. Welfare
impacts can then provide a signal about the relative importance of different impacts, and so help
to set priorities with regard to adaptation or research. Second, if the concept of welfare is
(ideally) a net measure, then it should be possible to aggregate the effects of climate across
disparate indicators. Quantitative measures that use the same metric can, potentially, be summed
to generate net measures of welfare, and gauge progress over time, or under different policy or
adaptation scenarios.
Given the value of welfare both as a multi-dimensional concept, and as one that facilitates
comparisons, the economic approach to welfare analysis—which monetizes or puts dollar values
on impacts—is one means of comparing disparate impacts. Further—and this is the second
advantage of the economic approach—dollar values of impacts can be aggregated, and so
provide net measures of changes in impacts that can be useful to policy makers. This section of
the chapter discusses the foundation of economic valuation, the distinction between market and
non-market effects (only the latter are covered in this paper), and describes some of the valuation
tools that economists use for non-market effects. An appendix covers these issues in additional
detail, and also describes the challenges that economic valuation faces when used as a tool for
policy analysis in the long term context of climate change.
Fundamental to the economic approach is a notion that a key element of support for decision-
making is an understanding of the magnitude of costs and benefits, so that the tradeoffs implicit
in any decision can be balanced and compared. However, the economic approach, when
interpreted as requiring a strict cost-benefit test, is not appropriate in all circumstances, and is
viewed by some as controversial in the context of climate change.12 Benefit cost analysis is one
tool available to decision makers; in the context of climate change; other decision rules and tools,
or other definitions of welfare, may be equally, or more relevant. For example, the recent
Synthesis Report of the IPCC Fourth Assessment (IPCC, 2007a) presents an average social cost
{i.e., damages) of carbon in 2005 of $12 per ton of CO2, but also notes that the range of the
roughly 100 peer-reviewed estimates of this value is -$3 to $95/tCC>2.13 IPCC attributes this very
broad range to differences in assumptions on climate sensitivity, response lags, the treatment of
risk and equity, economic and non-economic impacts, the inclusion of potentially catastrophic
losses, and discount rates. IPCC therefore suggests consideration of an "iterative risk
management process" to support decision-making.14 Estimated benefits and costs therefore can
provide information relevant to decision makers, but some of the methodologies and data
information generated and made available, but it would represent a set of variables continuously maintained and
used to describe policy choices.
12 See Arrow el al., 1996 - at page 7, "There may be factors other than economic benefits and costs that agencies will
want to weigh in decisions, such as equity within and across generations. In addition, a decision maker may want to
place greater weight on particular characteristics of a decision, such as potential irreversible consequences."
13 See IPCC 2007a, page 23.
14 IPCC further notes that existing analyses suggest costs and benefits of mitigation are roughly comparable in
magnitude, "but do not as yet permit an unambiguous determination of an emissions pathway or stabilization level
where benefits exceed costs." (IPCC 2007a page 23).
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necessary to provide a relatively complete assessment may be unavailable, as discussed
subsequently in this section.15
4.3.1 Economic Valuation
The framework that economists employ reflects a specific view of human welfare and how to
measure it. Economists define the value of something—be it a good, service, or state of the
world—by focusing on the well-being, utility, or level of satisfaction that the individual derives.
The basic economic paradigm assumes that individuals allocate their available income and time
to achieve the greatest level of satisfaction. The value of a good—in terms of the utility or
satisfaction it provides—is revealed by the tradeoffs that individuals make between that good
and other goods, or between that good and income.16 The term "willingness to pay" (WTP) is
used by economists to represent the value of something, i.e., the individual's willingness to trade
money for that particular good, service, or state of the world.
Economists distinguish between market and non-market goods. Market goods are those that can
be bought and sold in the market, and for which a price generally exists. Market behavior and, in
particular, the prices that are paid for these goods, is a source of information on the economic
value or benefit of these goods. The economic benefit—the amount that members of society
would in aggregate be willing to pay for these goods—is related to, but frequently greater than,
market prices.
Non-market goods are those that are not bought and sold in markets. Consequently, climate
change impacts that involve non-market effects—such as health effects, loss of endangered
species, and other effects—are difficult to value in monetary terms. Economists have developed
techniques for measuring non-market values, by inferring economic value from behavior
(including other market behavior), or by asking individuals directly.
A number of studies have attempted to value the range of effects of climate change. For the US,
some of the most comprehensive studies are the Report to Congress completed by U.S. EPA in
1989 (U.S. EPA, 1989), Cline (1992), Nordhaus (1994), Fankhauser (1995), Mendelsohn and
Neumann (1999), Nordhaus and Boyer (2000), and a body of work by Richard Tol (e.g., Tol,
2002 and Tol, 2005). In all of these studies, the focus is largely on market impacts, particularly
the effects of climate change on agriculture, forestry, water resource availability, energy demand
(mostly for air conditioning), coastal property, and in some cases, health.
Non-market effects, however, are less well characterized in these studies (Smith et al., 2003);
where comprehensive attempts are made, they usually involve either expert judgment or very
rudimentary calculations, such as multiplying the numbers of coastal wetland acres at risk of
inundation from sea-level rise by an estimate of the average non-market value of a wetland. One
such comprehensive attempt generated a value for 17 ecosystem services from 16 ecosystem
types (Costanza et al., 1997), but also generated controversy and criticism from many
15 Other factors that might be considered, in addition to economic estimates, include emotions, perceptions, cultural
values, and other subjective factors, all of which can play a role in creating preferences and reaching decisions.
Those factors are beyond what we can evaluate in this chapter.
16 Although economists are careful to distinguish between the metrics of utility and money as distinct, valuation
metric in dollar units (rather than units of utility) may be generally viewed as the outcomes of individual preference
expressions among goods, income, and time.
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economists (Bockstael etal., 2000; Toman, 1998; see National Research Council 2004 for a
summary). Other analysts have attempted to define measures to reflect non-market ecosystem
services in terms similar to those used for Gross Domestic Product (Boyd, 2006), or indicators of
ecosystem health that reflect ecological contributions to human welfare (Boyd and Banzhaf,
2006).17 While there are several well-done valuation analyses for non-market effects of climate
change (as described later in this chapter), it is fair to characterize this literature as opportunistic
in its focus; where data and methods exist, there are high quality studies, but the overall coverage
of non-market effects remains inadequate.
4.3.2 Impacts Assessment and Monetary Valuation
The process of estimating the welfare effects of climate change involves four steps: (1) estimate
climate changes; (2) estimate physical effects of climate change, (3) estimate the impacts on
human and natural systems that are amenable to valuation and (4) value or monetize effects. The
first step requires estimating the change in relevant measures of climate, including temperature,
precipitation, sea-level rise, and the frequency and severity of extreme events. The second step
involves estimating the physical effects of those changes in climate. Such effects might include
changes in ecosystem structure and function, human exposures to heat stress, changes in the
geographic range of disease vectors, or flooding of coastal areas. In the third step, the physical
effects of climate change are translated into measures that economists can value, for example the
number and location of properties that are vulnerable to floods, or the number of individuals
exposed to and sensitive to heat stress. Many analyses that reach this step in the process, but not
all, also proceed on to the fourth step, valuing the changes in dollar terms. .
The simplest approach to valuation would be to apply a unit valuation approach - for example,
the cost of treating a nonfatal case of heat stress or malaria attributable to climate change is a
first approximation of the value of avoiding that case altogether. In many contexts, however, unit
values can misrepresent the true marginal economic impact of these changes. For example, if
climate change reduces the length of the ski season, individuals could engage in another
recreational activity, such as golf. Whether they might prefer skiing to golf at that time and
location is something economists might try to measure.
This step-by-step linear approach to effects estimation is sometimes called the "damage
function" approach. A damage function approach might imply that we look at effects of climate
on human health as separate and independent from effects on ecology and recreation, an
assumption that ignores the complex economic interrelationships among goods and services and
individual decisions regarding these. Recent research suggests that the damage function
approach, under some conditions, may be both overly simplistic (Freeman, 2003) and sometimes
subject to serious errors (Strzepekand Smith, 1995; Strezpek et al., 1999).
Economists have a number of techniques available for moving from quantified effects to dollar
values. In some cases, the values estimated in one situation—e.g., one ecosystem or species—
can be transferred and used to value another. For example, value or benefits transfer is
commonly used by federal agencies such as the US EPA and US Forest Service to value
recreation when there is insufficient time or budget to conduct original valuation studies
17 Some political economists also emphasize the role of explicit recognition of non-market environmental values as
an important step in improving the well-being of poor populations (Boyce and Shelley, 2003).
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(Rosenberger and Loomis, 2003). Techniques commonly used by economists to value non-
market goods and services include:
¦ Revealed preference. Revealed preference, sometimes referred to as the indirect valuation
approach, involves inferring the value of a non-market good using data from market
transactions (U.S. EPA, 2000; Freeman, 2003). For example, the value of a lake for its
ability to provide a good fishing experience can be estimated by the time and money
expended by the angler to fish at that particular site, relative to all other possible fishing
sites. Or, the amenity value of a coastal property that is protected from storm damage (by
a dune, perhaps) can be estimated by comparing the price of that property to other
properties similar in every way but the enhanced storm protection.
¦ Stated preference. Stated preference methods, sometimes referred to as the direct
valuation, are survey methods that estimate the value individuals place on particular non-
market goods based on choices they make in hypothetical markets. The earliest stated
preference studies involved simply asking individuals what they would be willing to pay
for a particular non-market good. The best studies involve great care in constructing a
credible, though still hypothetical, trade-off between money and the non-market good of
interest (or bundle of goods) to discern individual preferences for that good and hence,
WTP.
¦ Replacement or avoided costs. Replacement cost studies approach non-market values by
estimating the cost to replace the services provided to individuals by the non-market
good. For example, healthy coastal wetlands may provide a wide range of services to
individuals who live near them (such as filtering pollutants present in water). A
replacement cost approach would estimate the value of these services by estimating
market costs for replacing the services provided by the wetlands. Analogously, the cost of
health effects can be estimated using the cost of treating illness and of the lost workdays,
etc. associated with illness.
¦ Value of inputs. This approach calculated value based on the contribution of an input into
some productive process. This approach can be used to determine the value of both
market and non-market inputs, for example, fertilizer, water, or soil, in farm output and
profits
In the remainder of this section, we briefly discuss the relationship between climate change and
four non-market effects (human health, ecosystems, recreation and tourism, and amenities), and
discuss economic estimates of these effects using these techniques.
4.3.3 Human Health
In the US, climate change is likely to measurably affect health outcomes known to be associated
with weather and climate, including heat-related illnesses and deaths , health effects due to
storms, floods, and other extreme weather events, health effects related to poor air quality, water-
and food-borne diseases, and insect-,tick-,and rodent-borne diseases. In addition to changes in
mortality and morbidity, climate change may affect health in more subtle ways. Good health is
more than the absence of illness; it includes mental health, the ability to function physically (to
climb stairs or walk a mile), socially (to move freely in the world), and in a work environment.
Please see Chapter 2 of this report, which provides an overview of health effects that have been
associated with climate change.
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Despite our understanding of the pathways linking climate and health effects, there is uncertainty
as to the magnitude and geographic and temporal variation of possible impacts on morbidity and
mortality in the US, primarily due to a poor understanding of many key risk factors and
confounding issues, such as behavioral adaptation and variability in population vulnerability
(Patz et al., 2001). Even where our understanding of underlying climate and health relationships
is better, few studies have attempted to explicitly link these findings to climate change scenarios
to quantitatively estimate health impacts. Economists have relatively well established (although
sometimes controversial) techniques for valuing mortality and some forms of morbidity, which
could, in theory be applied to quantified impacts assessments.
4.3.3.1 Overview of Health Effects of Climate Change
The US is a developed country with a temperate climate. It has a well-developed health
infrastructure and government and non-governmental agencies involved in disaster planning and
response, both of which can help to mitigate potential health effects from climate change.
Nevertheless, certain regions of the US will face difficult challenges arising from some of the
following health effects.
¦ Illnesses and deaths due to heatwaves. A likely impact in the US is an increase in the
severity, duration, and frequency of heatwaves (Kalkstein and Greene, 1997; IPCC,
2007c). This, coupled with an aging (and therefore more vulnerable) population, will
increase the likelihood of higher mortality from exposure to excessive heat (see, for
example, Semenza et al., 1996, and Knowlton etal., 2007).
¦ Injuries and death from extreme weather events. Climate change is projected to alter the
frequency, timing, intensity, and duration of extreme weather events, such as hurricanes
and floods (Fowler and Hennessey, 1995). The health effects of these extreme weather
events range from the direct effects, such as loss of life and acute trauma, to indirect
effects, such as loss of shelter, large-scale population displacement, damage to sanitation
infrastructure (drinking water and sewage systems), interruption of food production,
damage to the health care infrastructure, and psychological problems such as post
traumatic stress disorder (Curriero et al., 2001).
¦ Illnesses and deaths due to poor air quality. Climate change can affect air quality by
modifying local weather patterns and pollutant concentrations (such as ground level
ozone), by affecting natural sources of air pollution, and by changing the distribution of
airborne allergens (Morris etal., 1989; Sillman and Samson, 1995). Many of these effects
are localized and, for ozone, compounded by assumptions of trends in precursor
emissions. Despite these uncertainties, all else being equal, climate change is projected to
contribute to or exacerbate ozone-related illnesses.
¦ Water- andFoodborne Diseases. Altered weather patterns, including changes in
precipitation, temperature, humidity, and water salinity, are likely to affect the
distribution and prevalence of food- and waterborne diseases resulting from bacteria,
overloaded drinking water systems, and increases in the frequency and range of harmful
algal blooms (Weniger etal., 1983; MacKenzie etal., 1994; Lipp and Rose, 1997;
Curriero et al., 2001).
¦ Insect-, Tick-, and Rodent-borne Diseases. Vector-borne diseases, such as plague,
Lyme's disease, malaria, hanta virus, and dengue fever have distinct seasonal pattern,
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suggesting that they may be sensitive to climate-driven changes in rainfall and
temperature (Githeko and Woodward, 2003). Moderating factors, such as housing
quality, land-use patterns, vector control programs, and a robust public health
infrastructure, are likely to prevent the large-scale spread of these diseases in the United
States.
4.3.3.2 Quantifying the Health Impacts of Climate Change
A large epidemiological literature exists on the health effects associated with climate change,
particularly the mortality effects associated with increases in average monthly or seasonal
temperature, and with changes in the intensity, frequency, and duration of heatwaves. As
described in Chapter 2, there is considerable speculation concerning the balance of climate
change-related decreases in winter mortality compared with increases in summer mortality,
although researchers suspect that declines in winter mortality associated with climate change are
unlikely to outweigh increases in summer mortality (McMichael el a I., 2001; Kalkstein and
Greene, 1997; Davis, 2004).
Net changes in mortality are difficult to estimate because, in part, much depends on complexities
in the relationship between mortality and the changes associated with global change. Using
average temperatures to estimate cold-related mortality, for example, is complicated by the fact
that many factors contribute to winter mortality (such as spread of the influenza virus). Similarly,
increased summer mortality may be affected not only by average temperature, but also by other
temperature factors, such as variability in temperature, or the duration of heat waves. Moreover,
quantifying projected temperature-related mortality requires going beyond epidemiology and (for
example) projecting adaptive behaviors, such as the use of air conditioning, expanded public
programs (such as heat warning systems), or migratory patterns.
Few studies have attempted to link the epidemiological findings to climate scenarios for the
United States, and studies that have done so have focused on the effects of changes in average
temperature, with results dependent on climate scenarios and assumptions of future
adaptation.18 Moreover, many factors contribute to winter mortality, making highly uncertain
how climate change could affect mortality. No projections have been published for the U.S. that
incorporate critical factors, such as the influence of influenza outbreaks. Below, we report the
results of these studies in order to give a sense of the magnitude of mortality that might be
associated with temperature changes associated with climate change and, by intimation, the
magnitude of potential changes in economic welfare. The conclusions should be considered
preliminary, however, in part because of the complexities in estimating mortality under future
climate scenarios. Moreover, none of the studies reported below traces through the quantitative
implications of various climate scenarios for mortality in all regions of the United States using
region-specific data, suggesting a clear need for future research.
18 McMichael et al. (2004) estimate the impact of climate change on DALYs (Disability-Adjusted Life Years)
associated with waterborne and vector-borne illness for WHO regions. (DALYs represent the sum of life-years lost
due to premature death and productive life years lost due to chronic illness or injury.) For the US, it is not
anticipated that climate change will lead to loss of life or years of life due to chronic illness or injury from
waterborne or foodborne illnesses. However, there will likely be an increase in the spread of several food- and
water-borne pathogens among susceptible populations depending on the pathogens' survival, persistence, habitat
range and transmission under changing climate and environmental conditions.
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Quantifying the relationship between climate change and cases of injury, illness, or death
requires an exposure-response function that quantifies the relationship between a health endpoint
(e.g., premature mortality due to cardiovascular disease (CVD), cases of diarrheal disease) and
climate variables (e.g., temperature and humidity). The exposure-response function can be used
to compute the relative risk of illness or death due to a specified change in climate, e.g., a
temperature increase of 2.5°C. Applying this relative risk to the baseline incidence of the illness
or death in a population yields an estimated number of cases associated with the climate
scenario.
Two studies have attempted to link exposure-response functions to future climate scenarios and
thereby develop temperature-related mortality estimates.19 McMichael el al. (2004) estimate the
effects of average temperature changes associated with projected climates resulting from
alternative emissions scenarios, by WHO region. For the AMR-A region, which includes the
United States, Canada, and Cuba, they estimate the impact on cardio-vascular mortality relative
to baseline conditions in 1990. Effects are estimated for average temperature projections
associated with three alternative emissions scenarios: (1) no control of GHG emissions,20
(2) stabilization at 750 parts-per-million (ppm) of CO2 equivalent by 2210, and (3) stabilization
at 550 ppm C02 equivalent by 2170.21
McMichael et al. (2004) bases the estimates of the effects of average temperature changes on
mortality from cardio-vascular disease (CVD) for AMR-A on Kunst et al. (1993). Kunst et al.
(1993) find CVD mortality rates to be lowest at 16°C, and to increase by 0.5% for every degree
C below 16°C and increase by 1.1% for each degree above 16°C. In applying these results to
future climate scenarios, McMichael et al. (2004) assume that people will adjust to higher
average temperatures; thus, the temperature at which mortality rates reach a minimum is adjusted
by scenario. No adjustment is made for attempts to mitigate the effects of higher temperatures
through (for example) increased use of air-conditioning. The effect of the climate scenarios for
the North American region (AMR-A), reported for 2020 and 2030, is, on net, zero—reductions
in CVD mortality due to warmer winter temperatures cancel out increases in CVD mortality due
to warmer summer temperatures.
Hayhoe et al. (2004) examine the impacts on climate and health in California of projected
climate change associated with two emissions scenarios. The emissions scenarios are similar to
those used in McMichael et al. (2004): (1) stabilization at 970 ppm of CO2 and (2) stabilization
at 550 ppm of CO2.22 In Los Angeles, by the end of the century, the number of heatwave days
(3 or more days with temperatures above 32 °C) increases fourfold under scenario B1 and six to
eight times under scenario Alfi. From a baseline of 165 excess deaths in the 1990s, heat-related
deaths in Los Angeles are projected to increase two to three times under scenario B1 and five to
seven times under scenario Alfi by 2090.
19 These studies use climate scenarios that are associated with different emissions scenarios from IPCC (2000), the
so-called SRES scenarios.
20 McMichael et al. (2004) represent unmitigated emissions using the IS92a emissions scenario presented in IPCC
(2000).
21 Climate scenarios are projected for 2025 and 2050 using the HadCM2 model at a resolution of 3.75° longitude by
2.5° latitude and interpolated to other years.
22 Hayhoe uses two SRES (IPCC 2000) emissions scenarios: Alfi (corresponding to 970 ppm of C02) and B1
(corresponding to 550 ppm of C02).
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These results can be compared with those of an earlier study that employed a composite climate
variable to examine the impact of extreme temperatures on daily mortality under future climate
scenarios. Kalkstein and Greene (1997) analyzed the effect of temperature extremes (both hot
and cold) on mortality for 44 US cities in the summer and winter. They then applied these results
to climate projections from two GCMs for 2020 and 2050. In 2020, under a no-control scenario,
excess summer deaths in the 44 cities were estimated to increase from 1,840 to 1,981-4,100,
depending on the GCM used. The corresponding figures for 2050 were 3,190-4,748 excess
deaths.
4.3.3.3 Valuation of Health Effects
In benefit-cost analyses of health and safety programs, mortality risks are commonly valued
using the "value of a statistical life" (VSL)—the sum of what people would pay to reduce their
risk of dying by small amounts that, together, add up to one statistical life. This approach allows
valuation economists to focus on how people respond to and implicitly value mortality risk in
their daily decisions, rather than attempting to value the lives lost, per se (U.S. EPA, 2000). This
approach also responds to the type of data that is typically available; the excess deaths associated
with a particular climate scenario are indeed the number of statistical lives that would be lost.
Willingness to pay for a current reduction in risk of death (e.g., over the coming year) is usually
estimated from compensating wage differentials in the labor market (a revealed preference
method), or from contingent valuation surveys (a stated preference method) in which people are
asked directly what they would pay for a reduction in their risk of dying. The basic idea behind
compensating wage differentials is that jobs can be characterized by various attributes, including
risk of accidental death. If workers are well-informed about risks of fatal and non-fatal injuries,
and if labor markets are competitive, riskier jobs should pay more, holding worker and other job
attributes constant (Viscusi, 1993). In theory, the impact of a small change in risk of death on the
wage should equal the amount a worker would have to be compensated to accept this risk. For
small risk changes, this is also what the worker should pay for a risk reduction.
For the compensating wage approach to yield reliable estimates of the VSL, it is necessary that
workers be informed about fatal job risks and that there be sufficient competition in labor
markets for compensating wage differentials to emerge.23. To measure these differentials
empirically requires accurate estimates of the risk of death on the job—ideally, broken down by
industry and occupation. The researcher must also be able to include enough other determinants
of wages that fatal job risk does not pick up the effects of other worker or job characteristics.
Empirical estimates of the value of a statistical life based on compensating wage studies
conducted in the U. S. lie in the range of $0.6 million to $13.5 million (1990 dollars) (Viscusi,
1993; U.S. EPA, 1997), which is the rough equivalent of $0.7 million to $16.5 million in year
2000 dollars.24
23 Estimates of compensating wage differentials are often quite sensitive to the exact specification of the wage
equation Black el al. (2003), in a reanalysis of data from U.S. compensating wage studies requested by the USEPA,
conclude that the results are too unstable to be used for policy.
24 Adjusted using the GDP implicit price deflator produced by the Bureau of Economic Analysis US Department of
Commerce, available at http://www.bea.gOv/national/nipaweb/TableView.asp#Mid
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This challenge is compounded by the long-term nature of climate risks, which suggests that
much of the premature mortality associated with higher temperatures will occur in the future.
Indeed, McMichael eial. (2004) and Kalkstein and Greene (1997) estimate mortality based on
climate effects around the years 2020 and 2050; Hayhoe etal. (2004) analyze impacts in 2070-
2099.
It is also the case that the majority of the health effects of climate change will be felt by persons
65 and over. Recent attempts to examine how the VSL varies with worker age (Viscusi and
Aldy, 2007) suggest that the VSL ranges from $9.0 million (2000 dollars) for workers aged 35-
44 to $3.7 million for workers aged 55-62. Contingent valuation studies (Alberini et al., 2004)
also suggest that the VSL may decline with age. Further, economic theory suggests that, under
some assumptions, persons are willing to pay less to reduce a risk they will face in the future
(say, at age 65) than they are willing to pay to reduce a risk they face today (Cropper and
Sussman, 1990). Both these factors may affect the economic value that would be attached to
excess mortality estimates, such as those derived by Kalkstein and Greene (1997).
