United States
Environmental Protection
Agency
CLIMATE CHANGE IN THE UNITED STATES
Benefits
of Global Action
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FIND US ONLINE
EPA's climate change website
features a user-friendly
interface for this report with
downloadable graphics. To view
information about EPA's Climate
Change Impacts and Risk
Analysis (CIRA) project, share
your thoughts on this effort,
and access the corresponding
Technical Appendix for this
report, please visit EPA's website
at: www.epa.gov/cira.
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3 INTRODUCTION
6 SUMMARY OF KEY FINDINGS
10 CIRA FRAMEWORK
12 Temperature Projections
14 Precipitation Projections
15 Sea Level Rise Projections
16 Levels of Certainty
18 Boundaries of Analysis
20 SECTORS
22 Health
24 Air Quality
26 Extreme Temperature
28 Labor
30 Water Quality
32 Infrastructure
34 Bridges
36 Roads
38 Urban Drainage
40 Coastal Property
42 Coastal Property: Environmental Justice
44 Electricity
46 Electricity Demand
48 Electricity Supply
50 Water Resources
52 Inland Flooding
54 Drought
56 Water Supply and Demand
58 Agriculture and Forestry
60 Crop and Forest Yields
62 Market Impacts
64 Ecosystems
66 Coral Reefs
68 Shellfish
70 Freshwater Fish
72 Wildfire
74 Carbon Storage
76 OVERVIEW OF RESULTS
78 National Highlights
80 Regional Highlights
82 CONCLUSION
84 ENDNOTES
H «
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CONTRIBUTORS
The Climate Change Impacts and Risk Ana lysis (CIRA) project is coordinated by EPA's Office of Atmospheric
Programs - Climate Change Division, with significant contributions from a number of collaborators,
including the Massachusetts Institute of Technology's Joint Program on the Science and Policy of Global
Change, the Pacific Northwest National Laboratory's Joint Global Change Research Institute, the National
Renewable Energy Laboratory, academic researchers, and the following consulting firms: Industrial
Economics, Inc. (lEc), Stratus Consulting, RTI International, and ICF International. Support for the report's
production and design was provided by Industrial Economics, Inc.
PEER REVIEW
The methods and results of the climate change impacts analyses described herein have been peer reviewed
in the scientific literature. In addition, this summary report was peer reviewed by seven external, independent
experts, a process coordinated by Eastern Research Group, Inc. EPA gratefully acknowledges the following
reviewers for their useful comments and suggestions: Donald Boesch, Larry Dale, Kristie Ebi, Anthony
Janetos, Denise L Mauzerall, Michael Meyer, and Timothy Randhir. The information and views expressed in
this report do not necessarily represent those of the peer reviewers, who also bear no responsibility for any
remaining errors or omissions. Details describing this review, and a comprehensive reference list for the
CIRA peer reviewed literature, can be viewed in the online Technical Appendix of this report (www.epa.gov/
cira/downloads-cira-report).
RECOMMENDED CITATION
EPA. 2015. Climate Change in the United States: Benefits of Global Action. United States Environmental
Protection Agency, Office of Atmospheric Programs, EPA 430-R-15-001.
' •*
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The Earth's changing climate is affecting human health and the environment in many
ways. Across the United States (U.S.), temperatures are rising, snow and rainfall patterns
are shifting, and extreme climate events are becoming more common. Scientists are
confident that many of the observed changes in the climate are caused by the increase in
greenhouse gases (GHGs) in the atmosphere. As GHG emissions from human activities increase,
many climate change impacts are expected to increase in both magnitude and frequency over
the coming decades, with risks to human health, the economy, and the environment.
Actions can be taken now to reduce GHG emissions and avoid many of the adverse impacts of
climate change. Quantifying the benefits of reducing GHG emissions (i.e., how GHG mitigation
reduces or avoids impacts) requires comparing projections of climate change impacts and dam-
ages in a future with policy actions and a future without policy actions. Looking across a large
number of sectors, this report communicates estimates of these benefits to the U.S. associated
with global action on climate change.
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About this Report
This report summarizes and communicates the results of EPA's ongoing Climate Change Impacts and Risk Analysis (CIRA) project.
The goal of this work is to estimate to what degree climate change impacts and damages to multiple U.S. sectors (e.g., human
health, infrastructure, and water resources) may be avoided or reduced in a future with significant global action to reduce GHG
emissions, compared to a future in which current emissions continue to grow. Importantly, only a small portion of the impacts of
climate change are estimated, and therefore this report captures just some of the total benefits of reducing GHGs.
To achieve this, a multi-model framework was developed to estimate the impacts and damages to the human health and
welfare of people in the U.S. The CIRA framework uses consistent inputs (e.g., socioeconomic and climate scenarios) to enable
consistent comparison of sectoral impacts across time and space. In addition, the role of adaptation is modeled for some of the
sectors to explore the potential for risk reduction and, where applicable, to quantify the costs associated with adaptive actions.
The methods and results of the CIRA project have been peer reviewed in the scientific literature, including a special issue of
Climatic Change entitled, "A Multi-Model Framework to Achieve Consistent Evaluation of Climate Change Impacts in the United
States."1 The research papers underlying the modeling and results presented herein are cited throughout this report and are listed
in Section B of the Technical Appendix.
Interpreting the Results
This report presents results from a large set of sectoral impact
models that quantify and monetize climate change impacts in
the U.S., with a primary focus on the contiguous U.S., in futures
with and without global GHG mitigation. The CIRA analyses are
intended to provide insights about the potential direction and
magnitude of climate change impacts and the benefits (avoided
impacts) to the U.S. of global emissions reductions. However,
none of the estimates presented in this report should be
interpreted as definitive predictions of future impacts at a
particular place or time.
The CIRA analyses do not evaluate or assume specific GHG
mitigation or adaptation policies in the U.S. or in other world
regions. Instead, they consider plausible scenarios to illustrate
potential benefits of significant GHG emission reductions
compared to a business-as-usual future.The results should not
be interpreted as supporting any particular domestic or global
mitigation policy or target. A wide range of global mitigation
scenarios could be modeled in the CIRA framework,2 and results
would vary accordingly. For ease of communicating results,
however, this report focuses on a future where the increase in
average global temperature is limited to approximately 2°C
(3.6°F) above preindustrial levels—a goal relevant to interna-
tional discussions on GHG emission reductions.3
This report includes as many climate change impacts as
feasible at present, but is not all-inclusive. It is not intended
to be as comprehensive as major assessments, such as those
conducted by the U.S. Global Change Research Program
(USGCRP), which capture a wider range of impacts from the
published literature.4 By using a consistent set of socioeco-
nomic and climate scenarios, CIRA produces apples-to-apples
comparisons of impacts across sectors and regions—some-
thing that is not always achieved, or even sought, in the
major assessments. Also, the assessments typically do not
monetize damages, nor do they focus on quantifying mitiga-
tion benefits. CIRA's ability to estimate how global GHG
mitigation may benefit the U.S. by reducing or avoiding
climate change impacts helps to fill an important literature
and knowledge gap.
The CIRA analyses do not serve the same analytical purpose
nor use the same methodology as the Social Cost of Carbon
(SCC), an economic metric quantifying the marginal global
benefit of reducing one ton of carbon dioxide (CO2).5 In
addition, the costs of reducing GHG emissions,6 and the health
benefits associated with co-reductions in other air pollutants,
are well-examined elsewhere in the literature7 and are beyond
the scope of this report.
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Roadmap to the Report
SUMMARY OF
KEY FINDINGS
CIRA FRAMEWORK
SECTORS
Health
Infrastructure
Electricity
Water Resources
Agriculture and Forestry
Ecosystems
OVERVIEW OF
RESULTS
CONCLUSION
TECHNICAL APPENDIX
(available a t www.epa.gov/cira)
Provides an overview of key findings and highlights of the report.
Introduces the CIRA project, describes and briefly presents the climate projections used in the
analyses, and discusses key uncertainties and boundaries of analysis.
Summarizes the major findings of each of the 20 impact analyses within the six broad sectors
listed to the left, including:
• Background on the impact being estimated, along with a brief summary of the analytical
approach to estimating the impact;
• Key findings and graphics depicting the risks of inaction and the benefits of global-scale
GHG mitigation; and
• References to the underlying peer-reviewed research upon which these estimates are based.
Presents national and regional highlights from the 20 sectoral impact analyses.
Describes the over-arching conclusions of the report.
• Provides a list of all peer-reviewed research papers underlying the CIRA project;
• Provides comparisons of key CIRA findings to those of the assessment literature; and
• Describes the treatment of adaptation across the sectoral analyses.
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Climate change poses significant risks to humans and the environment. The
CIRA project quantifies and monetizes the risks of inaction and benefits to the
U.S. of global GHG mitigation within six broad sectors (water resources, electricity,
infrastructure, health, agriculture and forestry, and ecosystems). Looking across the
impact estimates presented in this report, several common themes emerge.1
Global GHG
Mitigation Avoids
Costly Damages
in the U.S.
For nearly all sectors
analyzed, global GHG
mitigation is projected to
prevent or substantially
reduce adverse impacts
in the U.S. this century
compared to a future
without emission reduc-
tions. For many sectors,
the projected benefits of
mitigation are substantial;
for example, in 2100
mitigation is projected to
result in cost savings of
$4.2-$7.4 billion associated
with avoided road mainte-
nance. Global GHG mitigation is also projected to avoid the loss of 230,000-360,000 acres of
coldwater fish habitat across the country compared to a future without emissions reductions.
Global GHG
Mitigation Reduces
the Frequency of
Extreme Weather
Events and
Associated Impacts
Global GHG mitigation is
projected to have a substantial
effect on reducing the
incidence of extreme tem-
perature and precipitation
events by the end of the
century, as well as the impacts
to humans and the environ-
ment associated with these
extreme events.2 For example,
by 2100 mitigation is project-
ed to avoid 12,000 deaths
annually associated with
extreme temperatures in 49
U.S. cities, compared to a
future with no emission
reductions. Inclusion of the
entire U.S. population would
greatly increase the number
of avoided deaths, while
accounting for adaptation
could reduce this number.
The Benefits of GHG Mitigation Increase over Time
Fora large majority of sectors analyzed, the
benefits of GHG mitigation are projected to
be greater in 2100 than in 2050. In addition,
the benefits of GHG mitigation are often not
apparent until mid-century. This delay in
benefits is consistent with many studies,3 and
is attributable to inertia in the climate system.
Therefore, decisions we make today can have
long-term effects, and delaying action will
likely increase the risks of significant and costly
impacts in the future.
I
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Adaptation Can Reduce Overall
Damages in Certain Sectors
Adaptation can substantially reduce certain impacts of
climate change regardless of whether future GHG levels are
low or high. For example, the estimated damages to coastal
property from sea level rise and storm surge in the contigu-
ous U.S. are $5.0 trillion through 2100 (discounted at 3%4) in
a future without emission reductions. When cost-effective
adaptation along the coast is included, the estimated da mag-
es are reduced to $810 billion.
Impacts Vary across Time and Space
Important regional changes may be masked when results are presented at the national level. For example, the wildfire analysis
reveals that the projected changes in the Southwest and Rocky Mountain regions are the primary drivers of national trends of
increasing wildfire activity over time.
The temporal scale of climate change impacts is also important. While some impacts are likely to occur gradually over time,
others may exhibit threshold (tipping point) responses to climate change, as large changes manifest over a short period of time.
For example, high-temperature bleaching events projected to occur by 2025 are estimated to severely affect coral reefs in the
Caribbean. Therefore, simply analyzing an impact in one time period (e.g., 2100) may mask important temporal dynamics that are
relevant to decision makers.
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SUMMARY OF KEY FINDINGS
Estimated Benefits to the U.S. in 2100
This graphic presents a selection of the estimated benefits of global GHG mitigation in 2100 for major U.S.
sectors. Unless otherwise noted, the results presented below are estimates of annual benefits (or disbenefits)
of mitigation in the year 2100.* Importantly, only a small portion of the impacts of climate change are estimated,
and therefore this report captures just some of the total benefits of reducing GHGs.
HEALTH
AIR QUALITY
An estimated 57,000
fewer deaths from
poor air quality
in 2100
EXTREME TEMPERATURE
In 49 major U.S. cities,
an estimated
12,000 fewer deaths
from extreme
temperature in 2100
LABOR
Approximately
$110 billion
in avoided
damages from
lost labor due
to extreme
temperatures
in 2100
WATER QUALITY
An estimated
$2.6-$3.0 billion
in avoided
damages from
poor water
quality in 2100f
ELECTRICITY
ELECTRICITY
DEMAND
An avoided
increase in
electricity demand
ofl.1%-4.0%
in 2050*
ELECTRICITY
SUPPLY
An
estimated
$10-$ 34
billion in
savings on
power
system costs
in 2050*
INFRASTRUCTURE
BRIDGES
An estimated
720-2,200 fewer
bridges made
structurally
vulnerable
in2100f
ROADS
An estimated
$4.2-$7.4 billion
in avoided
adaptation costs
in 2100f
URBAN DRAINAGE
In 50 U.S. cities, an
estimated $50
million-$6.4 billion in
avoided adaptation
costs in 2100f
COASTAL PROPERTY
Approximately $3.1
billion in avoided
damages and
adaptation costs from
sea level rise and
storm surge in 2100
* Monetary estimates for this summary are presented for either 2050 or 2100 only, and are undiscounted (2014$). See the Sectors section for the use of discounting throughout this report.
f Estimated range of results relies upon climate projections from two climate models showing different patterns of precipitation in the U.S. The IGSM-CAM projects a relatively "wetter" future for most of the U.S.
compared to the drier Ml ROC model (seethe CIRA Framework section of this report for more information).
8
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For detailed information on the results, please refer to the Sectors section of this report.
WATER RESOURCES
INLAND
FLOODING
Estimates range
from approximately
$2.8 billion in
avoided damages to
$38 million in
increased damages
in 2100t
DROUGHT
An estimated
40%-59% fewer
severe and extreme
droughts in 2100t
SUPPLY &
DEMAND
An estimated
$11-$180 billion in
avoided damages
from water
shortages in key
economic sectors
in2100f
AGRICULTURE AND FORESTRY
AGRICULTURE
An
estimated
$6.6-$ 11
billion in
avoided
damages to
agriculture
in 2100
ECOSYSTEMS
CORAL REEFS
An avoided loss
of approximately
35% of current
Hawaiian coral in
2100, with a
recreational value
of $1.1 billion
SHELLFISH
An avoided loss of
approximately
34% of the U.S.
oyster supply, 37%
of scallops, and
29% of clams
in 2100
FRESHWATER
FISH
An estimated
230,000-360,000
acres of cold-
water fish habitat
preserved
in2100f
FORESTRY
An estimated
$520 million to
$1.5 billion
in avoided
da mages to
forestry in 2100
WILDFIRE
An estimated
6.0-7.9 million
fewer acres
burned by
wildfires in
2100f
CARBON
STORAGE
An estimated
1.0-26 million
fewer tons of
carbon stored
in vegetation
in 2100t§
* Results reflect the estimated range of benefits from the reduction in demand and system costs resulting from lower temperatures associated with GHG mitigation. The Electricity section in this report presents an analysis
that includes the costs to the electric power sector of reducing GHG emissions.
§ See the Carbon Storage section of this report for cumulative results from 2000-2100, which show benefits of GHG mitigation for parts, and in some cases all, of the century.
9
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The primary goal of the CIRA project is to estimate the degree to which climate change
impacts in the U.S. are avoided or reduced in the 21st century under significant global GHG mitigation.
