6OORO9O4O

                        ects
     of Global Change on
 Human Health and Welfare
     and Human Systems
U.S. Climate Change Science Program
 Synthesis and Assessment Product 4.6


           September 2008

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  FEDERAL EXECUTIVE TEAM
  Director, Climate Change Science Program	William J. Brennan

  Director, Climate Change Science Program Office	Peter A. Schultz

  Lead Agency Principal Representative to Climate Change Science Program,
  National Program Director for the Global Change Research Program,
  U.S. Environmental Protection Agency	JoelD. Scheraga

  Product Lead, Global Ecosystem Research and Assessment Coordinator,
  Global Change Research Program, U.S. Environmental Protection Agency	Janet L. Gamble

  Chair, Synthesis and Assessment Product Advisory Group
  Associate Director, National Center for Environmental
  Assessment, U.S. Environmental Protection Agency	Michael W. Slimak

  Synthesis and Assessment Product Coordinator,
  Climate Change Science Program Office	Fabien J.G. Laurier

  Special Advisor, National Oceanic and
  Atmospheric Administration	Chad McNutt


  EDITORIAL AND PRODUCTION TEAM
  Editor, U.S. Environmental Protection Agency	Janet L. Gamble

  Technical Advisor, Climate Change Science Program Office	David J. Dokken

  Technical Editor, ICF International	Melinda Harris

  Technical Editor, ICF International	Toby Krasney

  Reference Coordinator, ICF International	Paul Stewart

  Reference Coordinator, ICF International	Dylan Harrison-Atlas

  Reference Coordinator, ICF International	Sarah Shapiro

  Logistical and Technical Support, ICF International	Lauren Smith
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 provide recommendations for regulatory action.

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         Analyses of the Effects
           of Global Change  on
     Human Health and  Welfare
           and Human Systems
   Final Report, Synthesis and Assessment Product 4.6
   Report by the 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 Authors1
                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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July 2008
Members of Congress:

On behalf of the National Science and Technology Council, the U.S. Climate Change Science Program
(CCSP) is pleased to transmit to the President and the Congress this Synthesis and Assessment Product
(SAP), Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems.
This is part of a series of 21 SAPs produced by the CCSP aimed at providing current assessments of
climate change science to inform public debate, policy, and operational decisions. These SAPs are also
intended to help the CCSP develop future program research priorities. This SAP is issued pursuant to
Section 106 of the Global Change Research Act of 1990 (Public Law 101-606).

The CCSP's guiding vision is to provide the Nation and the global community with the science-based
knowledge  needed to manage the risks and  capture the opportunities associated with climate and related
environmental changes. The SAPs are important steps toward achieving that vision and help to translate
the CCSP's extensive observational and research database into informational tools that directly address
key questions being asked of the research community.

This SAP focuses on the effects of global change on human health and welfare and human systems.  It
was developed with broad scientific input and in accordance with the Guidelines for Producing CCSP
SAPs, the Federal Advisory Committee Act, the Information Quality Act, Section 515 of the Treasury
and General Government Appropriations Act for fiscal year 2001 (Public Law 106-554), and the
guidelines issued by the Environmental Protection Agency pursuant to Section 515.

We commend the report's authors for both the thorough nature of their work and their adherence to an
inclusive review process.
                             Sincerely,
Carlos M. Gutierrez
Secretary of Commerce

Chair, Committee on
Climate Change Science
and Technology Integration
Samuel W. Bodman
Secretary of Energy

Vice Chair, Committee on
Climate Change Science
and Technology Integration
John H. Marburger III
Director, Office of Science
and Technology Policy
Executive Director, Committee
on Climate Change Science and
Technology Integration

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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 Office
of Management and Budget'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 continents, 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 cases, later drafts of the report. Reviewers from within EPA included:
       Lisa Conner
       Barbara Glenn
       Ju-Chin Huang
       Sara Terry
   Adam Daigneault
   Doug Grano
   Stephen Newbold
Benjamin De Angelo
Matthew Heberling
Jason Samenow
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
Federal Agency Reviewers
                                 Christopher Weaver
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
        Mary Gant
        Indur M. Goklany
        Charlotte Skidmore
        Samuel P. Williamson
                        Department of Transportation
National Institutes of Environmental Health Sciences/NIH
                              Department of Interior
                    Office of Management and Budget
       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
        Katherine Farrell
        Hans Martin Fuessel
        Eric Holdsworth
        John Kinsman
        Kim Knowlton
        Sabrina McCormick
        J. Alan Roberson
        Gina Solomon
                             Edison Electric Institute
                                          AACDH
                                            PICIR
                             Edison Electric Institute
                             Edison Electric Institute
                   Natural Resources Defense Council
                           Michigan State University
                   American Water Works Association
                   Natural Resources Defense Council

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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 HICCAC
panel 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
        Co-chair
        Members
Tom Dietz
Barbara Entwisle
Howard Frumkin
Peter Gleick
Jonathan Patz
Roger Pulwarty
Eugene Rosa
Susan Stonich
               Michigan State University
             University of North Carolina
Centers for Disease Control and Prevention
                        Pacific Institute
                 University of Wisconsin
                               NOAA
             Washington State University
  University of California at  Santa Barbara
Thanks are also in order to Joanna Foellmer, the Designated Federal Official from within the National Center
for Environmental Assessment 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.

Summary

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.

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                          AUTHOR 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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 RECOMMENDED CITATIONS
 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,
 TJ. 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. 1-11.

 For Chapter  I:

 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. 13-37.

 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. 39-87.

 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. 89-109.

 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. 111-168.

 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. 169-176.
vi

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CO
<
Executive Summary
Abstract	I
ES. I  Climate Change and Vulnerability	I
ES.2 Climate Change and Human Health	3
ES.3 Climate Change and Human Settlements	8
ES.4 Climate Change and Human Welfare	10

CHAPTER

 I  Introduction	13
I.I Scope and Approach of SAP 4.6	13
1.2 Climate Change in the United States:
       Context for an Assessment of Impacts on Human Systems	16
       1.2.1 Rising Temperatures	17
       1.2.2 Trends in Precipitation	18
       1.2.3 Rising Sea Levels and Erosion of Coastal Zones	19
       1.2.4 Changes in Extreme Conditions	20
1.3 Population Trends and Migration Patterns:
       A Context for Assessing Climate-related Impacts	22
       1.3.1 Trends in Total U.S. Population	22
       1.3.2 Migration Patterns	24
1.4 Complex Linkages:The Role of Non-climate Factors	26
       1.4.1 Economic Status	26
       1.4.2 Technology	27
       1.4.3 Infrastructure	27
       1.4.4 Human and Social Capital and Behaviors	28
       1.4.5 Institutions	29
       1.4.6 Interacting Effects	29
1.5 Reporting Uncertainty in SAP 4.6	30
1.6 References	32


Z Effects of Global Change on Human Health	39
2.1 Introduction	39
2.2 Observed Climate-sensitive Health Outcomes in the United States	40
       2.2.1 Thermal Extremes: Heat Waves	40
       2.2.2 Thermal Extremes: Cold Waves	42
       2.2.3 Extreme Events: Hurricanes, Floods, and Wildfires	42
       2.2.4 Indirect Health Impacts of Climate Change	44
2.3 Projected Health Impacts of Climate Change in the United States	50
       2.3.1 Heat-related Mortality	50
       2.3.2 Hurricanes, Floods,Wildfires and Health Impacts	52
       2.3.3 Vector-borne and Zoonotic Diseases	53
       2.3.4 Water- and Food-borne Diseases	53
       2.3.5 Air Quality Morbidity and Mortality	53
2.4 Vulnerable Regions and Subpopulations	61
       2.4.1 Vulnerable  Regions	61
       2.4.2 Specific Subpopulations at Risk	62
2.5 Adaptation	65
       2.5.1 Actors and  Their Roles and Responsibilities for Adaptation	66
       2.5.2 Adaptation Measures to Manage
       Climate Change-Related Health Risks	68
2.6 Conclusions	68
2.7 Expanding the Knowledge Base	73
2.8 References...                                                    ...75

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     I-
     o
     u
     o
     CO
     f
VIII
•5 Effects of Global Change on Human Settlements	89
3.1 Introduction	89
       3.1.1 Purpose	89
       3.1.2 Background	89
       3.1.3 Current State of Knowledge	90
3.2 Climate Change Impacts and the
       Vulnerabilities of Human Settlements	90
       3.2.1 Determinants of Vulnerability	90
       3.2.2 Impacts of Climate Change on Human Settlements	92
       3.2.3 The Interaction of Climate Impacts
       with Non-climate Factors	96
       3.2.4 Realizing Opportunities from
       Climate Change in the United States	98
       3.2.5 Examples of Impacts on
       Metropolitan Areas in the United States	98
3.3 Opportunities for Adaptation of
       Human Settlements to Climate Change	100
       3.3.1 Perspectives on Adaptation by Settlements	101
       3.3.2 Major Categories of Adaptation Strategies	102
       3.3.3 Examples of Current Adaptation Strategies	103
       3.3.4 Strategies to Enhance Adaptive Capacity	104
3.4 Conclusions	104
3.5 Expanding the Knowledge Base	105
3.6 References	106


4 Effects of Global Change on Human Welfare	 I I
4.1 Introduction	 I I
4.2 Human Welfare, Well-being, and Quality of Life	 12
       4.2.1 Individual Measures of Well-being	 14
       4.2.2The Social Indicators Approach	 15
       4.2.3 A Closer Look at Communities	120
       4.2.4 Vulnerable Populations, Communities, and Adaptation	123
4.3 An Economic Approach to Human Welfare	124
       4.3.1 Economic Valuation	126
       4.3.2 Impacts Assessment and Monetary Valuation	127
       4.3.3 Human Health	128
       4.3.4 Ecosystems	133
       4.3.5 Recreational Activities and Opportunities	140
       4.3.6 Amenity Value of Climate	147
4.4 Conclusions	151
4.5 Expanding the Knowledge Base	153
4.6 References	154
4.7 Appendix	163

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o
U
J Common Themes and Research Recommendations	169
5.1 Synthesis and Assessment Product 4.6: Advances in the Science	169
       5.1.1 Complex Linkages and a Cascading
       Chain of Impacts Across Global Changes	169
       5.1.2 Changes in Climate Extremes and Climate Averages	170
       5.1.3 Vulnerable Populations and Vulnerable Locations	171
       5.1.4 The Cost of and Capacity for Adaptation	172
       5.1.5 An Integrative Framework	172
5.2 Expanding the Knowledge Base	173
       5.2.1 Human Health Research Gaps	174
       5.2.2 Human Settlements Research Gaps	175
       5.2.3 Human Welfare Research Gaps	176
                         Glossary and Acronyms	177
                                                                                                ix

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             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 RWeaver, U.S.
                                            Environmental Protection Agency; Melinda Harris, ICF International;
                                            Randy Freed, ICF International
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— 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. 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 well-being in the United
States. Because climate change forecasts are
generally not specific enough for the scale of

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The U.S. Climate Change Science Program
                              Executive Summary
                        local decision-making, this report adopts a
                        vulnerability perspective in assessing impacts
                        on human society.

                        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,
by 2100 the  U.S. 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. Many rapidly growing cities and towns
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 at risk over
the next several decades.

Climate  is only one of a number of global
changes that affect human well-being. 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

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
from climate because they fundamentally shape
the nature and scope of human vulnerability.
Understanding the impacts of climate change
and variability on the quality of life in the
United States  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 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 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; and 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.

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 percent by 2010
and 20 percent by 2030 (more than 50 million

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The U.S. Climate Change Science Program
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 United  States 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 all have the potential
to affect public health through direct and
indirect health risks. SAP 3.3  indicates that
there is  evidence for increased  sea surface
temperatures in the tropical Atlantic and there
is a strong correlation to Atlantic tropical storm
frequency, duration, and intensity. However, a
valid 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 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.

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The U.S. Climate Change Science Program
                              Executive Summary
                        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
                        air-borne 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
                        in 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.
Changes in precipitation patterns will affect
water supplies nationwide, with precipitation
varying across regions and over time. Likely
reductions in snow melt, 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 water flows from snow melt.
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.

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            Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 The U.S. Climate Change Science Program
                               Executive Summary
                         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, 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 is expected to be
                         challenged, especially in locales with relatively
                         limited social and political capital.

                         Finally, population growth and economic
                         development are 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, live in
                         one of 673 coastal counties. Coastal areas—
                         particularly those on gently sloping coasts and
                         zones with gradual land subsidence—will be at
                         risk from sea level rise, impacts especially those
                         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 involve living conditions and 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. However, 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 radia-
   tive forcing scenarios, often based on simulations
   by climate models. Climate projections are distin-
   guished from climate predictions, in that the former
   critically depend on the emissions/concentration/ra-
   diative forcing scenario used, and therefore on highly
   uncertain assumptions of future socioeconomic and
   technological development.
10

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 percent 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.
                                                                                                         II

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
                                           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
 I.I SCOPE AND APPROACH
OF 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 (such as prevention,
response, and treatment strategies) that could
be revised, supplemented, or implemented to
protect human health and determine 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,
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                                      Chapter
                        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.