The potential health effects associated with climate change are much broader than the changes in
excess mortality discussed above. The effects of climate on illness have been examined in the
literature, as indicated in the previous section; however, there have been few attempts to examine
the implications of these studies for future climate scenarios. In addition to quantified estimates
of mortality and morbidity, themselves indications of well-being and welfare, a range of
economic techniques that have been developed for use in cost-benefit analyses of health and
safety regulations could be applied to many of the endpoints that may be affected by climate
change, as suggested by Table 4.3. Before these methods could be applied, however, the impacts
of climate change must be translated into physical damages.
It is also the case that good health is more than the absence of illness. All of the dimensions of
functioning measured in standard questionnaires (including various health outcomes surveys
(HCFR, 2004) may be affected by changes in climate. From a valuation perspective, we would
expect changes in functional limitations (stiffness of joints, difficulty walking) not to be linked
directly to climate or to weather, but rather to be instrumental in people's location decisions and,
thus, reflected in wages and property values. The relationship between climate and wages and
property values are discussed in the subsequent section on Amenity values.
4.3.4 Ecosystems
Human welfare depends on the Earth's ecosystems and the services that they provide, where
ecosystem services may be defined as "the conditions and processes through which natural
ecosystems, and the species that make them up, sustain and fulfill human life" (Daily, 1997).
These services contribute to human well-being and welfare by contributing to basic material
needs, physical and psychological health, security, and economic activity, and in other ways (see
Table 4.4). For example, a variety of ecosystem changes may be linked to changes in human
health, from changes that encourage the expansion of the range of vector-borne diseases
(discussed in Chapter 2) to the frequency and impact of floods and fires on human populations,
due to changes in protection afforded by ecosystems.
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The ability of the biosphere to continue providing these vital goods and services is being strained
by human activities, such as habitat destruction, releases of pollutants, over-harvesting of plants,
fish and wildlife, and the introduction of invasive species into fragile systems. The recent
Millennium Ecosystem Assessment reported that of 24 vital ecosystem services, 15 were being
degraded by human activity (MA, 2005). Climate change is an additional human stressor that
threatens to intensify and extend these adverse impacts to biodiversity, ecosystems, and the
services they provide.
Changes in temperature, precipitation, and other effects of climate change will have direct
effects on ecosystems. Climate change will also indirectly affect ecosystems, via, for example,
effects of sea level rise on coastal ecosystems, decision-makers' responses to climate change (in
terms of coastline protection or land use), or increased demands on water supplies in some
locations for drinking water, electricity generation, and agricultural use. Understanding how
these changes alter economic welfare requires identifying and potentially valuing changes in
ecosystems resulting from climate change. Getting to the point of valuation, however, requires
establishing a number of linkages—from projected changes in climate to ecosystem change, to
changes in services, to changes in the value of those services—as illustrated in Figure 4.2. The
scientific community has not, thus far, focused explicitly on establishing these linkages in the
context of climate change. Consequently, the published literature is somewhat fragmented,
consisting of discussions of climate effects on ecosystems and of valuation of ecosystems and
their services (in only a few cases do the latter focus on climate change).
Figure 4.2 Steps from Climate Change to Economic Valuation of Ecosystem Services
Already observed effects (see reviews in Parmesan and Yohe, 2003; Root et al., 2003; Parmesan
and Galbraith, 2004) and modeling results indicate that climate change is very likely to have
major adverse impacts on ecosystems (Peters and Lovejoy, 1992; Bachelet et al., 2001; Lenihan
et al., 2006; Galbraith et al., 2006). It is also likely that these changes will adversely affect the
services that humans and human systems derive from ecosystems (MA, 2005). Climate change
may affect ecosystems in the US within this century in the following ways.
Shifting, breakup and loss of ecological communities. As climate changes, species that are
components of communities will be forced to shift their ranges to follow cooler temperatures
either poleward or upward in elevation. In at least some cases, this is likely to result in the
breakup of communities as organisms respond to temperature change and migrate at different
rates. In general, study projections include: northern extensions of the ranges of southern
broadleaf forest types, with northward contractions of the ranges of northern and boreal conifer
forests; elimination of alpine tundra from much of its current range in the United States; and the
replacement of forests by grasslands, shrub-dominated communities, and savannas, particularly
in the south (e.g., VEMAP, 1995; Melillo et al, 2001; Lenihan etal., 2006). Because of different
intrinsic rates of migration, communities may not move intact into new areas (Box 4.1).
Another potential community effect of climate change is the facilitation of community
penetration and degradation by invasive weeds that will replace more sensitive native species
(Malcolm and Pitelka, 2000)
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Extinctions of plants and animals and reduced biodiversity. While some species may be able
to adapt to changing climate conditions, others will be adversely affected. It is very likely that
one result of this will be to accelerate current extinction rates, resulting in loss in biodiversity.
The most vulnerable species within the United States may be those that are currently confined to
small, fragmented habitats that may be sensitive to climate change. This is the case with Edith's
checkerspot, a western butterfly species that is already undergoing local subpopulation
extinctions due to climate change (Parmesan, 1996). Other potentially vulnerable organisms
include those that are restricted to alpine tundra habitats (Wang et al., 2002), or to coastal
habitats which may be inundated by sea level rise (Galbraith et al., 2002).
Range shifts. Faced with increasing temperatures, populations of plants and animals will attempt
to track their preferred climatic conditions by shifting their ranges. Range shifts will be limited
by factors such as geology (in the case of plants that are confined to certain soil types), or the
presence of cities, agricultural land, or other human activities that block northward migration.
Some individual species in North America and the US are already undergoing range shifts (Root
et al., 2003; Parmesan and Galbraith, 2004). The red fox in the Canadian arctic shifted its range
northward by up to 600 miles during the 20th century, with the greatest expansion occurring
where temperature increases have been the largest (Hersteinsson and Macdonald, 1992). More
generally, a number of bird species have shifted their ranges northward in the United States over
the past few decades. While some of these changes may be attributable to non-climatic factors, it
is very likely that some are due to climate change (Root et al., 2003; Parmesan and Galbraith,
2004).
Timing changes. The timing of major ecological events is often triggered or modulated by
seasonal temperature change. Changes in timing may already be occurring in the breeding
seasons of birds, hibernation seasons of amphibians, and emergences of butterflies in North
America and Europe (Bebee, 1995; Crick et al., 1997; Brown et al., 1999; Dunn and Winkler,
1999; Root et al., 2003; Roy and Sparks, 2000). Disconnects in timing of interdependent
ecological events may be accompanied by adverse effects on sensitive organisms in the United
States. Such effects have already been observed in Europe where forest-breeding birds have been
unable to advance their breeding seasons sufficiently to keep up with the earlier emergence of
the arboreal caterpillars with which they feed their young. This has resulted in declining
productivity and population reductions in at least one species (Both et al., 2006).
Changes in ecosystem processes. Ecosystem processes, such as nutrient cycling,
decomposition, carbon flow, etc., are fundamentally influenced by climate. Climate change is
likely to disrupt at least some of these processes. While these effects are difficult to quantify,
some types of changes can—and have been observed. Increasing temperatures over the past few
decades on the North Slope of Alaska have resulted in a summer breakdown of the permanently
frozen soil of the Alaskan Tundra and increased activity by soil bacteria that decompose plant
material. This has accelerated the rate at which CO2 (a breakdown product of the decomposition
of the vegetation and also a greenhouse gas) is released to the atmosphere—changing the Tundra
from a net sink (absorber) to a net emitter of CO2 (Oechel et al., 1993; Oechel et al., 2000).
Indirect effects of climate change. Climate change may also result in "indirect" ecological
effects as it triggers events (the frequency and intensity of fires, for example) that, in turn,
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adversely affect ecosystems. In U.S. forest habitats, increased temperatures are very likely to
result in increased frequency and intensity of wildfires, especially in the arid west, leading to the
breakup of contiguous forests into smaller patches, separated by shrub and grass dominated
communities that are more resistant to the effects of fire (Lenihan el al., 2006). Other major
indirect effects are likely to include the loss of coastal habitat through sea level rise (Warren and
Niering, 1993; Ross et al., 1994; Galbraith et al., 2002), and the loss of coldwater fish
communities (and the recreational fishing that they support) as water temperatures increase
(Meyer et al., 1999).
The linkages between these types of changes and the provision of ecosystem services are
difficult to define. While ecologists have developed a number of metrics of ecosystem condition
and functioning (e.g., species diversity, presence/absence of indicator species, primary
productivity, nutrient cycling rates), these do not generally bear an obvious relation to metrics of
services. In some cases, such as species diversity and bird population sizes, direct links might be
drawn to services (in this case, opportunities for bird watching). However, in many, if not most
cases, the linkages between stressor effects, change in ecosystem metrics, and service flows, are
more obscure. For example, it is known that freshwater wetlands can remove contaminants from
surface water (Daily, 1997) and this is an important service. However, the specific ways in which
wetlands do this—in terms of the ecological processes and linkages within the system—are not
well understood, probably vary between different types of wetland (e.g., beaver swamps vs.
cattail stands), and may vary spatially and temporally.
4.3.4.1 Economic Valuation of Effects on Ecosystems
Ecosystems are generally considered non-market goods: although land itself can be bought and
sold, there is no market for ecosystem services per se, and so land value is only a partial measure
of the value of the full range of ecosystem services provided. From the perspective of human
welfare and climate change, however, we are concerned less with the ecosystems or the land on
which they are located, than with the diverse services they provide, as illustrated in Table 4.4.
Economic valuation of changes in ecosystem services will be easier in cases where there are
relationships between market goods and the ecosystem services being valued. For example,
ecosystem changes may result in changes in the availability of goods and services that are traded
on markets, as in the case of provisioning services, such as food, fisheries, pharmaceuticals etc.
In other cases, market counterparts to the services may exist, as in the case of regulating services;
for example, insights into the value of water purification services can come from looking at the
(avoided) cost of a water purification plant to substitute for the ecosystem service. Services, such
as water purification, may also have relationships with market goods and services (e.g., as an
input into the production process) that make it possible to estimate economic values at least in
part or approximately.
Many ecosystem services are, however, truly non-market, in that there are no market
counterparts by which to estimate their value. Recreational uses of ecosystems fall into this
category, and so economists have developed means of inferring values from behavior (e.g., travel
cost), as discussed in the next section), and in other ways. Most of the support services and
cultural values of ecosystems are also in the "true" non-market category. Value can arise even if
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a good or service is not explicitly consumed, or an ecosystem even experienced.25 Thus, it can
be difficult to define, much less to measure the value of changes in these non-market services. To
value these services, economists typically use stated preference (direct valuation) methods, a
method that can be used not only for non-market services, but also to value services in other
categories, such as the value that individuals place on clean drinking water or swimming
facilities.
Below we report on the relevant literature in two categories. First, we report on studies that have
looked at the non-market value of specific ecosystems or species. Since only a few of these
studies attempt to value the impacts of climate change on ecosystems, we also highlight some
non-market studies from the more general literature on ecosystem valuation, which can provide
insights into the magnitude of potential values of services that might be vulnerable to climate
change. Next we look at a different approach to valuation of ecosystems—a more "top-down"
approach—which has been adopted both to look at the effects of climate change and more
broadly at the total value of ecosystems. As the discussions indicate, the treatment of climate
change, per se has been very sparse. Moreover, the lack of studies reflects, in part, a need to
develop analytical linkages between the physical effects of climate on ecosystems, the services
valued by humans, and appropriate techniques to value changes of the types, and with the
breadth, indicated by studies of the effects of global change on ecosystems.
4.3.5.2 Valuation of the Effects of Climate Change on Selected Ecosystem and Species
Although climate change appears in a number of studies, it is often as a context for the scenario
presented in the study for valuation, and so the study cannot be interpreted as valuation of
climate change or climate effects per se. Only a few studies can be said to value the economic
impacts of climate change on a particular ecosystem.
Two studies, Layton and Brown (2000) and Layton and Levine (2003) estimate total values for
preventing Colorado (Rocky Mountain) forest loss due to climate change, based on data from the
same stated choice or preference survey. The survey was conducted with Denver-area residents,
who were expected to be familiar with forested regions in their nearby mountains. Respondents
were given detailed information about climate change impacts on these forests, including
changes in tree line elevation over both 60-year and 150- year time horizons, and asked to make
choices between alternatives, allowing recovery of implied willingness to pay (WTP). Layton
and Brown (2000) found WTP in the range of $10 to $100 per month, per respondent, to prevent
forest loss, with the range depending, in part, on the amount of forest lost. Layton and Levine
(2003) reanalyzed the same data set, using a different approach that focuses on understanding
respondents' least preferred, as well as most preferred, choices. They found that respondents'
value of forest protection depends also on the time horizon—preventing effects that occur further
into the future are valued less than nearer term effects.
Kinnell et al. (2002) designed and implemented several versions of stated preference studies that
explored the impacts of wild bird (duck) loss due to either adverse agricultural practices, climate
25 Economists have devoted much effort to defining the source of non-market values of ecosystems, coining such
terms as "use" and "non-use" value, consumption value, existence value, and invoking, as reasons why people care
about ecosystesm, the moral philosophies inherent in terms such as stewardship, spiritual values, etc. (see for
example, Freeman (2003).
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change, or both. The respondents consisted of Pennsylvania duck hunters, although the
hypothetical ecosystem impacts occurred in the Prairie Pothole region, which is in the northern
Midwestern states and parts of Canada. The authors considered a hypothetical loss in duck
populations, with a scenario that presented some respondents with a 30% loss, and other with a
74% loss, some with a 40 year time horizon, and others with a 100 year time horizon. The study
cannot be viewed as an estimate of willingness to pay to avoid climate change; however, it is
interesting because it suggests that recreational enthusiasts are willing to pay for ecosystem
impacts that they do not necessarily expect to use. In addition, the study provides evidence that
the context of climate change or other cause of ecosystem harm (in this case agricultural
practices)—irrespective of the level of harm—may affect respondents' valuation of the harm.
Although very few studies have valued climate change impacts on ecosystems, economists have
conducted numerous studies (primarily using direct valuation methods) of ecosystem values in
particular geographic locations, often focusing on charismatic species, or specific types of
ecosystems, such as wetlands, in a particular location. In some cases, the estimated values are
linked to specific services that the species or ecosystem provide, but in many the services
provided are somewhat ambiguous, and it is not always clear what aspect of the species, habitat,
or ecosystem is driving the individual respondent's economic valuation.
A number of studies indicate that people value the protection of species or ecosystems. Some of
these studies find potentially significant species values, ranging from a few dollars to hundreds
of dollars per year, per person. For example, MacMillan el al. (2001) estimate the value of
restoring woodlands habitat, and separately evaluate the reintroduction of the wolf and the
beaver to Scottish highlands. In the United States, species such as salmon and spotted owls, as
well as their habitat, have been examined in connection to their respective controversies.
Studies have also looked at the value of ecosystems or changes in ecosystems. In the former
case, economists use either the value of productive output (harvest) as an indicator of value, or
respondents value protecting the ecosystem. For example, numerous coastal wetland and beach
protection studies have used a variety of non-market valuation approaches. A survey of a number
of these studies reports values ranging from $198 to approximately $1500 per acre (Woodward
and Wui, 2001).
Some studies have looked explicitly at the services provided by ecosystems. For example,
Loomis et al. (2000) consider restoration of several ecosystem services (dilution of wastewater,
purification, erosion control, as fish and wildlife habitat, and recreation) for a 45-mile section of
the Platte River, which runs east from the State of Colorado into western Nebraska. Average
values are about $21 per month for these additional ecosystem services for the in-person
interviewees. While these studies and their values are generally informative, transferring values
from studies like the ones above to other ecosystems, and using the results to estimate values
associated with climate change impacts, can be problematic.
4.3.4.3 Top-down Approaches to Valuing the Effects of Climate Change and Ecosystem
Services
From the perspective of deriving values for ecosystem changes (or changes in ecosystem
services) associated with climatic changes, one difficulty with the above studies is that the focus
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is on discrete changes to particular species or geographic areas. It is therefore difficult to know
how these studies relate to, or shed light on, the types of widespread and far-reaching changes to
ecosystems (and the services they provide) that will result from climate change. Consequently,
some studies have attempted to value ecosystems in a more aggregate or holistic manner. While
these studies do not focus specifically on the US, they are indicative of an alternative approach
that recognizes the interdependence of ecosystems and their components, and therefore deserve
some discussion.
Several models include values for non-market damages, worldwide, resulting from projected
climate change. These impact studies have been conducted at a highly aggregated level; most of
the models are calibrated using studies of the United States which are then scaled for application
to other regions (Warren et al., 2006).
A study of total ecosystem values, but not undertaken in the context of climate change, is the
highly publicized study by Costanza et al. (1997), which offers a controversial look at valuing
the "entire biosphere." Because their reported estimated average value of $33 trillion per year
exceeds the global gross national product, economists have a difficult time reconciling this
estimate with the concept of economic value (WTP); since WTP cannot equal twice income.
Ehrlich and Ehrlich (1996) and Pimental et al. (1997) are studies by natural scientists that have
attempted to value ecosystems or in the case of the latter, biodiversity. These are important
attempts to indicate the value of ecosystems, but the accuracy and reliability of the values are
questionable. To paraphrase a study by several prominent environmental economists that is
slightly critical of all of these studies, economists do not have any fundamental difference of
opinion with these natural scientists about the importance of ecosystems and biodiversity, rather
it is with the correct use of economic value concepts in these applications (see Bockstael et al.,
2000).
4.3.5 Recreational Activities and Opportunities
Ecosystems provide humans with a range of services, including outdoor recreational
opportunities. In turn, outdoor recreation contributes to individual wellbeing by providing
physical and psychological health benefits. In addition, tourism is one of the largest economic
sectors in the world, and it is also one of the fastest growing (Hamilton and Tol, 2004); the jobs
created by recreational tourism provide economic benefits not only to individuals but also to
communities.26 A number of studies have looked at the qualitative effects of climate change on
recreational opportunities {i.e., resources available) and activities in the US, but only a few have
taken this literature the additional step of estimating the implications of climate change for
visitation days or economic welfare. This section describes the results of this research into the
impacts on several forms of recreation and reports the economic benefits and losses associated
with these changes at the national level.
Slightly more than 90% of the U.S. population participates in some form of outdoor recreation,
representing nearly 270 million participants (Cordell etal., 1999), and several billion days spent
each year in a wide variety of outdoor recreation activities. According to Cordell et al. (1999),
the number of people participating in outdoor recreation is highest for walking (67%), visiting a
beach or lakeshore or river (62%), sightseeing (56%), swimming (54%) and picnicking (49%).
26 Effects on jobs, income, and similar metrics are considered market impacts, and are not discussed here.
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Most days are spent in activities such as walking, biking, sightseeing, bird-watching, and wildlife
viewing (Cordell et al., 1999), because of the high number of days per bicycle rider and bird
watcher, but the range of outdoor recreation activities in the United States is as diverse as its
people and environment. While camping, hunting, backpacking and horseback riding attract a
fraction of the people who go biking or bird-watching, these other specialized activities provide a
very high value to their devotees. Many of these devotees of specialized outdoor recreation
activities are people who "work to live," i.e., specialized weekend recreation is one of their
rewards for the 40+ hour workweek.
Climate change resulting from increasing average temperatures as well as changes in
precipitation, weather variability (including more extreme weather events), and sea level rise, has
the potential to affect recreation and tourism along two pathways. Figure 4.3 illustrates these
direct and indirect effects of climate change on recreation. Since much recreation and tourism
occurs out of doors, increased temperature and precipitation have a direct effect on the
enjoyment of these activities, and on the desired number of visitor days and associated level of
visitor spending (as well as tourism employment). Weather conditions are considered one of the
four greatest factors influencing tourism visitation (Pileus Project, 2007). In addition, much
outdoor recreation and tourism depends on the availability and quality of natural resources (Wall,
1998), Consequently, climate change can also indirectly affect the outdoor recreational
experience by affecting the quality and availability of natural resources (and, thus, the
availability and quality of recreational experience) used for recreation such as beaches, forests,
wetlands, snow, and wildlife.
Figure 4.3. Direct and Indirect Effects of Climate Change on Recreation
Effects of climate change can be both positive and negative. The length of season for and
desirability of several of the most popular activities—walking, visiting a beach, lakeshore, or
river, sightseeing, swimming, and picnicking (Cordell et al., 1999)—will likely be enhanced by
small near- term increases in temperature. However, long-term higher increases in temperature
may eventually have adverse effects on activities like walking, and result in sufficient sea level
rise to reduce publicly accessible beach areas, just at the time when demand for beach recreation
to escape the heat is increasing. In contrast, some activities are likely to be unambiguously
harmed by even small increase in global warming, such as snow and ice-dependent activities.
In some ways, one can interpret the direct effects of climate change as influencing the demand
for recreation and the indirect effects as influencing the supply of recreation opportunities. For
example, warmer temperatures make Whitewater boating more desirable. However, the warmer
temperatures may reduce river flows since there is less snowpack, higher evapotranspiration, and
greater water diversions for irrigated agriculture. Some studies cited below look only at the direct
effects, while others represent the combined effect of the direct and indirect pathways.
Direct effects. To date, most studies of the direct effects of climate change on recreation and
tourism have been qualitative, although a few have been quantitative. Qualitatively, we would
expect both positive and negative effects of climate change on different recreational activities.
Many of the qualitative studies rely simply on intuition to suggest that increases in air and water
temperatures will have a positive effect on outdoor recreation visitation in two ways: (a) more
enjoyment from the activity; (b) a longer season in which to enjoy the activity (DeFreitas, 2005;
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Scott and Jones, 2005; Scott, Jones and Konopek (2007). Hall and Highman (2005) note that
climate change may provide more days of "ideal" temperatures for water- based recreation
activities and some land based recreation activities such as camping, picnicking and golf.
The recreational activities most obviously harmed by warmer climate are sports that require
snow or cold temperatures, such as downhill and cross country skiing, snowmobiling, ice fishing,
and snowshoeing. Reductions in visitor use (see, for example, the studies reported in Table 4.5)
occur primarily from shorter season, particularly early in the year at such traditional times as
Thanksgiving and Spring break. But with warmer temperatures, there is also less precipitation as
snow and more as rain on snow, which contributes to a much shallower snowpack and harder
snow. Further, recreating in freezing rain or slushy temperatures is not a pleasant experience,
reducing benefits from skiing, snowshoeing, and snowmobiling, further reducing use.
Some recreation areas that are already hot during the summer recreation season will see
decreases in use. For example, the Death Valley National Park, Joshua Tree National Park, and
Mesa Verde National Park are all projected to be "intolerably hot" reducing visitation (Saunders
and Easley, 2006).
Most quantitative studies of the effects of climate change on recreation evaluate specific
projected changes in temperature and/or precipitation, such as a 2.5°C increase in temperature
over the next fifty years. Two quantitative studies look at effects of temperature change in
Canadian recreation.27 Scott and Jones (2005) project that the golf season in Banff, Canada could
be extended by at least one week and up to eight weeks. The combined effect of warmer
temperatures lengthening the golfing season, and the increasing the desirability of golfing during
the existing season, together result in an increase in the rounds of golf played by between 50%
and 86%. (Similar increases might be expected for golf in northern states of the U.S. such as
Minnesota, Wisconsin, New York, etc. with longer golf seasons.) Scott et al. (2006) and Scott
and Jones (2005) suggest that some of the previously projected large (30% to 50%) reductions in
length of ski seasons at northern ski areas (e.g., in Canada, Michigan, and Vermont) can be
reduced (to 5% to 25%) through the use of advanced snowmaking. While use of advanced
snowmaking to minimize reductions in ski season seems plausible for the studied northern ski
areas, it is doubtful that snowmaking would benefit ski areas in California, New Mexico, Oregon
and West Virginia where the Thanksgiving and "Spring Break" periods are already too warm for
successful snowmaking or retention of snow made in some years.