The CIRA framework is designed to assess the physical impacts and economic damages of climate
change in the U.S. In this report, the benefits (or disbenefits) of global GHG mitigation are assessed as the
difference between the impacts in futures with and without mitigation policy using multiple models driven by —>
11 Design GHG Emissions Scenarios
GHG emissions from human activities, and
the resulting climate change impacts and
damages, depend on future socioeconomic
development (e.g., population growth,
economic development, energy sources, and
technological change). Emissions scenarios
provide scientifically credible starting points
for examining questions about an uncertain
future and help us visualize alternative
futures.2They are neither forecasts nor
predictions, and the report does not assume
that any scenario is more or less likely than
another. GHG emissions scenarios are
illustrations of how the release of different
amounts of climate-altering gases and
particles into the atmosphere will produce
different climate conditions in the U.S. and
around the globe.
To allow for a better understanding of the
potential benefits of global-scale GHG
mitigation, the CIRA results presented in this
report consider two emissions scenarios (see
Table 1): a business-as-usual future in which
GHG emissions continue to increase
unchecked (referred to as the Reference
scenario), and a mitigation scenario in which
global GHG emissions are substantially
reduced (referred to as the Mitigation
scenario).3-4These scenarios were developed
using the Massachusetts Institute of Technolo-
gy's Emissions Predictions and Policy Analysis
(EPPA) model,5the human systems compo-
nent within the Integrated Global System
Model (IGSM). EPPA provides projections of
world economic development and emissions,
including analysis of proposed emissions
control measures.These measures include, for
example, limiting GHGs from major emitting
sectors, such as electricity production and
transportation. EPPA-IGSM, along with a
linked climate model, provide a consistent
framework to develop GHG emission and
climate scenarios for impacts assessment.
Table 1 provides information on the
characteristics of each emissions scenario in
2100. Similar to the Representative Concen-
tration Pathways (RCPs) used by the Intergov-
ernmental Panel on Climate Change (IPCC) in
its Fifth Assessment Report,6 the CIRA
scenarios are based on different trajectories
of GHG emissions and radiative forcing—a
metric of the additional heat added to the
Earth's climate system caused by anthropo-
genic and natural emissions.
Figure 1 compares the two primary CIRA
scenarios used throughout this report to the
RCPs, showing that these scenarios fall within
the range of IPCC's latest projections.The
CIRA emissions scenarios provide illustrations
for analytical comparison and do not
represent specific policies. For more informa-
tion about the design of these scenarios,
please refer to Paltsev et al. (2013).7
Table 1. Characteristics of the Reference and Mitigation Scenarios in 2100
BUSINESS AS USUAL
"REFERENCE"
GHG RADIATIVE FORCING (IPCC/RCP METHOD)
9.8 W/m2 (8.6 W/m2)
GLOBAL GHG EMISSIONS
-2.5 x 2005 levels
ATMOSPHERIC CO, CONCENTRATION
GLOBAL EMISSIONS REDUCTIONS
"MITIGATION"
3.6 W/m2 (3.2 W/m2)
-0.28 x 2005 levels
826 ppm
JMflMJd!!
1750ppm
ATMOSPHERIC GHG CONCENTRATION (CO2 EQUIVALENT
462 ppm
500ppm
STEP 1 | DESIGN GHG EMISSIONS SCENARIOS
Two scenarios are used throughout this report:
• Businesses usual or the "Reference" scenario
• Global emissions reductions or the "Mitigation" scenario
STEP 2 | PROJECT FUTURE CLIMATE
• Temperature
• Precipitation
• Sea level rise
• C02 concentration
• Sea surface temperature
• Cloud cover
• Wind speed
• Relative humidity
• Solar radiation
10
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a consistent set of climatic, socioeconomic, and technological scenarios. A three-step approach for assessing
benefits includes developing GHG emissions scenarios; simulating future climate under these scenarios; and
applying these projections in a series of coordinated impacts analyses encompassing six sectors (health,
infrastructure, electricity, water resources, agriculture and forestry, and ecosystems). For more information
on the objectives and design of the CIRA framework, please refer to Martinich et al. (2015).x
Figure 1. Comparison of CIRA
Scenarios to the IPCC RCPs8
la. GHG Emissions
140
-Si 120
100
2000 2025 2050 2075
2100
1 b. Radiative Forcing9
2000 2025
2050
2075 2100
1 c. CO, Concentration
1000
300
2000 2025 2050 2075 2100
^^ Reference
RCP 8.5 RCP 6.0
•Mitigation
-RCP 4.5 RCP 2.6
2 | Project Future Climate
To simulate future climate in the U.S., CIRA primarily uses the IGSM-CAM framework, which
links the IGSM to the National Center for Atmospheric Research's Community Atmosphere
Model (CAM). The IGSM-CAM simulates changes in a large number of climate variables, such
as temperature and precipitation, at various temporal scales. Other outputs include: sea level
rise, atmospheric C02 concentration, cloud cover, wind speed, relative humidity, and solar
radiation.10The CIRA climate projections are briefly described in the following pages of this
report. As described in the Levels of Certainty section, results using other climate models
with different patterns of projected precipitation are compared to the IGSM-CAM results for
sectoral analyses that are sensitive to changes in precipitation (e.g., drought and flooding).
Specifically, results under the IGSM-CAM projections, which estimate a wetter future for most
of the contiguous U.S., are complemented with drier projections to investigate the influence
on impact estimates. Additional information on the development and characteristics of the
CIRA climate projections can be found in Monieretal. (2014)."
3 | Analyze Sectoral Impacts
This report analyzes 20 specific climate change impacts in the U.S., which are categorized
into six broad sectors (health, infrastructure, electricity, water resources, agriculture and
forestry, and ecosystems). The impacts were selected based on the following criteria:
sufficient understanding of how climate change affects the sector; the existence of data to
support the methodologies; availability of modeling applications that could be applied in
the CIRA framework; and the economic, iconic, or cultural significance of impacts and
damages in the sector to the U.S. It is anticipated that the coverage of sectoral impacts in
the CIRA project will expand in future work.
To quantify climate change impacts in each sector, process-based or statistical models
were applied using the socioeconomic and climate scenarios described above.This
approach, which ensures that each model is driven by the same inputs, enables consistent
comparison of impacts across sectors and in-depth analysis across regions and time. Many
of the analyses explore the potential for adaptation to reduce risks and quantify the costs
associated with adaptive actions (see the Sectors section of this report and Section D of the
Technical Appendix for more information).12 Lastly, the CIRA analyses investigate key
sources of variability in projecting future climate, as further discussed in the Levels of
Certainty section.
STEP 3 | ANALYZE SECTORAL IMPACTS
HEALTH
• Air quality
• Extreme temperature
• Labor
• Water quality
INFRASTRUCTURE
• Bridges
• Roads
• Urban drainage
• Coastal property
ELECTRICITY
• Electricity demand
• Electricity supply
WATER
RESOURCES
• Inland flooding
• Drought
• Water supply and
demand
AGRICULTURE
AND FORESTRY
• Crop and forest yields
• Market impacts
ECOSYSTEMS
• Coral reefs
• Freshwater fish
• Carbon storage
11
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CIRA FRAMEWORK
Temperature Projections
Global Temperature Change
Global mean temperature under the CIRA Reference scenario is projected to increase by over 9°F by 2100
(Figure 1).This estimated increase is consistent with the USGCRP Third National Climate Assessment, which
projects a range of 5-11°F by 21OO.13-14 To help illustrate the magnitude of such a change in global mean
temperature, the last ice age, which covered the northern contiguous U.S. with ice sheets, was approximately
9°F cooler than today. While some areas will experience greater increases than others. Figure 1 presents the
average change that is projected to
occur across the globe under the
Reference and Mitigation scenarios.
As shown, temperatures in the
Mitigation scenario eventually
Figure 1. Change in Global Mean Temperature
with and without Global GHG Mitigation
Time series of global annual mean surface air temperature
relative to present-day (1980-2009 mean) for IGSM-CAM under the
Reference and Mitigation scenarios with a climate sensitivity (CS)'5 of3°C.
10-,
9-
„ 8-
Ll_
5 7-
o 6-
•* 5-
a 0
D
2 4'
OJ
Q.
01
>- 2\
1
2000 2025 2050 2075
^^ Reference Mitigation
Temperature Equal to 2°C Above Pre-lndustrial
2100
stabilize, though due to the inertia of
the climate system, stabilization is
not reached until several decades
after the peak in radiative forcing.
The Reference scenario continues to
warm, reaching a temperature
increase of a I most five times that of
the Mitigation scenario by the end of
the century. This demonstrates that
significant GHG mitigation efforts
can stabilize temperatures and avoid
an additional 7°F of warming this
century, but due to climate system
inertia, benefits may not be apparent
for several decades.
Limiting Future
Warming to 2°C
Limiting the future increase in
global average surface tempera-
ture to below 2°C (3.6°F) above
preindustrial levels is a common-
ly regarded goal for avoiding
dangerous climate change
impacts.16 Global temperatures,
however, have already warmed
0.85°C (1.5°F) from preindustrial
times.17-18The level of global GHG
mitigation achieved under the
CIRA Mitigation scenario is
consistent with the amount
required to meet the 2°C target
(Figure 1),19and therefore the
estimates presented in this
report describing the potential
benefits to the U.S. of global
GHG mitigation are a reasonable
approximation of the benefits
that would result from meeting
this goal.
Temperature Change in the U.S.
Under the Reference scenario, the largest increases in average temperature across the contiguous U.S. by 2100 are projected to occur in the
Mountain West—up to a 14°F increase from present-day average temperature (Figure 2). The northern regions are also likely to see larger
temperature increases than the global average (up to 12°F, compared to a global average of 9.3°F), while the Southeast is projected to experience
a relatively lower level of overall warming (but comparable to the global average increase). Under the Mitigation scenario, temperature increases
across the country are far lower compared to the Reference, with no regions experiencing increases of more than 4°F.
Figure 2. Distribution of Temperature Change with and without Global GHG Mitigation
Change in annual mean surface air temperature relative to present-day (1980-2009 average) for IGSM-CAM under the Reference and Mitigation scenarios (CS 3°C).
2025
2050
2075
2100
Reference
Mitigation
12
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Seasonal and Extreme Temperatures
Just as presenting global
average temperature changes
masks geographic patterns of
variability, presenting annual
average temperature changes
conceals seasonal patterns of
change. Some seasons are
expected to warm faster than
others, and the impacts of warm-
ing will also vary by season. For
example, in some regions,
greater levels of warming may
occur in the winter, but warming
in summer will matter most for
changes in the frequency and
intensity of heat waves. Figure 3
provides an illustrative example
of the changes in average
summertime temperature that
select states may experience
over time with and without
global GHG mitigation. Under
the Reference scenario, summer-
time temperatures in some
northern states are projected to
feel more like the present-day
summertime conditions in
southern states. However, under
the Mitigation scenario, states
are projected to experience
substantially smaller changes.
In addition to increasing
average summertime tempera-
tures, climate change is projected
to result in an increase in extreme
temperatures across most of the
contiguous U.S. In the Mountain
West, for example, the hottest
days of the year are estimated to
be over 14°F hotter than today
under the Reference scenario by
the end of the century (Figure 4).
Many parts of the Midwest and
Northeast are projected to
experience increases in extreme
temperatures ranging from 7-10°F,
an amount similarto the increase
in average summertime tempera-
tures. These changes are project-
ed to be far less severe under the
Mitigation scenario, however, with
no regions experiencing increases
of more than 4°F.
Figure 3. Change in Summertime Temperatures for Select States
with and without Global GHG Mitigation
The map compares mean summertime (June, July, and August) temperature in South Dakota, Illinois, and Maryland in
2050 and 2100 under the Reference and Mitigation scenarios to states with similar present-day temperatures. For example,
the projected mean summertime temperature in Illinois in 2100 under the Reference scenario (83°F) is projected to be
analogous to the mean summertime temperature in Louisiana from 1980-2009 (81 °F). In other words, without global GHG
mitigation, Illinois summers by 2100 are projected to "feel like" present-day Louisiana summers. The maps are not perfect
representations of projected climate, as other factors such as humidity are not included, but they do provide a way of
visualizing the magnitude of possible changes in the summertime conditions of the future.
--!_,— T
Figure 4. Change in Magnitude of Extreme Heat Events
with and without Global GHG Mitigation
Change in the extreme heat index (T99)—the temperature of the hottest four days, or 99h percentile, of the year—simulated by
the IGSM-CAM for 2100 (average 2085-2115) relative to the baseline (average 1981-2010) (CS 3°C).2°
Reference
Mitigation
13
-------
CIRA FRAMEWORK
Precipitation Projections
Precipitation in the U.S.
2050
The IGSM-CAM projects future
changes in annual mean precipi-
tation over the course of the 21st
century under the Reference
and Mitigation scenarios (Figure
1). Under the CIRA Reference
scenario, the model estimates
increasing precipitation over 2025
much of the U.S., especially over
the Great Plains. However, the
western U.S. is estimated to
experience a decrease in precipi-
tation compared to present day.
Under the Mitigation scenario,
a similar but less intense pattern
of increasing precipitation is
projected over much of the
country, particularly in the
central states.
As projections of future
precipitation vary across
individual climate models, the
CIRA analyses use outputs from
additional climate models (see
the Levels of Certainty section of
this report). Compared to
multi-model ensemble projec-
tions presented in the IPCC and
USGCRP, the CIRA projections
exhibit some regional differenc- 2100
es in the pattern of projected
precipitation. A comparison
between the CIRA climate
projections and those presented
in these assessment reports can
be found in Section E of the
Technical Appendix.
Figure 1. Percentage Change in Annual Mean Precipitation
with and without Global GHG Mitigation
Percentage change in annual mean precipitation from the historical period (1980-2009) for
IGSM-CAM under the Reference and Mitigation scenarios (CS 3°C).
Reference
Mitigation
2075
% Change
-50 -40 -30 -20-10 0 10 20 30 40 50 60
less precipitation ^ ^ more precipitation
Extreme Precipitation
Figure 2 shows the change in the intensity of extreme precipita-
tion events from present day to 2100. Blue areas on this map
indicate that the future's heaviest precipitation events will be
more intense compared to today. Under the Reference, the
IGSM-CAM shows a general increase in the intensity of extreme
precipitation events, except over California. The increase is
particularly strong over the Northeast, Midwest, and Southeast.
Global GHG mitigation is likely to greatly reduce the increase in
intensity of extreme precipitation events, as shown in the right
panel of Figure 2.
Figure 2. Change in the Intensity of Extreme Precipitation
with and without Global GHG Mitigation
Change in the extreme precipitation index (P99) simulated by IGSM-CAM for the
2085-2 1 15 period relative to the 1981-2010 period (CS 3°C). The P99 index reflects
the precipitation of the four most rainy days of the year, or the 99th percent He.2'
Reference Mitigation
-.23
.23 in/day
-6-5-4-3-2-10123456 mm/day
n r
less precipitation •
more precipitation
14
-------
CIRA FRAMEWORK
Sea Level Rise Projections
Global Sea Level Rise
Figure 1 shows the change in global mean sea level from present
day to 2100 under the Reference and Mitigation scenarios.
Global mean sea levels are projected to rise about 56 inches by
2100 under the Reference and about 37 inches under the
Mitigation scenario. These results fall within the range for risk
planning presented in the Third National Climate Assessment
of 8-79 inches by 2100, with the Reference scenario's rate being
slightly larger than the Assessment's likely range of 12-48
inches.22'23 As shown in Figure 1, global sea level rise is similar
across the CIRA scenarios through mid-century, primarily due
to inertia in the global climate system and lasting effects from
past GHG emissions. As a result, it is not until the second half of
the century that global GHG mitigation results in a reduction in
sea level rise compared to the Reference.
The projections for global sea level rise account for dynamic
ice-sheet melting by estimating the rapid response of sea levels
to atmospheric temperature change.24These adjustments
incorporate estimates of ice-sheet melt from the empirical
model of Vermeer and Rahmstorf (2009),25'26 using the decadal
trajectory of global mean surface air temperature results from
the IGSM as inputs.27
Figure 1. Change in Global Mean Sea Level
with and without Global GHG Mitigation
o
1990 2000
2025
2050
2075
2100
•Reference ^Mitigation
Sea Level Rise in the U.S.