                        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 freedom,
                        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 the following:

•  Avoid maladaptive responses;
•  Establish protocols to detect and measure
   risks and to manage risks proactively
   when possible;
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
•  Leverage technical and  institutional
   capacity;
•  Reduce  current  vulnerabilities to
   climate change;
•  Develop adaptive capacity to address  new
   climate risks that  exceed  conventional
   adaptive responses; and,
•  Recognize and respond to impacts that  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 et al., 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 et al., 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,
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.
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                                     Chapter
                        The  scale and complexity of these built
                        environments, transportation networks, energy
                        and resource demands, and the interdependence
                        of these systems and their populaces, suggest
                        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
                        Intermountain 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:
•  Changes in climate in the united states;
•  Population trends, migration patterns, and the
   distribution of people across settlements;
•  Non-climate stressors and their interactions
   with climate change to realize complex
   impacts; and,
•  A discussion of the handling of uncertainty
   in reporting scientific results.

 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.
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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
increase in their intensity and duration since
the 1970s (Christensen etal., 2007).

The  following  sections provide a brief
introduction to climate change as a context for the
following chapters on impacts and adaptation.
SAP 4.6  does not evaluate climate change
projections as they are 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), the
IPCC 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)."
•  "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 percent  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  different 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 et al., 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 I.la). The
degree of warming has varied by region across
the United States, with the West and Alaska
I
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         The U.S. Climate Change Science Program
                                                                                  Chapter I
I
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).

The current generation of global climate models,
run with  IPCC SRES  scenarios  of future
greenhouse gas emissions, simulates 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
                        1896
                                1916
                                         1936
                                                  1956
                                                           1976
                                                                    1996
                      1896
                               1916
                                        1936
                                                1956
                                                         1976
                                                                  1996
                 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)
States is projected to exceed 2°C, with projected
increases in summertime temperatures ranging
between 3 and 5°C (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 Lib). Broken
down by season, winter precipitation around
the coastal areas, including the West, Gulf,  and
Atlantic coasts, has been increasing by up to 30
percent while precipitation in the central part of
the country (the Midwest and the Great Plains)
has been decreasing by up to 20 percent. 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
percent in summer rainfall over California  and
the Pacific Northwest, and decreases on  the
order  of 20 to 40  percent 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 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).
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
Global model simulations summarized in the
North American Chapter of the IPCC Fourth
Assessment Report show moderate increases
in precipitation (10 percent 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 past 50 years, changes in the timing of
snow  melt has shifted the schedule of snow-fed
stream flow in the western part of the country
earlier by 1 to 4 weeks. (Stewart et al., 2005).
The seasonal "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 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 U.S. coasts 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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                                                                                 Chapter
I
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 past 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
(Kunkele/fl/.,2004).

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 et 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 3.3, 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
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 percent across much of the Midwest and
Northeast over the past 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 etal, 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 et al., 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 as well as a lack of
cloudiness/low 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 percent: by comparison, in 1934 the area
affected by drought was as high as 65  percent
(CCSP, 2008). In recent years, the drought-
affected area ranged between 35 and 40 percent
(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 et
al, 2004; Andreadis and Lettenmaier, 2006).
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 The U.S. Climate Change Science Program
                                      Chapter I
                         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 el 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 et al., 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. SAP 3.3 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 that  is consistent with more frequent
                         and intense hurricanes (CCSP, 2008).
For North Atlantic hurricanes,  SAP 3.3
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, SAP
3.3 concluded that "frequency changes are
currently too uncertain for confident projection
(CCSP, 2008)." SAP 3.3 also found that the
spatial distribution of hurricanes will likely
change. Storm surge is likely to increase due to
projected sea level rise, although the degree to
which this 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 U.S. population numbered some  280
million individuals in 2000.' In  1900, the U.S.
population numbered about 76 million people;
fifty years later the population had roughly
doubled to 151 million people.
1 Information on historical U.S population data and
  current population estimates and projections can be
  found at http://www.census.gov/.
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 etal., 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, Bl, 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)

The U.S. 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 United States.
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 A1/B1 and B2 scenarios fall
below the Census middle projection.

1.3.1.1  Aging of the Population

The U.S. population has not only increased
by 300  percent over the  past century, it has
also shifted in its demographic  structure. For
example, in 1900 less than 4 percent of the
U.S. population was 65 years or older; currently
about 12 percent 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 percent of the total
population. Nearly 5 percent of the projected
population in 2050, over 20 million people, will
be 85 years or older (He etal., 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.

The projected increase in the elderly population
is an  important variable  in projections of
2 See Census website 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.
                                                                             Census 1990 low
                                                                             Census 1990 mid
                                                                          — Consul 1990 high
                                                                             SRESA1.B1
                                                                          — SRESA2
                                                                         	SRESB2
        2000   2010   2020   2030   2040   2050   2060   2070   2080   2090
                                                                    2100
Figure 1.2 U.S. Population Projections 2000-2IOO
Data source: Census Population Projections http://www.census.gov/population/www/projections/natsum-TI.html
SRES Population Projections: http://sres.ciesin.columbia.edu/tgcia/
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 The U.S. Climate Change Science Program
                                      Chapter I
       Figure 1.3 Population Pyramids of the U.S. 2000 and 2050 (Interim Projections based on 2000 Census)
       Data source: Census Population Projections http://www.census.gov/ipc/www/usinterimproj/
                         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 heat waves, 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  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 (U.S.
                         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 percent to
47 percent 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).

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). More
than 50 percent of the U.S. 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 et al., 1999). With
rapidly growing communities near coastlines,
property damages can 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 America  is 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 percent had recently moved from out
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              Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
     Projected change in county
     population (percent), 1970 to 2030
U.S. Population and Growth Trends
Change in county population, 1970-2030
Each block on map illustrations on county in the U.S. The height of each
block is proportional to that county's population density in the year 2000,
so the volume of the block is proportioned to the county's total population.
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.
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)
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.).

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:
4 http://www.census.gov/Press-Release/www/2002/
  sumfile3.html
5 Study methodologies include: aggregate studies of
  population changes alongside regional characteris-
  tics, explanatory models developed from individual
  migration data and individual surveys.
                  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.
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 The U.S. Climate Change Science Program
                                     Chapter I
                         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 requires 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 these factors
                        in a consistent way.

                        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 that 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).

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
United States to adapt to climate change.

 1.4.1 Economic  Status

The United States is a developed economy
with GDP approaching $14 trillion and a per
capita income of $38,611  in 2007 (US BEA,
2008). The U.S. economy has large private
and public sectors, with strong emphasis on
market mechanisms and private ownership
(Christensen et al., 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).
However,  with the aging of the population
(described in Section 1.3.1.1) 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
26

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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).

 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 Americans'
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-have contributed to America's material
well being while reducing vulnerability to
climate. Many of the currently  deployed
adaptive strategies that protect human beings
from climate involve technology (e.g., warning
systems, air conditioning and heating, pollution
controls, building design, storm 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;Gublere/a/.,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 to evaluate vulnerability.

 1.4.3  Infrastructure

Communities have  reduced, and can further
reduce, their vulnerability to adverse climate
effects through investments in infrastructure.
United States 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
infrastructure, 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.
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 The U.S. Climate Change Science Program
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                        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 United States when
                        compared with less-developed countries (Cohan
                        and Miller, 2001). This reflects 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 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 feet. 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 (i.e., the
knowledge, experience, and expertise of its
citizens), 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 country's human capital,
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; Felling 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
exposures to extreme heat can also substantially
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems

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 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 that
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. 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
                                                                                                           29

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 The U.S. Climate Change Science Program
                         cities was still double the suburban rate, there
                         were 1 million more people living in poverty in
                         America's suburbs. Many of 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
                                      Chapter I
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 processes.6 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
6 SAP 4.6 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.
                            Mi
                            c
                         «
                          00
                          (U  Q-
                          £  «
                         —I  C
                             O
High agreement,
limited evidence
Medium agreement,
limited evidence
Low agreement,
limited evidence
High agreement,
medium evidence
Medium agreement,
medium evidence
Low agreement,
medium evidence
High agreement,
much evidence
Medium agreement,
much evidence
Low agreement,
much evidence
                                        Amount of evidence (number and quality of independent sources)
                         Figure 1.5 Considerations in determining confidence
                         Source: IPCC Guidance Notes on risk and uncertainty (2005)
30

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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.

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 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). Moreover,
the authors do not 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.
              Table I.I Description of likelihood: probabilistic assessment of
              outcome having occurred or occurring in the future based on quan-
              titative anal/sis or elicitation of expert views.
Likelihood Terminology Likelihood of the
Occurrence/Outcome
Virtually certain
Very likely
Likely
About as likely as not
Unlikely
Very unlikely
Exceptionally unlikely
> 99 percent probability
> 90 percent probability
> 66 percent probability
33 - 66|percent
probability
< 33 percent probability
< 10 percent probability
< 1 percent probability
                                                                                                              31

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 The U.S. Climate Change Science Program
                                          Chapter
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
2.1  INTRODUCTION

Climate change can affect health directly and
indirectly. Directly, extreme weather events
(floods, droughts, windstorms, fires, and heat
waves) 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 food-borne 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 change can also
affect the incidence of diseases associated with
air pollutants and aeroallergens (Bernard et al,
2001).1  The cause-and-effect chain from climate
change to changing patterns of health outcomes
is 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.
1  Any of various air-borne substances, such as pollen
  or spores, that can cause an allergic response.
The 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 water-borne 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
   (RoseetaL, 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
   (Gubler et al., 2001).
                                                                                                           39

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 The U.S. Climate Change Science Program
                                      Chapter 2
                         •  Multiple uncertainties preclude any definitive
                           statement on the direction of potential future
                           change for each of the health outcomes
                           assessed (Patz et al, 2000).
                         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 SAP 4.6 updates the 2000 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 food-
                         borne 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: (1) studies that
increase our understanding of the associations
between weather variables and health outcomes
raise possible concerns about the impacts of a
changing climate, and (2) studies that project
the burden of health outcomes using scenarios
of socioeconomic and climate change.

It  is important to note that  this 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
considers 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 heat waves, 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 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 11 U.S. cities (Curriero
et 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
40

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
hyperthermia reported as a contributing factor
(CDC, 2005). These numbers are underestimates
of the total mortality associated with heat
waves 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 et al, 2006;
Medina-Ramon et al., 2006). Among the most
well-documented heat waves 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 heat waves 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 et al, 2006; Schwartz et al, 2004;
Semenza et al., 1999).

Age,  fitness, body composition, and level of
activity are important determinants of how the
human body responds to exposure to thermal
extremes (DeGroot et al, 2006; Havenith et
al, 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 et al, 2005; Gouveia et al, 2003;
Greenberg et al, 1983; O'Neill  et al, 2003;
Schwartz, 2005;  Jones et al, 1982; Kovats et
al, 2004; Schwartz et-al, 2004; Semenza et
al, 1999; Watkins etal, 2001). A sociological
analysis of the 1995 Chicago heat wave found
that people living in neighborhoods without
public gathering  places  and active street
      -20
                          20         40         60
                         Temperature (degrees Fahrenheit)
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 Wash-
ington, 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)

life were at higher risk,  highlighting  the
important role that community and societal
characteristics can  play in determining
vulnerability (Klinenberg, 2002).

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 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; Rene?al., 2006).
                                                                                                             41

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 The U.S. Climate Change Science Program
                                      Chapter 2
                         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 et al., 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
                         African American 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 et al., 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 et al., 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 climate 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 the question of how climate
change could affect mortality highly uncertain.
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
stress disorder  [PTSD], depression) of these
events are  likely to be especially important but
are difficult to assess (Middleton et al., 2002;
Russoniello et al,  2002; Verger et al, 2003;
North et al, 2004;  Fried et al, 2005; Weisler
et al, 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
42

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
3 hurricane and its path was forecast well in
advance, there was a secondary failure  of the
levee system in Louisianna. 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 2.3 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.

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 al, 2003; Gedalof et al, 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
al., 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 al.,  2006). Data
providing a time-series summary of deaths
similar to the data in  Figures 2.2 and 2.3 were
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.
Figure 2.2 Annual Deaths Attributed to Hurricanes in the United States,
1900 and  1940-2005
Source: NOAA, 2007
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 challenges
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 PTSD. Shortly after Katrina, a Centers for
Disease Control and Prevention poll found that
      1940  1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000  2005 2010
                                 Year
Figure 2.3 Annual Deaths Attributed to Flooding in the United States,
1940-2005
Source: NOAA, 2007a
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 The U.S. Climate Change Science Program
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                         nearly half of all survey respondents indicated
                         a need for mental health care, yet less than 2
                         percent were receiving professional attention
                         (Weisler et al, 2006).

                         2.2.4 Indirect Health Impacts of
                         Climate Change

                         The observation that most vector-, water- or
                         food-borne 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 food-borne diseases, although many
                         water- and food-borne diseases are zoonotic.

                         2.2.4.1 Vector-borne 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 United States, it is
                         unlikely that more cases of dengue fever will
be observed because most people are protected
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, the distubution of other
diseases changed either because of suitable
environmental conditions (including climate)
or enhanced detection (examples include
Lyme disease, ehrlichioses, and Hantavirus
pulmonary syndrome), or have been 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 involve weather/climate,
ecosystem change, social and behavioral factors
simultaneously, 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.