Some studies have used natural variations in temperature to evaluate the effects of climate on
recreation (including measures on monthly, seasonal and inter-annual variation). Two of these
have found that while visitation increases with initial increases in temperature, visitation actually
decreases as temperature increases even further (Hamilton and Tol, 2004; Loomis and
Richardson, 2006). Two of the quantitative studies, which look not only at visitor days but also
at monetary measures of economic welfare, are discussed in more detail below, following the
discussion of indirect effects.
27 Scott and Jones (2005) used +1C to +5C in their scenarios and Scott et al. (2006) used +1.5C to +3C in their low
impact scenario and +2C to +8C in their high impact scenario.
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Indirect effects. While increased temperature may increase the demand for some outdoor
recreation activities, in some cases climate change may reduce the supply of natural resources on
which those recreational activities depend. As noted above, reduced snowpack for winter
activities has been projected in the Great Lakes (Scott et al., 2005), in northern Arizona (Bark-
Hodgins and Colby, 2006) and at a representative set of ski areas in the United States (Loomis
and Crespi, 1999).28
For example, lower in-stream flows and lower reservoir levels have consistently been shown to
reduce recreation use and benefits (Shaw, 2005). Thus, changes associated with climate can
reduce opportunities for summer boating and other water sports. When less precipitation falls as
snow in the winter, and more falls as rain in the spring, early spring season run-off will increase.
Summer river flows will be correspondingly lower, at times when demand for whitewater
boating is higher. Human responses to the physical changes associated with climate change may
exacerbate natural effects reducing recreational opportunities. For example, many current
reservoirs are not designed to handle huge spring inflows, and thus this water may be "spilled,"
which lowers reservoir levels during the summer season. These lower reservoir levels are then
drawn down more rapidly as higher temperatures increase evapotranspiration and increase
irrigation releases. In turn, the resulting lower reservoir may leave boat docks, marinas, and boat
ramps inaccessible.
Ecosystems that provide recreational benefits may also be at risk from climate change. Wetlands
are another recreational environment that is at risk from climate change. Wetland based
recreation include wildlife viewing and waterfowl hunting. With sea level rise, many existing
coastal wetlands will be lost, and given existing development inland, these lost wetlands may not
be naturally replaced (Wall, 1998). The higher temperatures and reduced water availability is
also expected to adversely affect freshwater wetlands in the interior of the country. As such
waterfowl hunting and wildlife viewing may be adversely affected.
Higher water temperatures and lower stream flows are projected to reduce coldwater trout
fisheries (U.S. EPA, 1995; Ahn et al., 2000) as well as native and hatchery stocks of Chinook
salmon in the Pacific Northwest (Anderson et al., 1993). Given trout and Chinook salmon
sensitivity to warm water temperatures, these affects are not surprising. However, Anderson et
aVs estimated magnitude of 50% to 100% reduction in Chinook spawning returns is quite large.
Reductions of such magnitude will have a substantial adverse effect on recreational salmon catch
rates, and possibly whether recreational fishing would even be allowed to continue in some areas
of the Pacific Northwest. However, from a national viewpoint, fishing participation for trout,
cool water species and warm water species dominates geographically specialized fishing like
Chinook salmon. Warmer water temperatures are projected to eliminate stream trout fishing in 8-
10 states and result in a 50% reduction in coldwater stream habitat in another 11-16 states
depending on the GCM model used (U.S. EPA, 1995). This could adversely affect up to 25% of
U.S. fishing days (Vaughan and Russell, 1982). This 25% loss may be an upper limit as some
28 Higher temperatures (while they increase snowmelt reducing the snow skiing season) may have two subtle effects:
(a) stimulating demand for snow skiing due to warmer temperatures, for those skiers who prefer "spring skiing" due
to the warmer temperatures even if the snow conditions are less than ideal; and (b) reduced snowmelt opens up the
high mountains for hiking, backpacking and mountain biking activities somewhat earlier than is the case now, which
may lead to increases in those visitor use days.
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coldwater stream anglers may substitute to less affected coldwater lakes/reservoirs or switch to
cool/warm-water species such as bass (U.S. EPA, 1995). Studies that better account for
substitution effects, such as Ahn el al. (2000), indicate a 2-20% drop in benefits of trout fishing
depending on the projected degrees of temperature increase which ranged from 1°C to 5°C.
Sea level rise reducing beach area and beach erosion are concerns with climate change that may
make it difficult to accommodate the increased demand for beach recreation (Yohe et al., 1999).
In the near term, recreational forests may also be adversely affected by climate change. Although
forests may slowly migrate northward and into higher elevations, in the short run there may be
dieback of forests at the current forest edges (as these areas become too hot), resulting in a loss
of forests for recreation. In the long term, however, several analyses suggest forest species
composition and migration due as well as net increases in forest area due to carbon dioxide
fertilization (Joyce et al., 2001; Iverson and Matthews, 2007). Thus, eventually there may be
resurgence in forest recreation.
Saunders and Easley (2006) find that natural resources of many western National Parks, National
Recreation Areas, and National Monuments resources will be adversely affected by climate
change. The most common adverse effects are reductions in some wildlife species, loss of
coldwater fishing opportunities and increasing park closures due to wildfire associated with
stressed and dying forest stands. The text box discusses in more detail potential effects of climate
change on one park: Rocky Mountain National Park, which has been the subject of both
ecological and economic analysis.
4.3.5.1 Economic Studies of Effects of Climate on Recreation
Changes in economic welfare due to the effects of climate change on non-market resources, such
as recreation, can be evaluated in several ways. First, since decisions regarding recreational
activities depend on both direct and indirect effects of climate, changes in human well-being (as
a result of these changes) will be reflected in changes in visitor use. Social scientists believe
changes in visitor use are motivated by people "voting with their feet" to maintain or improve
their well-being. In the face of higher temperatures, people may seek relief, for example, by
visiting the beach or water skiing at reservoirs more frequently to cool down. Similarly, reduced
opportunities for recreation due to indirect effects of climate change will also be reflected in
reduced visitation days. Thus, one metric of effects on human well-being is the change in
visitation days.
Second, recreational trips—for example, to reservoirs and beaches—have economic implications
to the visitor and the economy. Visitors allocate more of their scarce time and household budgets
to the recreational activities that are now more preferred in a warmer climate. This reflects their
"willingness to pay" for these recreational activities, which is a monetary measure of the benefits
they receive from the activity. Numerous economic studies provide estimates of the value of
changes in diverse recreational activities, using various economic techniques (such as travel
cost29 analysis and stated preference methods) (see Section 3 of this chapter and the chapter
Appendix for more information). While these studies typically do not focus directly on climate
29 The travel cost method traces out a demand curve for recreation using travel cost as proxies for the price of
recreation, along with the corresponding number of trips individual visitors take at these travel costs. From the
demand curve, the net willingness to pay or consumer surplus is calculated.
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change, they can be used to extract values for the types of changes that are projected to be
associated with climate change.
Third, some people who do not currently visit unique natural environments may value climate
stabilization policies that preserve these natural environments for future visitation. These people
have what economists call a value for preserving their option—their ability— to visit the
environments in the future (Bishop, 1982). This option value is much like purchasing trip
insurance to guarantee that if one wanted to go in the future, that conditions would be as they are
today.
As discussed below, economists have available a number of well-studied and techniques to
evaluate the impacts of climate change on at least some of the recreational service provided by
ecosystems. However, only a few studies have looked explicitly at the effects of climate change
on recreation in the US. More research is needed to understand the linkages between weather and
recreation, and to extrapolate results to the range of recreational activities throughout the US.
Change in visitation days. Two studies (Loomis and Crespi, 1999; Mendelsohn and
Markowski, 1999) have examined the effects of climate on recreational opportunities
comprehensively for the entire US. These studies both examined the effects of 2.5°C and 5°C
increases in temperature, along with a 7% increase in precipitation. The studies used similar
methodologies to estimate visitor days for a range of recreational opportunities. Each study
looked at slightly different effects, but between them examined a mix of direct and indirect
climate effects, including direct effects of higher temperatures on golf and beach recreation
visitor days, and indirect effects of snow cover on skiing. Both studies estimate changes in
visitation days due to climate change, and then use the results of a number of economic valuation
studies to place monetary values on the visitation days. The studies find that, as expected, near-
term climate change will increase participation in activities such as water-based recreation, and
reduce participation in snow sports.
Table 4.5 presents the results of the two studies. The results suggest that relatively high
participation recreation activities such as beach and stream recreation gain, and low participation
activities like snow skiing lose. Although the percentage drop in visitor days of snow sports is
much larger than the percentage increase in visitor days in water-based recreation, the larger
number of water-based sports participants more than offsets the loss in the low participation
snow sports. Thus, on net, there is an overall net gain in visitation associated with the assumed
increases of 2.5°C in temperature and 7% in precipitation.30
The methods used to forecast visitation were slightly different between the two studies. To
estimate visitor days for all recreation activities, Mendelsohn and Markowski regressed state
level data on visitation by recreation activity as a function of land area, water area, population,
monthly temperature and monthly precipitation. The Loomis and Crespi study used a similar
30 Geographic regions within the U.S. will experience different gains and losses. Currently hot areas with less access
to water resources (e.g., New Mexico) may suffer net overall reductions in recreation use to due higher heat that
makes walking, sightseeing, and picnicking less desirable. States with substantial water resources (lakes, seashores)
may gain visitor days and tourism. Currently cold areas such as the Dakotas and New York may see increases in
some recreation due to longer summer seasons.
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approach to Mendelsohhn and Markowski for some activities, such as golf. Other forecasting
techniques were used for other activities; for example, for beach recreation, they used detailed
data on to individual beaches in the Northeastern, Southern and Western United States to
estimate three regional regression equations to project beach use, and the response of reservoir
recreation to climate change was analyzed using visitation at U.S. Army Corps of Engineers
reservoirs.
For some of the recreational activities, the Loomis and Crespi study included indirect, as well as
direct, effects. For example, the reservoir models incorporated climate-induced reductions in
reservoir surface area besides temperature and precipitation. Similarly, the estimate of visitor
days for snow skiing used projected changes in the number of days of minimum snow cover to
adjust skier days proportionally. In some cases, only indirect (supply) effects were included, as
in the case of stream recreation, water fowl hunting, bird viewing and forest recreation. Since
these estimates do not include changes in visitation associated with direct effects of climate we
have less confidence in the accuracy of these results, than we do for reservoir recreation which
takes into account both demand and supply effects on recreation use.
Valuation of gains and losses in visitor days. Since different activities may have different
levels of enjoyment provided to the visitor (and, therefore, different economic values), adding up
changes in visitation days to produce a "net change" is not an accurate representation of the
overall change in well-being. The two studies discussed above used net willingness to pay as a
measure of value of each day of recreation (Section 3 of this chapter provides a discussion of the
concept of willingness to pay as a common economic measure of changes in welfare).
To date there have been few original or primary valuation studies of climate change per se on
recreation; the case study on Rocky Mountain National Park presented below provides one of the
few examples. Other studies include Scott and Jones (2005), which focused on Banff National
Park, Scott et al. (2006), which looked at snow skiing, Scott et al. (2007), which focused on
Waterton National Parks, and Pendleton and Mendelsohn (1998), which estimated values for
fishing in the northeastern US.31 There have, however, been hundreds of recreation valuation
studies; the values from these studies (generally travel cost or stated preference) can be applied
to other applications using a "benefit transfer" approach, and applying average values of
recreation from previous studies to value their respective visitor days.
Loomis and Crespi (1999) and Mendelsohn and Markowski (1999) estimate the overall net gain
in visitor benefits, using the change in visitor days reported in Table 4.5 and estimated values of
a visitation day reported in the literature. Loomis and Crespi (1999) adopt a disaggregated
activity approach, and Mendelsohn and Markowski (1999) apply a state level approach.32 Both
31 The three papers by Scott are discussed elsewhere in this paper. Pendleton and Mendelsohn use a random utility
model of recreational fishing in the northeastern U.S. They find that, while catch rates of rainbow trout would
decrease, catch rates of other trout and pan fish would increase. On net, recreational fishing benefits (under a climate
scenario associated with a doubling of atmospheric C02 concentrations) are reduced in the state of New York, but
there are offsetting gains in more northern states like Maine.
32 As noted above, Mendelsohn and Markowski (1999) used state level regression modeling to estimate effects on all
activities. In contrast, Loomis and Crespi (1999), used different regression models and different geographic scales
for different recreation activities to take advantage of the more micro-level datasets available for beach and reservoir
recreation.
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of these studies find that temperature increases of 5°C and up result in increased benefits.
However, as noted below, the case study of Rocky Mountain National Park suggests that extreme
heat is likely (based on the model results) to cause these visitor benefits to decrease at some
point.
Visitors are somewhat adaptable to climate change in the recreation activities they choose and
when they choose them. Thus, recreation represents one situation with opportunities to reduce
the adverse impacts of climate change, or increase its benefits, via adaptation. As noted by
Hamilton and Tol (2004), warmer temperatures may shift visitors northward, and up into the
mountains. Thus currently cool areas (e.g., Maine, Minnesota, Washington) may gain, and warm
areas (e.g., Florida, Arizona) may lose, tourism.
Some adaptive responses can be expensive, and may be of limited effectiveness; such as
snowmaking at night, which is often mentioned as an adaptation for downhill skiing (Irland el
al., 2001). Other adaptive behavior may include moving some outdoor recreation activities
indoors. For example, bouldering is now taking place in climbing gyms on artificial climbing
walls. Running on a treadmill in an air conditioned gym may be a substitute for running out of
doors for some people, but casual observation suggests that many people prefer to run out doors
when weather permits. Unless preferences adjust to increased temperatures, there may be a loss
in human well-being from substituting the treadmill in the air conditioned gym for the out of
doors. Box 4.2 summarizes a case study of the impacts of climate change on Rocky Mountain
National Park.
4.3.6 Amenity Value of Climate
It is well established that preferences for climate affect where people choose to live and work.
The desire to live in a mild, sunny climate may reflect health considerations. For example,
people with chronic obstructive lung disease or angina may wish to avoid cold winters. Warmer
climates may be more pleasant for persons with arthritis. Climate preferences may also reflect
the desire to reduce heating and/or cooling costs. Certain climates may be complementary to
leisure activities. For example, skiers may wish to live in colder climates, sunbathers in warmer
ones. Or a particular climate may simply make life more enjoyable in the course of everyday life.
We would also expect based on the evidence that, in addition to preferring certain temperatures
and more sunshine, people would prefer to reduce the risk of experiencing abrupt climate events
such as hurricanes and floods.
While climate itself is not bought and sold in markets, the goods that are integral to location
decisions—such as housing and jobs—are market goods. Consequently, economists look at
behavior with regard to location choice (the prices that are paid for houses and the wages that are
accepted for jobs) in order to determine how large a role climate plays in these decisions and,
therefore, how valuable different climates are to the general public. The remainder of this section
discusses methods that have been used to estimate the amenity values people attach to various
climate attributes, as well as the value they attach to avoiding extreme weather events.
Unfortunately, few studies have rigorously estimated climate amenity values (e.g., the value of a
2°C change in mean January temperature) for the United States and then used these values to
estimate the dollar value of various climate scenarios.
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4.3.6.1 Valuing Climate Amenities
People's preferences for climate attributes should be reflected in their location decisions. Other
things equal, homeowners should be willing to pay more for housing (and so bid up housing
prices) in more desirable climates, and so property values should be higher in those climates.
Similarly, workers should be willing to accept lower wages to live in more pleasant climates; if
climate also affects firms' costs, however, actual wages may rise or fall due to the interaction
between firms and workers (Roback, 1982).
Early attempts to estimate how much consumers will pay for more desirable climates start from
the view that a good—such as housing or a job—is a bundle of attributes that are valued by the
homeowner or worker. The price the consumer pays for the good (such as a house) is actually a
composite of the prices that are implicitly paid for all the attributes of the good. Using a
statistical technique (known as a hedonic value function), economists can estimate the price of a
particular attribute, such as climate. The hedonic property value function, thus, describes how
housing prices vary across cities as a function of housing characteristics and locational amenities,
such as climate, crime, air quality, or proximity to the ocean. Similarly, the hedonic wage
function relates the observed wages to job characteristics (such as occupation and industry),
worker characteristics (such as education and years of experience), and locational amenities.
The value of locational amenities—i.e., how much individuals are willing to pay for amenities—
can be inferred from these estimated hedonic wage and property value functions. Extracting this
value, however, assumes that workers and homeowners are mobile, i.e., that they can choose
where to live fairly freely within the United States. Similarly, it assumes that, in general,
individuals have moved to where they would like to live (at the moment), so that housing and job
markets are in what is said to be "equilibrium." It also assumes that workers and homeowners
have good information about the location to which they are moving, and that sufficient options
(in terms of jobs and houses and amenities) are available to them. The estimates of the value of a
particular amenity—such as climate—will be more accurate the more nearly these assumptions
are met.
A number of hedonic wage and property value studies have included climate, among other
variables, in their analyses: by Hoch and Drake (1974); Cropper and Arriaga-Salinas (1980);
Cropper (1981); Roback (1982); Smith (1983); Blomquist etal. (1988); Gyourko and Tracy
(1991). The first four studies estimate only hedonic wage functions, while the last three estimate
both wage and property value equations. As Moore (1998) and Gyourko and Tracy (1991) note,
this literature suggests that climate amenities are reflected to a greater extent in wages than in
property values.33 Roback (1982), Smith (1983), and Blomquist etal. (1988) all find sunshine to
be capitalized in wages as an amenity, while heating degree days are capitalized as a disamenity
(Roback, 1982, 1988; Gyourko and Tracy, 1991).
33 The effect of weather variables on property values is mixed, with Blomquist el al. (1988) finding property values
to be negatively correlated with precipitation, humidity and heating and cooling degree days, but Roback (1982)
finding property values positively correlated with heating degree days. Gyourko and Tracy (1991) find heating and
cooling degree days negatively correlated with housing expenditures, but humidity positively correlated.
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More recent studies using the hedonic approach include Moore (1998) and Mendelsohn (2001),
who use their results to estimate the value of mean temperature changes in the United States
associated with future climate scenarios. Moore uses aggregate wage data for Metropolitan
Statistical Areas (MSAs) to estimate the responsiveness of wages with respect to climate
variables for various occupations. Climate is captured by annual temperature, precipitation and
by the difference between average July and average January temperature. Moore estimates that a
4.5° C increase in mean annual temperature would be worth between $30 and $100 billion
(1987$) assuming that precipitation and seasonal variation in temperature remain unchanged.
Mendelsohn (2001) uses county-level data on wages and rents to estimate hedonic wage and
property value models. Separate equations are estimated for wages in retail, wholesale, service
and manufacturing jobs. Climate variables, which include average January, April, June and
October temperature and precipitation, enter each equation in quadratic form. Warmer
temperatures are generally associated with lower wages and lower rents, although the former
effect is larger in magnitude. Mendelsohn uses the results of these models to estimate the impact
of a uniform increase in temperature of 1°C, 2°C and 3.5°C, paired, alternately with an 8% and a
15% increase in precipitation. The results suggest that warming produces positive benefits in
every scenario except the 3.5°C temperature change. Averaging across estimates produced by the
3 models for each of the 6 scenarios suggests annual net benefits (in 1987$) of $25 billion.
Unfortunately, hedonic wage and property value studies have limitations that have caused them
to be replaced by alternate approaches to analyzing data on location choices. One drawback of
the hedonic approach is that, as mentioned above, it assumes that national labor and housing
markets exist and are in equilibrium. As Graves and Mueser (1993) and Greenwood etal. (1991)
point out, if national markets are not in equilibrium, inferring the value of climate amenities from
hedonic wage and property value studies can lead to badly biased results. A second problem is
that variables that are correlated with climate (e.g., the availability of recreational facilities) may
be difficult to measure; hence, climate variables may pick up their effects. In hedonic property
value studies, for example, the use of heating and cooling degree days to measure climate
amenities is problematic because their coefficients may capture differences in construction and
energy costs as well as climate amenities per se. A related problem in hedonic wage equations is
that more able workers may locate in areas with more desirable climates. If ability is not
adequately captured in the hedonic wage equation, the coefficients of climate amenities will
reflect worker ability as well as the value of climate.
Cragg and Kahn (1997) were the first to relax the national land and labor market equilibrium
assumption by estimating a discrete location choice model. Using Census data, they model the
location decisions of people in the United States who moved between 1975 and 1980. Movers
compare the utility they would receive from living in different states—which depends on the
wage they would earn and on the cost of housing, as well as on climate amenities—and are
assumed to choose the state that yields the highest utility. This allows Cragg and Kahn to
estimate the parameters of individuals' utility functions and thus infer the rate at which they will
trade income for climate amenities.
The drawback of this study is that it estimates the preferences of movers, who may differ from
the general population. An alternate approach (Bayer etal., 2006; Bayer and Timmins, 2005) is
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to acknowledge that moving is costly and to explain the location decisions of all households,
assuming that all households are in equilibrium, given moving costs. Unfortunately, the discrete
choice literature has yet to provide reliable estimates of the value of climate amenities in the
United States.
4.3.6.2 Valuing Hurricanes, Floods, and Extreme Weather Events
It is sometimes suggested that the value people place on avoiding extreme weather events can be
measured by the damages that such events cause, or by the premiums that people pay for flood or
disaster insurance. Ex post losses associated with extreme weather events represent a lower
bound to the value people place on avoiding these events, as long as people are risk averse. It is
also the case that people can purchase insurance only against the monetary losses associated with
floods and hurricanes; hence, insurance premiums will not capture the entire value placed on
avoiding these events.
The value of avoiding extreme weather events should be reflected in property values, assuming
that people are informed about risks: houses in an area with high probability of hurricane damage
should sell for less than comparable houses in an area with a lower chance of hurricane damage,
holding other amenities constant. To estimate the value of avoiding these events correctly is,
however, tricky; it can be difficult, for example, to disentangle hurricane risk (a negative effect)
from proximity to the coast (an amenity).
Recent studies use natural experiments to determine the value of avoiding hurricanes and floods.
Hallstrom and Smith (2005) use property value data before and after hurricane Andrew in Lee
County, Florida, a county that did not suffer damage from the hurricane, to determine the impact
of people's perceptions of hurricane risk on property values. They find that property values in
special flood hazard areas of Lee County declined by 19% after hurricane Andrew. The
magnitude of this decline is significant, and agrees with Bin and Polasky (2004). Bin and
Polasky find that housing values in a flood plain in North Carolina declined significantly after
hurricane Floyd, compared to houses not at risk. For the average house, the decline in price
exceeded the present value of premiums for flood insurance, suggesting that the latter are,
indeed, a lower bound to the value of avoiding floods.
4.4 Conclusions
The study of the impacts of climate change on human welfare, well-being, and quality of life, is
still developing. Many studies of impacts on particular sectors—such as health or agriculture—
discuss, and in some cases quantify, effects that have clear implications for welfare. Studies also
hint at changes that are perhaps less obvious, but also have welfare implications (such as changes
in outdoor activity levels and how much time is spent indoors) and point also to effects with far
more dramatic consequences (such as breakdown in public services and infrastructure associated
with possible extreme events of the magnitude of Katrina). Adaptation, too, has welfare
implications that studies do not always point out, such as the costs (financial and psychological)
to the individual of changing behavior.