Figure 2 shows projected
relative sea level rise under
the Reference scenario for
select areas along the U.S.
coast in 2100. For each coastal
area, global rates of sea level
change under the two
scenarios were adjusted to
account for vertical land
movement (e.g., subsidence
or uplift) using tide gauge
data.28 Areas located along
the Gulf of Mexico and
Atlantic Coast are projected
to experience greater sea
level rise, due to compound-
ing effects of land subsidence,
while areas along the West
Coast are estimated to
experience relatively lower
levels of rise.
Figure 2. Projected Sea Level Rise along the Contiguous U.S. Coastline in 2100
Map shows projected relative (to land) sea level rise under the Reference scenario for select coastal counties in the contiguous
U.S. Projections are based on global mean sea level rise in 2100 (56 inches), adjusted for local subsidence and uplift.29
Sea Level Rise in 2100
47-55 in (119-139 cm)
¥ 56-65 in (142-165 cm)
t
t
66-75 in (167-190 cm)
76-87 in (193-220 cm)
15
-------
CIRA FRAMEWORK
FnG CIRA
projecting future climate:
prOJ6Ct was designed to investigate the relative importance of four key sources of uncertainty inherent to
Future GHG emissions: Future emissions will be driven by population
growth, economic growth, technology advancements, and decisions
regarding climate and energy policy. Sensitivity analyses explore the
uncertainty associated with varying levels of future GHG emissions
under different policy scenarios.
Climate sensitivity: Future climate change depends on the response
of the global climate system to rising GHG concentrations (i.e., how
much temperatures will rise in response to a given increase in
atmospheric C02).This response is complicated by a series of feed-
backs within Earth's climate system that act to amplify or diminish an
initial change.30Climate sensitivity is typically reported as the change
in global mean temperature resulting from a doubling in atmospheric
C02 concentration.
Natural variability: Natural, small- to medium-scale variations within
Earth's climate system, such as El Nino events and other recurring
patterns of ocean-atmosphere interactions, can drive increases or —^
Emissions Scenarios
The CIRA framework includes scenarios with different levels of
GHG emissions: a business-as-usual scenario with unconstrained
emissions ("Reference") and a total radiative forcing of 9.8 W/m2 by
2100 (8.6 W/m2 using the IPCC method for calculating radiative
forcing); a stabilization scenario reflecting global-scale reductions
in GHG emissions, with a total radiative forcing of 4.2 W/m2 by
2100 (3.8 W/m2 using IPCC method; this scenario is not featured in
this report); and a more stringent stabilization scenario with greater
emissions reductions ("Mitigation") and a total radiative forcing of
3.6 W/m2 by 2100 (3.2 W/m2 using IPCC method).34Results using the
Reference and Mitigation scenarios are the focus of this report.
Figure 1. Temperature Change in 2100 Relative to
Present Day for the CIRA Emissions Scenarios
Changes in surface air temperature in 2100 (2091-2110 mean) relative
to present-day (1991-2010 mean).35
Radiative Forcing 9.8 W/m2
"Reference Scenario"
Stabilization at 4.2 W/m2
(not featured in this
report)
Stabilization at 3.6 W/m2
"Mitigation Scenario"
3.6
5.4
7.2
10.8
12.6
Climate Sensitivity
The four climate sensitivity values considered are 2,3,4.5, and 6°C,
which represent, respectively, the lower bound (CS 2°C), best estimate
(CS 3°C), and upper bound (CS 4.5°C) of likely climate sensitivity based
on the IPCC Fourth Assessment Report (AR4),36 and a low-probability/
high-risk climate sensitivity (CS 6°C).37 Results using a climate sensitivity
of 3°C are the focus of this report.
Figure 2. Influence of Climate Sensitivity on Global
Temperature Change Relative to Present Day
Temperature change relative to the historic baseline (mean 1980-2009) under the
Reference and Mitigation scenarios. The bold lines represent the results using a
climate sensitivity of3°C, and the shaded areas represent the range of temperature
anomaly outcomes when using climate sensitivities of2°C and 6°C.
16
14-
"
§10
2000 2025 2050 2075
^— Reference ^— Mitigation
2100
Figure 3. Future Temperature Change under
Different Climate Sensitivities
Increases in surface air temperature in 2100 (2091-2110 mean) under the
Reference scenario relative to present-day (1991-2010 mean).3"
CS 2°C CS 3°C
CS4.5°C
CS6°C
3.6
7.2
10.8
14.1
18
10
21.6 °F
12 °C
16
-------
decreases in global or regional temperatures, as well as affect
precipitation and drought patterns around the world. These types of
natural variability cause uncertainty in temperature and precipitation
patterns over timescales ranging from months up to a decade or more,
but have a smaller effect on Earth's climate system over longer periods
oftime.31
Climate model: Different types of global-scale physical and statistical
models are used to study aspects of past climate and develop
projections of future change. The climate is very complex and is
influenced by many uncertain factors; as a result, each model is
different and produces different results. These complex models
provide useful information both individually, by allowing the explora-
tion of potential futures, and collectively, by providing insight on the
level of agreement across models.
The CIRA uncertainty framework, described in detail in Monier et al.
(2014),32 explores these four major sources of uncertainty, including
the influence that each could have on future temperature or precipita-
tion in the U.S. While the effects of each source of uncertainty are not
described for each sectoral impact discussed in this report, some of
the impacts described in the Sectors section explore the potential
influence of these factors. Maps presented in this section are adapted
from Monier etal. (2014).33
Natural Variability
For each emissions scenario and climate sensitivity combination, the IGSM-CAM was simulated five times with slightly different initial conditions
("initializations") to account for uncertainty due to natural variability. Some sectors in the report use the average result of the five initializations.
Figure 4. The Effect of Natural Variability on Future Climate Projections
Increases in surface air temperature in 2100 (2091-2110 mean) relative to present-day (1991-2010 mean) for each of the IGSM-CAM initializations.39
INITIAL CONDITION 1 INITIAL CONDITION 2 INITIAL CONDITION 3 INITIAL CONDITION 4 INITIAL CONDITION 5
3.6
5.4
7.2
10.8
Climate Model
The results presented in this report rely primarily upon climate projections from the IGSM-CAM. To analyze the
implications of a broader set of climate model outputs, the CIRA framework uses a pattern scaling method in
the IGSM40 for three additional climate models, plus a multi-model ensemble mean from the IPCC AR4 archive.
As shown in Figure 5, there is better agreement across climate models with regard to temperature projections,
and higher variability with regard to precipitation projections.41
• The NCAR Community Climate System Model version 3 (CCSM3.0) was chosen to compare with the IGSM- CAM model. Both have the
same atmospheric and land components and similar biases over land.
• Bjerknes Centre for Climate Research Bergen Climate Model version 2.0 (BBCR_BCM2.0) was chosen because this model projects the
largest increases in precipitation over the contiguous U.S.
• Model for Interdisciplinary Research on Climate version 3.2 medium resolution (MIROC3.2_medres) was chosen because this model
projects decreases in precipitation over much of the contiguous U.S. Results using this "drier" pattern are shown in several sections of this
report to provide comparison to the "wetter" IGSM-CAM simulations, which generally show increases in precipitation for much of the
country (excluding the West). This comparison helps to bound uncertainty in future changes in precipitation for the contiguous U.S.
Figure 5. Climate Model Uncertainty for Future Projections
Changes in temperature and precipitation in 2100 (2091-2110 mean) relative to present-day (1991-2010 mean)
for different climate models. Values assume a climate sensitivity of 3 °C under the Reference scenario.
CCSM
(Same atmosphere as \GSM-CAM)
BCCR
Ml ROC
MULTI-MODEL MEAN
Temperature
4 72 10-8 12-6 °F
01 234567 °C
Precipitation
-.6 -.4 -.2 0 .2 .4 .6 mm/day
Future Climate
Change Across
Uncertainty
Sources
Investigation of the relative
contribution of the four
sources of uncertainty
described in this section
reveals that temperature
change is most influenced by
decisions regarding whether
to reduce GHG emissions and
the value of climate sensitivity
used (GHG emissions scenario
being the dominant
contributor). The contribu-
tions from different climate
models and natural variability
for temperature change are
small in comparison. It is
worth noting that the GHG
emissions scenario is the only
source of uncertainty that
society has control over.
Conversely, these same four
sources of uncertainty
contribute in roughly equal
measure to projected
changes in precipitation over
the U.S., with large spatial
differences.42
17
-------
CIRA FRAMEWORK
Boundaries of Analysis
The design of the CIRA project allows the results to be interpreted as the potential benefits (avoided
impacts) to many economically important sectors of the U.S. due to global-scale actions to mitigate GHG
emissions. The analytical approach offers a number of advantages, including consistency in the use of socio-
economic and climate change scenarios across a wide range of sectoral impact and damage models, and
exploration of the changes in impacts and damages across key sources of uncertainty.
As with any study, there are some analytical boundaries of the CIRA project and its underlying analyses that
are important to consider, several of which are described below43 Future work to address these limitations
will strengthen the estimates presented in this report, including the broader use of ranges and confidence
intervals. Limitations specific to the individual sectoral analyses are described in the Sectors section of this
report, as well as in the scientific literature underlying the analyses.
Emission and
Climate Scenarios
With the goal of presenting a
consistent and straightfor-
ward set of climate change
impact analyses across
sectors, this report primarily
presents results for the
Reference and Mitigation
scenarios under a single
simulation (initialization) of
the IGSM-CAM climate model
and assumes a climate
sensitivity of 3°C. As de-
scribed in the Levels of
Certainty section, a large
number of emissions and
climate scenarios were
developed under the CIRA
project, reflecting various
combinations of emissions
scenarios, climate models,
climate sensitivity, and climate
model initializations. However,
only some of these emissions
and climate scenarios have
been simulated across all
sectoral analyses, primarily
due to the level of effort
necessary to run each scenario
through the large number of
sectoral models of the CIRA
project. Analyzing results
under the full set of scenarios
would further characterize the
range and potential likelihood
of future risks.
Coverage of Sectors and Impacts
The analyses presented in this report cover a broad range of potential
climate change impacts in the U.S., but there are many important
impacts that have notyet been modeled in CIRA. Examples of these
impacts include changes in vector-borne disease, morbidity from
poor air quality, impacts on specialty crops and livestock, and a large
number of effects on ecosystems and species. Without information
on these impacts, this report provides only partial insight into the
potential risks of climate change, and therefore does not account for
all potential benefits of mitigation.
In addition, it is important to note that impacts are only partially
valued economically in some sectors. For example, the Wildfire section presents estimated response and
fuel management costs, but not other damages (e.g., health effects from decreased air quality, and property
damages). A more complete valuation approach would likely increase the damages described in this report.
Finally, this report does not present results on the possibility of large-scale, abrupt changes that have
wide-ranging and possibly catastrophic consequences, such as the intensification of tropical storms, or the
rapid melting of the Greenland or West Antarctic ice sheets.44^ general, there are many uncertainties
regarding the timing, likelihood, and magnitude of the impacts resulting from these abrupt changes, and
data limitations have precluded their inclusion in the analyses presented in this report. Their inclusion
would assist in better understanding the totality of risks posed by climate change and the potential for
GHG mitigation to reduce or avoid these changes.
icand Atmospheric Adm
Variability Across Climate Models
The choice of climate model in an impact analysis can influence patterns of future climate change. Within
a number of the CIRA analyses, this uncertainty was evaluated through the use of "pattern scaling,"a
method by which the average change produced by running a climate model is combined with the specific
geographic pattern of change calculated from a different model in order to approximate the result that
would be produced by the second model. In this report, analyses that are sensitive to changes in precipi-
tation are presented using both the IGSM-CAM (relatively wetter for the contiguous U.S.) and MIROC
(relatively drier) climate models. However, not all sectoral impact models used pattern scaling in addition
to the IGSM-CAM simulations, particularly for those impacts primarily driven by temperature, where there
is generally more agreement across climate models. Finally, we note the limitation that pattern scaling is
not a perfect representation of alternate models.45
18
-------
Sectoral Impacts Modeling
.
With the exception of the electricity demand and
supply sections of this report, the impact estimates
presented were developed using a single sectoral
impact model. While these models are complex
analytical tools, the structure of the model, and
how it may compare to the design of similar
applications, can create important uncertainties
that affect the estimation of impacts.46The use of
additional models for each sector would help
improve the understanding of potential impacts in
the future. The results presented in this report were
developed with little or no interactions among the impact sectors. As a result, the estimated impacts
may omit important and potentially unforeseen effects. For example, the wildfire projections present-
ed in this report will likely generate meaningful increases in air pollution, a potentially important
linkage for the air quality analysis. Similarly, there are numerous connections among the agriculture,
water, and electricity sectors that affect the impacts estimates in each.47 Although some of these
interactions are captured within integrated assessment models, it is difficult for these broader
frameworks to capture all of the detail provided in the CIRA sectoral analyses. Improved connectivity
between CIRA sectoral models will aid in gaining a more complete understanding of climate change
impacts across sectors in the U.S.
Variability in Societal Characteristics
The impacts of climate change will not affect Americans equally. In addition to regional differences in
impacts, socioeconomic factors (e.g., income, education) affect adaptive capacity and can make some
communities more vulnerable to impacts. These issues are explored in the Coastal Property section, but
the rest of the sectors do not analyze impacts across different levels of social vulnerability.
Feedbacks
The CIRA project uses a linear
path from changes in
socioeconomics and the
climate system to impacts
(with consistent inputs across
multiple models). The
socioeconomic scenarios that
drive the CIRA modeling
analyses do not incorporate
potential feedbacks from
climate change impacts to the
climate system (e.g., GHG
emissions from forest fires)
and from sectoral damages to
the economy (e.g., significant
expenditures on "climate
defensive"adaptation would
likely reduce available financial
capital to the economy for
productive uses, or increase
the cost of financing capital
expenditures).
Geographic Coverage
The report does not examine
impacts and damages
occurring outside of U.S.
borders. Aside from their own
relevance for policy-making,
these impacts could affect the
U.S. through, for example,
changes in world food
production, migration, and
concerns for national security.
In addition, the primary
geographic focus of this report
is on the contiguous U.S., with most of the sectoral analyses
excluding Hawaii, Alaska, and the U.S. territories.This omission is
particularly important given the unique climate change vulnerabili-
ties of these high-latitude and/or island locales. Finally, several
sectoral analyses assess impacts in a limited set of major U.S. cities,
and incorporation of additional locales would gain a more
comprehensive understanding of likely impacts.
Use of Point
Estimates
Results in this report are
primarily presented as point
estimates. For some sectors,
ranges are provided based on
the design of the underlying
modeling analysis (i.e., the
approach yields confidence
intervals) or because of the
scenarios used in that sector.
Regarding the latter, the use
of wetter and drier climate
projections for sectors
sensitive to changes in
precipitation provides ranges
of estimates bounding this
uncertainty source. The
uncertainties and limitations
described in this section,
along with others detailed
throughout this report and in
the underlying CIRA literature,
signify that the estimates
described in this report should
not be interpreted as defini-
tive predictions of future
impacts at a particular place
and time. The further
exploration of these uncer-
tainties, including the
development of ranges for all
impact projections, will further
strengthen the CIRA results.
19
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• Sectors
24 | Air Quality
26 | Extreme
Temperature
28 I Labor
30 | Water Quality
Electricity
34 | Bridges
36 I Roads
38 | Urban Drainage
40 | Coastal Property
46 | Electricity
Demand
48 | Electricity
Supply
ABOUT THE RESULTS
Unless otherwise noted, results presented in this section were developed using the following:
Emissions scenarios: The results are presented for the
CIRA Reference and Mitigation scenarios.
Climate models: The results primarily rely upon climate
projections from the IGSM-CAM. For sectors sensitive
to changes in precipitation, results are also presented for
the drier MIROC climate model.