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 counterintuitive 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 also are important.
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
2.2.4.2 Water-borne and
Food-borne Diseases

Water- and food-borne 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 food-borne disease with known
etiology, bacteria (Salmonella) accounted for
55 percent and viruses accounted for 33 percent
(Lynch et al., 2006). Viral associated outbreaks
rose from  16  percent in 1998 to  42 percent in
2002, primarily due to increases in norovirus
(Lynch  et al., 2006).  In recreational water,
bacteria accounted for 32 percent of outbreaks,
parasites  (primarily  Cryptosporidium) for
24 percent, and viruses 10 percent (Dziuban
et al., 2006). Similarly  in drinking water
outbreaks of known etiology, bacteria were
the most  commonly identified agent (29
percent, primarily Campylobacter),  followed
by parasites  and  viruses (each identified 5
percent 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 percent and 68 percent of reported
recreational and drinking water outbreaks,
respectively (Dziuban et al., 2006;  Liang et
al, 2006).

Water- and food-borne disease remain highly
underreported (e.g., Mead et al., 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 et al. (1999) estimated that more than 210
million cases of gastroenteritis occur annually in
the United States, including more than 900,000
hospitalizations and more than 6,000 deaths.
More recently, Herikstad etal. (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 et al,
1999). While bacteria continue to cause the
majority of documented food- and water-borne
outbreaks (Lynch et al,  2006; Liang et al,
2006), the majority of sporadic (non-outbreak)
cases of disease are caused by viruses (67
percent; primarily noroviruses), followed by
bacteria (30 percent, primarily Campylobacter
and Salmonella) and parasites (3 percent,
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 and older adults (>80
years) each make up more than 25 percent of
hospitalizations involving gastroenteritis, but
older adults contributed to 85 percent of the
associated deaths (Gangarosa et al, 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 water-
borne 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 food-borne disease associated  with fresh
produce is growing  (FDA, 2001; Powell and
Chapman, 2007). Storm events and flooding
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                         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 al., 2006; Naumova et
                         al,  2006), Australia (D'Souza et al., 2004),
                         and several countries across Europe (Kovats
                         et al., 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 al., 2004; Naumova et al, 2006)
                         and changes in  eating habits during warm
                         summer months  (i.e., outdoor eating) (Fleury
                         et al., 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 al., 1995; Mouslim
                         et al., 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 a/,, 2005; Fleury et
al., 2006; Naumova et al., 2006). However,
in several other European countries,
campylobacteriosis rates peak earlier, before
high annual temperatures, and in those cases
temperature accounts for only 4 percent of
the interannual variability (Kovats, et al.,
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.

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 etal, 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 al., 2002; Meites et
al., 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 percent of sporadic
shellfish-related illnesses and over 95 percent
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 percent since 1996 (Vugia
etal.,  2006). Vibrio species are more frequently
associated with warm climates (e.g., Janda et
al., 1988; Lipp et al., 2002). Coincident with
proliferation in the environment, human cases
also occur during warm temperatures. In the
United States, the highest case rates occur in the
summer months (Dziuban et al., 2006). Given
the close association between temperature, the
pathogen, and disease, increasing temperatures
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
may increase the geographic range and disease
burdens of Vibrio pathogens (e.g., Lipp et al.,
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 al.,
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 al, 2003; Randa et al, 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 al., 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 al, 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 water-borne and to a lesser
extent food-borne 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 al, 2001; King and Monis,
2006). Between 2003 and 2004, of the 30
reported outbreaks of gastroenteritis from
recreational water, 78.6 percent were due to
Cryptosporidium and 14.3 percent were due
to Giardia (Dzuiban et al, 2006). Giardia has
historically been the most commonly diagnosed
parasite in the United States. Between 1992
and 1997 there were 9.5 cases of Giardia per
100,000 people (Furness et al, 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 etal, 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 et al, 2000; Casman et al, 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 percent (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
et al, 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 percent of food-borne
disease, and the vast majority of these are due
to norovirus (Mead et al, 1999). Rotavirus
accounts for a much smaller  fraction of viral
food-borne disease (Mead et al, 1999), but is
a significant cause of diarrheal disease among
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 The U.S. Climate Change Science Program
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                          infants and young children (Charles et al.,
                          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
                          et al., 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 water-borne outbreaks associated
                          with drinking water in the United States between
                          1948 and 1994 found that 51 percent of outbreaks
                          occurred following a daily precipitation event
                          in the 90th percentile and 68 percent 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 water-borne 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 Walkerton, Ontario was contaminated
                          with E. coli O157:H7 and Campylobacter during
                          rains that surpassed the 60-year event mark
                          for the region and the 100-year event mark in
     Figure 2.4. Drinking Water-borne Disease Outbreaks and 90th percentile
     Precipitation Events (a two month lag precedes outbreaks); 1948-1994.
     Source: Curriero et al., 2001
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).

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 more than twice the rate of
gastrointestinal illness following the flood as
before it (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, MINI) 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 et al,
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
(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 (Kolivras and
Comrie, 2003).  Its incidence varies seasonally
and annually,  which may be due partly to
climatic variations (Kolivras and Comrie,
2003; Zender and Talamantes, 2006). If so,
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 for ozone and
fine paniculate 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 fossil fuels) and volatile
organic compounds (VOCs) (emitted both by
burning of fossil 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 etal., 1991). In addition, epidemiologic
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 etal., 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 air-borne 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,
decreased lung function, aggravated asthma,
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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                         development of chronic bronchitis, heart attack,
                         and arrhythmias (Dockery et al., 1993; Samet
                         et al., 2000; Pope et al, 1995, 2002, 2004;
                         Pope and Dockery, 2006; Dominici et al, 2006;
                         Laden etal, 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
                         et 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 than
                         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
                         percent per degree temperature increase over
                         the baseline rate. Jacobson estimated that about
                         40 percent 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 et al,
2002; Wayne et al, 2002; Singer et al, 2005;
Ziska et al, 2005; Rogers et al, 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 air-borne 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
regionally 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  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
50

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 portion
of the population over age 65 is projected
to be 13 percent by 2010 and 20 percent 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 heat
waves, 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 etal., 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, heat wave 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 past 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.
Table 2.1. Projections of Impacts of Climate Change on Heat-Related Mortality
Location Period Adaptation Projected Impact on Heat- Related Deaths
considered
Lisbon,
Portugal3
8 Australian
cites4
New York, NY*
California*
Boston, MA7
2020s, 2050s compared to
1980-1998
2100 compared to 1900s
2050s compared to 1990s
2090s compared to 1990s
projections to 2100
compared to 1970-92
yes
no
yes
yes
yes
Increase of 57 percent- 1 13 percent in 2020s,
97 percent— 255 percent in 2050s, depending on
adaption
Increase of 1700 to 3200 deaths, depending on
policy approach followed and age structure of
population
Increase 47 percent to 95 percent; reduced by 25
percent with adaptation
Depending on emissions, mortality increases
2-7fold from 1990 levels, reduced 20-25 percent
with adaption
Decrease after 2010 due to adaptation
3 Dessai, 2003
4 Woodruff, 2005
5 Knowton, in press
6 Hayhoe, 2004
7 CLIMB, 2004
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).
                                                                                                            51

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 The U.S. Climate Change Science Program
                                      Chapter 2
                         In summary, given the projections of increases
                         in the frequency, intensity, and duration of heat
                         waves 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 heat
                         wave early warning systems, urban design
                         to reduce heat loads, and enhanced services
                         during heat waves.

                         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
                         et al, 2005; Trenberth, 2005; Halverson,
                         2006). Controversy over whether hurricane
                         intensity  increased over recent decades stems
                         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 (NOAA, 2007c).

Evidence suggests that the intensity of Atlantic
hurricanes  and tropical storms has increased
over the past few decades. SAP 3.3 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, SAP  3.3
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, SAP  3.3
concludes that "frequency changes are currently
too uncertain for confident projection" (CCSP,
2008). SAP 3.3  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 storm
surges 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;
Groismane?a/., 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 mean
precipitation with a disproportionate increase
in the frequency of extreme precipitation events
52

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
(Senior et al., 2002). Kim (2003) used a regional
climate model to project that a doubling of
CO2 concentrations in roughly 70 years could
increase the number of days with at least 0.5
mm of precipitation by roughly 33 percent
across the study's defined elevation gradients
in the western United States. Furthermore,
the IPCC concluded that it is very likely (>90
percent 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 et al., 2004; Fried et al., 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 at
which 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 Vector-borne 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 (TBE)  in Sweden
(Lindgren et al., 2000). Higher  minimum
temperatures  generally  were favorable to
the potential of expanding tick distributions
and greater local abundance of these vectors.
However, changing patterns of tick-borne
encephalitis 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
Food-borne 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, or
are capable of water-borne transport. Factors
that may affect these pathogens include changes
in temperature, precipitation, extreme weather
events (i.e., storms), and ecological shifts. 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.).

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
                                                                                                          53

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 The U.S. Climate Change Science Program
Chapter 2
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                                                                       60
                                                                       T3
                                                                                  57

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 The U.S. Climate Change Science Program
                                      Chapter 2
                         and absolute  amounts of emissions from
                         fuel combustion related to transportation,
                         space heating, energy production, and other
                         activities. Resulting vegetation patterns affect
                         biogenic (VOC) emissions that influence ozone
                         production.  Conversion of land cover 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 such as 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
                         United States 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 project
                         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 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 percent 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 a!., 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,
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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° model 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 CO2 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 Congestion
Mitigation and Air Quality Improvement
Program 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
change (Figure  2.5) (Hogrefe et  al,  2004c).
The influence of climate on mean ozone values
was similar in magnitude to the  influence of
rising global background concentrations 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 et al, 2004b). Climate change
shifted the distribution of ozone concentrations
toward higher values, with larger  relative
increases in future decades (Figure 2.6).
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 nitric oxide emissions
were projected to increase as temperatures rose.
Daily maximum ozone concentrations increased
by between 2 and 6 ppb (6-10 percent) 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 New York Climate & Health
Project (NYCHP) integrated model, PM2.5
concentrations were 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
paniculate 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
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     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.
     Source: Hogrefe et al., 2004c.
                         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.

                         The NYCHP 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 et
a/., 2007). Knowlton and colleagues computed
absolute and percentage increases in ozone-
related daily summer-season deaths in the NYC
metropolitan region in the 2050s 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. Projected increases in ozone-related
mortality due to climate change ranged from
0.4 to 7.0 percent across 31 counties. Bell and
colleagues expanded the analysis to 50 eastern
cities and examined both mortality and hospital
admissions (Bell et al., 2007). Average ozone
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
concentrations were projected to increase by
4.4 ppb (7.4 percent) in the 2050s; the range
was 0.8 percent to 13.7 percent. In addition,
ozone red alert days could increase by 68
percent. 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  (1996) definitions 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
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 The U.S. Climate Change Science Program
                                       Chapter 2
                         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 (EHE) 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).

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
                         Geographic Vulnerability of US Residents to Selected Climate Health Impacts
                               Location of Hurricane Landfalls,
                                         1995-2000
        Percentage of US Population 65
                 or older, 2000
                              Locations of Extreme Heat Events,
                                         1995-2000
          West Nile Virus Cases, 2004
                          Figure 2.7 a-d U.S. maps indicating counties with existing vulnerability to climate sensitive health
                          outcomes: (a) location of hurricane landfalls; (b) EHEs, defined by CDC as temperatures 10 or more
                          degrees Fahrenheit 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).
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
Table 2.3. Climate-Sensitive Health Outcomes and Particularly Vulnerable Groups
Climate-Sensitive Health Outcome
Heat-Related Illnesses and Deaths
Diseases and Deaths Related to Air Quality
Illnesses and Deaths Due to Extreme
Weather Events
Water- and Food-borne Illness
Particularly Vulnerable Groups
Elderly, chronic medical conditions, infants and
children, pregnant women, urban and rural poor,
outdoor workers
Children, pre-existing heart or lung disease, diabetes,
athletes, outdoor workers
Poor, pregnant women, chronic medical conditions,
mobility and cognitive constraints
Immunocompromised, elderly, infants; specific risks
for specific consequences (e.g., Campylobacter and
Guillain-Barre syndrome, £. coll OI57:H7)
Vector-borne Illnesses
Lyme Disease
Hantavirus
Dengue
Malaria
Children, outdoor workers
Rural poor, occupational groups
Infants, elderly
Children, immunocompromised, pregnant women,
genetic (e.g., G6PD status)
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 addition, children's relatively
naive immune systems  increase the risk of
serious consequences from water- and food-
borne diseases. Specific developmental factors
make them more vulnerable  to complications
from specific severe infections such as E coli
O157: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 et ai, 1998; cited in Hajat et
al., 2003) and long-term PTSD, depression, and
dissatisfaction with ongoing life (Bokszanin,
2000; cited in Hajat et al, 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 al.,
1996; Medina-Ramon et al., 2006); individuals
65 years of age and  older comprised 72 percent
of the heat-related deaths in the 1995 Chicago
heat wave (Whitman et al., 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 percent
of elderly households (CDC, 2004a). Also,
effects of ambient particulate matter on daily
mortality tend to be  greatest in older age groups
(Schwartz, 1995).
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                          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 al, 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 heat wave in Chicago
                          and Hurricane Katrina in 2005 (Box 2.1).