To our knowledge, no study has made a systematic survey of the myriad welfare implications of
climate change, much less attempted to quantify—nor yet to aggregate—them. An almost
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bewildering choice of typologies is available for categorizing effects on quality of life, well-
being, or human welfare. The social science and planning literatures provide not only a range of
typologies, but also an array of metrics that could be used to measure life quality.
This chapter explores one commonly used method: the social indicators approach. This approach
generally divides life quality effects into broad categories, such as economic conditions or
human health, and then identifies subcategories of important effects.
Most of the measures of well-being—including the social indicators approach—focus on
individual measures of well-being, although measured at the society level. There is, however,
another dimension to well-being—community welfare. Communities represent networks of
households, businesses, physical structures, and institutions and so reflect the interdependencies
and complex reality of human systems. Understanding how climate impacts communities, and
how communities are vulnerable—or can be made more resilient—in the face of climate change,
is an important component of understanding well-being and quality of life.
Economics offers one alternative to address the diversity of impacts: valuing welfare impacts in
monetary terms, which can then be summed. Estimating value, however, requires completing a
series of links—from projected climate change to quantitative measures of effects on
commodities, services, or conditions that are linked to well-being, and then valuing those effects
using economic techniques.
Regardless of the framework, estimating impacts on human well-being involves numerous and
diverse effects. This poses several critical difficulties:
¦ The large number of effects makes the task of linking impacts to climate change—
whether qualitatively or quantitatively—difficult.
¦ The interdependence of physical and human systems further complicates the process of
quantification—both for community effects, and also for ecosystems, raising doubts
about a piecemeal approach to estimation.
¦ The diversity of effects raises questions of how to aggregate effects in order to develop a
composite measure of well-being or other metrics that can be used for policy purposes.
4.5 Expanding the Knowledge Base
Despite the potential for impacts on human well-being, little research focuses directly on
understanding the relationship between well-being and climate change. Completely cataloging
the effects of global change on human well-being or welfare would be an immense undertaking,
and no well-accepted structure for doing so has been developed and applied. Moreover,
identifying the potentially lengthy list of climate-related changes in lifestyle, as well as in other,
more tangible, features of well-being (such as income), is itself a daunting task—and may
includes changes that are not easily captured by objective measures of well-being or quality of
life.
This chapter has looked at the climate impacts and economics literature in four areas of welfare
effects—human health, ecosystems, recreation, and climate amenities. For each of the non-
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market effects analyzed here, significant data gaps exist at each of the steps necessary to provide
monetized values of climate impacts. Although the economics literature for only a few areas of
effects is examined, it is probable that similar information gaps exist for the valuation of other
impacts of climate change, particularly those that involve non-market effects (see Table 4.1). In
addition, economic welfare—as with any other aggregative approach—does not adequately
address the question of how to deal with effects which may not be amenable to valuation or with
interdependencies among effects and systems.
Developing an understanding of the impacts of climate change on human welfare may require
taking the following steps:
¦ Develop a framework for addressing individual and community welfare and well-being,
including defining welfare/well-being for climate analysis and systematically
categorizing and identifying impacts on welfare/well-being
¦ Identify priority categories for data collection and research, in order to establish and
quantify the linkage from climate to welfare effects
¦ Decide which metrics should be used for these categories; more generally, which
components of welfare/well-being should be measured in natural or physical units, and
which should be monetized
¦ Investigate methods by which diverse metrics can be aggregated into a synthetic indicator
(e.g., vulnerability to climate change impacts, including drought, sea level rise, etc.), or at
least weighted and compared in policy decisions where aggregation is impossible
¦ Develop an approach for addressing those welfare effects that are difficult to look at in a
piecemeal way, such as welfare changes on communities or ecosystems.
¦ Identify appropriate top-down and bottom-up approaches for estimating impacts and
value (whether economic or otherwise) of the most critical welfare categories.
¦ Identify situations in which evaluation following the above steps is likely to be
prohibitively difficult, and determining alternative methods for approaching the topic of
the impact of global change on well-being.
Together, these steps should enable researchers to make progress towards promoting the
consistency and coordination in analyses of welfare/well-being that will facilitate developing the
body of research necessary to analyze impacts on human welfare, well-being, and quality of life.
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4.7 Appendix I:
Chapter 4: Human Welfare
Economic Valuation: An Introduction to Techniques and Challenges
Assessments of the benefits and costs, whether explicit or tacit, underlie all discussion and
debates over alternative actions regarding climate change. These assessments are frequently used
to inform such questions as: What actions are justified to ease adaptation to changing climate?
Or how much are we willing to pay to reduce emissions? (Jacoby, 2004). Ideally, such analyses
would be undertaken with complete and reliable information on benefits, converted into a
common unit, commensurable with costs and with each other (Jacoby, 2004). In reality,
however, while many impacts can be valued, some linkages from climate change to welfare
effects are difficult to quantify, much less value. This appendix describes the steps in developing
a benefits estimate, and the tools that economists have available for monetizing benefits. It also
briefly discusses some of the challenges in monetizing benefits, and weaknesses in the approach.
Estimating the Effects of Climate Change
The process of estimating the effects of climate change, including effects on human welfare,
involves up to four steps, illustrated in Figure 4A.1. Moving down from the top of Figure 4A.1,
the gray area occupies a larger portion of each box, indicating (in rough terms) that at each stage
it is more and more difficult to develop quantified, rather than qualitative, results. The first step
is to estimate the change in relevant measures of climate, including temperature, precipitation,
sea-level rise, and the frequency and severity of extreme events. This step is usually
accomplished by atmospheric scientists - some form of global circulation model (GCM) is
typically deployed. Some analyses stop after this step.
The second step involves estimating the physical effects of those changes in climate in terms of
qualitative changes in human and natural systems. These might include changes in ecosystem
structure and function, human exposures to heat stress, changes in the geographic range of
disease vectors, melting of snow on ski slopes, or flooding of coastal areas. A wide range of
disciplines might be involved in carrying out those analyses, deploying an equally wide range of
tools. Many analyses are complete once this step is completed - for example, we may be unable
to say anything more than that increases in precipitation will change an ecosystem's function.
The third step involves translating the physical effects of changes in climate into metrics
indicating quantitative impacts. If the ultimate goal is monetization, ideally these measures
should be amenable to valuation. Examples include quantifying the number and location of
properties that are vulnerable to floods, estimating the number of individuals exposed to and
sensitive to heat stress, or estimating the effect of diminished migratory bird populations on bird-
watching participation rates. Many analyses that reach this step in the process, but not all, also
proceed on to the fourth step.
The fourth step involves valuing or monetizing the changes. The simplest approach would be to
apply a unit valuation approach; for example, the cost of treating a nonfatal case of heat stress or
malaria attributable to climate change is a first approximation of the value of avoiding that case
altogether. In many contexts, however, unit values can misrepresent the true marginal economic
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impact of these changes. For example, if climate change reduces the length of the ski season,
individuals could engage in another recreational activity, such as golf Whether they might prefer
skiing to golf at that time and location is something economists might try to measure.
Figure 4A. I Estimating the Effects of Climate Change
Step 1: Estimate Climate Change
(magnitude & timing)
• Temperature
• Precipitation
• Sea-level rise
• Extreme weather events
r
Step 2: Estimate Physical Effects
(spatial & temporal distribution)
• Human exposure to heat stress
Non-quantified
• Change in ecosystem structure and
physical effects
function
• Arial extent of flooding
• Timing of snow melt
• Many more...
Step 3: Estimate Quantitative Impacts
• Number of sick individuals
• Changes in recreational participation rates
• Property losses
• Change in species populations
• Many more...
Impacts that can
not be quantified
f
Step 4: Value or "Monetize" Effects
• Lost property value
• Cost of illness
• Loss in recreational "use value"
• Loss of human welfare for other effects
Impacts that can not be
monetized
This step-by-step linear approach to effects estimation is sometimes called the "damage
function" approach. One practical advantage of the damage function approach is the separation
of disciplines—scientists can complete their work in steps 1 and 2, and sometimes in step 3, and
then economists do their work in step 4. The linear process can work well in cases where
individuals respond and change their behavior in response to changes in their environment,
without any "feedback" loop.
The linear approach is not always appropriate, however. A damage function approach might
imply that we look at effects of climate on human health as separate and independent from
effects on ecology and recreation, but at some level they are inter-related, as health care and
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recreation both require resources in the form of income. In addition, responding to heat stress by
installing air conditioning leads to higher energy demand, which in turn may increase greenhouse
gas emissions and therefore contribute to further climate change. Recent research suggests that
the damage function approach, under some conditions, may be both overly simplistic (Freeman,
2003) and subject to serious errors (Strzepek et al., 1999; Strzepek and Smith, 1995).
Monetizing and Valuing Non-Market Goods
Economists have developed a suite of methods to estimate willingness to pay for non-market
goods (see text for a discussion of the market vs. non-market distinction). These methods can be
grouped into two broad categories, based largely on the source of the data: revealed preference
and stated preference approaches (Freeman, 2003; U.S. EPA, 2000). Revealed preference,
sometimes referred to as the indirect valuation approach, involves inferring the value of a non-
market good using data from market transactions. For example, a lake may be valued for its
ability to provide a good fishing experience. This value can be estimated by the time and money
expended by the angler to fish at that particular site, relative to all other possible fishing sites. Or,
the amenity value of a coastal property that is protected from storm damage (by a dune, perhaps)
can be estimated by comparing the price of that property to other properties similar in every way
but the enhanced storm protection.
Stated And Revealed Preference Approaches
Accurate measurement of the non-market amenity of interest, in a manner that is not inconsistent
with the way market participants perceive the amenity, is critical to a robust estimate of value.
Revealed preference approaches include recreational demand models, which estimate the value
of recreational amenities through time and money expenditures to enjoy recreation; hedonic
wage and hedonic property value models, which attempt to isolate the value of particular
amenities of property and jobs not themselves directly traded in the marketplace based on their
price or wage outcomes; and averting behavior models, which estimate the value of time or
money expended to avert a particular bad outcome as a measure of its negative effect on welfare.
Stated preference approaches, sometimes referred to as direct valuation approaches, are survey
methods that estimate the value individuals place on particular non-market goods based on
choices they make in hypothetical markets.34 The earliest stated preference studies involved
simply asking individuals what they would be willing to pay for a particular non-market good.
The best studies involve great care in constructing a credible, though still hypothetical, trade-off
between money and the non-market good of interest to discern individual preferences for that
good and hence, willingness to pay (WTP). For example, economists might construct a
hypothetical choice between multiple housing locations, each of which differs along the
dimensions of price and health risk. Repeated choice experiments of this type ultimately map out
the individual's tradeoff between money and the non-market good. The major challenges in
stated preference methods involve study design, particularly the construction of a reasonable and
credible market for the good, and estimation of a valuation function from the response data.
34 The contingent valuation method (CVM), or a modern variants, a stated choice model (SCM), are forms of the
stated preference methods.
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In theory, if individuals understand the full implications of their market choices, in real or
constructed markets, then both revealed and stated preference approaches are capable of
providing robust estimates of the total value of non-market goods. When considering the
complex and multidimensional implications of climate change in the application of revealed and
stated preference approaches, it can be extraordinarily challenging to ensure that individuals are
sufficiently informed that their observed or stated choices truly reflect their preferences for a
particular outcome. As a result, these methods are most often applied to a narrowly defined non-
market good, rather than to a complex bundle of non-market goods that might involve multiple
tradeoffs and synergistic or antagonistic effects that would be difficult to disentangle.
In addition to market or non-market goods that reflect some use of the environment, value can
arise even if a good or service is not explicitly consumed, or even experienced. For example,
very few individuals would value a polar bear for its ability to provide sustenance - those who do
might not express that value through a direct market for polar bear meat, but by hunting for the
bear. Whether through a market or in a non-market activity, those individuals have value for a
consumptive use—once enjoyed, that good is no longer available to others to enjoy. In addition
to the consumptive users, a small but somewhat larger number of individuals might travel to the
Arctic to see a polar bear in its natural environment. These individuals might express a value for
polar bears, and their "use" of the bear is non-consumptive, but in some sense it does nonetheless
affect others' ability to view the bear—if too many individuals attempt to view the bears, the
congestion might cause the bears to become frightened or, worse, domesticated, diminishing the
experience of viewing them.
A third, perhaps much larger group of individuals will never travel to see a polar bear in the
flesh. But many individuals in this group would experience some diminishment in their overall
quality of life if they knew that polar bears had become extinct. This concept is called "non-use
value". Although there are several categories of non-use value - some individuals may wish to
preserve the future option to visit the Arctic and see a bear, others to bequeath a world with polar
bears to future generations, and others might value the mere existence of the bears out of a sense
of environmental stewardship. While not all economists agree that non-use values ought to be
relevant to policy decisions (Diamond and Hausman, 1993), there is broad agreement that they
are difficult to measure, because the expression of non-use values does not result in measurable
economic behavior (that is, there is no "use" expressed). Those that recognize non-use values
acknowledge that they are likely to be of greatest consequence where a resource has a
uniqueness or "specialness" and loss or injury is irreversible, for example in the global or local
extinction of a species, or the distribution of a unique ecological resource (Freeman, 2003).
Other Methods of Monetizing
Analysts can employ other non-market valuation methods: avoided cost or replacement cost, and
input value estimates. These methods do not measure willingness to pay as defined in welfare
economic terms, but because the methods are relatively straightforward to apply and the results
often have a known relationship to willingness to pay, they provide insights into non-market
values. This chapter focuses on willingness to pay measures, but recognizes that alternative
methods may provide insights and sometimes be more manageable (or appropriate) to estimate a
particular non-market value, given data constraints and the limitations imposed by available
methods.
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Cost of illness studies estimate the change in health expenditures resulting from the change in
incidence of a given illness. Direct costs of illness include costs for hospitalization, doctors' fees,
and medicine, among others. Indirect costs of illness include effects such as lost work and leisure
time. Complete cost of illness estimates reflect both direct and indirect costs. Even the most
complete cost of illness estimates, however, typically underestimate willingness to pay to avoid
incidence of illness, because they ignore the loss of welfare associated with pain and suffering
and may not reflect costs of averting behaviors the individuals have taken to avoid the illness.
Some studies suggest that the difference between cost of illness and willingness to pay can be
large, but the difference varies greatly across health effects and individuals (U.S. EPA, 2000).
Replacement cost studies approach non-market values by estimating the cost to replace the
services provided to individuals by the non-market good. For example, healthy coastal wetlands
may provide a wide range of services to individuals who live near them; they may filter
pollutants present in water; absorb water in times of flood; act as a buffer to protect properties
from storm surges; provide nursery habitat for recreational and commercial fish; and provide
amenities in the form of opportunities to view wildlife. A replacement cost approach would
estimate the value of these services by estimating market costs for treating contaminants,
containing floods, providing fish from hatcheries, or perhaps restoring an impaired wetland to
health.
The replacement cost approach is limited in three important ways: 1) the cost of replacing a
resource does not necessarily bear any relation to the welfare enhancing effect of the resource; 2)
as resources grow scarce, we would expect their value would be underestimated by an average
replacement cost; 3) Complete replacement of ecological systems and services may be highly
problematic. Replacement cost studies are most informative in those conditions where loss of the
resource would certainly and without exception trigger the incidence of replacement costs - in
reality, those conditions are not as common as they might seem, because in most cases there are
readily available substitutes for those services, even if accessing them involves incurring some
transition costs.
Finally, value can also be calculated using the contribution of the resource as an input into a
productive process. This approach can be used for both market and non-market inputs. For
example, it can be used to estimate the value of fertilizer, as well as water or soil, in farm output
and profits. An ecosystem's service input into a productive process could, in theory, be used in
this same way.
Issues in Valuation and Aggregation
The topic of issues in valuation is far larger than can be covered here. We focus only on
identifying in a superficial way a few of the most important issues, in the context of climate
change.
By virtue of the simple process of aggregation, the economic approach creates some difficulties.
These difficulties are not specific to the economic approach, however; any method of
aggregation would face the same limitations.
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SAP 4.6 Chapter 4: Human Welfare
¦ Aggregation, by balancing out effects to produce a "net" effect, masks the positive and
negative effects that comprise net effects, hides inequities in the distribution of impacts,
or large negative impacts that fall on particular regions or vulnerable populations.
¦ Any method of aggregation must make an explicit assumption about how to aggregate
over time, i.e., whether to weight future benefits the same as current benefits (economic
analyses generally discount the future, i.e., weight it less heavily in decision making than
the present, for a number of reasons)
¦ The method of putting diverse impacts on the same yardstick ignores differences in how
we may wish to treat these impacts from a policy perspective, and assumes that all
impacts are equally certain or uncertain, despite differences in estimation and valuation
methods. These differences may be particularly apparent, for example, for non-market
and market goods.
Several potential criticisms of the economic approach in the context of climate change relate
more directly to how economists approach the task of valuation. One issue is the assumption of
stability of preferences over time. Economic studies conducted today, whether revealed or stated
preference, reflect the actions and preferences of individuals today, expressed in today's
economic, social, and technological context. For an issue such as climate change, however,
impacts may occur decades or centuries hence. The valuation of impacts that occur in the future
should depend on preferences in the future. For the most part, however, while there are some
rudimentary ways in which economists model changes in technology or income, there is no
satisfactory means of modeling changes in preferences over time.
A second issue is the treatment of uncertainty. Economic analysis under conditions of imperfect
information and uncertainty is possible, but is one of the most difficult undertakings in
economics. While some climate change impacts may be relatively straight-forward, valuation of
many climate change impacts requires analysis and use of welfare measures that incorporate
uncertainty. When imperfect information prevails, the valuation measure must factor in errors
that arise because of it, and when risk or uncertainty prevail, the most commonly used valuation
measure is the option price. Two related concepts are option value, and expected consumer's
surplus. All three concepts are more complicated than the discussion here can do justice to, but
briefly:
¦ Expected consumer's surplus, E[CS] is just consumer's surplus (CS), or value in welfare
terms, weighted by the probabilities of outcomes that yield CS. For example, if a hiker
gets $5 of CS per year in a "dry" forest and $10 in a wet forest (one that is greener) and
the probability of the forest being dry is 0.40 and of it being wet is 0.60, then the E[CS] =
0.40 X $5 + 0.60 X $10. Expected consumer's surplus is really an ex-post concept,
because we must know CS in each state after it occurs.
¦ Option price (OP) is the WTP that balances expected utility (utility weighted by the
probabilities of outcomes) with and without some change. It is a measure of WTP the
individual must express before outcomes can be known with certainty, i.e., a true ex ante
welfare measure. For example, the hiker might be willing to pay $8 per year to balance
her expected utility with conditions being wet, versus conditions being dry. The $8 might
be a payment to support a reduction in dryness otherwise due to climate change.
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SAP 4.6 Chapter 4: Human Welfare
¦ Option value (OV) is the difference between OP and E[CS], A related concept is called
quasi-option value and pertains to the value of waiting to get more information.
A third issue concerns behavioral paradoxes. Most economic analyses, particularly if they
involve uncertain or risky outcomes, require rationality in the expression of preferences. Such
basic axioms as treating gains and losses equally, reacting to a series of small incremental gains
with equal strength to a single large gain of the same aggregate magnitude, and viewing gains
and losses from an absolute rather than relative or positional scale are particularly important to
studies that rely on expected utility theory - that individuals gain and lose welfare in proportion
to the product of the likelihood of the gain or loss and its magnitude. Several social and
psychological science studies, however, suggest that under many conditions individuals do not
behave in a manner consistent with this definition of rationality. For example, prospect theory,
often credited as resulting from the work of Daniel Kahneman and Amos Tversky, suggests that
behavior under risk or uncertainty is better explained both by reference to a status quo reference
point and acknowledgement of unequal treatment of risk aversion when considering losses and
gains, even when it can be shown that a different behavior would certainly make the individual
better off.
Finally, the issue of perspective—"whose lens are we looking through"—is critical to welfare
analysis, particularly economic welfare. In health policy, for example, thinking about whether it
is worthwhile to invest in mosquito netting to control malaria depends on whether you are at
CDC, are a provider of health insurance, or are an individual in a place where malaria risk is
high. In general, the perspective of valuation focuses on the valuation of individuals who are
directly affected, and who are living today. The perspectives of public decision makers may be
somewhat different from those of individuals, since they will take into account social and
community consequences, as well as individual consequences.
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4.8 Boxes
Box 4.1 Effects of Climate Change on Selected US Ecosystems
At their most extreme, community changes could result in the loss of entire habitats valued by the general
public. For example, sea level rise puts much of the freshwater wetland that comprises Florida Everglades
National Park at risk (Glick and Clough, 2006). Even relatively modest sea level rise projections could result in
the conversion of much of this low-lying area to brackish or intertidal marine and mangrove habitats. Another
such extreme example is alpine tundra habitat in mountain ranges in the contiguous states. Since tundra lies at
the highest elevations, there is little or no opportunity for the plants and animals that comprise this ecosystem
to respond to increasing temperatures by moving upward. Thus, one of the probable effects of climate change
will be the further fragmentation and loss of this unique habitat (VEMAP, 1995; Root el al., 2003; Lenihan el
al., 2006).
California already reports an example of how climate change might modify major marine ecological
communities. Over the final four decades of the 20th century the average annual ocean surface temperature off
the California coast warmed by approximately 1.5°C (Holbrook el al., 1997). Sagarin el al. (1999) found that
the intertidal invertebrate community at Monterey has changed since first it was characterized in the 1930s.
Many of the coolwater species have retracted their ranges northward, to be replaced by southern warm water
species. The community that exists there now is markedly different in its make-up from that which existed
prior to warming of the coastal California Current.
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SAP 4.6 Chapter 4: Human Welfare
Box 4.2 Case Study of the Effects of Climate Change on Rocky Mountain National Park
One of the National Parks most closely studied to determine the net effect of direct and indirect
effect of climate change on visitation, visitor benefits and tourism employment is Rocky
Mountain National Park (RMNP) in Colorado. This alpine national park is located at elevations
ranging from 7,000 to 14,000 feet above sea level. It is known for elk viewing, hiking, tundra
flowers, snowcapped peaks, and one of Colorado's most visible and recognizable 14,000 foot
peaks, Longs Peak.
Loomis and Richardson (2006) compared two approaches to estimating the effect of climate
change on visitation and employment in RMNP. The first approach examined variations in
monthly visitation in response to historic variations in temperature. The results of this first
approach showed a statistically significant positive effect of temperature on visitation (see
Loomis and Richardson (2006) for more details). However, increased visitation slowed as
temperatures got hotter and hotter, and visitation even declined during one summer of very high
temperatures (60 days over 80°F) by 7.5%.
The second approach used a survey that portrayed the direct effects (e.g., temperature) and
indirect effects (e.g., changes in elk and ptarmigan (an alpine bird), or percent of the park in
tundra). Visitors were then asked to indicate if they would change their visits to RMNP or length
of stay in the park. The surveys used three climate change scenarios, one produced by the
Canadian Climate Center (CCC) indicating a 4°F increase in temperature by 2020, a Hadley
climate scenario that forecasted a 2°F temperature increase by 2020, and an extreme heat
scenario designed to capture very hot future conditions (50 days with temperatures above 80°F,
as compared to 3 days currently). All climate change scenarios were used with wildlife models to
estimate the increase in elk populations and decrease in ptarmigan populations. The extreme heat
survey found similar results to that of the monthly visitation model.