Climate sensitivity: The results assume a climate sensitivity
of3.0°C.
Accounting for inflation: The results are presented in
constant 2014 dollars.1
Discounting: To estimate present value, annual time
series of costs are discounted at a 3% annual rate, with a
base year of 2015.2 Annual estimates (i.e., costs in a given
year) are not discounted.
Reporting of estimates: For consistency, results are
reported with two significant figures.
-------
52 | Inland Flooding
54 | Drought
56 | Water Supply
and Demand
60 | Crop and Forest
Yields
62 | Market Impacts
.
66 I Coral Reefs
68 I Shellfish
70 I Freshwater Fish
72 I Wildfire
74 | Carbon Storage
-------
Air Quality
Extreme
Temperature
-------
Weather and climate play a
significant role in our health
and well-being. As a society, we
have structured our day-to-day behaviors
and activities around historical and current
climate conditions. Increasing GHGs in the
atmosphere are changing the climate faster
than any time in recent history.3 As a result,
the conditions we are accustomed to and
the environment in which we live will change
in ways that affect human health. In addition
to creating new problems, changes in the
climate can exacerbate existing human health
stressors, such as air pollution and disease.
Many of the adverse effects brought on by
climate change may be compounded by how
our society is changing, including population
growth, an aging population, and migration
patterns that are concentrating development
in urban and coastal areas.
HOW ARE PEOPLE VULNERABLE
TO CLIMATE CHANGE?
Climate change is projected to harm human
health in a variety of ways through increases
in extreme temperature, increases in
extreme weather events, decreases in air
quality, and other factors.4 Extreme heat
events can cause illnesses and death due to
heat stroke, cardiovascular disease, respirato-
ry disease, and other conditions. Increased
ground-level ozone is associated with a
variety of health problems, including reduced
lung function, increased frequency of asthma
attacks, and even premature mortality.5
Higher temperatures and changes in the
timing, intensity, and duration of precipita-
tion affect water quality, with impacts on the
surface water we use. There are a variety of
other impacts driven by climate change that
are expected to pose significant health haz-
ards, including increases in wildfire activity
(see the Wildfire section of this report).6
WHAT DOES CIRA COVER?
CIRA analyzes the potential impacts of
climate change on human health by focusing
on air quality, extreme temperature mortali-
ty, labor, and water quality. Analyses of many
other important health effects are not in-
cluded in CIRA; these include, for example,
impacts from increased extreme weather
events (e.g., injury or death from changes in
tropical storms), air pollution from wildfires,
and vector-borne disease (e.g., Lyme disease
and West Nile virus).
Water Quality
-------
1 Unmitigated climate
change is projected to
worsen air quality across
large regions of the U.S.,
especially in eastern, mid-
western, and southern
states. Impacts on ozone
and fine particulate matter
pollution are projected to
be especially significant for
densely-populated areas.
The analysis holds emissions
of traditional air pollutants
constant at current levels to
isolate the climate change
related impact on air quality.
2 Global GHG mitigation is
projected to reduce the
impact of climate change
on air quality and the
corresponding adverse
health effects related to air
pollution. Mitigation is
estimated to result in
significant public health
benefits in the U.S., such as
avoiding 13,000 premature
deaths in 2050 and 57,000
premature deaths in 2100.
Economic benefits to the
U.S. of avoided premature
deaths are estimated at
$160 billion in 2050, and
$930 billion in 2100.
24
Climate Change and
Air Quality Health Effects
Changes in climate are projected to affect air
quality across the U.S. In already polluted
areas, warmer temperatures are anticipated
to increase ground-level ozone (03), a
component of smog, and increase the
number of days with poor air quality.7
Changes in weather patterns may also affect
concentrations of fine particulate matter
(PM2.s), a mixture of particles smaller than 2.5
micrograms per cubic meter (ug m3), emitted
from power plants, vehicles, and wildfires.
Inhaling ozone and fine particulate matter can lead to a broad range of adverse health effects,
including premature mortality and aggravation of cardiovascular and respiratory disease.8-9
Risks of Inaction
Without global GHG mitigation, climate change is projected to have a substantial effect on air
quality across the contiguous U.S., with important regional differences (Figure 1). Ozone
concentrations are projected to increase in the Reference scenario in more densely-populated
regions, such as the East, Midwest, and South, while some less densely-populated areas
experience decreases in ozone concentrations.10 Although the national annual average ozone
concentration is projected to decrease slightly (1.3 ppb+/- 0.2) by 2100, human exposure to
ozone is projected to increase, driven by increasing concentrations in densely-populated areas.
Climate-driven ozone increases are especially substantial during summer months. By 2100, the
U.S.-average 8-hour-maximum ozone concentration in June-August is projected to increase
4.7 ppb (95% confidence interval ± 0.5).11
Unmitigated climate change is projected to exacerbate fine particulate matter pollution,
especially in the Midwest and East.The annual U.S.-average PM2.sconcentrations are projected to
increase by 0.3 ug m3(± 0.1) in 2050 and 0.7 ug m3(± 0.1) in 2100 in the Reference scenario.12
Projections that climate change will lead to increased ozone in polluted regions are consis-
tent with the assessment literature. There is less agreement regarding the magnitude of climate
change effects on particulate matter, with the exception of increasing wildfire activity on
particulates.13The results presented in this report add to this emerging area of research.
Figure 1. Projected Impacts of Unmitigated Climate Change
on Air Pollution in the U.S.
Estimated change in annual-average ground-level hourly ozone (Oj ppb) and fine particulate matter
(PM2s, pg m3) from 2000 to 2100 under the Reference scenario.
Ozone
Fine Particulate
Matter
I I
-7.5 -6.5 -5.5 -4.5 -3.5 -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5
-------
Reducing Impacts through
GHG Mitigation
Global GHG mitigation is projected to avoid significant adverse impacts to air quality that
would occur under the Reference scenario in densely-populated areas. Figure 2 shows air
quality changes in the Mitigation scenario, which are much smaller than those under the
Reference (Figure 1). Despite smaller reductions in ozone in some less densely-populated
areas, global GHG mitigation is projected to reduce the increase in the annual-average,
8-hour-maximum, population-weighted ozone concentration by approximately 2.6 ppb (95%
confidence interval ± 0.3) that would occur in the Reference in the U.S.
Global GHG mitigation is also projected to lessen the adverse effects of climate change
on fine particulate matter pollution in the U.S. In 2100, the increase in the annual-average
population-weighted PM2.s concentration under the Reference is reduced by approximately
1.2 ug rrr3(± 0.1) underthe Mitigation scenario.
Reducing the impacts of climate change on air quality through global GHG mitigation is
projected to result in significant health benefits across the U.S. For example, the Mitigation
scenario is estimated to prevent an estimated 13,000 premature deaths in 2050 (95% confidence
interval of 4,800-22,000) and 57,000 premature deaths in 2100 (95% confidence interval of
21,000-95,000) compared to the Reference.14 Economic benefits to the U.S. of these avoided
deaths are estimated at $160 billion and $930 billion in 2050 and 2100, respectively. In addition
to reducing premature mortality, global GHG mitigation would result in other health benefits not
presented here, including reduced respiratory- and cardiovascular-related hospital admissions.15-16
Figure 2. Projected Impacts on Air Pollution in the U.S.
with Global GHG Mitigation
Estimated change in annual-average ground-level hourly ozone (03, ppb) and fine particulate matter
(PM2A PS m~3) from 2000 to 2100 under the Mitigation scenario.
-7.5 -6.5 -5.5 -4.5 -3.5 -2.5 -1.5 -0.5 0.5 1.5 2.5 3.5
5.5 6.5 7.5
Treatment of Co-Benefits
This analysis does not quantify the additional
benefits to air quality and health that would
stem from simultaneous reductions in
traditional air pollutants along with GHG
emissions (both are emitted from many of
the same sources). Incorporating these
"co-benefits," which recent analyses17 and
assessments18 indicate could provide large,
near-term benefits to human health, would
result in a more comprehensive understand-
ing of air quality and climate interactions.
The CIRA analysis assesses the impact
of climate change on air quality across
the contiguous U.S. through changes
in ground-level ozone and fine
particulate matter (PM2.5) concentra-
tions.19 Future concentrations of these
pollutants are simulated in an atmo-
spheric chemistry model, driven by
weather patterns from the CIRA
climate projections. The analysis
projects future concentrations for five
initializations of the IGSM-CAM
climate model under the Reference
and Mitigation scenarios in 30-year
periods centered on 2050 and 2100
(with 95% confidence intervals based
on the difference in mean across the
initializations). Despite assumptions
about growth in GHG emissions in the
Reference and Mitigation scenarios,
emissions of the traditional air pollut-
ants are kept fixed at present-day levels
to isolate the climate change-related
impact on air quality. Changes in
pollution due to projected increases in
wildfires and changes in sea salt and
dust are not considered. Pollutant
concentrations are used to estimate
changes in air pollution exposure in
people. The Environmental Benefits
Mapping and Analysis Program
(BenMAP) is applied to estimate health
effects (with 95% confidence interval
based on concentration response
functions in BenMAP).20To monetize
the effects of changing mortality, a
value of statistical life (VSL) of $9.45
million for 2010 (2014$) is used,
adjusted to future years by assuming
an elasticity of VSL to gross domestic
product (GDP) per capita of O.4.21
For more information on the
approach, models used, and results
for the air quality sector, please
refer to Garcia-Menendez et al.
(2015).22
25
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KEY FINDING
Without global GHG
mitigation, the average
number of extremely hot
days in the U.S. is projected
to more than triple from
2050 to 2100. The projected
reduction in deaths from
extremely cold days is more
than offset by the projected
increase in deaths from
extremely hot days. This
result holds for all reported
future years, indicating that
unmitigated climate
change clearly poses an
increasing health risk from
extreme temperatures.
Global GHG mitigation is
projected to result in
approximately 12,000
fewer deaths from extreme
temperature in the 49
modeled cities in 2100.
Inclusion of the entire U.S.
population would greatly
increase the number of
avoided deaths, but ac-
counting for adaptation
could decrease the number.
26
II
Climate Change and Extreme
Temperature Mortality
Climate change will alter the weather conditions that we
are accustomed to. Extreme temperatures are projected to
rise in many areas across the U.S., bringing more frequent
and intense heat waves and increasing the number of
heat-related illnesses and deaths.23 Exposure to extreme
heat can overwhelm the body's ability to regulate its
internal temperatures, resulting in heat exhaustion and/or
heat stroke, and can also exacerbate existing medical
problems, such as heart and lung diseases.24 During a 1995
heat wave in Chicago, an estimated 700 individuals died as
a result of the extreme heat.25 Warmer temperatures a re also expected to result in fewer
extremely cold days, which may also reduce deaths associated with extreme cold.26
Risks of Inaction
Climate change poses a significant risk to human health as more days with extreme heat are
projected to cause more deaths over time. Without global GHG mitigation, the average number
of extremely hot days is projected to more than triple from 2050 to 2100, while the number of
extremely cold days is projected to decrease. The projected increase in deaths due to more
frequent extremely hot days is much larger than the projected decrease in deaths due to fewer
extremely cold days, a finding that is consistent with the conclusions of the assessment litera-
ture.27 Under the Reference, the net increase in projected deaths from more extremely hot days
and fewer extremely cold days in 49 cities is approximately 2,600 deaths in 2050, and 13,000
deaths in 2100, but accounting for adaptation could decrease these numbers. Figure 1 shows the
net mortality rate from extreme hot and cold temperatures by city in the Reference scenario.
Figure 1. Projected Extreme Temperature Mortality in Select Cities
Due to Unmitigated Climate Change
Estimated net mortality rate from extremely hot and cold days (number of deaths per 100,000 residents)
under the Reference scenario for 49 cities in 2050 and 2100. Red circles indicate cities included in the analysis;
cities without circles should not be interpreted as having no extreme temperature impact.
Reference 2050
Baseline 2000
Combined Mortality Rate
(deaths/IOOk)
0-2
i 3-4
(5-8
9- 10
. 11 -14
I 15-18
Reference 2100
-------
Reducing Impacts through
GHG Mitigation
As shown in Figure 2, the projected mortality
rates under the Mitigation scenario show small
changes through 2100, unlike in the Reference
where rates increase substantially. As a result,
the net benefits associated with GHG mitiga-
tion increase over time. As shown in Figure 3,
global GHG mitigation is estimated to result in
significant public health benefits across the
U.S. by substantially reducing the risk of
extreme temperature-related deaths that
would occur under the Reference. Under the
Mitigation scenario, extreme temperature
mortality is reduced by 64% in 2050 and by
93% in 21OO28 compared to the Reference. For
the 49 cities analyzed, global GHG mitigation is
projected to save approximately 1,700 U.S.
lives in 2050, and approximately 12,000 U.S.
lives in 2100 (Figure 3).
In 2050, the economic benefits of GHG
mitigation are estimated at $21 billion,
increasing to $200 billion in 2100 (see the
Approach section for more information). It is
important to note that these projections
reflect only the results for the 49 cities
included in this study; corresponding national
benefits would be much larger.
Figure 3. Avoided Extreme
Temperature Mortality
in 49 U.S. Cities Due to Global
GHG Mitigation
14,000
12,000
10,000
8,000
6,000 -
4,000
2,000
2050
2100
The analysis also examines the implications
of adjusting temperature thresholds to
account for potential adaptation of the human
body to warmer temperatures. Specifically,
the analysis assumes that the human health
response to extreme temperatures in all 49
cities was equal to that of Dallas. Using this
approach, results show that mitigation would
still save a projected 5,500 lives in 2100
compared to the Reference.
Figure 2. Projected Extreme Temperature Mortality in Select Cities
with Global GHG Mitigation
Estimated net mortality rate from extremely hot and cold days (number of deaths per 100,000 residents)
under the Mitigation scenario for 49 cities in 2050 and 2100. Red circles indicate cities included in the analysis;
cities without circles should not be interpreted as having no extreme temperature impact.
Mitigation 2050
Baseline 2000
Combined Mortality Rate
(deaths/IOOk)
0-2
) 3-4
9- 10
I 11 - 14
I 15- 18
Mitigation 2100
The CIRA analysis estimates the
number of deaths over the course of
the 21st century attributable to
extreme temperatures in 49 cities in
the contiguous U.S., which account
for approximately one third of the
national population. City-specific
relationships between daily deaths (of
all causes) and extreme temperatures
are combined with the IGSM-CAM
projections of extremely hot and cold
days using city-specific extreme
temperature thresholds to estimate
future deaths from heat and cold in
the Reference and Mitigation scenari-
os. Extremely hot days are defined as
those with a daily minimum tempera-
ture warmer than 99 percent of the
days in the period 1989-2000. Ex-
tremely cold days are defined as those
with a daily maximum temperature
colder than 99 percent of the days in
the period 1989-2000. As a result, the
study explicitly addresses the ques-
tion of the net mortality impact of
climate change on future extreme
temperature days. The potential
impact of future population change is
accounted for using an EPA demo-
graphic model (ICLUS).29To monetize
the effects of changing mortality, a
baseline value of statistical life (VSL) of
$9.45 million for 2010 (2014$) is used,
adjusted to future years by assuming
an elasticity of VSL to GDP per capita
of 0.4.30The results presented in this
section have been updated since Mills
et al. (2014) to include additional cities
and more recent mortality rate data.31
Finally, this analysis did not estimate
impacts across ages or socioeconomic
status. As these demographics
change, they could impact the results
presented here.
For more information on the CIRA
approach and results for the
extreme temperature mortality
sector, please refer to Mills et al.
(2014).32
27
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KEY FINDING
Without global GHG
mitigation, labor hours in
the U.S. are projected to
decrease due to increases
in extreme temperatures.
Over 1.8 billion labor hours
are projected to be lost in
2100, costing an estimated
$170 billion in lost wages.