                          Studies of heat waves 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
                          et 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
                          al., 2002). Financial stress plays a role, as one
                          study of the 1995 Chicago heat wave found that
                          concern about the affordability of utility bills
                          influenced individuals to limit air conditioning
                          use (Klinenberg, 2002). The risk for exposure
            Box 2.1 Vulnerable Populations and Hurricane Katrina
          In 2005, Hurricane Katrina caused more than 1,500 deaths along the Gulf Coast. Many of these victims
          were members of vulnerable subp'opulations, 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 percent of the state's identified victims were 75 years of age or older; 69 percent were above
          age 60 (LDHH, 2006). In Mississippi, 67 percent 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 percent 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 et
          al., 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 et 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).
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 heat waves 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 etai, 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
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 heat
waves 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.

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 vector-borne 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 et al., 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 vector-borne
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
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                         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, 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 are
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
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
decision support planning and response tools.
Medical and nursing 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.

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
    Box 2.2 Heat Wave Early Warning Systems
    Projections for increases in the frequency, intensity, and duration of heat waves suggest that more cities
    need heat wave 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 a/., 2004; Ebi and Schmier, 2005; Weisskopf et a/., 2002), and enhance preparedness
    following events such as the 1995 heat waves 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 heat waves
    (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 percent 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 of heat wave early warning systems is needed, including a determination of
    which components are effective and why (Kovats and Ebi, 2006; NOAA, 2005).
                                                                                                          67

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 The U.S. Climate Change Science Program
                                      Chapter 2
                         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 address current and future climate
                         change-related risks.

                         Table 2.4 summarizes the 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 heat wave, so 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
                         vector-borne diseases, primary prevention refers
                         to preventing exposure to infected vectors. In this
                         case, early warning systems can be considered
                         primary prevention.  For most vector-borne
                         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 measures. Table 2.5
lists some adaptation measures for health
impacts from heat  waves, extreme weather
events, vector-borne diseases, water-borne
diseases, and air quality. These measures are
generic because the local context, including
vulnerabilities and adaptive capacity, needs 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 heat wave should focus
on keeping cool and drinking lots of water. Box
2.3 provides tips for  dealing with extreme heat
waves 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
68

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            Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 The U.S. Climate Change Science Program
                                               Chapter 2
                         of adaptation actions should commence now
                         (Confalonieri et al.,  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 United States
                         to implement effective and timely adaptation
                         measures is assumed to 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
         might not be avoidable, even with attempts
         at adaptation. Severe health impacts will not
         be evenly distributed across populations and
           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 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 Website
  addresses for heat exposure symptoms
  and responses  .
• Open hotlines to  report concerns about
  individuals who may be at risk
• Coordinate broadcasts of EHE response
  information in newspapers and on television
  and radio.
Source: U.S. EPA, 2006
72

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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,  and to 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 from 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 heat waves  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.

•  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 VBZ diseases, air quality, pollen
   and mold counts, reporting of food- and
   water-borne 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 heat
   wave 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
                                                                                                          73

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 The U.S. Climate Change Science Program
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                           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 heat waves, and food- and
                           water-borne 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, assessing 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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              Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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                            Callaghan, W.M., S.A. Rasmussen, D.J. Jamieson,
                               S.J. Ventura, S.L. Fair, P.O. Sutton, T.J. Matthews,
                               B.E.  Hamilton, K.R. Shealy, D. Brantley,  and
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
                                           Effects  of Global Change
                                           on Human Settlements
 UJ
 Q.
* ^~
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
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,  the trend
                                 of households moving from urban centers to
                                 peripheries is reversing as many city centers
                                 renew and metropolitan areas continue to
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 The U.S. Climate Change Science Program
                                      Chapter 3
                        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).

                        3.1.3  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 discussions  and offer
                        illustrations from the relatively limited 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 are required in our understanding
                        of the impacts of and adaptation to climate change
                        across  different sectors and geographic regions,
                        differential vulnerabilities, and interventions to
                        build resilience. (NRC, 2007).

                        To some degree, gaps can be filled by referring
                        to several comprehensive  analyses that do
                        exist, including literature on effects of climate
                        variation on settlements and their responses,
                        research on climate change impacts on cities in
                        other parts of the world, and historical analogs
                        of responses of urban areas to significant
                        environmental changes. Box 3.1 presents a
                        historical perspective of U.S. urban  responses
                        to environmental change.  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, but more so  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.

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?
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
    BOX 3.1. U.S. Urban Responses to Environmental Change:
    An Historical 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).
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 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?
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                                       Chapter 3
                         3.2.2 Impacts of Climate Change
                         on Human Settlements

                         Impacts of climate  change on human
                         settlements vary regionally (see Boxes 3.2
                         and 3.3), 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 infrastriKtures.
                            Changes in precipitation patterns may lead to
                            reductions in melrwater, river flows, groundwater
                            levels, and in coastal areas may lead to saline
                            intrusion in rivers and groundwater, affecting
                            water supply. Meanwhile, 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.

                         3. Effects on energy requirements. Warming is
                            virtually certain to increase energy demand
                            in U.S. cities for cooling in buildings while
                            reducing demand 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  relative to surrounding
   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, 2001a).

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 et al., 2006).
92

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          Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
 BOX 3.2. Vignettes of Vulnerability—I
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 5 m, overtopping and
breaching sections of the city's 4.5 m defenses, flooding 70 to 80 percent of New Orleans, with 55
percent of the city's properties inundated by more than 1.2 m and maximum flood depths up to 6 m.
Approximately 1,101  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 percent of its pre-Katrina level (McCarthy et al., 2006).
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                                      Chapter 3
           BOX 3.3. Vignettes of Vulnerability-
           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 has 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.
                         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.
94
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 et 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, 2001a; Wilbanks et al., 2007b).

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         Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
 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 UHI 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 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 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 the following 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

The image on the left illustrates daytime surface heating for urban surfaces across the Georgia
Central Business District (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) (~I5-20°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
                                                                     UHI  (Quattrochi et a/.,
Figure 3.1. Example of urban surface temperatures  and albedo for the Atlanta,  20QQ)
Georgia Central Business District area derived from high spatial resolution (10m)
aircraft thermal remote sensing data.
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                                      Chapter 3
                         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, et
                         al., 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. Lt
                         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 UHI
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 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:
96

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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.
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 (Wilbanks, 2007c)

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 et 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 that has received the
most attention to date is insurance and finance
(Wilbanks, et al, 2007b).
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                                     Chapter 3
                         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 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.

                         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 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
et al., 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).
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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
eta/., 1999 eto/., 2001 et a/., 2000 et a/., 2004 Sumitani, 2005
Location:
Greater Los
Angeles
New York
Metropolitan
New York
Metropolitan
Boston
Metropolitan
Seattle
Coverage:
Water Supply
Water Quality
Water Demand
Sea level rise
Transportation
Communication
Energy
Public Health
Vector-borne Diseases
Food-borne Diseases
Temperature-related Mortality
Temperature-related Morbidity
Air-quality Related Mortality
Air-quality Related Morbidity
Other Health Issues
Ecosystems
Wetlands
Other Ecol. (Wildfires)
Urban Forests (Trees and
Vegetation)
Air Quality
X


X







X


X


X


X








X

X


X



X
X
X


X


X






X
X


X


X
X
X
X
X

X



X












X
X














X
Extent of:
Quantitative Analysis
Computer-based Modeling
Scenario Analysis
Explicit Risk Analysis
Low
None
None
None
Medium
Low
None
None
Medium
Low
Medium
None
High
High
High
Medium
Low
None
Medium
None
Involvement of:
Local Planning Agencies
Local Government Agencies
Private Industry
Non-profits
Citizens
None
None
None
None
None
None
None
None
None
None
High
High
None
Low
None
High
High
Low
High
Medium
High
High
None
None
None
Identification of:
Adaptation Options
Adaptation Cost
Extent of Integration Across
Systems
Attention to Differential
Impacts (e.g., on individual
types of businesses,
populations)
/

None
None
X

None
None
X
X
Low
Low
X
X
Medium
Low
X

Low
Low
                                                                                                               I
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       Table 3.2. Regional Vulnerabilities of Settlements to Impacts of Climate Change in the United States
Region Vulnerabilities Major Uncertainties
Metro NE
Larger NE
Mid-Atlantic
Coastal SE
Inland SE
Upper Midwest
Inner Midwest
Appalachians
Great Plains
Mountain West
Arid Southwest
California
Northwest
Alaska
Hawaii
Flooding, infrastructures, health, water supply,
sea level rise
Changes in local landscapes, tourism, water,
energy needs
Multiple stresses; e.g., interactions between
climate change and aging infrastructures
More intense storms, sea level rise, flooding,
heat stress
Water shortages, heat stress, UHI,
economic impacts
Lake and river levels, extreme weather
events, health
Extreme weather events, health
Ecological change, reduced demand for coal
Water supply, extreme events, stresses on
communities
Reduced snow, water shortages, fire, tourism
Water shortages, fire
Water shortages, heat stress, sea level rise
Water shortages, ecosystem stresses, coastal
effects
Effects of warming, vulnerable populations
Storms and other weather extremes,
freshwater supplies, health, sea level rise
Storm behavior, precipitation
Ecosystem impacts
Ecosystem impacts
Storm behavior, coastal land use, sea level rise
Precipitation change, development paths
Precipitation change, storm behavior
Storm behavior
Ecosystem impacts, energy policy impacts
Precipitation changes, weather extremes
Precipitation changes, effects on
winter snowpack
Development paths, precipitation changes
Temperature and precipitation changes,
infrastructure impacts
Precipitation changes, sea level rise
Warming, sea level rise
Storm characteristics, precipitation change
                        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 greenhouse gas
                        emissions and by showing leadership in
                        encouraging others to support such  actions
(see Box 3.5: Roles of Settlements in Climate
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
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    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 (GHG) (Selin and Vandeveer, 2005; Rabe, 2006; Selin, 2006).
    U.S. states and cities are joining such  initiatives as the International Council for Local Environmental
    Initiatives (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.3 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. 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 footnote3).
    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, an
    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 et 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.

    a Local governments participating in ICLEI's Cities for Climate Protection Campaign commit to a) conduct an energy- and
      emissions-inventory and fore-cast, b) establish an emissions target, c) develop and obtain approval for the Local Action
      Plan, d) implement policies and measures, and e) monitor and verify 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/cliraate/.
heat stress and  mortality, unchanged  by
adaptation. The Climate's Long Term Impacts
on Metro 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 actions that reduce vulnerabilities to
climate change impacts (or increase prospects
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                         for realizing benefits from climate change
                         impacts) and have other desirable aspects, 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 in
                         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. This suggests that
                         mechanisms exist to respond to concerns about
                         climate change. Urban designers and managers
                         deal routinely with uncertainties 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
   et al., 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.
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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 ai, 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 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 et
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.
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                        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 National Oceanic
                        and Atmospheric Administration, the Centers
                        for Disease Control and Prevention, and the
                        Department of Human  Services provides
                        information for municipal officials in the event
                        of an excessive heat event.1

                        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,
                        2001a). 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 and
   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).
                         1  For more information please see: http://www.epa.
                           gov/hiri/about/heatguidebook.html.
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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 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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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems

                                           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
4.1  INTRODUCTION

Human welfare is an elusive concept. There
is no single, commonly accepted definition or
approach to thinking about welfare. Clearly
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
and 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:
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                         •  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; and,
                         •  Providing examples  of climate  change
                           impacts on selected categories of well-
                           being and reporting indicators of economic
                           welfare for these categories.
                         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 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. They are
all often used interchangeably (Veenhoven,
1988, 1996, 2000; Ng, 2003; Rahman, 2007).
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
                                                                    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), 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.
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
community levels.2 For purposes of clarity in
this chapter,  we adopt the convention of the
Millenium Assessment (MA, 2005) and the
Intergovernmental Panel on Climate Change
(IPCC, 2007a), 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 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 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).
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.
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 embod-
  ied 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.
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 the
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 Millenium  Ecosystem Assessment on
Ecosystems and Human Weil-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;
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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                                       Chapter 4
                         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. We turn to these first,
                         and then next to place-focused indicators.

                         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;Guyatte/a/., 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 a/., 1995; Diener
and Diener, 1995).5 In such studies, subjective
valuations of life satisfaction are embedded in
                                                                       Some studies suggest that individual utility or hap-
                                                                       piness 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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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 a 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 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 Well-being

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 well-being," 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
                                                                                                          115

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 The U.S. Climate Change Science Program
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                         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 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), in some categories there are also
                         opportunities or potential positive impacts.