Table 4.6 shows the results of the CCC, Hadley, and Extreme Heat temperature scenarios on
visitation, visitor benefits and tourism employment as compared to current conditions. As
indicated in the table, applying visitor survey estimates of visitation change yields a 13.6%
increase with CCC and 9.9% increase with Hadley. Loomis and Richardson also report that
applying the historic visitation patterns to the same scenarios yields an 11.6% increase in
visitation with CCC and 6.8% with Hadley. Not only is there fairly good agreement between the
two methods, but the warmer CCC climate change scenario produces larger increases in
visitation. In the extreme heat scenario, however, visitations declines from current conditions.
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SAP 4.6 Chapter 4: Human Welfare
4.9 Tables
Table 4.1 Categorization of Weil-Being
Category of Well-
being
Description and Rationale
Components / Indicators of
Well-being
Illustrative Metrics / Measures of Well-
being
Examples of Negative Climate
Linkages*
Economic
conditions
The economy supports a mix of activities:
opportunities for employment, a strong
consumer market, funding for needed
public services, and a high standard of
living shared by citizens.
¦ Income and production
¦ Economic standard of living, e.g., wealth and
income, cost of living, poverty
¦ Economic development, e.g., business and
enterprise, employment
¦ Availability of affordable housing
¦ Equity in the distribution of income
¦ Gross Domestic Product (GDP)
¦ Wage rates (e.g., persons at minimum wage)
¦ Employment rates
¦ Business startups and job creation
¦ Housing prices
¦ Dependence on public assistance
¦ Families/children living in poverty
¦ Utility costs, gasoline prices, and other prices
Reduced job opportunities and wage rates
in areas dependent on natural resources,
such as agricultural production in a given
region that faces increased drought.
Higher electricity prices resulting from
increased demand for Air Conditioning as
average temperatures and frequency of
heat waves rise.
Natural resources,
environment, and
amenities
Resources enhance the quality of life of
citizens; pollution and other negative
environmental effects are kept below
levels harmful to ecosystems, human
health, and other quality of life
considerations; and natural beauty and
aesthetics are enhanced.
¦ Air, water, and land pollution
¦ Recreational opportunities
¦ Water supply and quality
¦ Natural hazards and risks
¦ Ecosystem condition and services
¦ Biodiversity
¦ Direct climate amenity effects
¦ Air and water quality indices
¦ Waste recycling rates
¦ Acreage, visitation, funding of recreational and
protected/preserved areas
¦ Water consumption and levels
¦ Deaths, injuries, and property loss due to
natural hazards
¦ Endangered and threatened species
Sea Level rise could both inundate coastal
wetland habitats (with negative effects on
marsh and estuarine environments
necessary to purify water cycle systems
and support marine hatcheries) and erode
recreational beaches.
Human health
Health care institutions provide medical
and preventive health-care services with
excellence, citizens have access to
services regardless of financial means,
and physical and mental health is
generally high.
¦ Mortality risks
¦ Morbidity and risk of illness
¦ Quality and accessibility of health care
¦ Health status of vulnerable populations
¦ Prenatal and childhood health
¦ Psychological and emotional health
¦ Deaths from various causes (suicide, cancer,
accidents, heart disease)
¦ Life expectancy at birth
¦ Health insurance coverage
¦ Hospital services and costs
¦ Infant mortality and care of elderly
¦ Subjective measure of health status
Increased frequency of heat waves in a
larger geographical area will directly affect
health, resulting in higher incidence of
heat-related mortality and illness. Climate
can also affect human health indirectly via
effects on ecosystems and water supplies.
Public and private
infrastructure
Transportation and communication
infrastructure enable citizens to move
around efficiently and communicate
reliably.
¦ Affordable, and accessible public transit
¦ Adequate road, air, and rail infrastructure
¦ Reliable communication systems
¦ Waste management and sewerage
¦ Maintained and available public and private
facilities
¦ Power generation
¦ Mass transit use and commute times
¦ Rail lines, and airport use and capacity
¦ Telephones, newspapers, and internet
¦ Waste tonnage and sewerage safety
¦ Congestion and commute to work
¦ Transportation accident rates
¦ Noise pollution
Melting permafrost due to warming in the
arctic damages road transport, pipeline,
and utility infrastructure, which in turn leads
to disrupted product and personal
movements, increased repair costs, and
shorter time periods for capital
replacement.
Government and
public safety
Governments are led by competent and
responsive officials, who provide public
services effectively and equitably, such
as order and public safety; citizens are
well-informed and participate in civic
activities.
¦ Electoral participation
¦ Civic engagement
¦ Equity and opportunity
¦ Municipal budgets and finance
¦ Public safety
¦ Emergency services
¦ Voter registration, turnout, approval
¦ Civic organizations membership rates
¦ Availability of public assistance programs
¦ Debt, deficits, taxation, and spending
¦ Crime rates and victimization
¦ Emergency first-responders per capita
Dislocations and pressures created by
climate change stressors can place
significant new burdens on police, fire and
emergency services.
Social and cultural
resources
Social institutions provide services to
those in need, support philanthropy,
volunteerism, patronage of arts and
leisure activities, and social interactions
characterized by equality of opportunity
and social harmony.
¦ Volunteerism
¦ Culture, arts, entertainment, and leisure
activities
¦ Education and human capital services
¦ Social harmony
¦ Family and friendship networks
¦ Donations of time, money, and effort
¦ Sports participation, library circulation, and
support for the arts
¦ Graduation rates and school quality
¦ Hate, prejudice, and homelessness
¦ Divorce rates, social supports
Disruptions in economic and political life
caused by climate change stressors or
extreme weather events associated with
climate change could create new conflicts
and place greater pressure on social
differences within communities.
* The focus is on negative impacts as potentially more troubling for quality of life; there are also positive impacts and opportunities in some
categories
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SAP 4.6 Chapter 4: Human Welfare
Table 4.2 An illustration of Possible Effects of Climate Change on Fishery Resources
Lin kages/Pathways
Category of Welfare Effect
Possible Metrics
Fishery resource declines as climate
changes
Natural resources, environment, and
amenities
Fish populations
Recreational opportunities decline
Natural resources, environment, and
amenities
Fish catch, visitation days
Related species and habitats are
affected
Natural resources, environment, and
amenities
Species number and diversity
Employment and wages in resource-
based jobs (including recreation) fall
as resources decline
Economic conditions
Number of jobs, unemployment
rate, wages
Incomes fall as jobs are lost
Economic conditions
Per capita income
More children live in poverty as jobs
are lost and incomes fall
Economic conditions
Families, children below poverty
level
Access to health care that is tied to
jobs and income falls
Human Health
Households without health
insurance increase
Increased mortality and morbidity as
a result of reduced health care
Human Health
Disease and death rates increase
Lack of jobs results in out-migration
Economic conditions
Working age population
decreases
Fewer new residents attracted,
because of reduced jobs and
amenities (recreation)
Social and cultural resources
Population growth rate slows
Less incentive/drive to participate in
community activities
Social and cultural resources
Drop in volunteerism civic
participation, completion of high
school
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SAP 4.6 Chapter 4: Human Welfare
Table 4.3 Techniques to Value Health Effects Associated with Climate Change
Health Effect
Economic Valuation Tools
Premature mortality (associated with
temperature changes, extreme
weather events and air pollution
effects)
Use of revealed preference techniques to value changes in risk of death (e.g., compensating wage
studies).
Use of stated preference studies to value changes in risk of death.
Use of foregone earnings as a lower bound estimate to the value of premature mortality.
Exacerbation of cardiovascular and
respiratory morbidity; morbidity
associated with water-borne or
vector-borne disease
Use of stated preference methods to elicit WTP to avoid illness (e.g., asthma attacks) or risk of
illness (heart attack risk) or injury.
Estimation of medical costs and productivity losses (known as the cost-of-illness (COI)) as a lower
bound estimate of the value of avoiding illness.
Injuries associated with extreme
weather events
Use of stated preference methods to elicit WTP.
Use of compensating wage studies that value risk of injury.
Use of COI as a lower bound estimate.
Impacts of climate change on
physical functioning; sub-clinical
effects
Use of stated preference methods to estimate WTP to avoid functional limitation.
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SAP 4.6 Chapter 4: Human Welfare
Table 4.4 Examples of Ecosystem Services Important to Human Welfare*
Service Category
Components of Service
Illustration of Service
Provisioning services
Food
Fiber
Fresh water
Genetic Resources
Pharmaceuticals
Harvestable fish, wildlife and plants
Timber, hemp, cotton
Water for drinking, hydroelectricity generation, and
irrigation
Regulating services
Air quality regulation
Erosion regulation
Water purification
Pest control
Crop pollination
Climate and water supply regulation
Protection from natural hazards
Local and global amelioration of extremes
Removal of contaminants by wetlands
Removal of timber pests by birds
Pollination of orchards by flying insects
Support services
Primary production
Soil formation
Photosynthesis
Nutrient and water cycling
Conversion of solar energy to plant material
Conversion of geological materials to soil by
addition of organic material and bacterial activity
Cultural services
Recreation/tourism
Aesthetic values
Spiritual/religious values
Cultural heritage
Natural sites for "green" tourism/recreation/nature
viewing
Existence value of rainforests and charismatic
species, "holy" or "spiritual" natural sites
*Based on a classification system developed for the Millennium Ecosystem Assessment (MA, 2005)
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SAP 4.6 Chapter 4: Human Welfare
Table 4.5 Comparison of Changes in US Visitor Days
Activity
Loomis and Crespi (1999)
Mendelsohn and Markowski (1999)
Boating
9.2%
36.1%
Camping
-2.0%
-12.7%
Fishing
3.5%
39.0%
Golf
13.6%
4.0%
Hunting
-1.2%
no change
Snow Skiing
-52.0%
-39.0%
Wildlife Viewing
-0.1%
-38.4%
Beach Recreation
14.1%
not estimated
Stream Recreation
3.4%
included in boating
Gain in Visitor Benefits
(in Billions)
$2.74
$2.80
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SAP 4.6 Chapter 4: Human Welfare
Table 4.6 Change in Visits, Jobs and Visitor Benefits with Three Climate Change Scenarios
Annual
Tourism
Visitor
Climate Scenario
Visits
% change
Jobs
Benefits
(Millions)
Current
3,186,323
6,370
$1,004
ccc
3,618,856
13.6%
7,351
$1,216
Hadley
3,502,426
9.9%
7,095
$1,157
Extreme Heat
2,907,520
-8.7%
5,770
$959
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SAP 4.6 Chapter 4: Human Welfare
4.10 Figures
Figure 4.1 Geography of Climate Change Vulnerability at the County Scale
Legend
r~1-1 J39 45--034*79
0 it: JT ¦ -C.M53I
Unee measures of climate clrange risk aie used to create tdt vultidl) illy itidex: expffifcd temperature change,
extreme weathei evait histoid and coas tal poxinity. Risk treasures are seo-referemed at the aouriyscale. He
expectedtswjwraijre change mile is treasured as the expeetedunit change inarerageitniTmumtempE^Eduie
fin degree s Cels ius) for a couity from2 004 Id 209?. TemsiatxK date are fiomtlie Hadty C enter. Hadley Cenier
monthly time se lies data on.ara'age miiiimirtiteni>eratiiE far tit United S tates are plotted ai the 0.5 x 0. j degree
of spatial resolution In case viiere climate cells irderseit couniyboundaiies, teinperalme data are aveiaged
across infeisecting clinate eels. To estimate extreite weathir event hEtoiywe summara tie muter of reported
injures and fatalities fromhyiio-meteiDbgic-al hazard events a-t the c ounty le wl from JanOl, 1900 b Jul 31,2004.
Higlier values otn our naturalhasjd casualty vstiabli reilact more proiDntsd histories cf injury and deatli fiorn
extreme weathei evmte. Casually data were oiJlected from the S paiial Haiaid Events and Losses Eiafeijase for -tit
Urnted i tales ^ tliUJ US J. ihe qmstai prorinity variable is measured dichotamnisly. A county receives a score
of 1 if it is designated b y the National Oceanic and Atmospheric Administratiori (IT OAAil as an"at-risk coastal"
couiiiy and a saare ot'U ill! e ret. WUA A defines a. county as -at-risJi ooasfel if at least 1 j percent of its total area
is located ina coastal-wateished. Hie vulneriility mien was c reateiby standardising thai smutting each
measure of diinate change liskfs-sioreU. He distutotimofvohieraijililyis divide! ititosiual'iuiiilites, with
darker coLoos reflectiiE hklir vulneiabiEtvlD climate change.
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SAP 4.6 Chapter 4: Human Welfare
Figure 4.2 Steps from Climate Change to Economic Valuation of Ecosystem Services
Climate Charge will result in
~temperature increase
~ prec pitatjon change
~ charges in extreme events
Direct Effects on Ecosystems
~ ExlinuLiuris
~ Range shfts
~ Communiy dissociation [
~ Timing changes
~ i hihUM in ecosystem processes
Indirect Effects on Ecosystems
~ Increased wildfires
~ Effects of sea leve rise on coastal
ecosystems
~Adaptation, e.g., CDasine
protEclion, changes in land use
1
Change?, in the ability of
ecosystems to provide services
I """
Effects of Changes in Services on
Human Welfare and Quality a1 Life
i
Economic valuation of changes in
qjality of life
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SAP 4.6 Chapter 4: Human Welfare
Figure 4.3 Direct and Indirect Effects of Climate Change on Recreation
Direct
Indirect
Climate Change:
+Temperature
+/- Precipitation
+Climate Variability
Use & Benefits:
Enjoyment & Comfort while in
outdoors
Visitor Days of outdoor recreation
demanded
Benefits of outdoor recreation
Effects on Outdoor Recreation
Effects of Climate Change:
. .Vegetation (forests)
. .Stream flows
. .Reservoir levels
. .Recreational Fisheries
. .Wildlife populations
. .Miles of Beaches
. .Length of season
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Synthesis and Assessment Product 4.6
Chapter 5: Common Themes and Research
Recommendations
Convening Lead Author: Janet L. Gamble, U.S. Environmental Protection Agency
Lead Authors: Kristie L. Ebi, ESS, LLC; Frances G. Sussman, Environmental Economics Consulting;
Thomas J. Wilbanks, Oak Ridge National Laboratory
Contributing Authors: Colleen E. Reid, ASPH Fellow; John V. Thomas, U.S. Environmental Protection
Agency; Christopher P. Weaver, U.S. Environmental Protection Agency
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SAP 4.6 Chapter 5: Research
Table of Contents
5.1 Synthesis and Assessment Product 4.6: Advances in the Science 3
5.1.1 Complex Linkages and a Cascading Chain of Impacts Across Global Changes 3
5.1.2 Changes in Climate Extremes and Climate Averages 4
5.1.3 Vulnerable Populations and Vulnerable Locations 5
5.1.4. The Cost of and Capacity for Adaptation 6
5.1.5 An Integrative Framework 6
5.2 Expanding the Knowledge Base 7
5.2.1 Human Health Research Gaps 9
5.2.2 Human Settlements Research Gaps 10
5.2.3 Human Welfare Research Gaps 10
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SAP 4.6 Chapter 5: Research
5.1 Synthesis and Assessment Product 4.6: Advances in the
Science
The Synthesis and Assessment Product 4.6 assesses the impacts of climate variability and
change on human systems in the United States. Each of the assessment chapters have
drawn on different literatures, with generally more available scientific knowledge on
impacts and adaptations related to human health, somewhat less related to human
settlements, and still somewhat less related to human welfare.
Several themes recur across these chapters and point to advances in the science of climate
impacts assessment and the development and deployment of adaptation responses.
1. Climate change is connected to other environmental and social changes in a
complex and dynamic fashion. In some cases climate change compounds other
global changes, while in other cases the impacts of climate change are determined
or moderated by other socioeconomic factors (5.1.1).
2. Extreme weather events will play a defining role, particularly in the near term,
shaping climate-related impacts and adaptive capacity. While impacts associated
with changes in climate averages may be less important now, these averages are
expected to have more pronounced long-run effects on sea level rise, permafrost
melt, glacial retreat, drought patterns and water supplies, etc. (5.1.2).
3. Climate change will have a disproportionate impact on disadvantaged groups in
communities across the United States. Some regions and some resources are more
vulnerable to climate impacts, such as coastal zones, drought-prone regions, and
flood-prone river basins (5.1.3).
4. Adaptation of infrastructure and services to climate change may be costly, but
many communities will have adequate resources. However, for places already
struggling to provide or maintain basic public amenities and services, the
additional costs of adaptation will impose a potentially-insupportable burden
(5.1.4.).
5. With such a complex scientific and policy landscape, an integrated multi-
disciplinary framework is needed to enable climate change impacts to be
measured in meaningful ways and for optimal mitigation and adaptation strategies
to be identified, developed, and deployed (5.1.5).
5.1.1 Complex Linkages and a Cascading Chain of Impacts Across Global
Changes
Climate is only one of a number of global changes that impact human well-being. The
major effects of climate will be shaped by interactions with non-climate stressors. As
such, climate change will seldom be the sole or primary factor determining a population's
or a location's well-being. The impacts of climate variability and change interact with
impacts tied to population growth and change and other socioeconomic endpoints (for
example, impacts on infrastructure capacity, water supplies, habitat preservation,
community growth and development, and access to health care). While this assessment
focuses on how climate change could affect the future health, well-being, and settlements
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SAP 4.6 Chapter 5: Research
in the United States, the extent of any impacts will depend on an array of non-climate
factors, including:
¦ Demographic changes related to the location, size, age and characteristics of
populations; population and regional vulnerabilities;
¦ Future social, economic, and cultural contexts;
¦ Availability of natural resources;
¦ Human, cultural and social capital;
¦ Advances in science and technology;
¦ Characteristics of the built environment;
¦ Land use change;
¦ Public health and public utility infrastructures; and,
¦ The capacity and availability of health and social services.
The effects of climate change very often spread from directly impacted areas and sectors
to other areas and sectors through extensive and complex linkages. The importance of
climate change depends on the directness of the climate impact coupled with
demographic, social, economic, institutional, and political factors, including, the degree
of preparedness. Consider the damage left by Hurricanes Katrina and Rita in 2005.
Damage was measured not only in terms of lives lost, but also on the devastating impacts
on infrastructure, neighborhoods, businesses, schools, and hospitals as well as in the
personal disruption of family and friends in established communities, with lost lives and
lost livelihoods, challenged psychological well-being, and exacerbation of chronic
illnesses. While the aftermath of a single hurricane is not the measure of climate change,
such an event demonstrates the disruptive capacity of extreme weather events.
5.1.2 Changes in Climate Extremes and Climate Averages.
Past and present climates have been, and are, variable. This variability in all likelihood
will continue into the future. Changes in climate occur as changes in particular weather
conditions, including extremes, in specific places (unfortunately, projections of climate
changes at small geographic scales remain highly uncertain). The meteorological
variables of interest from an impacts perspective include both changes in average
conditions and in extreme conditions. More gradual changes in average temperature and
precipitation have the potential to strongly affect, both positively and negatively, human
systems. For example, changes in the average length of the growing season can affect
agricultural practices and changes in the timing and amount of spring runoff can affect
water resource management. Effects such as these will not, however, be confined to a few
individual sectors, nor are the effects across all sectors independent (e.g., changes in
water supplies can impact agricultural practices such as irrigation).
Changes in the climate extremes, both those that accompany changes in mean conditions
(e.g., a shift in the entire temperature distribution) as well as changes in variability are
very often of more concern than changes in climate averages. Unfortunately these types
of changes (e.g., heat waves, drought, storms, seasonal high or low levels of temperature
or precipitation) have not always been projected by climate change models. Many human
systems have evolved to accommodate the "average climate" and some variation around
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SAP 4.6 Chapter 5: Research
this average. This evolution takes place in a dynamic social, economic, technological,
biophysical and political context, which determine the ability of human systems to cope.
Rapid onset extreme weather events in particular can do serious damage to a settlement's
infrastructure, public health, and overall community reputation and quality of life, from
which recovery may take years.
Finally key vulnerabilities are often defined by certain "thresholds," below which effects
are incidental but beyond where effects quickly become major. The severity of impacts is
therefore not only related to the rate and magnitude of climate change, but also to the
presence or absence of thresholds. In general, these climate-related thresholds for human
systems in the United States are not well-understood. Focused research on thresholds
would substantially improve understanding of climate impacts.
5.1.3 Vulnerable Populations and Vulnerable Locations
Impacts of climate variability and change on human systems are location- and
population-specific. For instance, in densely-developed coastlines, populations are
especially vulnerable to tropical storms, storm surge and flooding, just as the very old and
the very young residing in urban areas experience increases in cardiovascular and
pulmonary morbidity and mortality caused by extreme heat coupled with degraded air
quality. Native American peoples in Alaska and other low socio-economic communities
because of their decreased economic capacity to prepare for and respond to the impacts of
climate change. Just as there are differences across populations, there are important
differences in vulnerability across geographic regions, such as the exposure to extreme
events along the Gulf Coast and water supply issues in the southeast, the southwest and
the Inter-Mountain West.
With respect to health impacts from climate variability and change, specific
subpopulations may experience heightened vulnerability for climate-related health effects
associated with:
1. Biological sensitivity related to age (especially the very young and the very old),
the presence of pre-existing chronic medical conditions (such as the sensitivity of
people with chronic heart and pulmonary conditions to heat-related illness),
developmental characteristics, acquired factors (such as immunity), those taking
certain medications (e.g., some antihypertensive and psychotropic medications)
and genetic factors (such as metabolic enzyme subtypes that play a role in
vulnerability to air pollution effects).
2. Socioeconomic factors also play a critical role in determining vulnerability to
environmentally-mediated factors. The distribution of climate-related effects will
vary among those who live alone; those with limited rights (for instance, some in
the immigrant communities); by economic strata; by housing type and according
to other elements that either accentuate or limit vulnerability. Socioeconomic
factors may increase the likelihood of exposure to harmful agents, interact with
biological factors that mediate risk (such as nutritional status), and/or lead to
differences in the ability to adapt or respond to exposures or to early phases of
illness and injury.
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3. Given their location, the underlying vulnerability of some communities is
inherently high just as their adaptive capacity is similarly limited. Populations in
gently-sloping coastal areas are particularly vulnerable to sea level rise and
settlements along floodplains of large rivers are particularly vulnerable due to
projections of increased variability in precipitation. Projections of increased
frequencies of drought combined put the increasing populations of desert
southwest cities at risk.
It is essential that public health interventions and preventions recognize populations that
may experience interactive or synergistic effects of multiple risk factors for health
problems, both related to climate change and to other global changes. Poor communities
and households are already under stress from climate variability and climate-related
extreme events such as heat waves, hurricanes, and tropical and riverine flooding. Since
they tend to be concentrated in relatively high-risk areas, have limited access to services
and other resources for coping, they can be especially vulnerable to climate change.
These differential effects propagate concerns regarding social inequity and environmental
justice and increased pressure for adaptive responses from local, state, and federal
governments.
5.1.4. The Cost of and Capacity for Adaptation
U.S. society is capable of considerable adaptation, depending heavily on the competence
and capacity of individuals, communities, federal, state, and local governments, and
available financial and other social resources. While adaptation to climate change will
come at a cost that may reduce available resources to cope with other societal burdens,
potentials for adaptation through technological and institutional development and
behavioral changes are considerable, especially where such developments meet other
sustainable development needs.
With scarce resources, communities should also choose adaptation options with co-
benefits that help ameliorate other issues or where they can easily add climate concerns to
existing response plans. The focus on all-hazards response within public health agencies
can simply add climate impacts to its list of hazards for which to prepare. This will likely
improve their response plans to events in the near term such as storms that happen in a
variable climate, whether or not they increase in frequency or intensity with a changing
climate. Planting trees and green roofs to reduce urban heat islands has the added benefit
of creating a more aesthetically pleasing location that increasing well-being and by
decreasing energy use in these buildings. Thus, some adaptation measures can also
considered mitigation measures.