2 Global GHG mitigation
is estimated to save
1.2 billion labor hours and
$110 billion in wages in
2100 in the contiguous
U.S. that would otherwise
be lost due to unmitigated
climate change.
28
Climate Change and Labor
Climate change may affect labor in a number
of ways, but projections of hotter summer
temperatures raise a particular concern.
Extreme summer heat is increasing in the U.S.
and will be more frequent and intense in the
future.33 Heat exposure can affect workers'
health, safety and productivity.34 When
exposed to high temperatures, workers are at
risk for heat-related illnesses and therefore
may take more frequent breaks, or have to
stop work entirely, resulting in lower overall
labor capacity. This is especially true for
high-risk industries where workers are doing physical labor and have a direct exposure to
outdoor temperatures (e.g., agriculture, construction, utilities, and manufacturing).35
V
Risks of Inaction
Without global GHG mitigation, an increase in extreme heat is projected to have a large
negative impact on U.S. labor hours, especially for outdoor labor industries. In 2100, over 1.8
billion labor hours across the workforce are projected to be lost due to unsuitable working
conditions (95% confidence interval of 1.2-2.4 billion). These lost hours would be very costly,
totaling over $170 billion in lost wages in 2100 (95% confidence interval of $110-$220 billion).
As shown in Figure 1,the majority of the country is projected to experience decreases in
labor hours due to extreme temperature effects. In 2100, parts of the Southwest and Florida
are estimated to experience a decrease in hours worked for high-risk industries ranging from
-5% to -7%. Although the impacts vary by region, only a limited number of counties are
projected to experience increases in labor hours.
Figure 1. Impacts of Unmitigated Climate Change on Labor in the U.S.
Estimated percent change in hours worked from 2005 to 2050 and 2100 under the Reference scenario.
Estimates represent change in hours worked at the county level for high-risk industries only, and are normalized
by the high-risk working population in each county.
2050
2100
Percent Change
in Hours Worked
^•0.1% to 1.3%
Q^ -0.9% to 0%
I-1.9% to-1%
C^ -2.9% to -2%
^H -3.9% to -3%
^B -4.9% to -4%
^B -6.9% to -5%
-------
Reducing Impacts through
GHG Mitigation
At the national level, impacts to labor under the Mitigation scenario (Figure 2) are substantially
smaller compared to the Reference (Figure 1). Counties in the Southwest,Texas, and Florida
that are estimated to lose up to 7% of high-risk labor hours under the Reference in 2100 do not
experience such losses under the Mitigation scenario.
When comparing the two scenarios (Figure 3), global GHG mitigation is projected to prevent
the loss of approximately 360 million labor hours across the workforce in 2050, saving nearly
$18 billion in wages. In 2100, the avoided loss of labor hours more than triples, and losses are
substantially reduced over a majority of the contiguous U.S. Specifically, mitigation is estimated
to prevent the loss of nearly 1.2 billion labor hours and $110 billion in wages in 2100 compared
to the Reference.
Figure 2. Labor Impacts in the U.S. with Global GHG Mitigation
Estimated percent change in hours worked from 2005 to 2050 and 2100 under the Mitigation scenario.
Estimates represent change in hours worked at the county level for high-risk industries only, and are normalized
by the high-risk working population in each county.
2050
2100
Percent Change
in Hours Worked
^H 0.1% to 0.6%
Q^ -0.9% to 0%
|-1.9% to-1%
CD -2.9% to -2%
• -3.9% to -3%
Figure 3. Economic Impacts to Labor with and without Global GHG Mitigation
Estimated wages lost under the Reference and Mitigation scenarios for all labor categories in the
contiguous U.S. (billions 2014$). Error bars represent lower- and upper-95% confidence intervals of the
dose-response function (see the Approach section for more information).
250-,
2050
Reference
2100
I Mitigation
The CIRA analysis focuses on the
impact of changes in extreme tem-
peratures on labor supply36 across the
contiguous U.S. Specifically, the
analysis estimates the number of labor
hours lost due to changes in extreme
temperatures using dose-response
functions for the relationship between
temperature and labor from Graff Zivin
and Neidell (2014).37 Mean maximum
temperatures from the IGSM-CAM are
projected for two future periods (2050
and 2100,5-year averages centered on
those years) at the county level in the
CIRA Reference and Mitigation scenar-
ios. The analysis estimates the total
labor hours lost in all categories of the
labor force and also for workers in
high-risk industries (most likely to be
strongly exposed to extreme tempera-
ture), taking into account the CIRA
county-level population projections
from the ICLUS model.38 The fraction of
workers in high-risk industries is
calculated using Bureau of Labor
Statistics data from 2003-2007 and is
assumed to remain fixed over time for
each county.39 A range of estimates
for the dose-response function are
assessed and used to calculate confi-
dence intervals to show the sensitivity
of the results. The dose-response
functions are estimates of short-run
responses to changes in weather, and
as such do not account for longer-term
possibilities, such as acclimation of
workers, relocation of industries, or
technological advancements to
reduce exposure.
The analysis estimates the cost of
the projected losses in labor hours
based on the Bureau of Labor Statis-
tics'estimated average wage in 2005
($23.02 per hour in a 35 hour work
week),40 adjusted to 2100 based on the
projected change in GDP per capita.
For more information on the
CIRA approach for the labor
sector, please refer to Graff Zivin
and Neidell (2014)41 and Section
G of the Technical Appendix for
this report.
29
-------
1 Unmitigated climate
change is projected to
have negative impacts on
water quality in the U.S.,
particularly in the South-
west and parts of Texas.
2 Global GHG mitigation
is projected to prevent
many of the water quality
damages estimated under
the Reference scenario,
primarily by reducing the
warming of water bodies
across the country.
3 Under the Mitigation
scenario, costs associated
with decreased water
quality are reduced approx-
imately 82% in 2100
compared to the Reference,
corresponding to cost
savings of approximately
$2.6-$3.0 billion.
30
Climate Change and
Water Quality
Climate change is likely to have far-reaching
effects on water quality in the U.S. due to
increases in river and lake temperatures and
changes in the magnitude and seasonality
of river flows, both of which will affect the
concentration of water pollutants. These
physical impacts on water quality will also
have potentially substantial economic
impacts, since water quality is valued for
drinking water and recreational and
commercial activities such as boating,
swimming, and fishing.42-43The analysis
presented in this section estimates changes
in water quality, but does not quantify the
resulting health effects.
Risks of Inaction
Unmitigated climate change is projected to decrease water quality in the U.S. compared to a
future with no climate change. The Water Quality Index (WQI) calculated in the CIRA analysis
includes several key water quality constituents, including temperature, dissolved oxygen, total
nitrogen, and total phosphorus.44 The WQI serves as a measure of water quality; the higher the
WQI, the higher the water quality.
As shown in Figure 1, the WQI across the U.S. is projected to decline in the Reference
scenario in 2100 using both the IGSM-CAM and MIROC climate models. Parts of Texas and the
Southwest, in particular, are estimated to experience substantial WQI declines of 15-26% in
2100. Projections that climate change will decrease river and lake water quality are consistent
with the findings of the assessment literature.45
Figure 1. Effects of Unmitigated Climate Change on U.S. Water Quality in 2100
Percent change in the Water Quality Index in 2100 under the Reference scenario compared to the Control
(to isolate the effects of climate change). The WQI is calculated for the 2,1198-digit hydrologic unit codes (HUCs)
of the contiguous U.S., and aggregated to the 18 Water Resource Regions (2-digit HUCs).
IGSM-CAM
MIROC
Percent Change
in the Water
Quality Index
^H -26% to -20%
^B -19% to -15%
^•-14% to-10%
-9% to -5%
-4% to 0%
-------
Reducing Impacts through
GHG Mitigation
Global GHG mitigation is projected to reduce the increase in water temperature that is
estimated to occur under the Reference, with corresponding water quality benefits (i.e.,
avoided degradation) primarily due to better oxygenation.The effects of mitigation on total
nitrogen and total phosphorus concentrations vary by region, but the increase in total nitrogen
is reduced by up to 80% in some areas of the western U.S. compared to the Reference scenario.
Figure 2 presents the projected change in water quality damages in 2050 and 2100 under
the Reference and Mitigation scenarios for the IGSM-CAM and MIROC climate models. As
shown in the figure, increases in damages are projected in both scenarios, but most notably in
the Reference, where damages are estimated to increase by approximately $3.2-$3.7 billion in
2100. Under the Mitigation scenario, damages are reduced by approximately 82% compared to
the Reference in 2100, corresponding to approximately $2.6-$3.0 billion in avoided costs.
Figure 3 presents the avoided water quality damages in 2100 under the Mitigation scenario
compared to the Reference using the IGSM-CAM and MIROC climate models. As shown in the
figure, global GHG mitigation is projected to result in economic benefits relative to the
Reference across the entire contiguous U.S. California is projected to experience the greatest
benefits of mitigation in 2100, ranging from approximately $750 million to $1.0 billion.
Figure 2. Change in U.S. Water Quality Damages
with and without Global GHG Mitigation
"g
4.0 i
3.5 -
3.0 -
2.0
o 1.0
I °-5
I 0.0
2050 2100
IGSM-CAM
• Reference
2050
MIROC
Mitigation
2100
Figure 3. Benefits of Global GHG Mitigation for U.S. Water Quality in 2100
Avoided damages under the Mitigation scenario compared to the Reference in 2100 (millions 2014$).
Damages are calculated for the 2,119 8-digit HUCs of the contiguous U.S., and aggregated to the
18 Water Resource Regions (2-digit HUCs).
IGSM-CAM
MIROC
Millions of
Dollars
OtoSO
^| 51 to 100
^H 101 to 300
^| 301 to 500
^m 501 to 1,000
The CIRA analysis uses a series of linked
models to evaluate the impacts of climate
change on water quality in futures with and
without global GHG mitigation.The analysis
relies upon climate projections from two
climate models: IGSM-CAM, which projects
a relatively wetter future for most of the
U.S., and the drier MIROC model. The CIRA
temperature and precipitation projections
inform a rainfall-runoff model (CLIRUN-II)
that estimates river flow.46 A water demand
model projects water requirements of the
municipal and industrial (M&l), agriculture,
and other sectors. The runoff and demand
projections inform a water supply and
demand model that estimates reservoir
storage and release, and in turn produces
a time series of water allocations for the
various demands. After this allocation step,
the analysis relies on the QUALIDAD water
quality model to simulate a number of
water quality constituents in rivers and
reservoirs.47 Changes in overall water
quality are estimated using changes in the
Water Quality Index (WQI), a commonly
used metric that combines multiple
pollutant and water quality measures.
Finally, a relationship between changes in
the WQI and changes in the willingness to
pay for improving water quality is used to
estimate the economic implications of
projected water quality changes.
Results for the CIRA scenarios are
compared to a Control to isolate the effect
of climate change. See the Water Resources
section of this report for information on
projected changes in the Inland Flooding,
Drought, and Water Supply and Demand
sectors. Decreases in water quality due to
climate change will likely have an adverse
effect on human health due to, for example,
the increased risk of harmful aquatic blooms
and impacts on sources of drinking water.
Human health effects due to decreased
water quality are not estimated, but are
important considerations to fully under-
stand climate change impacts in this sector.
Inclusion of these effects would likely
increase the benefits of GHG mitigation.
For more information on the CIRA
approach and results for the water
quality sector, please refer to
Boehlertetal.48
31
-------
nfrastructure
-------
Infrastructure makes up the basic
physical and organizational structure of
our society and is by design interdepen-
dent and interconnected. Built infrastructure
includes urban buildings; systems for energy
transportation, water, wastewater, drainage,
and communication; industrial structures;
and other products of human design and
construction.1 U.S. infrastructure has enor-
mous value, both directly as a capital asset
and indirectly to support human well-being
and a productive economy.
Total public spending on transportation and
water infrastructure exceeds $300 billion
annually; roughly 25 percent of that total is
spent at the federal level and accounts for
three percent of total federal spending.2
Recent analyses point to large gaps between
existing capital and maintenance spending
and the level of expenditure necessary to
maintain current levels of services.3
HOW IS INFRASTRUCTURE VULNERABLE
TO CLIMATE CHANGE?
Experience over the past decade provides
compelling evidence of how vulnerable
infrastructure can be to climate change
effects, including sea level rise, storm surge,
and extreme weather events.4 Climate change
will put added stress on the nation's aging
infrastructure to varying degrees over time.
Sea level rise and storm surge, in combination
with the pattern of heavy development in
coastal areas, are already resulting in damage
to infrastructure such as roads, buildings,
ports, and energy facilities. Floods along the
nation's rivers, inside cities, and on lakes
following heavy downpours, prolonged rains,
and rapid melting of snowpack are damaging
infrastructure in towns and cities, on farm-
lands, and in a variety of other places across
the nation. In addition, extreme heat is dam-
aging transportation infrastructure such as
roads, rails, and airport runways.
WHAT DOES CIRA COVER?
CIRA analyzes potential climate change
impacts and damages to four types of infra-
structure in the U.S.: roads, bridges, urban
drainage, and coastal property. Analyses of
several important types of infrastructure are
not included in CIRA, particularly telecommu-
nications and energy transmission networks,
and the Urban Drainage analysis only ana-
lyzes impacts in 50 cities of the contiguous
U.S. Further, some analyses in this sector
assume that adaptation measures will be
well-timed. This likely results in conservative
estimates of future damages, as history has
shown that infrastructure investment and
maintenance are often not implemented in
optimal, well-timed ways.
Urban
Drainage
Coastal
Property
-------
Without reductions in
global GHG emissions, an
estimated 190,000 inland
bridges across the nation
will be structurally vulnera-
ble because of climate
change by the end of the
century. In some areas,
more than 50% of bridges
are projected to be vulner-
able as a result of unmiti-
gated climate change.This
analysis estimates the
damages of climate change
in terms of increased costs
to maintain current levels
of service (i.e. adaptation
costs). Without adaptation,
climate change could render
many bridges unusable,
leading to large economic
damages.
Global GHG mitigation is
estimated to substantially
reduce the number of
bridges across the U.S. that
become vulnerable in the
21st century by reducing the
projected increase in peak
river flows under the Refer-
ence scenario.
Global GHG mitigation is
projected to reduce adapta-
tion costs that would be
incurred under the Refer-
ence scenario.The benefits
of global GHG mitigation
are estimated at $3.4-$42
billion from 2010-2050 and
$10-$15 billion from 2051-
2100 (discounted at 3%).
34
Climate Change and Bridges
Road bridges are a central component of the
U.S. transportation system. With the average
U.S. bridge now over 40 years old, however,
more than 250 million vehicles cross structur-
ally deficient bridges on a daily basis.5 Similar
to other transportation infrastructure, bridges
are vulnerable to a range of threats from
climate change.6Currently, most bridge
failures are caused by scour, where swiftly
moving water removes sediment from around
bridge structural supports, weakening or
destroying their foundations. Increased
flooding and long-term river flow changes caused by climate change are expected to increase
the frequency of bridge scour, further stressing the aging U.S. transportation system.
Risks of Inaction
Increased inland flooding caused by climate change threatens bridges across the U.S. and risks
a net increase in maintenance costs. Figure 1 shows the number and percent of bridges in each
hydrologic region of the contiguous U.S. identified as vulnerable to climate change in the late 21st
century under the Reference scenario using the IGSM-CAM climate model. In total, approximately
190,000 bridges are identified as vulnerable. In addition, the costs of adapting bridges to climate
change under the Reference scenario are estimated at $170 billion for the period from 2010 to
2050, and $24 billion for the period from 2051 to 2100 (discounted at 3%). The higher costs
during the first half of the century a re primarily due to the large number of vulnerable bridges
that require strengthening in the near term in the face of increasing peak river flows due to
climate change. These findings regarding near-term bridge vulnerability and adaptation costs
due to unmitigated climate change are consistent with the findings of the assessment literature.7
Figure 1. Bridges Identified as Vulnerable in the Second Half of the
21st Century Due to Unmitigated Climate Change
Estimated number ofvulnemble bridges in each of the 2-digit hydrologic unit codes (HUCs) of the contiguous
US. in the period from 2051-2100 under the Reference scenario using the IGSM-CAM climate model. The map
also shows the percentage of inland bridges in each HUC that are vulnerable due to climate change.