                         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 Gross Domestic Product
                         (GDP), GDP per capita, and rates of adult
                         literacy), improvements  occur in human
                         health outcomes such as infant mortality, rates
                         of morbidity, and 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
                         6  Sources that contributed to the development of Table
                            4.1 include: MA (2005); Sufian, 1993; Rahman, 2007,
                            and Lambiri, et 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/qofl99.htm What Matters in Greater Phoenix
                            1999 Edition: Indicators of Our Quality of Life;
                            and http://www.jcci.org/statistics/qualityoflife.aspx
                            Tracking the Quality of Life in Jacksonville.
                         1  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 com-
                            munity resilience and human needs  of subsistence,
                            reproduction,  security, affection, understanding,
                            participation, leisure, spirituality, creativity, iden-
                            tity, and freedom. See also Rothman, Amelung, and
                            Poleme (2003).
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 a/., 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
etal., 2001).

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 become associated with these factors.
Communities with greater levels of social and
116

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          Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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118

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 context
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 has 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.

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
8 In addition to variants on the social indicators ap-
  proach, other types of taxonomies are possible—for
  example a taxonomy based on broad systems (at-
  mospheric, 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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                        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 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).

                        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.

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, the 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 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

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
  0 95 190  380   570   760
                    3 Miles
-1.45945--0.64479
-0.64478--0.37238
-0.37237--0.06522
-0.06521-0.49810
0.49811 -20.74817
     Three measures of climate change risk are used to create the vulnerability index: expected
     temperature change, extreme weather event history, and coastal proximity. Risk measures are
     geo-referenced at the county scale. The expected temperature change variable is measured as the
     expected unit change in average minimum temperature (in degrees Celsius) for a county from 2004
     to 2099. Temperature data are from the Hadley Center. Hadley Center monthly time series data on
     average minimum temperature for the United States are plotted at the 0.5 x 0.5 degree of spatial
     resolution. In cases where climate cells intersect county boundaries, temperature data are averaged
     across intersecting climate cells. To estimate extreme weather event history, we summarize the
     number of reported injuries and fatalities from hydo-meterological hazard events at the county
     level Jan Ol, I960 to Jul 31, 2004. Higher values on our natural hazard casualty variable reflect more
     pronounced histories of injury and death from extreme weather events. Casualty data were collected
     from the Spatial Hazard Events and Losses Database for the United States (SHELDUS). The coastal
     proximity  variable is measured dichotomously. A country receives a score of I if it is designated by
     the National Oceanic and Atmospheric Administration (NOAA) as an  "at-risk-coastal" county,  and a
     score of 0 if it is not. NOAA defines a county as at-risk-coastal if at least 15 percent of its total area
     is located in a coastal watershed. The vulnerability index was  created by standardizing then summing
     each measure of climate change risk (z-score). The distribution of vulnerability is divided into equal
     quintles, with darker colors reflecting higher vulnerability to climate change.
Figure 4.1 Geography of Climate Change Vulnerability at the County Scale
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      Table 4.2 An illustration of Possible Effects of Climate Change on Fishery Resources
Linkages/Pathways Category of Welfare Effect Possible Metrics
Fishery resource declines as climate
changes
Recreational opportunities decline
Related species and habitats are
affected
Employment and wages in resource-
based jobs (including recreation) fall as
resources decline
Incomes fall as jobs are lost
More children live in poverty as jobs
are lost and incomes fall
Access to health care that is tied to
jobs and income falls
Increased mortality and morbidity as a
result of reduced health care
Lack of jobs results in out-migration
Fewer new residents attracted,
because of reduced jobs and amenities
(recreation)
Less incentive/drive to participate in
community activities
Natural resources, environment, and
amenities
Natural resources, environment, and
amenities
Natural resources, environment, and
amenities
Economic conditions
Economic conditions
Economic conditions
Human health
Human health
Economic conditions
Social and cultural resources
Social and cultural resources
Fish populations
Fish catch, visitation days
Species number and diversity
Number of jobs, unemployment
rate, wages
Per capita income
Families, children below poverty
level
Households without health
insurance increase
Disease and death rates increase
Working age population decreases
Population growth rate slows
Drop in volunteerism, civic
participation, completion of high
school
                         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
                         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.
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;
Pagan, 2001; Poriting, 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, environmental,
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 United
States, continuing growth and  development
creates both pressures  on the natural and built
environments and opportunities  for moving in
sustainable directions.
122

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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; Berke et al, 2006).  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  and ethnicity, and  by 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. Many of the 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. Their 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 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
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                         of vulnerability is a viable one and can be
                         measured and applied to communities  in a
                         Geographic Information System 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

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.
                          10 In the natural hazards and disasters field, a single
                            term—mitigation—refers both to adaptation to haz-
                            ards 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 ap-
  proach 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 information gen-
  erated and made available, but it would represent a
  set of variables continuously maintained and used
  to describe policy choices.
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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  Cost-benefit
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, 2007b)
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/tCO2.i3 The IPCC attributes this very broad
12 See Arrow el a/., 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 2007b, page 23.
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. The
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
necessary to provide a relatively complete
assessment may be unavailable, as discussed
subsequently in this  section.15
14 The IPCC further notes that existing analyses sug-
  gest 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 2007b page 23).
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.
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                        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
                         16 Although economists are careful to distinguish be-
                           tween 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.
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
United States, 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 economists (Bockstael et
al., 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
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
welfare (Boyd and Banzhaf, 2006)." 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 (Strzepek and 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 U.S. EPA and U.S. Forest Service to
value recreation when there is insufficient time
or budget to conduct original valuation studies
(Rosenberger and Loomis, 2003). Techniques
commonly used by economists to value non-
market goods and services include:
17 Some political economists also emphasize the role of
  explicit recognition of non-market environmental val-
  ues as an important step in improving the well-being
  of poor populations (Boyce and Shelley, 2003).
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                           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. Likewise, 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, willingness to pay 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 calculates
   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 United States, 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.  See Chapter 2 of
this report, for an overview of health effects that
have been associated with climate change.

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 United States.
This is primarily due to a poor understanding
of many key risk factors and confounding
issues, such as  behavioral adaptation and
variability in population vulnerability (Patz
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 United States 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 United States will face difficult
challenges arising from some of the following
health effects.

•  Illnesses and deaths due to heat waves.
   A likely impact in the United States is
   an increase in the severity, duration,  and
   frequency of heat waves (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 etal., 1996,
   and Knowlton et al., 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
   (Currieroe/a/.,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 air-borne allergens (Morris
et al.,  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- and food-borne diseases. Altered
weather patterns, including changes in
precipitation, temperature, humidity,
and water salinity, are likely to  affect the
distribution  and prevalence of food- and
water-borne diseases resulting from bacteria,
overloaded drinking water systems, and
increases  in the frequency and range of
harmful algal blooms (Weniger et al., 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 patterns,
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.
if
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                         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 heat waves. 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 et ai, 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 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 United
States 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
due to 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 produc-
                                                                        tive 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 ill-
                                                                        nesses. However, there will likely be an increase
                                                                        in the spread of several food- and water-borne
                                                                        pathogens among susceptible populations depend-
                                                                        ing on the pathogens' survival, persistence, habitat
                                                                        range and transmission under changing climate and
                                                                        environmental conditions.
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 etal. (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 CO2
equivalent by 2170.21

McMichael et al.  (2004) bases the estimates
of the effects of average temperature changes
on mortality from 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 percent for every degree C
below 16°C and  increase by 1.1 percent for each
degree above 16°C. In  applying these results
to future climate scenarios, McMichael et al.
19 These studies use climate scenarios that are associ-
  ated with different emissions scenarios from IPCC
  (2000), the so-called SRES scenarios.
20 McMichael et al. (2004) represent unmitigated emis-
  sions using the lS92a 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.
(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 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 heat wave days  (3  or more  days with
temperatures above 32°C) increases fourfold
under scenario Bl 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 Bl and five to seven times
under scenario Alfi by 2090.

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)
22 Hayhoe uses two SRES (IPCC 2000) emissions
  scenarios: Alfi (corresponding to 970 ppm of CO2)
  and Bl (corresponding to 550 ppm of CO2).
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                         analyzed the effect of temperature extremes
                         (both hot and cold) on mortality for 44 U.S.
                         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 cost-benefit  analyses of health and  safety
                         programs, mortality risks are commonly valued
                         using the "value of a statistical life" (VSL)—
                         defined as 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 United States 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

The  challenge  in valuating health effects  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
et al. (2004) and Kalkstein and Greene (1997)
estimate mortality based on climate effects
around the years 2020 and 2050; Hayhoe et al.
(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
23 Estimates of compensating wage differentials are
  often quite sensitive to the exact specification of the
  wage equation. Black et 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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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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  below in Section 4.3.6
             on amenity  values.

             4.3.4 Ecosystems

             Human welfare depends, in  many ways, 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.
Table 4.3 Techniques to Value Health Effects Associated with Climate Change
          Health Effect
  Premature mortality (associated
  with temperature changes,
  extreme weather events, and air
  pollution effects)
  Exacerbation of cardiovascular
  and respiratory morbidity;
  morbidity associated with water-
  borne or vector-borne disease
  Injuries associated with extreme
  weather events
  Impacts of climate change on
  physical functioning; sub-
  clinical effects
                         Economic Valuation Tools
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.
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.
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.
Use of stated preference methods to estimate WTP to avoid functional limitation.

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       Table 4.4 Examples of Ecosystem Services Important to Human Welfare*
             Service Category
         Provisioning services
     Components of Service
Food
Fiber
Fresh water
Genetic resources
Pharmaceuticals
              Illustration of Service
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).
                          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).

                                     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
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
                              Climate change will result in
                              •  temperature increase
                              •  precipitation change
                              •  changes in extreme events
       Direct effects on ecosystems
       • extinctions
       • range shifts
       • community dissociation
       • timing changes
       • changes in ecosystem processes
      Indirect effects on ecosystems
      • increased wildfires
      • effects of sea level rise on
       coastal ecosystems
      • adaptation, e.g., coastline
       protection, changes in land use
                              Changes in the ability of
                              ecosystems to provide services
                              Effects of changes in services on
                              human welfare and quality of life
                              Economic valuation of changes
                              in quality of life
Figure 4.2 Steps from Climate Change to Economic Valuation of Ecosystem Services
adversely affect the services that humans and
human systems derive from ecosystems (MA,
2005). Climate change may affect ecosystems
in the United States 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 et
al., 2006). Because of different intrinsic rates
of migration, ecological communities may not
move intact into new areas (Box 4.1).

Another potential ecological 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).

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

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           BOX 4.1. Effects of Climate Change on Selected U.S. Ecosystems
           At their most extreme, ecological 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 (Click 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 et al., 2003; Lenihan et 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 I.5°C (Holbrook et al., 1997). Sagarin et
           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 ecological community that exists there now is markedly
           different in its make-up from that which existed prior to warming of the coastal California Current.
                         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 that 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 United States  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
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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,
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 ecological communities that are
more resistant to the effects of fire (Lenihan et
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 however, are 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 a good or service is not explicitly
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                         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—that 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,
                         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 invok-
                           ing, as reasons why people care about ecosystesm,
                           the moral philosophies inherent in terms such as
                           stewardship, spiritual values, etc. (see for example,
                           Freeman (2003)).
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.

4.3.4.2 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 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 etal. (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
change, or both. The respondents  consisted
of Pennsylvania duck hunters, although the
hypothetical ecosystem impacts occurred in the
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 percent loss, and
others with a 74 percent 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 WTP 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  et 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 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
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                         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 United States, 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 that  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.  Ehrlich and Ehrlich (1996)
                         and Pimental etal. (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 well-being 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 United States,
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 percent of the U.S.
population participates in some form of outdoor
recreation, representing nearly 270 million
participants (Cordell et al., 1999), and several
billion  person-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 percent), visiting a beach
or lakeshore or river (62  percent), sightseeing
(56 percent), swimming (54 percent) and
picnicking (49 percent). Most days are spent in
activities such as walking, biking, sightseeing,
bird-watching, and wildlife viewing (Cordell et
al., 1999), 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
26 Effects on jobs, income, and similar metrics are con-
   sidered market impacts, and are not discussed here.
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 such as beaches, forests, wetlands,
snow, and wildlife (Wall, 1998). Consequently,
climate change can also indirectly affect the
outdoor recreational experience by affecting the
quality and availability of natural resources used
for 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
   Climate change:
   • + temperature
   • +/- precipitation
   • + climate variability
   Effects of climate change:
   Changes in:
   ...vegetation (forests)
   ...stream flows
   ...reservoir levels
   ...recreational fisheries
   ...wildlife populations
   ...miles of beaches
   ...snow, ice
   ...length of season
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
          Effects on outdoor
          recreaton use and benefits:
          •  enjoyment and comfort
            while outdoors
          •  visitor days of outdoor
            recreation
          •  benefits of outdoor
            recreation
Figure 4.3 Direct and Indirect Effects of Climate Change on Recreation
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                         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, and
                         (b) a longer season in which to enjoy the activity
                         (DeFreitas, 2005; 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
27 Scott and Jones (2005) used +1°C to +5°C in their
  scenarios and Scott etal. (2006) used +1.5°C to +3°C
  in their low impact scenario and +2 C to +8 C in
  their high impact scenario.
                         Table 4.5 Comparison of Changes in U.S. Visitor Days
Activity Loomis and Crespi (1999) Mendelsohn and Markowski (1999)
Boating
Camping
Fishing
Golf
Hunting
Snow Skiing
Wildlife Viewing
Beach Recreation
Stream Recreation
Gain in Visitor
Benefits (in Billions)
9.2 percent
-2.0 percent
3.5 percent
13.6 percent
-1.2 percent
-52.0 percent
-O.I percent
14.1 percent
3.4 percent
$2.74
36.1 percent
-12.7 percent
39.0 percent
4.0 percent
no change
-39.0 percent
-38.4 percent
not estimated
included in boating
$2.80
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
eight weeks. The combined effect of warmer
temperatures lengthening the golfing season,
and the increasing desirability of golfing
during the existing season, together result in an
increase in the rounds of golf played by between
50 percent and 86 percent. Similar increases
might be expected for golf in northern states of
the United States such as Minnesota, Wisconsin,
New York, etc. with longer golf seasons. Scott
etal. (2006) and Scott and Jones (2005) suggest
that some  of the previously projected large (30
percent to 50 percent) reductions in length of ski
seasons at northern  ski areas (e.g., in Canada,
Michigan, and Vermont) can  be reduced (to
5 percent to  25 percent) 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 in some
years the  Thanksgiving and "Spring Break"
periods are already too warm for successful
snowmaking or retention of snow made.