5.1.5 An Integrative Framework
The impacts of climate variability and change on human health and human settlements
are fairly well characterized in broad terms, although additional research is needed to
refine impact assessments and provide better decision support (particularly with respect
to deploying adaptation measures). Human well-being is an emerging concept, and in
theory could encompass human health and settlements. As an organizing principle,
human well-being could provide a paradigm for identifying and categorizing climate
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impacts, and may ultimately provide a framework for integrating multiple impacts into an
internally-consistent, coherent framework for assessing costs, benefits, and tradeoffs. The
potential for utilizing concepts of human well-being to develop an integrating framework
is not yet mature. Additional conceptual work and research will be needed, such as
valuation methodologies (in the case of economic welfare), or developing metrics of
well-being or quality of life (in the case of a place-based indicators, or similar, approach).
As an integrating concept, human well-being can provide insight into the determinants of
human happiness. Just as health can be considered a component of well-being {i.e.,
physical health is closely tied to individual measures of happiness, contentment, and
quality of life) aspects of human settlements also determine well-being and could be
incorporated into a broader framework of well-being or welfare.
An alternative integrating framework could revolve around settlements or the more
expansive concept of communities (See Section 4.2.3 for a fuller discussion). There is a
growing awareness that the built environment can have a profound impact on our health
and quality of life1. A major goal of community design is to create more vibrant and
livable communities, making sure that they address the needs of residents and improve
their quality of life. More specifically, "Green communities", "Smart communities",
"Smart growth" and "Sustainable development" are intended to offer alternatives to
traditional settlement patterns, aiming to meet the goals of creating livable, desirable
communities while minimizing the collective footprint of communities on natural
resources, ecosystems and pollution. As an integrating framework, communities could be
evaluated based on how well they protect human health and welfare. Put slightly
differently, adaptation could be realized as increasing resilience within communities.
Resilience is measured by a community's capacity for absorbing climate changes and the
shocks of extreme events without breakdowns in its economy, natural resources, and
social systems. Resiliency, as a central concept in measuring the vulnerability and
adaptability of communities and individuals, depends not only on physical infrastructure,
but also on social infrastructure and the natural environment. As with welfare, these
concepts involving settlements or communities as an integrating framework are not yet
mature.
5.2 Expanding the Knowledge Base
The present state of the science suggests that opportunities remain for addressing critical
research areas. The SAP 4.6 concludes that climate observations and modeling are
becoming increasingly important for a wide segment of public and private sector entities,
such as water resource managers, public health officials, agribusinesses, energy
providers, forest managers, insurance companies, and urban and transportation planners.
In order to more accurately portray the consequences of climate change and support
better-informed adaptation strategies, research efforts should focus on:
¦ Deriving socioeconomic scenarios that describe how the world may evolve in the
future, including assumptions about changes in societal characteristics,
1 See for example, the CDC web-site on healthy places: www.cdc.gov/healthyplaces/
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governments and public policy, as well as economic and technological
development;
¦ Connecting those socioeconomic scenarios with downscaled climate models to
create projections of future changes in climate, including the intensity and
severity of extreme weather events, at the regional and local scales;
¦ Characterizing the costs of climate change, both those that relate to impacts and
those that relate to response strategies (including adaptation and mitigation);
¦ Estimating the damages avoided by stabilizing or reducing emissions;
¦ Determining the factors that contribute to synergies between adaptive capacity
and sustainable development as well as synergies between adaptation and
mitigation;
¦ Pursuing cross-disciplinary efforts that focus on the human dimensions of climate
change in an integrated fashion;
¦ Improving capacity to incorporate scientific knowledge about climate, including
uncertainty, in existing adaptation strategies;
¦ Conducting research at regional and sectoral levels that promote analyses of the
response of human and natural systems to multiple stresses. Impacts of climate
change are most damaging when they occur in a context of multiple climate and
non-climate stressors;
¦ Evaluating the adaptation strategies that effectively address challenges presented
by current non-climate stressors (e.g., land use and population dynamics) as well
as anticipated climate change impacts and develop comprehensive estimates of
these co-benefits;
¦ Implementing adaptation measures to address the near- and long-term responses
to climate change, using regional and local stakeholders as key stakeholders in the
development of effective, responsive, and timely adaptation policies;
¦ Advancing the concept of human welfare as an integrating framework by
developing methods to achieve comparable and comprehensive valuations across
diverse impacts and sectors;
¦ Determining which climate impacts exhibit thresholds. Threshold-based damage
functions can be fundamentally different in their nature and extent than
continuous damage functions;
¦ Supporting research on impacts and the development, implementation and
evaluation of adaptive responses by collecting high quality time-series
measurements and other observations of both climate and human systems; and,
¦ Identifying early effects of changing weather patterns on climate-sensitive
outcomes.
This report concludes that periodic assessments of the impacts of global change on
human health, human settlements, and human welfare are necessary to support a rapidly
developing knowledge base, especially related to impacts and adaptation. Gaps should be
addressed that characterize exposure and sensitivity at the local or regional level.
Research should evaluate the adaptive capacity of places and institutions to climate-
induced risks. Key research and development areas should address short-term risk
assessment and evaluation of the costs and effectiveness of near-term adaptive strategies
as well as longer-term impacts and responses.
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The following sections provide a more detailed discussion of research needs and
recommendations by topic: human health, human settlements, and human welfare. There
is significant overlap across topics with opportunities for investigating cross-disciplinary
pursuits of research opportunities and adaptation responses.
5.2.1 Human Health Research Gaps
An important shift in perspective has occurred since the Health Sector Assessment of the
First National Assessment in 2001. There is a greater appreciation of the complex
pathways by which weather and climate affect individual and societal health and well-
being. In the research community, there is a more finely-honed understanding of the
interaction of multiple non-climate, social, and behavioral factors and impacts on risks
from injury and disease. While significant gaps remain, several gaps identified in the
First National Assessment have been addressed, including:
¦ A more finely honed understanding of the differential effects of temperature
extremes by community, demographic, and biological characteristics;
¦ Improved characterization of the exposure-response relationships to extreme heat;
and,
¦ Improved understanding of the public health burden posed by climate-related
changes from heat waves and air pollution.
Despite these advances, the body of literature has only limited quantitative
projections of future impacts. Research related to the human health impacts of climate
change will lead to a better understanding in this area.
The following specific suggestions for research on climate change and human health:
¦ Increase the skill with which we characterize exposure-response relationships,
including identifying thresholds and particularly vulnerable groups, considering
relevant factors that affect the geographic range and incidence of climate-sensitive
health outcomes, and including disease ecology and transmission dynamics;
¦ Develop quantitative models of possible health impacts of climate change that can
be used to explore a range of socioeconomic and climate scenarios;
¦ Evaluate effectiveness of current adaptation projects, including the costs and
benefits of interventions. For example, heat wave and health early warning
systems have not been effective; further research is needed to understand how
public health messages can be made more helpful;
¦ Characterize with local stakeholders the local and regional scale vulnerability and
adaptive capacity related to the potential risks and the time horizon over which
climate risks might arise; and,
¦ Anticipate requirements for infrastructure such as may be needed to provide
protection against extreme events, to alter urban design to decrease heat islands,
and to maintain drinking and wastewater treatment standards and source water
and watershed protection.
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5.2.2 Human Settlements Research Gaps
Chapter 3 examines the vulnerabilities and impacts of climate change and variability on
human settlements. The following list enumerates topics where a better understanding of
the linkages between climate change and human settlements is appropriate.
¦ Advance the understanding of settlement vulnerabilities, impacts, and adaptive
responses in a variety of different local contexts around the country.
¦ Develop plans for out-migration from vulnerable locations via realistic, socially
acceptable strategies for shifting human populations away from vulnerable zones.
¦ Improve the understanding of vulnerable populations (such as the urban poor and
native populations on rural, tribal lands) that have limited capacities for response
to climate change in order to provide a basis for adaptation research that addresses
social justice and environmental equity concerns.
¦ Improve the understanding of how urban decision-making is changing as
populations become more heterogeneous and decisions become more
decentralized especially as this affects adaptive responses.
¦ Improve abilities to associate projections of climate change in U.S. settlements
with changes in other driving forces related to impacts, such as changes in
metropolitan/urban patterns, changes in transportation infrastructure and
technological change. With continued growth in vulnerable regions, research is
needed to consider alternative growth futures and to minimize the vulnerability of
new development, to insure that communities adopt measures to manage
significant changes in sea level, temperature, rainfall and extreme weather events.
¦ Improve the understanding of relationships between settlement patterns (both
regional and intra-urban) and resilience/adaptation.
¦ Improve the understanding of vulnerabilities of urban population inflows and
outflows to climate change impacts.
¦ Improve the understanding of second and third-order impacts of climate change in
urban environments, including interactive effects among different aspects of the
urban system.
¦ Review current policies and practices related to climate change responses to help
inform community decision-makers and other stakeholders about potentials for
relatively small changes to make a large difference.
Meeting these needs is likely to require well-developed partnerships across local, state,
and federal governments, industry, non-governmental organizations, foundations,
stakeholders, resource managers, urban planners, public utility and public health
authorities, and the academic research community.
5.2.3 Human Welfare Research Gaps
Despite the potential for impacts on human well-being, little research focuses directly on
understanding the relationship between well-being and climate change. Completely
cataloging the effects of global change on human well-being or welfare would be an
immense undertaking, and no well-accepted structure for doing so has been developed
and applied. Moreover, identifying the potentially lengthy list of climate-related changes
in lifestyle, as well as in other, more tangible, features of well-being (such as income), is
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itself a daunting task—and may include changes that are not easily captured by objective
measures of well-being or quality of life.
Developing an understanding of the impacts of climate change on human welfare will
require steps designed to develop a framework for addressing individual and community
welfare and well-being, as well as to fill the data gaps associated with the estimation and
quantification of effects.
Regarding climate change and human welfare, there is a range of topics associated with
human welfare impacts and adaptations where improved understanding would be useful.
¦ Design an appropriate method for systematically categorizing and identifying
impacts on welfare/well-being.
¦ Identify priority categories for data collection and research in order to establish
and quantify the linkage from climate to effects on welfare/well-being.
¦ Decide which metrics should be used for these categories; more generally, which
components of welfare/well-being should be measured in natural or physical
units, and which should be monetized.
¦ Investigate methods by which diverse metrics can be aggregated, or at least
weighted and compared in policy decisions where aggregation is impossible.
¦ Develop an approach for addressing those human welfare effects that are difficult
to look at in a piecemeal way, such as welfare changes on communities or
ecosystem services.
¦ Identify appropriate top-down and bottom-up approaches for estimating impacts
and value (whether economic or otherwise) of the most critical categories of
welfare/well-being.
Together, these steps should enable researchers to make progress towards promoting the
consistency and coordination in analyses of welfare/well-being that will facilitate
developing the body of research necessary to analyze impacts on human welfare, well-
being, and quality of life.
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6 Glossary and Acronyms
6.1 Glossary
Sources: Derived from the Intergovernmental Panel on Climate Change
Third and Fourth Assessment Reports, Working Group II and other sources as
indicated.
Words in italics indicate that the following term is also contained in this glossary.
A
Acclimatization
The physiological adaptation to climatic
variations.
Adaptability
See Adaptive capacity.
Adaptation
Adjustment in natural or human systems to a
new or changing environment. Adaptation to
climate change refers to adjustment in
natural or human systems in response to
actual or expected climatic stimuli or their
effects, which moderates harm or exploits
beneficial opportunities. Various types of
adaptation can be distinguished, including
anticipatory and reactive adaptation, private
and public adaptation, and autonomous and
planned adaptation.
Adaptation assessment
The practice of identifying options to adapt
to climate change and evaluating them in
terms of criteria such as availability,
benefits, costs, effectiveness, efficiency, and
feasibility.
Adaptation benefits
The avoided damage costs or the accrued
benefits following the adoption and
implementation of adaptation measures.
Adaptation costs
Costs of planning, preparing for, facilitating,
and implementing adaptation measures,
including transition costs.
Adaptive capacity
The ability of a system to adjust to climate
change (including climate variability and
extremes) to moderate potential damages, to
take advantage of opportunities, or to cope
with the consequences.
Aeroallergens1
Any of various airborne substances, such as
pollen or spores, that can cause an allergic
response.
Aggregate impacts
Total impacts summed up across sectors
and/or regions. The aggregation of impacts
requires knowledge of (or assumptions
about) the relative importance of impacts in
different sectors and regions. Measures of
aggregate impacts include, for example, the
total number of people affected, change in
net primary productivity, number of systems
undergoing change, or total economic costs.
Albedo
The fraction of solar radiation reflected by a
surface or object, often expressed as a
percentage. Snow-covered surfaces have a
high albedo; the albedo of soils ranges from
high to low; vegetation-covered surfaces and
oceans have a low albedo. The Earth's
albedo varies mainly through varying
cloudiness, snow, ice, leaf area, and land-
cover changes.
1 The American Heritage® Dictionary of the
English Language, Fourth Edition. Retrieved
November 21, 2007, fromDictionary.com
website:
http://dictionary.reference.com/browse/aeroaller
gen
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Algal bloom
A reproductive explosion of algae in a lake,
river or ocean.
Ancillary benefits
The ancillary, or side effects, of policies
aimed exclusively at climate change
mitigation. Such policies have an impact not
only on greenhouse gas emissions, but also
on resource use efficiency, like reduction in
emissions of local and regional air pollutants
associated with fossil-fuel use, and on issues
such as transportation, agriculture, land-use
practices, employment, and fuel security.
Sometimes these benefits are referred to as
"ancillary impacts" to reflect that in some
cases the benefits may be negative. From the
perspective of policies directed at abating
local air pollution, greenhouse gas
mitigation may also be considered an
ancillary benefit, but these relationships are
not considered in this assessment.
Anthropogenic
Resulting from or produced by human
beings.
Anthropogenic emissions
Emissions of greenhouse gases, greenhouse
gas precursors, and aerosols associated with
human activities. These include burning of
fossil fuels for energy, deforestation, and
land-use changes that result in net increase
in emissions.
Aquifer
A stratum of permeable rock that bears
water. An unconfined aquifer is recharged
directly by local rainfall, rivers and lakes,
and the rate of recharge will be influenced
by the permeability of the overlying rocks
and soils.
Arid regions
Ecosystems with less than 250 mm
precipitation per year.
Atmosphere
The gaseous envelop surrounding the Earth.
The dry atmosphere consists almost entirely
of nitrogen (78.1% volume mixing ratio) and
oxygen (20.9% volume mixing ratio),
together with a number of trace gases, such
as argon (0.93% volume mixing ratio),
helium, and radiatively active greenhouse
gases such as carbon dioxide (0.035%
volume mixing ratio) and ozone. In addition,
the atmosphere contains water vapor, whose
amount is highly variable but typically 1%
volume mixing ratio. The atmosphere also
contains clouds and aerosols.
B
Baseline
The baseline (or reference) is any datum
against which change is measured. It might
be a "current baseline," in which case it
represents observable, present-day
conditions. It might also be a "future
baseline," which is a projected future set of
conditions excluding the driving factor of
interest. Alternative interpretations of the
reference conditions can give rise to
multiple baselines.
Biofuel
A fuel produced from organic matter or
bombustible oils produced by plants.
Examples of biofuel include alcohol, black
liquor from the paper-manufacturing
process, wood, and soybean oil.
Biogenic2
Produced by living organisms or biological
processes.
c
Carbon dioxide (C02)
A naturally occurring gas, and also a by-
product of burning fossil fuels and biomass,
as well as land-use changes and other
industrial processes. It is the principal
anthropogenic greenhouse gas that affects
the Earth's radiative balance. It is the
reference gas against which other
greenhouse gases are measured and has a
Global Warming Potential of 1.
Cholera
An intestinal infection that results in
frequent watery stools, cramping abdominal
2 The American Heritage® Dictionary of the
English Language, Fourth Edition. Retrieved
November 21, 2007, fromDictionary.com
website:
http://dictionary.reference.com/browse/biogenic
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pain, and eventual collapse from
dehydration.
Chronic obstructed pulmonary disease
(COPD)3
Chronic obstructive pulmonary disease, or
COPD, refers to a group of diseases that
cause airflow blockage and breathing-related
problems. It includes emphysema, chronic
bronchitis, and in some cases asthma.
Climate
Climate in a narrow sense is usually defined
as the "average weather" or more rigorously
as the statistical description in terms of the
mean and variability of relevant quantities
over a period of time ranging from months
to thousands or millions of years. The
classical period is 30 years, as defined by
the World Meteorological Organization
(WMO). These relevant quantities are most
often surface variables such as temperature,
precipitation, and wind. Climate in a wider
sense is the state, including a statistical
description, of the climate system.
Climate change
Climate change refers to any change in
climate over time, whether due to natural
variability or as a result of human activity.
This usage differs from that in the United
Nations Framework Convention on Climate
Change (UNFCCC), which 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'. See also climate
variability.
Climate change commitment
Due to the thermal inertia of the ocean and
slow processes in the biosphere, the
cryosphere and land surfaces, the climate
would continue to change even if the
atmospherica composition was held fixed at
today's values. Past changes in atmospheric
position leads to a 'committed' climatic
change which continues for as long as a
radiative imbalance persists and until all
3 Definition taken from
http://www.cdc.gov/nceh/airpollution/copd/copd
faq.htm visited on November 21, 2007.
components of the climate system have
adjusted to a new state. The further change
in temperature after the composition of the
atmosphere is head constant is referred to as
the committed warming or warming
commitment. Climate change commitment
includes other future changes, for example
in the hydrological cycle, in extreme
weather events, and in sea-level rise.
Climate model (hierarchy)
A numerical representation of the climate
system based on the physical, chemical, and
biological properties of its components, their
interactions and feedback processes, and
accounting for all or some of its known
properties. The climate system can be
represented by models of varying
complexity—that is, for any one component
or combination of components a "hierarchy"
of models can be identified, differing in such
aspects as the number of spatial dimensions,
the extent to which physical, chemical or
biological processes are explicitly
represented, or the level at which empirical
parametrizations are involved. Coupled
atmosphere/ocean/sea-ice general
circulation models (AOGCMs) provide a
comprehensive representation of the climate
system. There is an evolution towards more
complex models with active chemistry and
biology. Climate models are applied, as a
research tool, to study and simulate the
climate, but also for operational purposes,
including monthly, seasonal, and interannual
climate predictions.
Climate prediction
A climate prediction or climate forecast is
the result of an attempt to produce a most
likely description or estimate of the actual
evolution of the climate in the future (e.g., at
seasonal, interannual, or long-term time-
scales). See also climate projection and
climate (change) scenario.
Climate projection
A projection of the response of the climate
system to emission or concentration
scenarios of greenhouse gases and aerosols,
or radiative forcing scenarios, often based
upon simulations by climate models.
Climate projections are distinguished from
climate predictions in order to emphasize
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that climate projections depend upon the
emission/concentration/radiative forcing
scenario used, which are based on
assumptions, concerning, for example,
future socio-economic and technological
developments that may or may not be
realized, and are therefore subject to
substantial uncertainty.
Climate scenario
A plausible and often simplified
representation of the future climate, based
on an internally consistent set of
climatological relationships, that has been
constructed for explicit use in investigating
the potential consequences of anthropogenic
climate change, often serving as input to
impact models. Climate projections often
serve as the raw material for constructing
climate scenarios, but climate scenarios
usually require additional information such
as about the observed current climate. A
"climate change scenario" is the difference
between a climate scenario and the current
climate.
Climate system
The climate system is the highly complex
system consisting of five major components:
the atmosphere, the hydrosphere, the
cryosphere, the land surface and the
biosphere, and the interactions between
them. The climate system evolves in time
under the influence of its own internal
dynamics and because of external forcings
such as volcanic eruptions, solar variations,
and human-induced forcings such as the
changing composition of the atmosphere and
land-use change.
Climate variability
Climate variability refers to variations in the
mean state and other statistics (such as
standard deviations, the occurrence of
extremes, etc.) of the climate on all temporal
and spatial scales beyond that of individual
weather events. Variability may be due to
natural internal processes within the climate
system (internal variability), or to variations
in natural or anthropogenic external forcing
(external variability). See also climate
change.
Co-benefits
The benefits of policies that are
implemented for various reasons at the same
time—including climate change
mitigation— acknowledging that most
policies designed to address greenhouse gas
mitigation also have other, often at least
equally important, rationales (e.g., related to
objectives of development, sustainability,
and equity). The term co-impact is also used
in a more generic sense to cover both the
positive and negative sides of the benefits.
See also ancillary benefits.
Communicable Disease
An infectious disease caused by
transmission of an infective biological agent
(virus, bacterium, protozoan, or
multicellular macroparasite).
Confidence
In this Report, the level of confidence in a
statement is expressed using a standard
terminology defined in the Introduction. See
also uncertainty.
Coping range
The variation in climatic stimuli that a
system can absorb without producing
significant impacts.
Cost-effective
A criterion that specifies that a technology
or measure delivers a good or service at
equal or lower cost than current practice, or
the least-cost alternative for the achievement
of a given target.
D
DALY (Disability-adjusted life years)4
The sum of years of life lost due to
premature death and illness, taking into
account the age of death compared with
natural life expectancy and the number of
years of life lived with a disability. The
measure of number of years lived with the
disability considers the duration of the
disease, weighted by a measure of the
severity of the disease.
Dengue Fever
4 Definition from the glossary of the Millenium
Ecosystem Assessment, 2005.
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An infectious viral disease spread by
mosquitoes often called breakbone fever
because it is characterized by severe pain in
joints and back. Subsequent infections of the
virus may lead to dengue hemorrhagic fever
(DHF) and dengue shock syndrome (DSS),
which may be fatal.
Desert
An ecosystem with less than 100 mm
precipitation per year.
Desertification
Land degradation in arid, semi-arid, and dry
sub-humid areas resulting from various
factors, including climatic variations and
human activities. Further, the United
Nations Convention to Combat
Desertification defines land degradation as a
reduction or loss in arid, semi-arid, and dry
sub-humid areas of the biological or
economic productivity and complexity of
rain-fed cropland, irrigated cropland, or
range, pasture, forest, and woodlands
resulting from land uses or from a process or
combination of processes, including
processes arising from human activities and
habitation patterns, such as: (i) soil erosion
caused by wind and/or water; (ii)
deterioration of the physical, chemical, and
biological or economic properties of soil;
and (iii) long-term loss of natural vegetation.
Detection and attribution
Climate varies continually on all time scales.
Detection of climate change is the process
of demonstrating that climate has changed in
some defined statistical sense, without
providing a reason for that change.
Attribution of causes of climate change is
the process of establishing the most likely
causes for the detected change with some
defined level of confidence.
Disturbance regime
Frequency, intensity, and types of
disturbances, such as fires, inspect or pest
outbreaks, floods, and droughts.
Diurnal temperature range
The difference between the maximum and
minimum temperature during a day.
Dose-response function5
A mathematical relationship is established
which relates how much a certain amount of
exposure impacts on production, capital,
ecosystems, human health etc.
Downscaling
A method that derives local- to regional-
scale (10 to 100 km) information from
larger-scale models or data analyses.
Drought
The phenomenon that exists when
precipitation has been significantly below
normal recorded levels, causing serious
hydrological imbalances that adversely
affect land resource production systems.
E
Ecosystem
A system of interacting living organisms
together with their physical environment.
The boundaries of what could be called an
ecosystem are somewhat arbitrary,
depending on the focus of interest or study.
Thus, the extent of an ecosystem may range
from very small spatial scales to, ultimately,
the entire Earth.