Number of Vulnerable
Bridges 2051-2100
< 1,000
1,001 -5,000
^B 5,001 -10,000
••10,001 -20,000
•• > 20,000
-------
Reducing Impacts through
GHG Mitigation
As shown in Figure 2, global GHG mitigation is
projected to substantially reduce the number
of vulnerable bridges in many areas of the
contiguous U.S. compared to the Reference
scenario (Figure 1). For example, the percent-
age of vulnerable bridges in the Northwest
region, which includes Washington and parts
of Oregon and Idaho, is reduced from 56%
under the Reference to 25% under the
Mitigation scenario. At the national scale, the
total number of vulnerable bridges is reduced
by roughly 40,000 through 2050 compared to
the Reference scenario, and by over 110,000 in
the second half of the century.
In addition, the analysis estimates that
global GHG mitigation reduces the costs of
adaptation substantially relative to the
Reference scenario. In the period from 2010 to
2050, costs under the Mitigation scenario are
approximately $42 billion lower than under
the Reference (discounted at 3%). Although
adaptation costs are lower in the second half
of the century, costs under the Mitigation
scenario are nearly 60% lower than they are
under the Reference scenario, with savings
estimated at $15 billion (discounted at 3%).
These results rely upon climate projections
using the IGSM-CAM, which projects a
relatively wetter future for most of the U.S.
compared to the MIROC climate model (see
the Levels of Certainty section of this report for
more information).The projected benefits of
global GHG mitigation are lower with the drier
MIROC model (not shown) for the 2010-2050
period, at approximately $3.4 billion, but are
higher in the 2051 -2100 period, at approxi-
mately $10 billion (discounted at 3%).
Figure 2. Bridges Identified as Vulnerable in the Second Half of the
21st Century with Global GHG Mitigation
Estimated number ofvulnemble bridges in each of the 2-digit HUCs of the contiguous U.S. in the period
from 2051-2100 under the Mitigation scenario using the IGSM-CAM climate model. The map also shows
the percentage of inland bridges in each HUC that are vulnerable due to climate change.
Number of Vulnerable
Bridges 2051-2100
< 1,000
1,001 -5,000
^H 5,001 -10,000
^•10,001 -20,000
^H > 20,000
The CIRA analysis identifies inland
bridges in the contiguous U.S. that
may be vulnerable to increased peak
river flows due to climate change and
estimates the costs to adapt the at-risk
infrastructure.8The analysis relies
upon climate projections from two
climate models: IGSM-CAM, which
projects a relatively wetter future for
most of the U.S., and the drier MIROC
model. Bridge performance and
vulnerability are determined using the
National Bridge Inventory database
and are based on the following four
elements:
• substructure condition;
• channel and channel protection
condition;
• waterway adequacy; and
• vulnerability to scour.
The analysis estimates the timing of
bridge vulnerability (based on the
100-year, 24-hour storm event), and
the adaptation costs of maintaining
the current condition and level of
service of the at-risk bridges. Two
types of bridge fortification and the
costs of their implementation are
analyzed: the use of riprap (large rocks
and rubble) to stabilize bridge founda-
tions and the use of additional con-
crete to strengthen bridge piers and
abutments. Although there will likely
be significant changes to the nation's
bridges over the course of the centu-
ry—some bridges will be strength-
ened, some will deteriorate, some will
be removed, and new bridges will be
built—this analysis estimates the costs
of adapting the nation's existing bridge
infrastructure to different future
climates based on its current state (i.e.,
the additional costs due to climate
change are isolated).9'10
For more information on the CIRA
approach and results for the
bridges sector, please refer to
Neumann et al. (2014)" and Wright
etal.(2012).12
35
-------
Climate change is projected
to increase the cost of
maintaining road infrastruc-
ture. This analysis estimates
the damages of climate
change in terms of in-
creased costs to maintain
current levels of service (i.e.
adaptation costs). Without
adaptation, climate change
could render many road-
ways unusable, leading to
large economic damages.
2 In all regions, adaptation
costs associated with the
effects of higher tempera-
tures on paved roadways
are estimated to increase
over time. In the central
regions of the country, in
particular, changes in
precipitation patterns are
projected to increase costs
associated with re-grading
un paved roadways.
3 Without global GHG
mitigation, adaptation
costs in 2100 in the U.S.
roads sector are estimated
to range from $5.8-$ 10
billion.
4 Global GHG mitigation
is projected to avoid an
estimated $4.2-$7.4 billion
of the damages under the
Reference scenario in 2100.
36
Climate Change and Roads
The U.S. road network is one of the nation's
most important capital assets. Climate stress
on roads will likely change in the future, with
various potential impacts and adaptation
costs.13 For example, roads may experience
more frequent buckling due to increased
temperatures, more frequent washouts of
unpaved surfaces from increases in intense
precipitation, and changes in freeze-thaw
cycles that cause cracking.14
Risks of Inaction
Without reductions in global GHG emissions, the costs of maintaining, repairing, and replacing
pavement are projected to increase, which is consistent with the findings of the assessment
literature regarding adaptation costs for road infrastructure.15 Figure 1 presents the estimated
regional damages (in the form of adaptation costs) to the U.S. road network under the Refer-
ence scenario using the ISGM-CAM climate model.The greatest impacts are projected to occur
in the Great Plains region, where costs are mainly due to erosion of unpaved roads associated
with increased precipitation. Costs associated with the use of different pavement binders to
avoid cracking of paved roads are also high, particularly in the Midwest and Southeast regions,
and they increase over time in all regions due to the projected rise in temperature. Costs of
resealing roads after freeze-thaw events decrease over time as the climate changes, but the
magnitude of the decrease does not offset the projected increase in other costs.
Figure 1. Projected Impacts of Unmitigated
Climate Change on U.S. Road Infrastructure
Adaptation costs (billions 2014$, undiscounted) under the Reference scenario using the 1GSM-CAM climate
model. Results are presented for the six regions used in the Third National Climate Assessment.
I Unpaved Roads Costs
I Paved Roads Binder Costs
I Paved Roads Reseal Costs
GREAT PLAINS
-------
Reducing Impacts through
GHG Mitigation
Adaptation costs for the
U.S. road network are
substantially reduced
with global GHG mitiga-
tion compared to the
Reference scenario
(Figure 2).These reduc-
tions are due in large part
to the effect of lower
temperatures under the
Mitigation scenario on
maintenance needs for
paved roads. Specifically,
costs associated with
asphalt binders account
fora large share of the
adaptation costs national-
ly under the Reference, and these costs are
significantly lower with mitigation. Costs
associated with adaptation for unpaved roads
are also substantially lower under the
Mitigation scenario, as heavy precipitation
events are projected to be less severe
compared to the Reference. Costs of resealing
roads after freeze-thaw cycles are projected
to decrease under both scenarios, but the
magnitude of the decrease does not offset
the projected increase in other costs.
By 2050, the adaptation costs under the
Reference scenario are substantially higher.
illustrating the benefits
that accrue overtime
with GHG mitigation. In
addition, although the
costs of adaptation
increase over the course
of the century under
both scenarios, they do
so at a much faster rate
under the Reference.
Under the Reference,
adaptation costs are
estimated at approxi-
mately $10 billion in
2100, whereas under the
Mitigation scenario costs
are estimated at $2.6
billion. As a result, global GHG mitigation is
projected to avoid over $7 billion in damag-
es in 21 00. These results rely upon climate
projections from the IGSM-CAM, which
projects a relatively wetter future for most of
the U.S. compared to the MIROC climate
model (see the Levels of Certainty section of
this report for more information). The
projected benefits of global GHG mitigation
are lower with the drier MIROC model (not
shown), at $4.2 billion in 2100, reflecting the
reduced impact of precipitation on unpaved
roads under both scenarios.16
Figure 2. Projected Impacts on U.S. Road Infrastructure
with and without Global GHG Mitigation
Costs of adaptation for the Reference and Mitigation scenarios using the IGSM-CAM climate
model (billions 2014$). The reduction in adaptation costs under the Mitigation scenario relative
to the Reference reflects the benefits of global GHG mitigation.
Reference
Mitigation
2025 2050 2075 2100 2025 2050 2075 2100
• Paved Roads Reseal Costs 11 Paved Roads Binder Costs Unpaved Roads Costs
The CIRA approach assesses four risks
to road infrastructure associated with
climate change:
• rutting of paved roads from
precipitation;
• rutting of paved roads caused by
freeze-thaw cycles;
• cracking of paved roads due to
high temperatures; and
• erosion of unpaved roads from
precipitation.
The CIRA analysis examines the
implications of changes in climate
over time for the U.S. road network
based on stressor-response functions
for each of the above effects. The
analysis considers the effects of
temperature and precipitation, but
does not include impacts due to sea
level rise and storm surge, which
would likely increase damages to
roads. The analysis relies upon climate
projections from two climate models:
IGSM-CAM, which projects a relatively
wetter future for most of the U.S., and
the drier MIROC model.
The costs of adaptation to effective-
ly counteract the climate change
impacts and maintain roads at their
current levels of service are estimated
for each of the CIRA scenarios. As
there will be continued maintenance
needs over time, this analysis focuses
on the additional costs due to climate
change.The response measures
include more frequent resealing to
avoid rutting; use of different pave-
ment binders during resurfacing to
avoid cracking of asphalt-paved
roads; and more frequent re-grading
of unpaved roads to minimize erosion
impacts. This analysis assumes
well-timed adaptation to maintain
service levels, a potentially overly
optimistic assumption given that
infrastructure investments are
oftentimes delayed.
For more information on the CIRA
approach and results for the roads
sector, please refer to Neumann et
al. (2014)17 and Chinowsky et al.
(2013).18
37
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Climate change is project-
ed to result in increased
adaptation costs for urban
drainage systems in cities
across the U.S., particularly
in the Great Plains region.
Without global GHG
mitigation, adaptation
costs in 2100 associated
with the 50-year, 24-hour
storm in 50 major U.S.
cities are projected to
range from $1.1-$12 billion.
Global GHG mitigation
is projected to result in
cost savings for urban
drainage systems in these
cities ranging from $50
million to $6.4 billion in
2100 for the 50-year,
24-hour storm, depending
on the climate model used.
Inclusion of all U.S. cities
would likely increase the
cost savings by a substan-
tial amount.
38
Climate Change and Drainage
Urban drainage systems capture and treat
stormwater runoff and prevent urban flooding.
During storm events, the volume of runoff
flowing into drainage systems and the ability of
these systems to manage runoff depend on a
variety of site-specific factors, such as the
imperviousness of the land area in the drainage
basin. Changes in storm intensity associated
with climate change have the potential to
overburden drainage systems, which may lead
to flood damage, disruptions to local transpor-
tation systems, discharges of untreated sewage to waterways, and increased human health
risks.19 In areas where precipitation intensity increases significantly, adaptation investments
maybe necessary to prevent runoff volumes from exceeding system capacity.
Risks of Inaction
Without global GHG mitigation, climate change is projected to result in increased adaptation
costs for urban drainage infrastructure, a finding that is consistent with the conclusions of the
assessment literature.20 Figure 1 presents the projected costs for the 50 modeled cities in 2050
and 2100 under the Reference scenario using the IGSM-CAM climate model for the three
categories of storm events modeled (24-hour events with precipitation intensities occurring
every 10,25, and 50 years).21 The average per-square-mile costs are projected to be highest in
the Great Plains region in both 2050 and 2100 due to the projected increase in heavy precipita-
tion in that region. Adaptation costs are estimated to be relatively low in the Southwest due to
the projected reduction in precipitation in that region.
Figure 1. Projected Impacts of Unmitigated Climate Change
on U.S. Urban Drainage Systems
Weighted average per-square-mile adaptation costs (millions 2014$, undiscounted) in 2050 and 2100 for the
10-, 25-, and 50-year storms under the Reference scenario using the IGSM-CAM climate model. Costs for each of
the 50 modeled cities (shown) are aggregated to the six regions used in the Third National Climate Assessment.
NORTHWEST
GREAT PLAINS
NORTHEAST
Columbus Baltimore
•Washington D.C
iLexington Tthesapeake
$2.5
$2.0
$1.5
$1.0
$0.5
10-year 25-year 50-year
2050 Costs
-------
Reducing Impacts through
GHG Mitigation
Global GHG mitigation is projected to result in
substantial adaptation cost savings for urban
drainage systems in the 50 modeled cities
(Figure 2). Overall, cost savings are projected
to be higher in 2100 than in 2050, and increase
according to the intensity of the storm
modeled, with the greatest savings occurring
for the 50-year, 24-hour storm. For this
particular storm event, total adaptation costs
for the modeled cities are projected to be $12
billion in 2100 under the Reference. Under the
Mitigation scenario, these costs are reduced to
approximately $5.5 billion, which represents a
cost savings of approximately $6.4 billion. Cost
savings for the 10- and 25-year storms under
the Mitigation scenario are approximately $3.9
billion and $5.1 billion, respectively, in 2100.
Looking across the contiguous U.S., the Great
Plains region is projected to experience the
largest reductions in adaptation costs as a
result of global GHG mitigation. These results rely upon climate projections from the IGSM-CAM,
which projects a relatively wetter future for most of the U.S. compared to the MIROC climate
model (seethe Levels of Certainty section of this report for more information). Using the drier
MIROC model, projected benefits of GHG mitigation for the modeled cities associated with the
50-year, 24-hour storm event are estimated at $50 million.
Figure 2. Projected Impacts on Urban Drainage Systems in 50 U.S. Cities
with and without Global GHG Mitigation
Projected adaptation costs in 2050 and 2100 for the Reference and Mitigation scenarios using the IGSM-CAM
climate model (billions 2014$). The values of the red bars represent the sum of all adaptation costs
shown in Figure 1 for the years 2050 and 2100.
2100
10-year storm 25-year storm 50-year storm
10-year storm 25-year storm 50-year storm
I Reference • Mitigation
The CIRA analysis estimates the costs
of adapting urban drainage systems
to meet future demands of increased
runoff associated with more intense
rainfall under climate change. The
analysis relies upon climate projec-
tions from two climate models:
IGSM-CAM, which projects a relatively
wetter future for most of the U.S., and
the drier MIROC model. Adaptive
actions focus on the use of best
management practices to limit the
quantity of runoff entering stormwater
systems. While many site-specific
factors influence the effect of climate
change on a given drainage system,
the CIRA analysis uses a streamlined
approach that allows for the assess-
ment of potential impacts in multiple
U.S. cities under the CIRA scenarios.22
Specifically, the analysis uses a
reduced-form approach for projecting
changes in flood depth and the
associated costs of flood prevention,
based on an approach derived from
EPA's Storm Water Management
Model (SWMM).
The simplified approach yields
impact estimates in units of average
adaptation costs per square mile for a
total of 50 cities across the contiguous
U.S. (see Figure 1) for three categories
of 24-hour storm events (those with
precipitation intensities occurring
every 10,25, and 50 years—metrics
commonly used in infrastructure
planning) and four future time periods
(2025, 2050, 2075, and 2100). The
analysis assumes that the systems are
able to manage runoff associated with
historical climate conditions, and
estimates the costs of implementing
the adaptation measures necessary to
manage increased runoff under
climate change.
For more information on the CIRA
approach and results for the urban
drainage sector, please refer to
Neumann etal. (2014)23 and Price et
al.(2014).24-25
39
-------
KEY FINDING
A large area of U.S. coastal
land and property is at risk
of inundation from global
sea level rise, and an even
larger area is at risk of
damage from storm surge,
which will intensify as sea
levels continue to rise.