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). Following the discussion of
indirect effects 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.

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).2»

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.
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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                        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 etal, 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 a/.'s estimated magnitude of 50 percent to
                        100 percent 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 percent 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 percent of U.S. fishing days (Vaughan and
Russell, 1982). This 25 percent loss may be an
upper limit as some 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  et al.  (2000), indicate a 2-20 percent
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 etal., 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. Box 4.2  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.
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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 WTP 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 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
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.
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 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 United States.
More research is needed to understand the
linkages between weather and recreation, and
to extrapolate results to the range of recreational
activities throughout the United States.

Change in visitation days. Two studies
(Loomis and Crespi, 1999; Mendelsohn and
Markowski, 1999) have comprehensively
examined the effects of climate on recreational
opportunities for the entire United States. These
studies both  examined the effects of 2.5°C and
5°C increases in temperature,  along with a
7 percent 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
wf,
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                          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 percent
                          in precipitation.30

                          The methods  used  to forecast visitation were
                          slightly different between the two studies. To
                          estimate visitor days for all recreation activities,
                          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.
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
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 two 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, in
addition  to temperature  and  precipitation the
reservoir models incorporated climate-induced
reductions in reservoir surface area. 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 WTP  as a measure
of value of each day of recreation (Section 3 of
this chapter provides a discussion of the concept
of WTP 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
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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
United States.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 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
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
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 United States. 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
  CO2 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 ef-
  fects 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.
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 et
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
IP
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           BOX 4.2. 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 in 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 percent.

           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  percent increase with CCC and 9.9
           percent increase with Hadley. Loomis and Richardson also report that applying the historic visitation
           patterns to the same scenarios yields an  11.6 percent increase in visitation with CCC and  6.8 percent 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.
                         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. Alternatively, a particular climate may
                         simply make life more enjoyable in the course of
                         everyday life. Based on the evidence one would
                         also expect 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.

4.3.6.1 Valuing Climate Amenities

People's preferences for climate attributes
should be reflected in their location decisions.
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
Table 4.6 Change in Visits, Jobs, and Visitor Benefits with Three Climate Change Scenarios
Visitor Benefits
Climate Scenario Annual Visits Change Tourism lobs
(Millions)
Current
CCC
Hadley
Extreme Heat
3,186,323
3,618,856
3,502,426
2,907,520

13.6 percent
9.9 percent
-8.7 percent
6,370
7,351
7,095
5,770
$1,004
$1,216
$1,157
$959
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 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.  See, for example,
studies  by Hoch and Drake (1974); Cropper
and Arriaga-Salinas (1980); Cropper (1981);
Roback  (1982);  Smith (1983); Blomquist et al.
(1988);  and  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  et al. (1988) all find sunshine
to  be capitalized in wages as an amenity,
while heating degree days are capitalized as a
33 The effect of weather variables on property values is
  mixed, with Blomquist et 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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                        disamenity (Roback, 1982,1988; Gyourko and
                        Tracy, 1991).

                        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 (in 1987 dollars) 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 percent and a  15 percent
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 dollars)
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 et al. (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.
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            Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
The drawback of this study is that it estimates
the preferences of movers, who may differ from
the general population. An alternate approach
(Bayer et al., 2006; Bayer and Timmins, 2005)
is 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. If people are risk
averse, ex post losses associated with  extreme
weather  events represent a lower bound to the
value people place on avoiding these events. It is
also the case that people can purchase insurance
only against the monetary losses associated
with floods and hurricanes. Thus, insurance
premiums will not capture the entire value
placed on avoiding these events.

Assuming that people are informed about risks,
the value of avoiding extreme weather events
should be reflected in property values, and,
holding other amenities constant, 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.
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  percent
after hurricane Andrew. The magnitude of
                 Key   West
          SOUTH
SOUTH
          Airport           Business
         Beaches           District
       LEFT  LANE    RIGHT   LANE
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 the 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 aggregate them. An almost bewildering
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                        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.
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 include 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-
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 that might 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.
mr
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4.7 APPENDIX
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 smaller 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 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
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          Step I: Estimate climate change
          (magnitude & timing)
          •  temperature
          •  precipitation
          •  sea-level rise
          •  extreme weather events
          Step 2: Estimate physical effects
          (spatial & temporal distribution)
          • human exposure to heat stress
          * change in ecosystem structure
           and function
          • arial extent of flooding
          • timing of snow melt
          • many more...
    Non-quantified
    physical effects
          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
          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
       Figure 4A.I Estimating the Effects of Climate Change
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. 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
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 WTP 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
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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,
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
34 The contingent valuation method (CVM), or a mod-
  ern variants, a stated choice model (SCM), are forms
  of the stated preference methods.
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.

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
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                         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 WTP as defined in  welfare economic
                         terms, but because the methods are relatively
                         straightforward to apply and the results often
                         have a known relationship to WTP, they provide
                         insights into non-market values. This chapter
                         focuses on WTP 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.

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 forhospitalization, 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 WTP 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 WTP  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
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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.

•  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
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                        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.
•  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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            Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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
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 has drawn on
different bodies of literature,  with generally
more available scientific knowledge on impacts
and adaptation related to human  health,
somewhat less related to human settlements,
and still 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.  The connections between climate change
   and other environmental and social changes
   are complex and dynamic. In some cases,
   climate change compounds the effects of
   other global changes. Socioeconomic factors
   can, in some cases, determine or moderate
   the impacts of climate change (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 for 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. Moreover, the impacts
of changes in climate will be tied to the effects
1
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                         of socioeconomic variables, such as population
                         growth, and how these influence key sectors and
                         decisions, such as infrastructure development,
                         habitat preservation, and access to health care.
                         Consequently, while this assessment focuses
                         on the mechanisms by which climate change
                         could affect future health, well-being,  and
                         settlements 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 affected 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, for example, the  damage caused by
                         Hurricanes Katrina and Rita in 2005. Damage
                         was measured  not only in  terms of lives  and
property lost, but also in the devastating
impacts on infrastructure, neighborhoods,
businesses, schools, and hospitals. In addition,
there have been consequences from continuing
disruptions to established  communities,
livelihoods, psychological well-being, and
the exacerbation of chronic illnesses. While
the impacts of a single hurricane  are not
readily linked to 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
changes in both average and extreme conditions.
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 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 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 (which
include prolonged and intense heat waves and
drought or severe storms) are especially difficult
to project using climate change models. Many
human systems have evolved to accommodate
the "average climate" and some variation around
this average. This evolution takes place in the
context of a variety of dynamic social, economic,
technological, biophysical, and political settings,
which together determine the ability of human
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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 might take years.

Finally, key vulnerabilities are often defined
by certain "thresholds," below which effects
are incidental but beyond which 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 our understanding
of climate impacts and our ability to cope with
extreme events.

5.1.3 Vulnerable Populations and
Vulnerable Locations

Impacts of climate variability and change on
human systems are location- and population-
specific. For instance, along densely developed
coastlines, populations are especially vulnerable
to tropical storms, storm surge, and flooding.
Likewise, the very old  and the  very  young
residing in urban areas are susceptible to
increases in  cardiovascular and pulmonary
morbidity and mortality caused by extreme
heat coupled with degraded air quality. Native
American peoples in Alaska and elsewhere are
vulnerable because of their limited 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
any or all of the following:

1.  Biological sensitivity  relates 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 immunizations from vaccines), the
   use  of certain  medications (e.g., some
   antihypertensive and psychotropic
   medications), and genetic factors (such as
   those that play a role in vulnerability to air
   pollution effects).

2. Socioeconomic factors  also play  a
   critical role  in determining vulnerability
   to environmental condition factors. The
   distribution of climate-related effects will
   vary among  those who live alone, among
   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
   can  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.

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 to  increased
   variability in precipitation. The potential
   for increased frequencies of drought put the
   increasing populations of desert Southwest
   cities at risk.
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                        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. 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 and have limited access to
                        services and other resources for coping, they
                        can be especially vulnerable to climate change.
                        These differential effects raise concerns about
                        social inequity and environmental justice and
                        increase pressure for adaptive responses from
                        local, state, and federal governments.

                        5.1.4 The Cost of and Capacity
                        for Adaptation

                        The United States is capable of considerable
                        adaptation. The  success of adaptation plans
                        and/or measures will depend 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 will likely reduce
                        resources available to cope with other societal
                        burdens, the potential for adaptation through
                        technological and institutional development and
                        behavioral changes is considerable, especially
                        where  such  options 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 creating green roofs can help reduce the
urban heat island effect. In addition to creating
more  aesthetically pleasing locations, green
roofs can also help with energy conservation
in the buildings upon which they are located.
Thus, some adaptation measures can also be
considered mitigation measures.

5.1.5 An Integrative Framework

Human well-being is  an  emerging concept,
and in theory could encompass human health
and settlements—the two key focuses of this
Product—as well as  other critical aspects
of the effect of climate  change on  human
systems and the services provided by natural
systems. As an organizing principle, human
well-being could  provide a paradigm for
identifying and categorizing climate impacts,
and may ultimately provide a framework
for integrating multiple impacts into an
internally consistent, coherent framework for
assessing costs, benefits, and tradeoffs. As an
integrating concept, human well-being  can
develop insights into the linkages between
climate change impacts and 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.

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). However, the
potential for utilizing concepts of human well-
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being to develop an integrating framework
is not yet mature. Additional conceptual
work and research will be needed, such as
developing 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).

An alternative integrating framework could
revolve around  settlements or the more
expansive concept of communities (see Section
4.2.3 for an elaborated discussion). There is a
growing awareness that the built environment
can have a profound impact on our health and
quality  of life.1 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.
1  See for example, the CDC website on healthy places:
  www.cdc.gov/healthyplaces/.
5.2 EXPANDING THE
KNOWLEDGE BASE

The present state of the science suggests that
opportunities remain for addressing critical
research areas. 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, governments,
   and public policy, as well as economic and
   technological development;
•  Connecting socioeconomic scenarios to
   downscaled climate models  in order to
   evaluate future actions that might address
   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;
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                           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, into existing adaptation
                           strategies;
                           Conducting research at regional and sectoral
                           levels that promotes understanding how
                           human and natural systems respond to
                           multiple stressors;
                           Evaluating the adaptation  strategies that
                           effectively address  challenges presented
                           by current non-climate stressors (e.g., land
                           use and population dynamics) and develop
                           comprehensive estimates of the co-benefits
                           of actions to address anticipated climate
                           change;
                           Investigating adaptation measures to address
                           the near- and long-term responses to climate
                           change, using regional and local stakeholders
                           as key contributors for recommending
                           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; and
•  Supporting the development, implementation,
   and evaluation of adaptive responses, as well
   as expanding our understanding of impacts,
   by collecting high quality time-series
   measurements and other observations of
   both climate and human systems.
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.

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:
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• A better understanding of the differential
  effects of temperature extremes  by
  community, demographic, and biological
  characteristics;
• Improved characterization of the exposure-
  response relationships for 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.

Specific suggestions for research on climate
change and human health include the following.

• 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.
              WARNING!
               Flash   Flood
5.2.2 Human Settlements
Research Gaps

Preceding chapters examine 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
  in so far as these changes affect adaptive
  responses.
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                        •  Improve researchers' 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 that 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 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 and, 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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                                            Glossary and Acronyms

                                            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
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 term is also
contained in this glossary.

A

Acclimatization

The  physiological adaptation to  climatic
variations.

Adaptability

See adaptive capacity.

Adaptation

Adjustment in natural or hitman 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.

Aeroallergens'

Any  of various air-borne substances, such as
pollen or spores, that can cause an allergic
response.
                                             The American Heritage® Dictionary of the English
                                             Language, Fourth Edition. Retrieved November 21,
                                             2007 from http://dictionary.reference.com/browse/
                                             aeroallergen.
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                        Aerosol

                        Particulate matter (solid or liquid) that is
                        larger than a molecule but small enough to
                        remain suspended in the atmosphere. Natural
                        sources include dust and clay particles from
                        weathered rocks and salt particles from  sea
                        spray, both of which are carried upward by the
                        wind. Aerosols are often considered pollutants
                        and can be created through human activities.
                        They are important in the both the atmosphere
                        and the Earth's climate system as nuclei for
                        condensation of water droplets and ice crystals,
                        participants in various chemical cycles, and as
                        absorbers/scatterers of solar radiation.