Ecosystem processes
The processes that underpin the integrity and
functioning of ecosystems, such as
decomposition, carbon cycling, or soil
renewal, etc.
Ecosystem services
Ecological processes or functions that have
monetary or non-monetary value to
individuals or society. There are (i)
supporting services such as productivity or
biodiversity maintenance, (ii) provisioning
services such as food, fibre, or fish, (iii)
regulating services such as climate
regulation or carbon sequestration, and (iv)
cultural services such as tourism or spiritual
and aesthetic appreciation.
El Nino Southern Oscillation (ENSO)
5 Definition modified from
http://stats.oecd.org/glossary /detail.asp?ID=6404
visited on November 21, 2007.
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SAP 4.6 Glossary and A cronyms
El Nino, in its original sense, is a warm
water current that periodically flows along
the coast of Ecuador and Peru, disrupting the
local fishery. This oceanic event is
associated with a fluctuation of the
intertropical surface pressure pattern and
circulation in the Indian and Pacific Oceans,
called the Southern Oscillation. This
coupled atmosphere-ocean phenomenon is
collectively known as El Nino Southern
Oscillation, or ENSO. During an El Nino
event, the prevailing trade winds weaken
and the equatorial countercurrent
strengthens, causing warm surface waters in
the Indonesian area to flow eastward to
overlie the cold waters of the Peru current.
This event has great impact on the wind, sea
surface temperature, and precipitation
patterns in the tropical Pacific. It has
climatic effects throughout the Pacific
region and in many other parts of the world.
The opposite of an El Nino event is called
La Nina.
Emissions
In the climate change context, emissions
refer to the release of greenhouse gases
and/or their precursors and aerosols into the
atmosphere over a specified area and period
of time.
Endemic
Restricted or peculiar to a locality or region.
With regard to human health, endemic can
refer to a disease or agent present or usually
prevalent in a population or geographical
area at all times.
Epidemic
Occurring suddenly in numbers clearly in
excess of normal expectancy, said especially
of infectious diseases but applied also
to any disease, injury, or other health-related
event occurring in such outbreaks.
Eutrophication
The process by which a body of water (often
shallow) becomes (either naturally or by
pollution) rich in dissolved nutrients with
a seasonal deficiency in dissolved oxygen.
Evaporation
The process by which a liquid becomes a
gas.
Evapotranspiration
The combined process of evaporation from
the Earth's surface and transpiration from
vegetation.
Exotic species
See introduced species.
Exposure
The nature and degree to which a system is
exposed to significant climatic variations.
Externality
See external cost.
External cost
Used to define the costs arising from any
human activity, when the agent responsible
for the activity does not take full account
of the impacts on others of his or her
actions. Equally, when the impacts are
positive and not accounted for in the actions
of the agent responsible they are referred to
as external benefits. Emissions of particulate
pollution from a power station affect the
health of people in the vicinity, but this is
not often considered, or is given inadequate
weight, in private decision making and there
is no market for such impacts. Such a
phenomenon is referred to as an
"externality," and the costs it imposes are
referred to as the external costs.
Extinction
The complete disappearance of an entire
species.
Extirpation
The disappearance of a species from part of
its range; local extinction.
Extreme weather event
An extreme weather event is an event that is
rare within its statistical reference
distribution at a particular place. Definitions
of "rare" vary, but an extreme weather event
would normally be as rare as or rarer than
the 10th or 90th percentile.
By definition, the characteristics of what is
called extreme weather may vary from place
to place. An extreme climate event is an
average of a number of weather events over
a certain period of time, an average which is
itself extreme (e.g., rainfall over a season).
F
Food security
6-6
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A situation that exists when people have
secure access to sufficient amounts of safe
and nutritious food for normal growth,
development and an active and healthy life.
Food insecurity may be caused by the
unavailability of food, insufficient
purchasing power, inappropriate
distribution, or inadequate use of food at the
household level.
Foodborne illness6
An illness caused by consuming foods or
beverages contaminated with any of many
different disease-causing microbes, or
pathogens, or poisonous chemicals, or other
harmful substances.
Footprint (ecological)7
An index of the area of productive land and
aquatic ecosystems required to produce the
resources used and to assimilate the wastes
produced by a defined population at a
specified material standard of living,
wherever on Earth that land may be located.
Forecast
See climate prediction and climate
projection.
G
General circulation
The large scale motions of the atmosphere
and the ocean as a consequence of
differential heating on a rotating Earth,
aiming to restore the energy balance of the
system through transport of heat and
momentum.
General Circulation Model (GCM)
See climate model.
GIS (Geographic Information Systems)8
A computerized system organizing data sets
through a geographical referencing of all
data included in its collections.
6 Definition modified from the Centers for
Disease Control and Prevention website:
http://www.cdc.gov/ncidod/dbmd/diseaseinfo/fo
odborneinfections_g.htm, viewed on November
21, 2007.
7 From the glossary of the Millenium Ecosystem
Assessment, 2005.
8 From the glossary of the Millenium Ecosystem
Assessment, 2005.
SAP 4.6 Glossary and A cronyms
Global surface temperature
The global surface temperature is the area-
weighted global average of (i) the sea
surface temperature over the oceans (i.e., the
sub-surface bulk temperature in the first few
meters of the ocean), and (ii) the surface air
temperature over land at 1.5 m above the
ground.
Globalization
The growing integration and
interdependence of countries worldwide
through the increasing volume and variety of
crossborder transactions in goods and
services, free international capital flows, and
the more rapid and widespread diffusion of
technology, information and culture.
Greenhouse effect
Greenhouse gases effectively absorb
infrared radiation, emitted by the Earth's
surface, by the atmosphere itself due to the
same gases, and by clouds. Atmospheric
radiation is emitted to all sides, including
downward to the Earth's surface. Thus
greenhouse gases trap heat within the
surface-troposphere system. This is called
the "natural greenhouse effect."
Atmospheric radiation is strongly coupled to
the temperature of the level at which it is
emitted. In the troposphere, the temperature
generally decreases with height. Effectively,
infrared radiation emitted to space originates
from an altitude with a temperature of, on
average, -19°C, in balance with the net
incoming solar radiation, whereas the
Earth's surface is kept at a much higher
temperature of, on average, +14°C. An
increase in the concentration of greenhouse
gases leads to an increased infrared opacity
of the atmosphere, and therefore to an
effective radiation into space from a higher
altitude at a lower temperature. This causes
a radiative forcing, an imbalance that can
only be compensated for by an increase of
the temperature of the surface-troposphere
system. This is the "enhanced greenhouse
effect."
Greenhouse gas
Greenhouse gases are those gaseous
constituents of the atmosphere, both natural
and anthropogenic, that absorb and emit
radiation at specific wavelengths within the
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SAP 4.6 Glossary and A cronyms
spectrum of infrared radiation emitted by
the Earth's surface, the atmosphere, and
clouds. This property causes the greenhouse
effect. Water vapor (H20), carbon dioxide
(C02), nitrous oxide (N20), methane
(CH4), and ozone (03) are the primary
greenhouse gases in the Earth's atmosphere.
Moreover there are a number of entirely
human-made greenhouse gases in the
atmosphere, such as the halocarbons and
other chlorine- and bromine-containing
substances, dealt with under the Montreal
Protocol. Besides C02, N20, and CH4, the
Kyoto Protocol deals with the greenhouse
gases sulfur hexafluoride (SF6),
hydrofluorocarbons (HFCs), and
perfluorocarbons (PFCs).
Gross Domestic Product
Gross Domestic Product (GDP) is the
monetary value of all goods and services
produced within a nation.
Gross National Product
Gross National Product (GNP) is the
monetary value of all goods and services
produced in a nation's economy, including
income generated abroad by domestic
residents, but without income generated by
foreigners.
Groundwater Recharge
The process by which external water is
added to the zone of saturation of an aquifer,
either directly into a formation or indirectly
by way of another formation.
H
Habitat
The particular environment or place where
an organism or species tend to live; a more
locally circumscribed portion of the total
environment.
Hantavirus
A virus in the family Bunyaviridae that
causes a type of haemorrhagic fever. It is
thought that humans catch the disease
mainly from infected rodents, either through
direct contact with the animals or by
inhaling or ingesting dust that contains
aerosolized viral particles from their dried
urine and other secretions.
Healthy Cities Program9
The WHO Healthy Cities programme
engages local governments in health
development through a process of political
commitment, institutional change, capacity
building, partnership-based planning and
innovative projects. It promotes
comprehensive and systematic policy and
planning with a special emphasis on health
inequalities and urban poverty, the needs of
vulnerable groups, participatory governance
and the social, economic and environmental
determinants of health. It also strives to
include health considerations in economic,
regeneration and urban development efforts.
Heat exhaustion10
Heat exhaustion is a phenomenon caused by
fluid loss, which in turn causes decreased
blood flow to vital organs. Reduced blood
flow from heat exhaustion can result in a
form of shock. Victims of heat exhaustion
often complain of flu-like symptoms hours
after exposure.
Heat index11
The heat index (HI), given in degrees F, is a
measure of how hot it feels when relative
humidity (RH) is combined with the actual
air temperature.
Heat island
An area within an urban area characterized
by ambient temperatures higher than those
of the surrounding area because of the
absorption of solar energy by materials like
asphalt.
Heat stroke12
9 Definition taken directly from
http://www.euro.who.int/healthy-cities on
November 21, 2007.
10 Definition from the U.S. Environmental
Protection Agency's Heat Island Glossary,
http://www.epa.gov/hiri/resources/glossary.html
#h, visited on November 21, 2007.
11 Defintion modified from NOAA's Heat Index
website,
http://www.crh. noaa.gov/jkl/?n=heat_index_calc
ulator, visited on November 21, 2007.
12 Definition from the U.S. Environmental
Protection Agency's Heat Island Glossary,
http://www.epa.gov/hiri/resources/glossary.html
#h, visited on November 21, 2007.
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SAP 4.6 Glossary and A cronyms
Heat stroke occurs when the body's heat
regulating mechanisms - including
convection, sweating, and respiration - fail.
The likelihood of heat stroke increases when
air temperatures are higher than skin
temperature, and when individuals are low
on fluids. Body temperatures can be raised
to the point at which brain damage and death
can result unless cooling measures are
quickly taken.
Human settlement
A place or area occupied by settlers.
Human system
Any system in which human organizations
play a major role. Often, but not always, the
term is synonymous with "society"
or "social system" (e.g., agricultural system,
political system, technological system,
economic system).
Hydrological systems
The systems involved in movement,
distribution, and quality of water throughout
the Earth, including both the hydrologic
cycle and water resources.
Hyperthermia13
Unusually high body temperature.
I
Ice sheet
A mass of land ice that is sufficiently deep
to cover most of the underlying bedrock
topography, so that its shape is mainly
determined by its internal dynamics (the
flow of the ice as it deforms internally and
slides at its base). An ice sheet flows
outward from a high central plateau with a
small average surface slope. The margins
slope steeply, and the ice is discharged
through fast-flowing ice streams or outlet
glaciers, in some cases into the sea or into
ice shelves floating on the sea. There are
only two large ice sheets in the modern
world, on Greenland and Antarctica, the
13 The American Heritage® Dictionary of the
English Language, Fourth Edition. Retrieved
November 21, 2007, fromDictionary.com
website:
littp: //die tio miry. refe rence. co ni/b row se/hy pe rtlie r
inia
Antarctic ice sheet being divided into East
and West by the Transantarctic Mountains;
during glacial periods there were others.
Ice shelf
A floating ice sheet of considerable
thickness attached to a coast (usually of
great horizontal extent with a level or gently
undulating surface); often a seaward
extension of ice sheets.
(Climate) Impact assessment
The practice of identifying and evaluating
the detrimental and beneficial consequences
of climate change on natural and human
systems.
(Climate) Impacts
Consequences of climate change on natural
and human systems. Depending on the
consideration of adaptation, one can
distinguish between potential impacts and
residual impacts. Potential impacts: All
impacts that may occur given a projected
change in climate, without considering
adaptation. Residual impacts: The impacts
of climate change that would occur after
adaptation. See also aggregate impacts,
market impacts, and non-market impacts.
Indicator14
Information based on measured data used to
represent a particular attribute,
characteristic, or property of a system.
Indigenous peoples
People whose ancestors inhabited a place or
a country when persons from another culture
or ethnic background arrived on the scene
and dominated them through conquest,
settlement, or other means and who today
live more in conformity with their own
social, economic, and cultural customs and
traditions than those of the country of which
they now form a part (also referred to as
"native," "aboriginal," or "tribal" peoples).
Industrial Revolution
A period of rapid industrial growth with far-
reaching social and economic consequences,
beginning in England during the second half
of the 18th century and spreading to Europe
and later to other countries including the
14 Definition taken from the Millenium
Ecosystem Assessment, Current State and
Trends Assessment Glossary, 2005
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SAP 4.6 Glossary and A cronyms
United States. The invention of the steam
engine was an important trigger of this
development. The Industrial Revolution
marks the beginning of a strong increase in
the use offossil fuels and emission of, in
particular, fossil carbon dioxide. In this
report, the terms "pre-industrial" and
"industrial" refer, somewhat arbitrarily, to
the periods before and after the year 1750,
respectively.
Inertia
Delay, slowness, or resistance in the
response of the climate, biological, or
human systems to factors that alter their rate
of change, including continuation of change
in the system after the cause of that change
has been removed.
Infectious diseases
Any disease that can be transmitted from
one person to another. This may occur by
direct physical contact, by common handling
of an object that has picked up infective
organisms, through a disease carrier, or by
spread of infected droplets coughed or
exhaled into the air.
Infrastructure
The basic equipment, utilities, productive
enterprises, installations, institutions, and
services essential for the development,
operation, and growth of an organization,
city, or nation. For example, roads; schools;
electric, gas, and water utilities;
transportation; communication; and legal
systems would be all considered as
infrastructure.
Integrated assessment
A method of analysis that combines results
and models from the physical, biological,
economic, and social sciences, and the
interactions between these components, in a
consistent framework, to evaluate the status
and the consequences of environmental
change and the policy responses to it.
Introduced species
A species occurring in an area outside its
historically known natural range as a result
of accidental dispersal by humans (also
referred to as "exotic species" or "alien
species").
Invasive species
An introduced species that invades natural
habitats.
IPCC15
A panel set up by the United Nations in
1988 to review scientific information on
climate change. This panel involves over
2,000 of the world's climate experts. Many
of the climate change facts and future
predictions we read about come from
information reviewed by the IPCC.
K
Kyoto Protocol
The Kyoto Protocol was adopted at the
Third Session of the Conference of the
Parties (COP) to the UN Framework
Convention on Climate Change (UNFCCC)
in 1997 in Kyoto, Japan. It contains legally
binding commitments, in addition to those
included in the UNFCCC. Countries
included in Annex B of the Protocol (most
member countries of the Organisation for
Economic Cooperation and Development
(OECD) and those with economies in
transition) agreed to reduce their
anthropogenic greenhouse gas emissions
(C02, CH4, N20, HFCs, PFCs, and SF6) by
at least 5% below 1990 levels in the
commitment period 2008 to 2012. The
Kyoto Protocol entered into force on 16
February 2005.
L
La Nina
See El Nino Southern Oscillation.
Land use
The total of arrangements, activities, and
inputs undertaken in a certain land cover
type (a set of human actions). The social and
economic purposes for which land is
managed (e.g., grazing, timber extraction,
and conservation).
Land-use change
15 Definition taken from the Climate Change
North Glossary at
http://www.climatechangenorth.ca/Hl_Glossary.
html on November 21, 2007.
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SAP 4.6 Glossary and A cronyms
A change in the use or management of land
by humans, which may lead to a change in
land cover. Land cover and land-use change
may have an impact on the albedo,
evapotranspiration, sources, and sinks of
greenhouse gases, or other properties of the
climate system, and may thus have an impact
on climate, locally or globally.
Landslide
A mass of material that has slipped downhill
by gravity, often assisted by water when the
material is saturated; rapid movement of a
mass of soil, rock, or debris down a slope.
Likelihood
The likelihood of an occurrence, an outcome
or a result, where this can be estimated
probabilistically, is expressed in this Report
using a standard terminology, defined in the
Introduction. See also uncertainty and
confidence.
Lyme disease
A vector-borne disease caused by the
spirochete Borrelia burgdorferi and
transmitted by Ixodes ticks, commonly
known as deer ticks. Symptoms include
skin lesions, fatigue, fever, and chills, and if
left untreated may later manifest itself in
cardiac and neurological disorders, joint
pain, and arthritis.
M
Maladaptation
Any changes in natural or human systems
that inadvertently increase vulnerability to
climatic stimuli; an adaptation that does not
succeed in reducing vulnerability but
increases it instead.
Malaria
Endemic or epidemic parasitic disease
caused by species of the genus Plasmodium
(protozoa) and transmitted by mosquitoes
of the genus Anopheles; produces high fever
attacks and systemic disorders, and kills
approximately 2 million people every year.
Market barriers
In the context of mitigation of climate
change, conditions that prevent or impede
the diffusion of cost-effective technologies
or practices that would mitigate greenhouse
gas emissions.
Market-based incentives
Measures intended to use price mechanisms
(e.g., taxes and tradable permits) to reduce
greenhouse gas emissions.
Market impacts
Impacts that are linked to market
transactions and directly affect Gross
Domestic Product (a country's national
accounts)—for example, changes in the
supply and price of agricultural goods. See
also non-market impacts.
Mitigation
An anthropogenic intervention to reduce the
sources or enhance the sinks of greenhouse
gases.
Mitigative capacity
The social, political, and economic
structures and conditions that are required
for effective mitigation.
Morbidity
Rate of occurrence of disease or other health
disorder within a population, taking account
of the age-specific morbidity rates. Health
outcomes include chronic disease
incidence/prevalence, rates of
hospitalization, primary care consultations,
disability-days (i.e., days when absent from
work), and prevalence of symptoms.
Mortality
Rate of occurrence of death within a
population within a specified time period;
calculation of mortality takes account of
age-specific death rates, and can thus yield
measures of life expectancy and the extent
of premature death.
N
Nitrogen oxides16
Compounds of nitrogen and oxygen
produced by the burning of fossil fuels.
No-regrets opportunities
See no-regrets policy.
No-regret options
Definition from
www.eia.doe.gov/oiaf/1605/95report/glossary.ht
ml visited on November 21, 2007.
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SAP 4.6 Glossary and A cronyms
See no-regrets policy.
No-regrets policy
One that would generate net social benefits
whether or not there is climate change. No-
regrets opportunities for greenhouse gas
emissions reduction are defined as those
options whose benefits such as reduced
energy costs and reduced emissions of
local/regional pollutants equal or exceed
their costs to society, excluding the benefits
of avoided climate change. No-regrets
potential is defined as the gap between the
market potential and the socio-economic
potential.
Non-linearity
A process is called "non-linear" when there
is no simple proportional relation between
cause and effect. The climate system
contains many such non-linear processes,
resulting in a system with a potentially very
complex behavior. Such complexity may
lead to rapid climate change.
Non-market impacts
Impacts that affect ecosystems or human
welfare, but that are not directly linked to
market transactions—for example, an
increased risk of premature death. See also
market impacts.
North Atlantic Oscillation (NAO)
The North Atlantic Oscillation consists of
opposing variations of barometric pressure
near Iceland and near the Azores. On
average, a westerly current, between the
Icelandic low pressure area and the Azores
high pressure area, carries cyclones with
their associated frontal systems towards
Europe. However, the pressure difference
between Iceland and the Azores fluctuates
on time scales of days to decades, and can
be reversed at times. It is the dominant
mode of winter climate variability in the
North Atlantic region, ranging from central
North America to Europe.
o
Ocean conveyor belt
The theoretical route by which water
circulates around the entire global ocean,
driven by wind and the thermohaline
circulation.
Opportunity
An opportunity is a situation or
circumstance to decrease the gap between
the market potential of any technology or
practice and the economic potential, socio-
economic potential, or technological
potential.
Opportunity costs
The cost of an economic activity forgone by
the choice of another activity.
Ozone (03)
Ozone, the triatomic form of oxygen (03), is
a gaseous atmospheric constituent. In the
troposphere it is created both naturally and
by photochemical reactions involving gases
resulting from human activities
(photochemical "smog"). In high
concentrations, tropospheric ozone can be
harmful to a wide-range of living organisms.
Tropospheric ozone acts as a greenhouse
gas. In the stratosphere, ozone is created by
the interaction between solar ultraviolet
radiation and molecular oxygen (02).
Stratospheric ozone plays a decisive role in
the stratospheric radiative balance. Its
concentration is highest in the ozone layer.
Depletion of stratospheric ozone, due to
chemical reactions that may be enhanced by
climate change, results in an increased
ground-level flux of ultraviolet-B radiation.
See also Montreal Protocol and ozone layer.
P
Parameterization
In climate models, this term refers to the
technique of representing processes, that
cannot be explicitly resolved at the spatial or
temporal resolution of the model (sub-grid
scale processes), by relationships between
the area- or time-averaged effect of such
sub-grid-scale processes and the larger scale
flow.
Pareto criterion/Pareto optimum
A requirement or status that an individual's
welfare could not be further improved
without making others in the society worse
off.
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SAP 4.6 Glossary and A cronyms
Particulates
Very small solid exhaust particles emitted
during the combustion of fossil and biomass
fuels. Particulates may consist of a wide
variety of substances. Of greatest concern
for health are particulates of less than or
equal to lOnm and 2.5 nm in diameter,
usually designated as PM10 and PM2.5,
respectively.
Pathogen17
An agent that causes disease, especially a
living microorganism such as a bacterium or
fungus.
Permafrost
Perennially frozen ground that occurs
wherever the temperature remains below
0°C for several years.
Photochemical smog
A mix of photochemical oxidant air
pollutants produced by the reaction of
sunlight with primary air pollutants,
especially hydrocarbons.
Point-source pollution
Pollution resulting from any confined,
discrete source, such as a pipe, ditch, tunnel,
well, container, concentrated animal feeding
operation, or floating craft. See also non-
point-source pollution.
Present value cost
The sum of all costs over all time periods,
with future costs discounted.
Projection (generic)
A projection is a potential future evolution
of a quantity or set of quantities, often
computed with the aid of a model.
Projections are distinguished from
"predictions" in order to emphasize that
projections involve assumptions concerning,
for example, future socio-economic and
technological developments that may or may
not be realized, and are therefore subject to
substantial uncertainty. See also climate
projection and climate prediction.
Proxy
17 The American Heritage® Dictionary of the
English Language, Fourth Edition. Retrieved
November 21, 2007, fromDictionary.com
website:
http://dictionary.reference.com/browse/pathogen
A proxy climate indicator is a local record
that is interpreted, using physical and
biophysical principles, to represent some
combination of climate-related variations
back in time. Climate-related data derived in
this way are referred to as proxy data.
Examples of proxies are tree ring records,
characteristics of corals, and various data
derived from ice cores.
Q
QALY (Quality Adjusted Life Year)18
A measure of the outcome of actions (either
individual or treatment interventions) in
terms of their health impact. If an action
gives a person an extra year of healthy life
expectancy, that counts as one QALY. If an
action gives a person an extra year of
unhealthy life expectancy (partly disabled or
in some distress), it has a value of less than
one. Death is rated at zero.
Quality of Life19
A scientific measure of personal well-being.
Categories used to define place-specific
quality of life include the inter-related
categories of economic conditions; natural
resources, environment, and amenities;
human health; public and private
infrastructure; government and public
safety; and social and cultural resources.