2 Without adaptation, unmiti-
gated climate change is
projected to result in
$5.0 trillion in damages for
coastal property in the
contiguous U.S. through
2100 (discounted at 3%).
Protective coastal adapta-
tion measures significantly
reduce total costs to an
estimated $810 billion.
Global GHG mitigation
reduces adaptation costs
for coastal areas, but the
majority of benefits occur
late in the century.
Areas of higher social
vulnerability are more
likely to be abandoned
than protected in response
to unmitigated sea level
rise and storm surge.
GHG mitigation decreases
this risk.
40
Climate Change and
Coastal Property
Coastal areas in the U.S. are some of the most
densely populated, developed areas in the
nation, and they contain a wealth of natural
and economic resources. Rising temperatures
are causing ice sheets and glaciers to melt and
ocean waters to expand, contributing to global
sea level rise at increasing rates. Sea level rise
threatens to inundate many low-lying coastal
areas and increase flooding, erosion, wetland
habitat loss, and saltwater intrusion into
estuaries and freshwater aquifers. The com-
bined effects of sea level rise and other climate
change factors, such as increased intensity of
coastal storms, may cause rapid and irrevers-
ible change.26
Areas at risk from sea level rise and
storm surge in the Tampa Bay area
in 2100 under the Reference scenario
Risks of Inaction
Sea level rise and storm surge pose increasingly large risks to coastal property, including costs
associated with property abandonment, residual storm damages, and protective adaptation
measures (e.g., elevating properties and armoring shorelines). As shown in Figure 1, the analysis
estimates that under the Reference scenario the cumulative damages to coastal property across
the contiguous U.S. will be $5.0 trillion through 2100 (discounted at 3%) if no adaptation
measures are implemented. If adaptation measures are taken, these damages are reduced to
$810 billion. Projections of increasing risks of sea level rise and storm surge for coastal property,
and of the potential for adaptation to reduce overall costs, are consistent with the findings of the
assessment literature.27The graphic above illustrates the importance of these potential impacts
at a local scale by identifying at-riskland in the Tampa Bay, FLarea. In this locale, approximately
83,000 acres are projected to beat risk of inundation due to sea level rise by 2100, and an
additional 51,000 acres are projected to beat risk of significant storm surge. The total area at
risk (130,000 acres) is approximately one and a half times the size of the City of Tampa.
Figure 1. Costs of Sea Level Rise and Storm Surge to Coastal Property
with and without Adaptation under the Reference Scenario
The step-wise nature of the graph is due to the fact that storm surge risks are evaluated every ten years,
beginning in 2005. Costs with adaptation include the value of abandoned property, residual storm
damages, and costs of protective adaptation measures (trillions 2014$).
6
5-
4-
o
Q
2-
I 1
2000 2025 2050
— Costs without Adaptation
2075 2100
• Costs with Adaptation
-------
Reducing Impacts through
GHG Mitigation
Under the Mitigation scenario, total costs (i.e., property damages and protective investments)
across the contiguous U.S. are estimated at $790 billion through 2100 (discounted at 3%), about
3% less than the Reference scenario.28 The effect of global GHG mitigation in reducing adapta-
tion costs is modest and is likely underestimated in this analysis for several reasons. First, as
described in the CIRA Framework section, global sea level rise is similar under the Reference and
Mitigation scenarios through mid-century. It is not until the second half of the century when the
benefits of reduced sea level rise under the Mitigation scenario become apparent. Further, the
proportional effect of global GHG mitigation in reducing the rate of sea level rise is smaller
under the CIRA scenarios compared to other scenarios in the literature.29
Second, when considering the present value total cost under the Reference and Mitigation
scenarios, avoided adaptation costs accrued in lateryearsare more heavily affected by discount-
ing.30 Third, the analysis assumes that coastal areas will implement cost-efficient and well-timed
adaptation measures in response to the risks under both the Reference and Mitigation scenarios.
Since many parts of the coastline are not sufficiently protected today, and because adaptation
measures that are taken are oftentimes not well-timed, the CIRA estimates for this sector likely
underestimate damages. For comparison purposes, the benefits of global GHG mitigation
increase by a factor of ten if adaptation measures are not implemented.
Figure 2 shows the costs of adaptation for coastal properties (including the value of properties
that are abandoned due to the severity of sea level rise or storm surge damages) for 17 key sites
under the Reference and Mitigation scenarios. As shown, costs are only modestly lower under
the Mitigation scenario. Costs vary a cross sites primarily due to the value of property at risk
and the severity of the storm surge threats. For example, adaptation costs are comparatively
higher in sites, such as Tampa and Miami, where there are many high-value properties in
low-lying areas and high levels of storm surge are projected in the future.
Figure 2. Costs to Coastal Property of Sea Level Rise and
Storm Surge through 2100
Costs are shown for 17 multi-county coastal areas that were modeled for sea level rise and
storm surge impacts and potential adaptation response (billions 2014$).
Reference
Mitigation
APPROACH
The CIRA analysis identifies at-risk coastal
property across the contiguous U.S. and
estimates the costs that would be incurred
due to climate change, with and without
adaptation. Importantly, impacts to other
coastal assets (e.g., roads and ecological
resources) are not estimated in this analysis.
The analysis relies upon sea level rise
projections through 21OO31 that account for
dynamic ice-sheet melting based on a
semi-empirical model,32 and are adjusted
for regional land movement using local tide
gauge data.33The analysis then uses a
tropical cyclone simulator34and a storm
surge model35 to estimate the joint effects
of sea level rise and storm surge for East
and Gulf Coast sites, and an ana lysis of
historic tide gauge data to project future
flood levels forWest Coast sites.36
Using EPA's National Coastal Property
Model, the CIRA analysis estimates how
areas along the coast may respond to sea
level rise and storm surge and calculates
the economic impacts of adaptation
decisions (i.e., damages due to climate
change). The approach uses four primary
responses to protect coastal land and
property: beach nourishment; property
elevation; shoreline armoring; and
property abandonment.The model
projects an adaptation response for areas
at risk based on sea level rise, storm surge
height, property value, and costs of
protective measures. Developed using a
simple metric to estimate potential
adaptation responses in a consistent
manner for the entire coastline, the
estimates presented here should not be
construed as recommending any specific
policy or adaptive action. Further, addition-
al adaptation options not included in this
analysis, such as marsh restoration, may be
appropriate and potentially more cost-ef-
fective for some locales.The analysis also
explores the potential impact of climate
change on socially disadvantaged
populations (see the Environmental Justice
section of this report).
For more information on the CIRA
approach and results for the coastal
property sector, please refer to Neu-
mann et al. (2014a)37 and Neumann et
al.(2014b).38
41
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COASTAL PROPERTY
I
Building on the coastal property impacts described in the previous section, this
analysis examines the environmental justice implications of projected sea level rise
and storm surge in the contiguous U.S. Specifically, the approach quantifies how sea
level rise and storm surge risks are distributed across different socioeconomic populations
along the U.S. coastline; how these populations are likely to respond; and what adaptation
costs (i.e., property damage and protection investments) will potentially be incurred.
The Social Vulnerability Index
The CIRA analysis uses the Social Vulnerability
Index (SoVI) to identify socially vulnerable
coastal communities in the U.S.39 SoVI was
developed to quantify social vulnerability
using county-level (and later Census
tract-level) socioeconomic and demographic
data. The index is a well-vetted tool, and does
not include any environmental risk factors,
thereby eliminating the risk of double
counting climate risk when socioeconomic
and demographic data are combined with sea
level rise and storm surge vulnerability.40The
CIRA analysis uses Census tract-level SoVI
values based on 2000 Census data for 26
demographic variables, capturing informa-
tion on wealth, gender, age, race, and
employment. Figure 1 shows the SoVI index
values for the four coastal regions used in the
analysis: Pacific (California through Washing-
ton), North Atlantic (Maine through Virginia),
South Atlantic (North Carolina through
Monroe County, Florida), and Gulf (Collier
County, Florida through Texas).
Figure 1. Social Vulnerability Index for the Coastal U.S.
Census tract-level SoVI values are regionally normalized to allow for comparisons of the SoVI scores within each
area. Areas with low So VI scores (i.e., people with lower social vulnerability) are shaded in green and areas with
higher SoVI scores (i.e., people with greater social vulnerability) are shaded in pink.
SoVI
^^| <-1.5 (LowVulnerability)
-1.4to-0.5
| |-0.4 to 0.5
0.6 to 1.5
^H>1.5(HighVulnerability)
=M No Data
L
42
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Case Study: Tampa Bay Area
EPA's National Coastal Property Model identifies areas
along the contiguous U.S. coastline that are likely to be
at risk from sea level rise and storm surge through
21OO.41-42 By layering these projections on top of the
SoVI results, following the approach described in
Martinich et al. (2013),43 the analysis assesses the
potential impact of sea level rise and storm surgeon
socially disadvantaged populations in coastal areas.
Figure 2 presents a case study of theTampa Bay, Florida
area (Pinellas and Hillsborough Counties).The area from
the water to the gray lines represents the projected area
at risk of inundation due to sea level rise, while the area
from the water to the black lines represents projected
areas at risk from significant storm surge damage in
21 OO.44 As shown, there are areas with higher socially
vulnerable populations (pink shading) near the city of
Tampa, in particular, that are projected to be at risk of
significant storm surge damages.
Figure 2. Social Vulnerability of Areas at Risk from Sea Level Rise and
Storm Surge in theTampa Bay Area by 2100 under the Reference Scenario
So VI
| <-1.5 (Low Vulnerability)
-1.4 to-0.5
I | -0.4 to 0.5
0.6 to 1.5
_ >1.5 (High Vulnerability)
^^~ Inland boundary of area
at riskof significant storm
surge damage
^^ Inland boundary of area
at riskof inundation due
to sea level rise
National Results
Figure 3 compares the number of people in the 17 multi-county
coastal areas (see previous section for locations) identified as at risk
due to climate change under the Reference and Mitigation scenarios,
by SoVI category. As shown, the Mitigation scenario reduces the
number of at-risk people compared to the Reference scenario for all
SoVI categories. The benefits of global GHG mitigation are particularly
high for the population identified by the SoVI as most socially
vulnerable; for this population, the number of at-risk people is reduced
by 23% under the Mitigation scenario compared to the Reference.
The CIRA analysis also projects adaptation responses based on sea
level rise, storm surge height, property value, and costs of adaptation.45
The model estimates whether people living in coastal areas are likely
to respond to climate threats by: 1) protecting property through
beach nourishment, property elevation, or shoreline armoring; 2)
abandoning property, or 3) incurring storm surge damages without
adapting. Figure 4 presents the adaptation results, by area, for the five
SoVI categories in the Reference. More area is likely to be abandoned
than protected across all social vulnerability categories. However, in
the most vulnerable SoVI categories (0.6-1.5 and greater than 1.5), a
relatively larger proportion of the area inhabited is likely to be
abandoned (89% and 86%, respectively) rather than protected
through adaptation measures (8% and 10%, respectively).
Figure 3. Social Vulnerability of Populations at Risk
from Sea Level Rise and Storm Surge through 2100
with and without Global GHG Mitigation
Vulnerability estimated in 17 multi-county coastal areas in the contiguous U.S.,
along with the estimated percent changes from Reference to Mitigation.
Less than-1.5 -1/4 to-0.5 -0/4 to 0.5 0.6 to 1.5 Greaterthan
(Low 1.5 (High
Vulnerability) Vulnerability)
• Reference •Mitigation
Figure 4. Adaptation Measures by
SoVI Category under the Reference Scenario
Less than -1.5
(Low
Vulnerability)
No Adaptation (Storm Surge Damage)
Property Elevation
Shoreline Armoring
0.6 to 1.5 Greaterthan
1.5 (High
Vulnerability)
Property Abandonment
• Beach Nourishment
43
-------
—_
"Tf
" :
„
•Si £«,;.
Electricity
Demand
-------
.
Electricity is an essential element
of modern life. It lights and cools
our homes, powers our computers,
supports the production of goods and ser-
vices, and enables critical infrastructure
services such as water treatment and tele-
communications. The generation of electricity
in the U.S., most of which comes from fossil
fuels, also contributes to climate change,
accounting for approximately 30% of U.S.
greenhouse gas emissions.1
HOW IS THE ELECTRICITY SECTOR
VULNERABLE TO CLIMATE CHANGE?
Climate change has implications for electricity
production, distribution, and use.2 For exam-
ple, coastal electricity infrastructure, such as
power plants and substations, are vulnerable
to storm surge and wind damage. Elevated
temperatures diminish thermal power plant
efficiency and capacity, and can reduce the
capacity of transmission lines. In addition,
effects on water supply alter the quantity and
temperature of cooling water available for
thermoelectric generation.3 On the demand
side, warmer winters decrease the demand
for heating. However, this reduction is smaller
than the increase in electricity demand for
cooling due to higher summer temperatures.
Across the U.S., higher minimum temperatures
increase the number of days in a year when
air conditioning is needed, and higher
maximum temperatures increase the peak
electricity demand, further stressing our
aging power grid.
WHAT DOES CIRA COVER?
Numerous studies highlight the potential for
emission reductions in the electricity sector,
yet fewer studies have explored the physical,
operational, and economic impacts of a chang-
ing climate on this sector. CIRA assesses the
impacts of rising temperatures on electricity
demand, system costs, and the generation mix
needed to meet increasing demand across the
contiguous U.S. through 2050.4 Importantly,
impacts to the demand and supply of other
energy sources (e.g., fuel for transportation)
are not estimated. Also, the electricity supply
analysis does not include the effects of climate
change on hydropower and water availability
for thermoelectric power generation. Addi-
tional work is necessary to further evaluate
climate change impacts on electricity supply,
particularly the effects of extreme heat events
and storm damage on capacity and reliability.
Finally, future work to improve connectivity
between the CIRA electricity, water, and
agriculture analyses will aid in better under-
standing potential cross-sector impacts.
Electricity
Supply
-------
KEY FINDINGS
Without global GHG
mitigation, rising tempera-
tures will likely result in
higher electricity demand
across the country, as the
increased need for air
conditioning outweighs
decreases in electric heat-
ing requirements. The
estimated percent increase
in electricity demand for air
conditioning is highest in
the Northeast and North-
west regions.
2 Global GHG mitigation,
which lessens the rise in
temperature, is projected
to lead to lower electricity
demand across all regions
of the country relative to
the Reference scenario.
46
Climate Change and
Electricity Demand
As air temperatures rise due to climate change, electricity demands for cooling are expected to
increase in every U.S. region.5 Higher summer temperatures, particularly during heat waves, will
likely increase peak electricity demand, placing more stress on the electricity grid and increasing
electricity costs. Although the majority of U.S. residential and commercial cooling demand is met
with electricity, less than 9% of heating demand is met with electricity.6-7 Therefore, although
higher average temperatures are expected to reduce electricity demands for heating, net electric-
ity use is projected to increase under climate change. This section presents estimated impacts on
electricity demand, but does not consider impacts on demand for other fuel sources used in
residential cooling or heating.
Risks of Inaction
Rising temperatures are projected to increase electricity demands for cooling. Figure 1 shows
the percent change in regional heating and cooling degree days (HDDs/CDDs, see Approach
for definitions) from 2005 to 2050 in the Reference scenario. Results are presented for the three
models used in the analysis (GCAM, ReEDS, and IPM), which exhibit similar trends of falling
HDDs (shown in purple) and rising CDDs (shown in orange).These trends are consistent with
projections described in the assessment literature.8Across the U.S., HDDs decrease between
18%-29% on average, with greater decreases occurring in the South due in part to already-high
temperatures. The increase in CDDs is highest in the Northeast and Northwest (68% and 71% on
average, respectively). The projected changes in HDDs and CDDs have implications for regional
electricity demand. Average U.S. electricity demand is projected to increase under the Reference
by 1.5%-6.5% by 2050, compared to a Control with no temperature change. Across the regions
and models shown in Figure 2, electricity demand is projected to increase by 0.5%-9.0%, with
the exception of the ReEDS model in the Northwest, which projects a decrease of 0.5%.9
Figure 1. Projected Impact of Unmitigated Climate Change on Regional Heating
and Cooling Degree Days from 2005 to 2050
Percent change in HDDs and CDDs from 2005 to 2050 under the Reference compared to a Control with no
temperature change. Results are presented for six regions and for the three models used in the analysis.