                        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.

                        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 is 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 percent volume mixing ratio)
and oxygen (20.9 percent volume mixing ratio),
together with a number of trace gases, such
as argon (0.93 percent volume mixing ratio),
helium, and  radiatively active greenhouse
gases such as carbon dioxide (0.035 percent
volume mixing ratio) and ozone. In addition,
the atmosphere contains water vapor, whose
amount is highly variable but typically 1 percent
volume mixing  ratio. The atmosphere also
contains clouds and aerosols.
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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.

Biodiversity

A term that refers to the variety and variability
among  living organisms and the ecological
systems in which they exist. Diversity can be
measured by the number of different items
and their relative  frequencies.  The items
are organized at many levels, encompassing
everything from ecosystems, to species, to
genes.

Biofuel

A fuel  produced from  organic matter or
combustible 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.

Biomass

The total dry weight of all living organisms that
can be sustained at each tropic level in a food
chain. Also, all biological materials, including
organic  material (dead and living) from above
and below ground, such as crops, grasses, roots,
animals, animal waste, etc.
Biosphere

The region of Earth and the atmosphere where
organisms exist. Also, a part of the global
carbon cycle that includes living organisms and
biogenic organic matter.

Bottom-up models

An approach to modeling that includes  both
technological and engineering details in the
analysis.
Carbon cycle

The term to describe the flow of carbon
through a system by various chemical, physical,
geological,  and biological processes. This
cycle is usually thought of as a series of four
main reservoirs of carbon interconnected by
pathways of exchange. The reservoirs include
the atmosphere, terrestrial biosphere (including
freshwater systems), oceans, and sediments
(including fossil fuels).

Carbon dioxide (CO2)

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 pain, and
eventual collapse from dehydration.

Chronic obstructive 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.
2 The American Heritage Dictionary of the English
  Language, Fourth Edition. Retrieved November
  21, 2007 from http://dictionary.reference.com/
  browse/biogenic.
3 Centers for Disease Control and Prevention (CDC),
  "Chronic Obstructive Pulmonary Disease." Re-
  trieved November 21, 2007 from http://www.cdc.
  gov/nceh/airpollution/copd/copdfaq.htm.
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                        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, 2003).
                        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"  (IPCC, 2007).  See also  climate
                        variability.

                        Climate change commitment

                        Due to the thermal inertia of the ocean  and
                        slow processes in the biosphere, the cryospere
                        and land surfaces, the climate would continue
                        to change  even if the atmospheric composition
                        was held fixed at today's values. Past changes
                        in atmospheric position lead to a "committed"
                        climatic change, which continues for as long
                        as a radiative imbalance  persists and until
                        all components of the climate system have
                        adjusted to a new state. The further change
                        in temperature after the composition of
                        the atmosphere is held 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 that climate projections depend
upon the emission/concentration/radz'a/z've
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.
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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 sensitivity

The equilibrium response of the climate to a
change in radiative forcing, such as a doubling
of carbon dioxide concentrations.

Climate system

The climate system is the  highly  complex
system consisting of five major components:
the atmosphere, the hydrosphere, the cryospere,
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 spatial and temporal 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.

Cryosphere

The component of Earth's climate system
that includes snow, ice, and permafrost on or
beneath land and ocean surfaces.
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                         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.

                         Deforestation

                         Those processes that result in the conversion
                         of forested lands for non-forest land uses.
                         This process is often considered to be a major
                         cause of enhanced greenhouse effect, because
                         the burning/decomposition of wood releases
                         carbon dioxide, and also because trees that once
                         removed carbon dioxide from the atmosphere
                         through the process of photosynthesis are no
                         longer present.

                         Dengue fever

                         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 and dengue shock
                         syndrome, which may be fatal.

                         Desert

                         An ecosystem with less than  100  mm
                         precipitation per year.

                         Desertification

                         According to the United Nations Convention
                         to Combat Desertification  (UNCCD),
                         desertification is "land degradation in arid, semi-
                         arid, and dry sub-humid areas resulting from
                         various factors, including climatic variations
                         and human activities" (United Nations, 2004).
                         Further, the UNCCD 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, insect 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 production,  capital,
ecosystems,  or human health.

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.
                         4 Millennium Ecosystem Assessment, 2005 glossary.
5 Modified from OECD Glossary of Statistical Terms.
  "Dose-response Function." Retrieved November
  21, 2007 from http://stats.oecd.org/glossary/detail.
  asp?ID=6404.
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Economic potential

The portion of technological potential for
reductions in  greenhouse gas emissions
or energy efficiency improvements  that
could be achieved cost-effectively through
activities like creation of markets, reduction of
market failures, or increases in financial and
technological transfers. In order to achieve
economic potential,  additional policies and
measures must be established to remove market
barriers.

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)

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.

Erosion

The wearing away of land  surfaces by wind
or water, which is intensified by land-clearing
activities related to farming, road building,
logging, or residential/industrial development.

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.
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                         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.

                         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 of his or her actions on others. 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.

                         Externality

                         See external cost.

                         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

Feedback

In relation to the climate, feedback is an
interaction mechanism between processes in
the climate system that occur when the result
of an initial process triggers  a change in a
second process, which  in turn  influences the
initial one again. Positive feedback occurs when
the original process is intensified, negative
feedback occurs when it is reduced.

Foodborne illness6

An illness caused by  consuming foods
or beverages contaminated with any of
many different disease-causing microbes,
pathogens, poisonous chemicals, or other
harmful substances.

Food security

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.
                                                                     6  Modified from CDC. "Foodborne Illness."
                                                                       Retrieved November 21, 2007 from http://
                                                                       ww.w.cdc.gov/ncidod/dbmd/diseaseinfo/
                                                                       foodborneinfections_g.htm.
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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.

Fossil fuel

The general term  for combustible geologic
deposits of organic material buried underground.
Fossil fuels are formed from decayed plant and
animal matter that  have been exposed to heat
and pressure in the Earth's crust for hundreds
of millions of years. Crude oil, coal, and natural
gas are all fossil fuels.
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 System)8

A computerized system organizing data sets
through a geographical referencing of all data
included in its collections.

Glacier

A mass of land  ice that flows downhill and is
constrained by its surrounding topography (i.e.
sides of a valley or surrounding peaks). Glaciers
are maintained by accumulation of snow at
high altitudes and balanced by melting at low
altitudes or discharge into the sea.
7 Millennium Ecosystem Assessment, 2005 glossary.

8 Millennium Ecosystem Assessment, 2005 glossary.
Globalization

The growing integration and interdependence
of  countries worldwide  through the
increasing volume and variety of cross
border transactions in goods and services;
free international capital flows; and the more
rapid and widespread diffusion of technology,
information, and culture.

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.

Global Warming Potential (GWP)

An index used to translate the emission levels
of various gasses into a common measure so
that their relative radiative forcing may be
compared without directly calculated changes
in atmospheric  concentrations. GWPs are
calculated as the  ratio of radiative forcing that
would result from the emissions of one kilogram
of a greenhouse gas to that from the emission
of one kilogram of carbon dioxide over a period
of time (usually 100 years).

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
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                          Glossary and Acronyms
                         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 spectrum
                         of infrared radiation emitted by the Earth's
                         surface, the atmosphere, and clouds. This
                         property causes the greenhouse effect. Water
                         vapor (H2O), carbon dioxide (CO2), nitrous
                         oxide  (N2O), methane  (CH4), and ozone (O3)
                         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 CO2, N2O, 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.

Halocarbon

A chemical that consists of carbon, sometimes
hydrogen, and either chlorine, fluorine, bromine,
or iodine.

Hantavirus

A virus in the family Bunyaviridae that causes
a type of hemorrhagic 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 program 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.
                                                                    9  World Health Organization. "Healthy Cities and
                                                                       Urban Governance." Retrieved November 21, 2007
                                                                       from http://www.euro.who.int/healthy-cities.

                                                                    10 U.S. Environmental Protection Agency. "Heat Island
                                                                       Effect Glossary." Retrieved November 21, 2007
                                                                       from http://www.epa.gov/hiri/resources/glossary.
                                                                       html#h.
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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

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).

Hydrofluorocarbons (HFCs)

Compounds that contain hydrogen, fluorine,
chlorine, and carbon atoms.  They have been
introduced as temporary replacements  for
chloroflourocarbons (CFCs) as they are less
potent at  destroying  stratospheric ozone.
However, they are considered both  ozone
depleting substances and greenhouse gases.
Hydrological systems

The systems involved in movement,
distribution, and quality of water throughout
the Earth, including both the hydrologic cycle
and water resources.

Hydrosphere

All the water present on Earth, including
liquid water (oceans, fresh water, underground
aquifers), frozen water (polar ice caps,,
floating ice, frozen upper layer of soil known
as permafrost), and  water vapor in the
atmosphere.

Hyperthermia13

Unusually high body temperature.
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 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.
11 Modified from NOAA. "Heat Index." Retrieved
  November 21, 2007 from http://www.crh.noaa.gov/
  jkl/?n=heat_index_calculator.

12 U.S. EPA. "Heat Island Effect Glossary."
13 The American Heritage Dictionary of the English
  Language, Fourth Edition. Retrieved November 21,
  2007  from http://dictionary.reference.com/browse/
  hyperthermia.
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                          Glossary and Acronyms
                         (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 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 of fossil 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 disease

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.

Infrared radiation

Heat energy emitted by the Earth's surface
and its atmosphere, some of which is strongly
absorbed by greenhouse gases and re-radiated
back towards the Earth's surface, creating the
greenhouse effect. Also describes the heat
energy emitted from all solids, liquids and
gases.

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.
                         14 Millennium Ecosystem Assessment, 2005, Current
                           State and Trends Assessment glossary.
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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.
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.
Kyoto Protocol

The Kyoto Protocol was adopted at the Third
Session of the Conference of the Parties 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 Organization for Economic Cooperation
and Development (OECD) and those with
economies in transition) agreed to reduce their
anthropogenic greenhouse gas emissions (CO2,
CR,, N2O, HFCs, PFCs, and SF6) by at least 5
percent below 1990 levels in the commitment
period 2008 to 2012. The Kyoto Protocol entered
into force on 16 February 2005.
15 Climate Change North. "Glossary." Retrieved
  November 21, 2007 from http://www.climat-
  echangenorth.ca/H l_Glossary.html.  .
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.

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

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.

La Nina

See El Nino Southern Oscillation.

Lifetime (atmospheric)

The lifetime of a greenhouse gas refers to the
approximate amount of time it would take for
the atmospheric pollutant concentration to
return to its natural level (assuming emissions
cease), as a result of either being converted to
another chemical compound or being taken
out of the atmosphere via a sink. This length of
time depends on both the pollutant's sources
and sinks, and its level  of reactivity. Average
lifetimes can vary from a week (e.g., sulfate
aerosols) to more than a century (e.g., CFCs,
carbon dioxide). Long lifetimes allow the
pollutant to mix throughout the atmosphere.

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.
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                          Glossary and Acronyms
                        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.

                        Market potential

                        The portion of economic potential for reductions
                        in greenhouse gas  emissions or improvements
                        in energy-efficiency that could  be achieved
                        under forecast market conditions; assuming
                        there are no new policies and measures
Methane (CH4)

A hydrocarbon greenhouse gas  produced
through anaerobic (without  oxygen)
decomposition of waste in landfills, animal
digestion, decomposition of animal wastes,
production and distribution of natural gas and
petroleum, coal production, and incomplete
fossil fuel combustion.

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.

Montreal Protocol

Titled Montreal Protocol on Substances that
Deplete  the ozone layer, this  international
agreement addresses the phase-out of ozone
depleting substances production and use. Under
the Protocol, several international organizations
report on the science of ozone depletion,
implement projects to help move away from
ozone depleting substances, and  provide a
forum for policy discussions. In the United
States, the Protocol is implemented under the
Clean Air Act Amendments of 1990.

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.
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Net primary production (NPP)

Refers to the increase in plant biomass or carbon
of a unit of landscape. NPP is equal to the Gross
Primary Production minus carbon lost through
autotrophic respiration.

Nitrogen oxides16

Compounds of nitrogen and oxygen produced
by the burning of fossil fuels.

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.

Non-point source pollution

A large, non-specific area that discharges
pollutants into surface and sub-surface water
flows, for example crop fields and urban
areas.

No-regrets opportunities

See no-regrets policy.

No-regrets options

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/
16 Energy Administration Information, "Glossary."
  Retrieved November 21, 2007 from http://www.eia.
  doe.gov/glossary/glossary _n.htm.
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.

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 cost

The cost of an economic activity forgone by the
choice  of another activity.

Ozone (O3)

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
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                          Glossary and Acronyms
                         ultraviolet radiation and molecular oxygen
                         (O2). 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.