R
Radiative forcing
Radiative forcing is the change in the net
vertical irradiance (expressed in Wm-2) at
the tropopause due to an internal change or
a change in the external forcing of the
climate system, such as, for example, a
change in the concentration of carbon
dioxide or the output of the Sun. Usually
radiative forcing is computed after allowing
18 Definition taken from
http://www.aihw.gov.au/publications/health/ah9
6/ah96-x04.html visited on November 21, 2007.
19 Definition modified from text within Chapter 5
of this document.
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SAP 4.6 Glossary and A cronyms
for stratospheric temperatures to readjust to
radiative equilibrium, but with all
tropospheric properties held fixed at their
unperturbed values.
Range shifts
Climate change-induced changes in the
geographical distributions of plants, animals
and ecosystems
Rapid climate change
The non-linearity of the climate system may
lead to rapid climate change, sometimes
called abrupt events or even surprises. Some
such abrupt events may be imaginable, such
as a dramatic reorganization of the
thermohaline circulation, rapid deglaciation,
or massive melting of permafrost leading to
fast changes in the carbon cycle. Others may
be truly unexpected, as a consequence of a
strong, rapidly changing, forcing of a non-
linear system.
Reference scenario
See baseline/reference.
Reinsurance
The transfer of a portion of primary
insurance risks to a secondary tier of
insurers (reinsurers); essentially "insurance
for insurers."
Relative sea level
Sea level measured by a tide gauge with
respect to the land upon which it is situated.
See also Mean Sea Level.
Revealed preference20
The use of the value of expenditure to
"reveal" the preference of a consumer or
group of consumers for the bundle of goods
they purchase compared to other bundles of
equal or smaller value.
Reservoir
A component of the climate system, other
than the atmosphere, that has the capacity to
store, accumulate or release a substance of
concern (e.g., carbon or a greenhouse gas).
Oceans, soils, and forests are examples of
carbon reservoirs. The term also means an
artificial or natural storage place for water,
such as a lake, pond or aquifer, from which
20 Definition http://www-
personal.umich.edu/~alandear/glossary/r.html
visited on November 21, 2007.
the water may be withdrawn for such
purposes as irrigation or water supply.
Resilience
Amount of change a system can undergo
without changing state.
Response time
The response time or adjustment time is the
time needed for the climate system or its
components to re-equilibrate to a new state,
following a forcing resulting from external
and internal processes or feedbacks. It is
very different for various components of the
climate system. The response time of the
troposphere is relatively short, from days to
weeks, whereas the stratosphere comes into
equilibrium on a time scale of typically a
few months. Due to their large heat capacity,
the oceans have a much longer response
time, typically decades, but up to centuries
or millennia. The response time of the
strongly coupled surface-troposphere system
is, therefore, slow compared to that of the
stratosphere, and mainly determined by the
oceans. The biosphere may respond fast
(e.g., to droughts), but also very slowly to
imposed changes. See lifetime for a
different definition of response time
pertinent to the rate of processes affecting
the concentration of trace gases.
Rodent-borne disease21
Disease that is transmitted between hosts by
a rodent (e.g. bubonic plague, hantavirus).
Runoff
That part of precipitation that does not
evaporate and is not transpired.
s
Salinization
The accumulation of salts in soils.
Salmonella22
21 Definition modified from definition of vector-
borne disease.
22 Definition modified from information on the
CDC's website:
http://www.cdc.gov/ncidod/dbmd/diseaseinfo/sal
monellosis_g.htm#What%20sort%20of%20germ
%20is%20 Salmonella visited on November 21,
2007.
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SAP 4.6 Glossary and A cronyms
There are many different kinds of
Salmonella bacteria. They pass from the
feces of people or animals to other people or
other animals and can cause diarrheal illness
in humans. Salmonella has been known to
cause illness for over 100 years. They were
discovered by a American scientist named
Salmon, for whom they are named.
Saltwater intrusion/encroachment
Displacement of fresh surface water or
ground water by the advance of saltwater
due to its greater density, usually in coastal
and estuarine areas.
Scenario (generic)
A plausible and often simplified description
of how the future may develop, based on a
coherent and internally consistent set
of assumptions about key driving forces
(e.g., rate of technology change, prices) and
relationships. Scenarios are neither
predictions nor forecasts and sometimes
may be based on a "narrative storyline."
Scenarios may be derived from projections,
but are often based on additional
information from other sources. See also
SRES scenarios, climate scenario, and
emission scenarios.
Sea-level rise
An increase in the mean level of the ocean.
Eustatic sea-level rise is a change in global
average sea level brought about by an
alteration to the volume of the world ocean.
Relative sealevel rise occurs where there is a
net increase in the level of the ocean relative
to local land movements. Climate modelers
largely concentrate on estimating eustatic
sea-level change. Impact researchers focus
on relative sea-level change.
Seawall
A human-made wall or embankment along a
shore to prevent wave erosion.
Semi-arid regions
Ecosystems that have more than 250 mm
precipitation per year but are not highly
productive; usually classified as range lands.
Sensitivity
Sensitivity is the degree to which a system is
affected, either adversely or beneficially, by
climate-related stimuli. The effect may be
direct (e.g., a change in crop yield in
response to a change in the mean, range, or
variability of temperature) or indirect
(e.g., damages caused by an increase in the
frequency of coastal flooding due to sea-
level rise). See also climate sensitivity.
Sequential decision making
Stepwise decision making aiming to identify
short-term strategies in the face of long-term
uncertainties, by incorporating additional
information over time and making mid-
course corrections.
Sequestration
The process of increasing the carbon content
of a carbon reservoir other than the
atmosphere. Biological approaches to
sequestration include direct removal of
carbon dioxide from the atmosphere through
land-use change, afforestation,
reforestation, and practices that enhance soil
carbon in agriculture. Physical approaches
include separation and disposal of carbon
dioxide from flue gases or from processing
fossil fuels to produce hydrogen- and carbon
dioxide-rich fractions and longterm storage
in underground in depleted oil and gas
reservoirs, coal seams, and saline aquifers.
See also uptake.
Sink
Any process, activity or mechanism that
removes a greenhouse gas, an aerosol, or a
precursor of a greenhouse gas or aerosol
from the atmosphere.
Smog23
Air pollution typically associated with
oxidants.
Snowpacks
A seasonal accumulation of slow-melting
snow.
Social cost
The social cost of an activity includes the
value of all the resources used in its
provision. Some of these are priced and
others are not. Non-priced resources are
referred to as externalities. It is the sum of
the costs of these externalities and the priced
23 Definition from The U.S. EPA's Terms of
Environment Glossary at
http://www.epa.gov/OCEPAterms/sterms.html
visited on November 21, 2007.
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SAP 4.6 Glossary and A cronyms
resources that makes up the social cost. See
also private cost and total cost.
Social indicators24
Broad, standardized measures of the quality
of life or other socio-economic conditions of
geographic areas such as nations,
metropolitan areas, or other areas; used to
assess health conditions, educational levels,
food availability, violence, and other
conditions.
Socio-economic scenarios
Scenarios concerning future conditions in
terms of population, Gross Domestic
Product and other socio-economic factors
relevant to understanding the implications of
climate change. See SRES scenarios.
Source
Any process, activity, or mechanism that
releases a greenhouse gas, an aerosol, or a
precursor of a greenhouse gas or aerosol
into the atmosphere.
Southern Oscillation
See El Nino Southern Oscillation.
Spatial and temporal scales
Climate may vary on a large range of spatial
and temporal scales. Spatial scales may
range from local (less than 100,000 km2),
through regional (100,000 to 10 million
km2) to continental (10 to 100 million km2).
Temporal scales may range from seasonal to
geological (up to hundreds of millions of
years).
SRES scenarios
SRES scenarios are emissions scenarios
developed by Nakicenovic et al. (2000) and
used, among others, as a basis for the
climate projections in the IPCC WGI
contribution to the Third Assessment Report
(IPCC, 2001a). The following terms are
relevant for a better understanding of the
structure and use of the set of SRES
scenarios:
(Scenario) Family. Scenarios that have a
similar demographic, societal, economic,
and technical-change storyline. Four
scenario families comprise the SRES
scenario set: Al, A2, Bl, and B2.
24 Definition from
http://srmdc.net/glossary.htm#s visited on
November 21, 2007.
(Scenario) Group. Scenarios within a
family that reflect a consistent variation of
the storyline. The Al scenario family
includes four groups designated as AIT,
A1C, A1G, and A1B that explore alternative
structures of future energy systems.
In the Summary for Policymakers of
Nakicenovic et al (2000), the A1C and A1G
groups have been combined into one
"Fossil-Intensive" A1FI scenario group. The
other three scenario families consist of one
group each. The SRES scenario set reflected
in the Summary for Policymakers of
Nakicenovic et al. (2000) thus consist of six
distinct scenario groups, all of which are
equally sound and together capture the range
of uncertainties associated with driving
forces and emissions.
Illustrative Scenario: A scenario that is
illustrative for each of the six scenario
groups reflected in the Summary for
Policymakers of Nakicenovic et al. (2000).
They include four revised scenario markers
for the scenario groups A IB, A2, Bl, B2,
and two additional scenarios for the A1FI
and AIT groups. All scenario groups are
equally sound.
(Scenario) Marker. A scenario that was
originally posted in draft form on the SRES
website to represent a given scenario family.
The choice of markers was based on which
of the initial quantifications best reflected
the storyline, and the features of specific
models. Markers are no more likely than
other scenarios, but are considered by the
SRES writing team as illustrative of a
particular storyline. They are included in
revised form in Nakicenovic et al. (2000).
These scenarios have received the closest
scrutiny of the entire writing team and via
the SRES open process. Scenarios have also
been selected to illustrate the other two
scenario groups.
(Scenario) Storyline. A narrative
description of a scenario (or family of
scenarios) highlighting the main scenario
characteristics, relationships between key
driving forces, and the dynamics of their
evolution.
Stabilization
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SAP 4.6 Glossary and A cronyms
The achievement of stabilization of
atmospheric concentrations of one or more
greenhouse gases (e.g., carbon dioxide or a
C02-equivalent basket of greenhouse
gases).
Stakeholder
A person or an organization that has a
legitimate interest in a project or entity, or
would be affected by a particular action or
policy.
Stated preference25
Stated preference approaches, sometimes
referred to as direct valuation approaches,
are survey methods that estimate the value
individuals place on particular non-market
goods based on choices they make in
hypothetical markets
Stimuli (climate-related)
All the elements of climate change,
including mean climate characteristics,
climate variability, and the frequency and
magnitude of extremes.
Storm surge
The temporary increase, at a particular
locality, in the height of the sea due to
extreme meteorological conditions (low
atmospheric pressure and/or strong winds).
The storm surge is defined as being the
excess above the level expected from the
tidal variation alone at that time and place.
Storyline
See SRES scenarios.
Streamflow
Water within a river channel, usually
expressed in m3 sec-1.
Stratosphere
The highly stratified region of the
atmosphere above the troposphere
extending from about 10 km (ranging from 9
km in high latitudes to 16 km in the tropics
on average) to about 50 km.
Submergence
A rise in the water level in relation to the
land, so that areas of formerly dry land
become inundated; it results either from a
sinking of the land or from a rise of the
water level.
Subsidence
25 Definition taken from SAP 4.6.
The sudden sinking or gradual downward
settling of the Earth's surface with little or
no horizontal motion.
Subsidy
Direct payment from the government to an
entity, or a tax reduction to that entity, for
implementing a practice the government
wishes to encourage. Greenhouse gas
emissions can be reduced by lowering
existing subsidies that have the effect of
raising emissions, such as subsidies to fossil-
fuel use, or by providing subsidies for
practices that reduce emissions or enhance
sinks (e.g., for insulation of buildings or
planting trees).
Sustainable development
Development that meets the needs of the
present without compromising the ability of
future generations to meet their own needs.
T
Technology
A piece of equipment or a technique for
performing a particular activity.
Thermal erosion
The erosion of ice-rich permafrost by the
combined thermal and mechanical action of
moving water.
Thermal expansion
In connection with sea level, this refers to
the increase in volume (and decrease in
density) that results from warming water. A
warming of the ocean leads to an expansion
of the ocean volume and hence an increase
in sea level.
Thermohaline circulation
Large-scale density-driven circulation in the
ocean, caused by differences in temperature
and salinity. In the North Atlantic, the
thermohaline circulation consists of warm
surface water flowing northward and cold
deepwater flowing southward, resulting in a
net poleward transport of heat. The surface
water sinks in highly restricted sinking
regions located in high latitudes.
Threshold
The level of magnitude of a system process
at which sudden or rapid change occurs. A
point or level at which new properties
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SAP 4.6 Glossary and A cronyms
emerge in an ecological, economic or other
system, invalidating predictions based on
mathematical relationships that apply at
lower levels.
Time-series studies26
Studies done using a set of data that
expresses a particular variable measured
overtime.
Top-down models
The terms "top" and "bottom" are shorthand
for aggregate and disaggregated models. The
top-down label derives from how modelers
applied macro-economic theory and
econometric techniques to historical data on
consumption, prices, incomes, and factor
costs to model final demand for goods and
services, and supply from main sectors, like
the energy sector, transportation, agriculture,
and industry. Therefore, top-down models
evaluate the system from aggregate
economic variables, as compared to bottom-
up models that consider technological
options or project specific climate change
mitigation policies. Some technology data
were, however, integrated into top-down
analysis and so the distinction is not that
clear-cut.
Total cost
All items of cost added together. The total
cost to society is made up of both the
external cost and the private cost, which
together are defined as social cost.
Trade effects
Economic impacts of changes in the
purchasing power of a bundle of exported
goods of a country for bundles of goods
imported from its trade partners. Climate
policies change the relative production costs
and may change terms of trade substantially
enough to change the ultimate economic
balance.
Transient climate response
The globally averaged surface air
temperature increase, averaged over a 20-
year period, centered at the time of C02
doubling (i.e., at year 70 in a 1% per year
26 Definition modified from the definition of
time-series data from the Millennium Ecosystem
Assessment, 2005.
compound C02 increase experiment with a
global coupled climate model).
Troposphere
The lowest part of the atmosphere from the
surface to about 10 km in altitude in mid-
latitudes (ranging from 9 km in high
latitudes to 16 km in the tropics on average)
where clouds and "weather" phenomena
occur. In the troposphere, temperatures
generally decrease with height.
Tundra
A treeless, level, or gently undulating plain
characteristic of arctic and subarctic regions.
u
Uncertainty
An expression of the degree to which a
value (e.g., the future state of the climate
system) is unknown. Uncertainty can result
from lack of information or from
disagreement about what is known or even
knowable. It may have many types of
sources, from quantifiable errors in the data
to ambiguously defined concepts or
terminology, or uncertain projections of
human behavior. Uncertainty can therefore
be represented by quantitative measures
(e.g., a range of values calculated by various
models) or by qualitative statements (e.g.,
reflecting the judgment of a team of
experts). See Moss and Schneider (2000).
See also confidence and likelihood.
Unique and threatened systems
Entities that are confined to a relatively
narrow geographical range but can affect
other, often larger entities beyond their
range; narrow geographical range points to
sensitivity to environmental variables,
including climate, and therefore attests to
potential vulnerability to climate change.
United Nations Framework Convention
on Climate Change (UNFCCC)
The Convention was adopted on 9 May
1992, in New York, and signed at the 1992
Earth Summit in Rio de Janeiro by more
than 150 countries and the European
Community. Its ultimate objective is the
'stabilization of greenhouse gas
concentrations in the atmosphere at a level
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SAP 4.6 Glossary and A cronyms
that would prevent dangerous anthropogenic
interference with the climate system'. It
contains commitments for all Parties. Under
the Convention, Parties included in Annex I
aim to return greenhouse gas emissions not
controlled by the Montreal Protocol to 1990
levels by the year 2000. The Convention
entered in force in March 1994. See also
Kyoto Protocol.
Urban Heat Island Effect27
The urban heat island effect is a measurable
increase in ambient urban air temperatures
resulting primarily from the replacement of
vegetation with buildings, roads, and other
heat-absorbing infrastructure. The heat
island effect can result in significant
temperature differences between rural and
urban areas.
Urbanization
The conversion of land from a natural state
or managed natural state (such as
agriculture) to cities; a process driven by net
rural-to-urban migration through which an
increasing percentage of the population in
any nation or region come to live in
settlements that are defined as "urban
centers".
V
Valley Fever (Coccidiomycosis)28
An infectious respiratory disease of humans
and other animals caused by inhaling the
fungus Coccidioides immitis. It is
characterized by fever and various
respiratory symptoms. Also called
coccidiomycosis.
Valuation29
27 Definition from the U.S. Environmental
Protection Agency's Heat Island Glossary,
http://www.epa.gov/hiri/resources/glossary.html
#h, visited on November 21, 2007.
28 The American Heritage® Dictionary of the
English Language, Fourth Edition. Retrieved
November 21, 2007, fromDictionary.com
website:
http://dictionary.reference.com/browse/valley
fever.
29 Definition taken from the glossary of the
Millenium Ecosystem Assessment, 2005.
The process of expressing a value for a
particular good or service in a certain
context (e.g., of decision-making) usually in
terms of something that can be counted,
often money, but also through methods and
measures from other disciplines (sociology,
ecology, and so on). See also Values.
Value added
The net output of a sector after adding up all
outputs and subtracting intermediate inputs.
Value of a statistical life (VSL)30
The sum of what people would pay to
reduce their risk of dying by small amounts
that, together, add up to one statistical life.
Values
Worth, desirability, or utility based on
individual preferences. The total value of
any resource is the sum of the values of the
different individuals involved in the use of
the resource. The values, which are the
foundation of the estimation of costs,
are measured in terms of the willingness to
pay (WTP) by individuals to receive the
resource or by the willingness of individuals
to accept payment (WTA) to part with the
resource.
Vector
An organism, such as an insect, that
transmits a pathogen from one host to
another. See also vector-borne diseases.
Vector-borne diseases
Disease that is transmitted between hosts by
a vector organism such as a mosquito or tick
(e.g., malaria, dengue fever, and
leishmaniasis).
Volatile Organic Compounds (VOCs)31
Organic compounds that evaporate readily
into the air. VOCs include substances such
as benzene, toluene, methylene chloride, and
methyl chloroform.
Vulnerability
The degree to which a system is susceptible
to, or unable to cope with, adverse effects of
climate change, including climate variability
and extremes. Vulnerability is a function of
the character, magnitude, and rate of climate
30 Definition taken from SAP4.6.
31 Definition from ATSDR's Glossary of Terms
at http://www.atsdr.cdc.gov/glossary.html#G-T-
visited on November 21, 2007.
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SAP 4.6 Glossary and A cronyms
variation to which a system is exposed, its
sensitivity, and its adaptive capacity.
w
Water consumption
Amount of extracted water irretrievably lost
during its use (by evaporation and goods
production) .Water consumption is equal to
water withdrawal minus return flow.
Water stress
A country is water-stressed if the available
freshwater supply relative to water
withdrawals acts as an important constraint
on development. Withdrawals exceeding
20% of renewable water supply has been
used as an indicator of water stress.
Water-use efficiency
Carbon gain in photosynthesis per unit water
lost in evapotranspiration. It can be
expressed on a short-term basis as the ratio
of photosynthetic carbon gain per unit
transpirational water loss, or on a seasonal
basis as the ratio of net primary production
or agricultural yield to the amount of
available water.
Water withdrawal
Amount of water extracted from water
bodies.
Waterborne diseases32
Diseases contracted through contact with
water that is infected with any of numerous
pathogens including Vibrio cholerae,
Campylobacter, Salmonella, Shigella, and
the diarrheogenic Escherichia coli.
Watershed33
The land area that drains into a particular
watercourse or body of water. Sometimes
used to describe the dividing line of high
ground between two catchment basins.
Welfare
An economic term used to describe the state
of well-being of humans on an individual or
collective basis. The constituents of well-
being are commonly considered to include
materials to satisfy basic needs, freedom and
choice, health, good social relations, and
security.
Well-being 34
A context- and situation-dependent state,
comprising basic material for a good life,
freedom and choice, health and bodily well-
being, good social relations, security, peace
of mind, and spiritual experience.
West Nile virus35
West Nile virus (WNV) is a single-stranded
RNA virus of the family Flaviviridae, genus
Flavivirus. The main lifecycle of WNV is
between birds and insects. Humans are most
often infected by a bite from an infected
mosquito. Most people infected with WNV
don't show any symptoms, whereas those
that do are often diagnosed with West Nile
Fever which can last up to two weeks.
Zoonoses
Diseases and infections which are naturally
transmitted between vertebrate animals and
people. See also zoonotic disease.
Zoonotic disease
A disease that normally exists in other
vertebrates but also infects humans, such as
dengue fever, avian flu, west Nile virus and
bubonic plague.
Definition modified from information on
CDC's website
http://www.cdc.gov/ncidod/dbmd/diseaseinfo/wa
terbornediseases t.htm visited on November 21,
2007.
33
Definition taken from the glossary of the
Millenium Ecosystem Assessment, 2005.
Definition modified from the Millenium
Ecosystem Assessment, Current State and
Trends Assessment Glossary, 2005
35 Definition modified from information on
http://www.cdc.gov/ncidod/dvbid/westnile/index
.htm
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SAP 4.6 Glossary and A cronyms
6.2 Acronyms
AAG
AAP
AIACC
AMR-A
CCP
CCSP
CDC
CLIMB
C02
CVD
DHS
ECHAM4
ENSO
EPA
FDA
FEMA
GCM
GDP
GIS
GISS
ICLEI
IPCC
MA
MM5
MSA
NAAQS
NACC
NAS
NAST
NEG/ECP
NGO
NO
NOAA
NRC
NYCHP
PM
PM2.5
PTSD
RADM2
RCM
RMNP
SAP
SRES
TBE
Association of American Geographers
American Academy of Pediatrics
Assessment of Impacts and Adaptations to Climate Change
North American Region
ICLEI's Cities for Climate Protection
Climate Change Science Program
Center for Disease Control
Climate's Long-Term Impacts on Metro Boston
Carbon Dioxide
Cardiovascular Disease
Department of Homeland Security
A model named after the European Centre for Medium Range Weather Forecasts
(ECMRWF), (giving it the first part of the name - EC), which was developed in
Hamburg (HAM)
El Nino/Southern Oscillation
Environmental Protection Agency
Food and Drug Administration
Federal Emergency Management Agency
General Circulation Model
Gross Domestic Product
Geographic Information Systems
NASA Goddard Institute for Space Studies
International Council for Local Environmental Initiatives
Intergovernmental Panel on Climate Change
Millennium Assessment
Mesoscale Model
Metropolitan Statistical Areas
National Ambient Air Quality Standards
U.S. National Assessment of Climate Change
National Academy of Sciences
National Assessment Synthesis Team
New England Governors and Eastern Canadian Premiers
Non-Governmental Organization
Nitric oxide
National Oceanic and Atmospheric Administration
National Research Council
New York Climate and Health Project
Particulate Matter
Particulate Matter (smaller than 2.5 micrometers)
Post-Traumatic Stress Disorder
Regional Acid Deposition Model, Version 2
Regional Climate Model
Rocky Mountain National Park
Synthesis and Assessment Products
Special Report on Emissions Scenarios
Tick-borne Encephalitis
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SAP 4.6 Glossary and A cronyms
UHI
Urban Heat Island Effect
UNDP
United Nations Development Programme
UNEP
United Nations Environmental Programme
U.S. BEA
United States Bureau of Economic Analysis
USD A
U.S. Department of Agriculture
USGCRP
United States Global Change Research Program
VBZ
Vector Born and Zoonotic
VEMAP
Virtual Earth Map
voc
Volatile Organic Matter
VSL
Value of Statistical Life
WHO
World Health Organization
WTP
Willingness to Pay
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