                         Ozone layer

                         A group of human-made chemicals composed
                         only of carbon and fluorine, introduced  as
                         alternatives (like hydroflourocarbons) to ozone
                         depleting substances. PFCs are emitted as by-
                         products of industrial processes,  and they are
                         used in manufacturing. While PFCs do not
                         harm the stratospheric ozone layer, they are
                         powerful greenhouse gases which high global
                         warming potential. Examples of PFCs are CF4
                         and C2F6. See Montreal Protocol.
                         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.

                         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.

Perfluorocarbons (PFCs)

A group of human-made chemicals composed
only of carbon and fluorine,  introduced as
alternatives (like hydroflourocarbons) to ozone
depleting substances. PFCs are emitted as by-
products of industrial processes, and they are
used in manufacturing. While PFCs do not
harm  the stratosphereic ozone layer, they are
powerful greenhouse gases which high global
warming potential. Examples of PFCs are CF4
and C2F6.

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.

Photosynthesis

Complex process that takes place in living green
plant cells that combines radiant energy from
the sun with water (H20) and carbon dioxide
(CO2) to produce oxygen (O2) and sugar,  such
as glucose (C6H12O6).

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.

Precursors

A term in photochemistry meaning a compound
antecedent to a pollutant. For example, volatile
organic compounds (VOCs) and nitric  oxides
of nitrogen react in sunlight to form ozone or
                                                                     17 The American Heritage Dictionary, Fourth Edition.
                                                                       Retrieved November 21,2007 from http://dictionary.
                                                                       reference.com/browse/pathogen.
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
other photochemical oxidants. As such, VOCs
and oxides of nitrogen are precursors.

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

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)i«

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.
18 Australian Institute of Health and Welfare. "Aus-
  tralia's Health 1996" glossary. Retrieved November
  21,2007 from http://www.aihw.gov.au/publications/
  health/ah96/ah96-x04.html.
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.
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, for example, a change in the
concentration of carbon dioxide or the output of
the Sun. Usually, radiative forcing is computed
after allowing for stratospheric temperatures
to readjust to radiative equilibrium, but with
all tropospheric properties held fixed at their
unperturbed values.

Rangelands

Lands (mostly grasslands) that support the
growth of plants that provide food (i.e., forage)
for grazing or browsing animals.

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.
19 Modified from text within Chapter 5 of this docu-
  ment.
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                          Glossary and Acronyms
                         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.

                         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 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.
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.

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

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. For
over 100 years, Salmonella have been  known
to cause illness. They were discovered by an
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
20 Deardorff's Glossary of International Economics.
  Retrieved November 21, 2007 from http://www-
  personal.umich.edu/~alandear/glossary/r.html.

21 Modified from definition of vector-borne disease.

22 Modified from information on the CDC's website
  retrieved November 21, 2007 from http://www.
  cdc.gov/nczved/dfbmd/disease_listing/salmonel-
  losis_gi.html.
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
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 sea
level 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 rangelands.

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).

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^b.s«7/«e/.s to produce hydrogen and
carbon dioxide-rich fractions, as well as long-
term storage in depleted oil and gas reservoirs,
coal seams, and saline aquifers.

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 resources  that makes  up the
social cost. See total cost.
                                            23 U.S. EPA. "Terms of Environment Glossary." Re-
                                              trieved November 21, 2007 from http://www.epa.
                                              gov/OCEPAterms/sterms.html.
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 The U.S. Climate Change Science Program
                          Glossary and Acronyms
                         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 potential

                         Represents the level of greenhouse gas mitigation
                         that would be reached by overcoming social and
                         cultural obstacles to using technologies that are
                         cost effective.

                         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.

                         Solar radiation

                         Energy from the sun, including ultra-violet
                         radiation, visible radiation, and infrared
                         radiation;  also referred to as  short-wave
                         radiation.

                         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).
                         24 Methods for Social Researchers in Developing
                           Countries. Glossary. Retrieved November 21, 2007
                           from http://srmdc.net/glossary.htnrfs.
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, 2001).
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.

   (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.

   (Scenario)  Illustrative:  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 A1B, 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
196

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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
  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 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

The achievement of stabilization of atmospheric
concentrations of one or more greenhouse gases
(e.g., carbon dioxide or a CO2-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.

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.

Streamflow

Water within a river channel, usually expressed
in m3 sec-1.

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

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 for fossil fuel use, or by providing
subsidies for practices that reduce emissions or
enhance sinks (e.g., for insulation of buildings
or planting trees).

Sulfur hexafluoride (SF6)

A colorless gas that is soluble in  alcohol and
ether, and slightly soluble in water. It is a very
powerful greenhouse gas used primarily in
electrical transmission and distribution systems,
and as a dielectric in electronics.

Sustainable development

Development that meets the needs of the present
without compromising the ability of future
generations to meet their own needs.
25 SAP 4.6.
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 The U.S. Climate Change Science Program
                          Glossary and Acronyms
                        Technological potential

                        The amount by which it is possible to create
                        a reduction in greenhouse gas emissions
                        or an improvement in energy efficiency by
                        implementing a technology or practice that has
                        already been demonstrated.

                        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 emerge
                        in an ecological, economic or other system,
                        invalidating predictions based on mathematical
                        relationships that apply at lower levels.

                        Time scale

                        The characteristic time it takes for a process to
                        be expressed.
Time-series studies26

Studies done using a set of data that expresses a
particular variable measured over time.

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 CO2 doubling (i.e., at
year 70 in a 1 percent per year compound CO2
increase experiment with a global coupled
climate model).
                                                                   26 Modified from Millennium Ecosystem Assessment,
                                                                     2005. "Time-Series Data."
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
Transpiration

The process by which water vapor is lost to the
atmosphere from living plants; the term can
also be used to describe the quantity of water
dissipated as such.

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.

Tropopause

The boundary between the troposphere and the
stratosphere.

Tundra

A treeless, level, or gently undulating plain
characteristic of arctic and subarctic regions.
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; a 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
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 into force in
March 1994. See also Kyoto Protocol.

Uptake

The addition of a substance  into a reservoir.
For example, the uptake of carbon-
containing substances is often called (carbon)
sequestration.

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."
27 U.S. EPA. "Heat Island Glossary." Retrieved No-
  vember 21, 2007 from http://www.epa.gov/hiri/
  resources/glossary.html#h.
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 The U.S. Climate Change Science Program
                           Glossary and Acronyms
                         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.

                         Valuation"

                         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). 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.
                         28 The American Heritage Dictionary of the English
                            Language, Fourth Edition. Retrieved November 21,
                            2007 from http://dictionary.reference.com/browse/
                            valley fever.

                         29 Millennium Ecosystem Assessment, 2005 glos-
                            sary.

                         30 SAP 4.6.
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
variation to which a system is exposed, its
sensitivity, and its adaptive capacity.
                                          :
w

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.

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.
31 Agency for Toxic Substances & Disease Registry
  (ATSDR). "ATSDR Glossary of Terms." Retrieved
  November 21, 2007 from http://www.atsdr.cdc.gov/
  glossary.html#G-T-.

32 Modified from CDC. "Preventing Bacterial Wa-
  terborne Diseases." Retrieved November 21, 2007
  from http://www.cdc.gov/ncidod/dbmd/diseaseinfo/
  waterbornediseases t.htm.
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             Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
Watershed"

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.

Water stress

A country is water-stressed if the available
freshwater supply relative to water withdrawals
acts as an important constraint on development.
Withdrawal exceeding 20 percent 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 trcmspirational 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.

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.

                            Z

                            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.
33 M i 11 e n n i u m
  2005 glossary.
Ecosystem  Assessment,
34 Modified from the Millennium Ecosystem Assess-
  ment, Current State and Trends Assessment Glos-
  sary, 2005.
                            35 Modified from CDC. "West Nile Virus." Retrieved
                              November 21, 2007 from http://www.cdc.gov/nci-
                              dod/dvbid/westnile/index.htm.
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 The U.S. Climate Change Science Program                                                        Glossary and Acronyms
                        References

                        IPCC, 2001: Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the
                           Third Assessment Report of the Intergovernmental Panel on Climate Change. J. T. Houghton,
                           Y. Ding, D. J. Griggs, M. Noguer, P. J. van der Linden and D. Xiaosu Eds. Cambridge University
                           Press, UK. pp 944

                        IPCC, 2007: Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth
                           Assessment Report of the IntergovernmentalPanel on Climate Change. B. Metz, O.R. Davidson,
                           P.R. Bosch,  R. Dave, L.A. Meyer (eds). Cambridge University Press, Cambridge, UK.

                        Moss, R.H., and S.H. Schneider, 2000:  Towards Consistent Assessment and Reporting of
                           Uncertainties in the IPCC TAR. In: Pachauri, R., and Taniguchi, T., eds., Cross-Cutting Issues
                           in the IPCC Third Assessment Report. Global Industrial and Social Progress Research Institute
                           (Tokyo) for  IPCC.

                        Nakicenovic, N., J. Alcamo, G. Davis, B. de Vries, J. Fenhann, S. Gaffin, K. Gregory, A. Griibler,
                           T.Y. Jung, T. Kram, E.L. LaRovere, L. Michaelis, S. Mori, T. Morita, W. Pepper, H. Pitcher, L.
                           Price, K. Raihi, A. Roehrl, H.-H. Rogner, A. Sankovski, M. Schlesinger, P. Shukla, S. Smith, R.
                           Swart, S. van Rooijen, N. Victor and Z. Dadi, 2000: Emissions Scenarios: A Special Report of
                           Working Group III of the Intergovernmental Panel on Climate Change. Cambridge University
                           Press, Cambridge, and New York, 599 pp.

                        United Nations, 1994:  United Nations Convention to Combat Desertification (UNCCD). UN
                           document number A/AC.241/27, United Nations, New York, NY, USA, 58 pp.

                        World Meteorological Organization (WMO), 2003: Climate: Into the 21st Century. Burroughs, W.
                           ed. Cambridge University Press, Cambridge, UK and New York, NY, USA.
202

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            Analyses of the Effects of Global Change on Human Health and Welfare and Human Systems
6.2 ACRONYMS


AAG        Association of American Geographers

AAP        American Academy of Pediatrics

AIACC      Assessment of Impacts and Adaptations to Climate Change

AMR-A      North American Region

AR4         IPCC's Fourth Assessment Report

CCC        Canada Climate Center

CCP        ICLEI's Cities for Climate Protection

CCSP        Climate Change Science Program

CDC        Centers for Disease Control and Prevention

CLIMB      Climate's Long-Term Impacts on Metro Boston

CO2         Carbon Dioxide

CVD        Cardiovascular Disease

DHS        Department of Homeland Security

ECHAM4    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)

EHE        Extreme Heat Event

ENSO        El Nino Southern Oscillation

EPA         Environmental Protection Agency

FDA         Food and Drug Administration

FEMA       Federal Emergency Management Agency

GCM        General Circulation Model

GDP        Gross Domestic Product

GHG        Greenhouse Gas

GIS         Geographic Information System

GISS        NASA Goddard Institute for Space Studies

ICLEI        International Council for Local Environmental Initiatives

IPCC        Intergovernmental Panel on Climate Change

MA         Millennium Assessment

MM5        Mesoscale Model

MSA        Metropolitan Statistical Area

NAAQS      National Ambient Air Quality Standards

NACC        U.S. National Assessment of Climate Change

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 The U.S. Climate Change Science Program
Glossary and Acronyms
                        NAS         National Academy of Sciences



                        NAST        National Assessment Synthesis Team



                        NEG/ECP    New England Governors and Eastern Canadian Premiers



                        NGO         Non-gGovernmental Organization



                        NO          Nitric Oxide



                        NOAA       National Oceanic and Atmospheric Administration



                        NRC         National Research Council



                        NYCHP      New York Climate and Health Project



                        PM          Particulate Matter



                        PM2.5       Particulate Matter (smaller than 2.5 micrometers)



                        PTSD        Post-traumatic Stress Disorder



                        RADM2      Regional Acid Deposition Model, Version 2



                        RCM         Regional Climate Model



                        RGGI        Regional Greenhouse Gas Initiative



                        RMNP       Rocky Mountain National Park



                        RPS         Renewable Portfolio Standards



                        SAP         Synthesis and Assessment Product



                        SHELDUS    Spatial Hazard Events and Losses Database for the United States



                        SRES        Special Report on Emissions Scenarios



                        TAR         IPCC's Third Assessment Report



                        TBE         Tick-borne Encephalitis



                        UHI         Urban Heat Island Effect



                        UNDP       United Nations Development Programme



                        UNEP       United Nations Environmental Programme



                        USBEA      United States Bureau of Economic Analysis



                        USDA        U.S. Department of Agriculture



                        USGCRP    United States Global Change Research Program




                        VBZ         Vector-borne and Zoonotic



                        VEMAP     Virtual Earth Map



                        VOC         Volatile Organic Compounds



                        VSL         Value of Statistical Life



                        WHO        World Health Organization



                        WTP         Willingness to Pay
204

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                   U.S. Climate Change Science Program
1717 Pennsylvania Avenue, NW  •  Suite 250 • Washington, D.C. 20006  USA
              I-202-223-6262 (voice) •  1-202-223-3065 (fax)
                      http://www.climatescience.gov

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