NORTHWEST
SOUTH CENTRAL
MIDWEST
NORTHEAST
Cooling Degree Days
(High temperatures,
A/C needed)
-------
Reducing Impacts through
GHG Mitigation
Global GHG emissions reductions under the Mitigation
scenario result in smaller increases in temperatures
compared to the Reference, thereby reducing cooling
demand across the country. Figure 2 illustrates this
effect, presenting the change in regional energy
demand in 2050 in the Reference and Mitigation
scenarios relative to a Control with no temperature
change. As shown, the change in demand in the
Mitigation scenario is consistently lower than in the
Reference across all of the models. This decrease in
demand is due in large part to lower temperatures under
the Mitigation scenario compared to the Reference, and
in the GCAM and ReEDS models the lower demand is
also due to an increase in electricity costs associated
with reducing GHG emissions. The impact of GHG
mitigation on electricity supply is discussed in greater
detail in the Electricity Supply section of this report.
Figure 2. Change in Regional Electricity Demand in 2050
with and without Global GHG Mitigation
Change in regional electricity demand for the Reference and Mitigation scenarios relative to a Control
(no temperature change). Results are presented for six regions and for each of the three
models used in the analysis (GCAM, ReEDS, and IPM).
PROAG
SOUTH CENTRAL
GCAM ReEDS IPM
The CIRA analysis examines how
rising temperatures under climate
change will affect electricity demand.
It applies a common set of tempera-
ture projections from IGSM-CAM to
three models of the U.S. electric
power sector:
• Global Change Assessment
Model (GCAM-USA): a detailed,
service-based building energy
model for the 50 U.S. states;10'11
• Regional Electricity Deployment
System Model (ReEDS): a technolo-
gy-rich model of the deployment
of electric power generation
technologies and transmission
infrastructure for the contiguous
U.S.;12and
• Integrated Planning Model (IPM®):
a dispatch and capacity planning
model used by the public and
private sectors to inform business
and policy decisions.13
The models project changes in electric-
ity demand as functions of changes in
heating and cooling degree-days
(HDDs/CDDs). HDDs and CDDs are
one way to measure the influence of
temperature change on energy
demand. They measure the difference
between outdoor temperatures and a
temperature that people generally find
comfortable indoors. These measure-
ments suggest how much energy
people might need to use to heat and
cool their homes and workplaces. The
analysis compares the results across
the CIRA scenarios, while also ac-
counting for non-climate changes in
electricity demand (e.g., population
and economic growth). To assess the
effect of rising temperatures in the
Reference and Mitigation scenarios,
changes in heating and cooling degree
days and electricity demand are
compared to a Control that assumes
temperatures do not change over time.
For more information on the CIRA
approach and results for the
electricity demand sector, please
refer to McFarland et al. (2015).14
47
-------
,1
KEY FINDING
Projected electricity supply
is higher in all three electric
power sector models under
the Reference scenario,
reflecting a higher demand
for cooling, and lower under
the Mitigation scenario as a
result of lower temperatures
and the demand response
toGHG mitigation.
The relative magnitude of
costs to the electric power
system are similar under
the Reference and Mitiga-
tion scenarios, highlighting
that the costs associated
with rising temperatures in
the Reference are compara-
ble to the costs associated
with reducing GHG emis-
sions in the Mitigation
scenario. Specifically, the
higher demands under
the Reference scenario
increase system costs by
1.7%-8.3% above the Con-
trol. Under the Mitigation
scenario, system costs
increase by 2.3%-10%
above the Control, or 0.6%-
5.5% above Reference
scenario costs.
48
Climate Change and
Electricity Supply
As described in the Electricity Demand section, warmer air temperatures under climate change
are expected to result in higher demand for electricity, leading to the need for increased
capacity in the power system to meet this demand. At the same time, higher temperatures
reduce the capacity of both thermal power plants and transmission lines.
The power sector accounts for the largest share of GHG emissions in the U.S.,15 and is also
considered the most cost-effective source of emission reductions under mitigation policies.16
A variety of impacts and changes are therefore expected to occur in this sector, including
changes in sector emissions, system costs, and generation mix (i.e., the assortment of fuels
used to generate electricity).
Effects on Electricity
Generation
In the CIRA analyses, a large amount of C02 reductions in the U.S. underthe Mitigation scenario
occur in the electricity sector.17 As a result, the generation capacity and mix of energy sources
used to produce electricity is projected to change over time. Figure 1 shows the projected
change in generation mix in 2050 from the three electric power sector models under the CIRA
scenarios. Projected electricity supply is higher in all three models under the Reference,
reflecting a higher demand for cooling, and lower under the Mitigation scenario as a result of
lower temperatures and the costs of reducing GHG emissions. For any given model, the supply
mix in the Reference does not differ substantially from the Control, which accounts for future
population and economic growth, but no temperature change. However, all three models
under the Mitigation scenario project substantial reductions in coal generation and expanded
generation from nuclear and renewables.
Figure 1. Electricity Generation by Technology and Scenario in 2050
with Percent Change in Generation from Control18
I Coal
I Coal w/CCS
iGas
Gas w/CCS
ION
I Nuclear
I Hydro
I Non-Hydro Renewables
I Other
-------
Change in System Costs
Rising temperatures under both scenarios,
especially under the Reference, result in
higher demands for electricity and increased
power system costs to expand capacity. At
the same time, altering the generation mix to
reduce GHG emissions imposes costs on the
power system. Figure 2 presents the percent
change in cumulative system costs under the
Reference and Mitigation scenarios compared
to a Control with no temperature change
(2015-2050, discounted at 3%). The costs
increase by 17%-8.3% under the Reference
and by 2.3%-10% under the Mitigation
scenario. The incremental system costs of the
Mitigation scenario above the Reference are
0.6%-5.5%, highlighting that the costs to the
electric power sector associated with rising
temperatures in the Reference are compara-
ble to the costs associated with reducing GHG
emissions in the Mitigation scenario. It is
important to note, however, that this does
not account for benefits of GHG mitigation
outside of the electricity sector, nor does it
examine other effects of climate change on
electricity supply, such as changes in cooling
water availability or extreme weather events.
Figure 2. Percent Change in Cumulative System Costs (2015-2050) in the
Reference and Mitigation Scenarios Compared to the Control
Grey bars represent the difference between the Reference and Mitigation scenarios.
12%
10%
1.2%
PROAG
GCAM
ReEDS
IPM
The CIRA analysis assesses impacts on
the U.S. electricity sector's supply side
using the same three models described
in the Electricity Demand section. The
models project changes in the genera-
tion mix needed to meet increasing
demand due to future warming and
socioeconomic changes (e.g., popula-
tion and economic growth) under the
CIRA scenarios. The three models also
estimate the corresponding system
costs—comprised of capital, opera-
tions and maintenance, and fuel
costs—and the changes in CO2
emissions over time. This analysis is
unique compared to the other sectoral
analyses of this report in that the costs
of GHG mitigation in the electric
power sector are estimated alongside
the benefits. The three electric power
sector models simulate these costs
over time, and the rationale for
presenting them here is to provide a
comparison between the increase in
power system costs due to mean
temperature increases under the two
scenarios and the costs associated
with reducing GHG emissions from
electric power generation. It is import-
ant to note that the effect of tempera-
ture change on generation accounts
for only a small portion of the total
effects of climate change on electricity
supply. Other important effects, such
as changes in hydropower generation
or the availability of cooling water for
thermoelectric combustion, are not
included. Inclusion of these impacts on
the electricity supply system would
likely increase the benefits of mitiga-
tion to this sector.
For more information on the CIRA
approach and results for the
electricity supply sector, please
refer to McFarland et al. (2015).19
49
-------
Inland
Flooding
Drought
-------
Water, a resource that sustains life
across the globe, is a vital compo-
nent of a productive economy,
providing a critical input to production in a
number of key economic sectors.1 In the U.S.,
water is used in many ways, including for
human consumption, agricultural irrigation,
power plant cooling, and hydropower genera-
tion. In addition, rivers, lakes, and oceans
allow for navigation, fishing, and recreation
activities. Water also plays an array of vital
roles in ecosystems, which in turn provide
crucial services that support human life.
Analyzing the effects of climate change on
water resources can be particularly challeng-
ing as climate variables affect both the supply
and demand of water in different ways, and
the impacts vary over space and time.
HOW IS WATER VULNERABLE TO
CLIMATE CHANGE?
The water cycle is inextricably linked to
climate, and climate change has a profound
impact on water availability at global,
regional, and local levels. As temperatures
rise, the rate of evaporation increases, which
makes more water available in the air for
precipitation but also contributes to drying
over some areas.2 Further, climate change
will result in increased intensity of precipita-
tion events, leading to heavier downpours.
Therefore, as climate change progresses,
many areas are likely to see increased
precipitation and flooding, while others will
experience less precipitation and increased
risk of drought. Some areas may experience
both increased flooding and drought. Many
of these meteorological changes, along with
their associated impacts, are already being
observed across the U.S. These changes,
combined with demographic, socioeconomic,
land use, and other changes, affect the avail-
ability, quality, and management of water
resources in the U.S.3
WHAT DOES CIRA COVER?
The CIRA analyses estimate impacts and
damages from three water resource-related
models addressing flooding, drought, and
water supply and demand (see the Health
section of this report for water quality
impacts). The models differ in the component
of the water sector assessed and geographic
scale, but together provide a quantitative
characterization of water sector effects that
no single model can capture. As the water
cycle is sensitive to changes in precipitation,
the analyses use a range of projections for
future precipitation (see the CIRA Framework
section for more information). Finally, future
work to improve connectivity between the
CIRA electricity, water, and agriculture analy-
ses will aid in better understanding potential
impacts to these sectors.
Water Supply
and Demand
-------
Warmer temperatures
under climate change are
projected to increase
precipitation intensity in
some regions of the contig-
uous U.S., raising the risk of
damaging floods.
2 The effect of global GHG
mitigation on flooding
damages is sensitive to
projected changes in
precipitation.The flooding
analysis using the
IGSM-CAM climate model,
which projects relatively
wet conditions for most of
the U.S., estimates that
mitigation will result in a
reduction in flood damages
of approximately $2.9
billion in 2100 compared
to the Reference. Using
the drier MIROC model,
the analysis projects that
mitigation will result in
disbenefits of approximately
$38 million in 2100.
52
Climate Change and
Inland Flooding
Extreme precipitation events have intensified
in recent decades across most of the U.S.,
and this trend is projected to continue.4
Heavier downpours can result in more
extreme flooding and increase the risk of
costly damages.5 Flooding affects human
safety and health, property, infrastructure,
and natural resources.6 In the U.S., non-coastal
floods caused over 4,500 deaths from 1959 to
2005 and flood-related property and crop
damages averaged nearly $8 billion peryear7
from 1981 to 2011.8The potential for
increased damages is large, given that climate
change is projected to continue to increase
the frequency of extreme precipitation events and amplify risks from non-climate factors such
as expanded development in floodplains, urbanization, and land-use changes.9
Risks of Inaction
Without GHG mitigation, climate change under the IGSM-CAM projections is estimated to
increase monetary damages associated with inland flooding across most of the contiguous U.S.
Figure 1 presents the projected flood damages in 2050 and 2100 under the Reference scenario.
As shown, substantial damages are projected to occur in more regions over time. By 2100, dam-
ages are projected to be significantly different from the historic period (at a 90% confidence
interval) in 11 of the 18 large watersheds (2-digit hydrologic unit codes). The greatest damages
are projected to occur in the eastern U.S. and Texas, with damages in these regions ranging
from $1.0-$3.7 billion in 21OO.10 Projections of increased flood damages across most of the U.S.
are consistent with the findings of the assessment literature.11
Figure 1. Estimated Flood Damages Due to Unmitigated Climate Change
Estimated flood damages under the Reference scenario in 2050 and 2100 for the IGSM-CAM climate model
(millions 2014$). Results are presented for the 18 2-digit hydrologic unit codes (HUCs) of the contiguous U.S.
Stippled areas indicate regions where the projected damages are significantly different from
the historic period (at a 90% confidence interval).
2050
2100
< 100
Millions of Dollars
101-500 •501-1,000 I • 1,001-2,000 ^•2,001-3,700
-------
Reducing Impacts through
GHG Mitigation
Under the relatively
wetter IGSM-CAM
climate projections,
global GHG mitigation is
projected to result in
increased flooding
damages compared to
today, but decreased
damages compared to
the Reference scenario
in most regions of the
contiguous U.S. As
shown in Figure 2,
damages are reduced in
10 out of 18 regions in
2050 and in 14 out of 18
regions in 2100, with
particularly pronounced differences between
the scenarios in 2100. In 2100, the modeled
reduction in damages is approximately $2.9
billion. By the end of the century, substantial
benefits are projected over much of the Great
Plains and Midwest regions, where damages
are estimated to be reduced between 30%
and 40% in many states.The four regions not
showing benefits of GHG
mitigation under the
IGSM-CAM projections
are located in the western
part of the U.S., which
also faces the highest risk
of drought, as described
in the Drought section of
this report.
Figure 2 also presents
results using the MIROC
climate model, which
projects a drier future
compared to the
IGSM-CAM model. Under
the MIROC projections,
flooding damages are
generally reduced under both the Reference
and Mitigation scenarios and, as a result,
there are modest disbenefits of mitigation
across most of the contiguous U.S. in 2050
and 2100. In 2100, damages are projected
to increase nationally by $38 million under
the Mitigation scenario compared to the
Reference.
Figure 2. Change in Flooding Damages Due to Global GHG Mitigation
Percent change in flooding damages for the Mitigation scenario compared to the Reference.
Results are presented for the 18 2-digit HUCs of the contiguous U.S. Negative values, shown in green,
reflect reductions in flooding damages from global GHG mitigation.
2050
2100
IGSM-CAM
(comparatively wet)
MIROC
(comparatively dry)
I -53% to -40%
Percent change in flooding damages
•-39% to-30% •-29%toO% •l%to30%
131% to 132%
less damages
more damages
The CIRA analysis quantifies how
climate change could affect inland
flooding damages in the contiguous
U.S. Given the complexities inherent
in projecting national flood damages,
including the need for small water-
shed-scale hydrologic modeling, the
results presented in this section should
be considered first-order estimates.
The analysis estimates changes in
inland (non-coastal) flood damages
following the approach described in
Wobus et al. (2013).12 Specifically, the
analysis applies statistical relation-
ships between historical precipitation
and observed flood damages in each
region of the U.S. to estimate the
probability of damaging events
occurring in a given year for the
baseline period (1983-2008). Flood
probabilities are then updated based
on precipitation projections for specific
events (i.e., 1-, 3-, 5-, and 7-day precipi-
tation totals) under the Reference and
Mitigation scenarios to estimate future
flood damages. The analysis relies
upon climate projections from two
climate models: IGSM-CAM, which
projects a relatively wetter future for
most of the U.S., and the drier MIROC
model. Damages are aggregated to the
18 U.S. Geological Survey National
Water Resource Regions (WRRs) for two
future periods (2050 and 2100), and are
then statistically compared to modeled
damages for the historic period.
Importantly, the estimated damages
do not include impacts on human
health or economic disruption. The
approach assumes that the distribution
of monetary damages from flooding,
including the effects of non-climate
risk factors, will not change in the
future.13 Finally, the value of damages
occurring in the future is scaled to
account for changes in wealth using
projected increases in per capita
income in the two CIRA scenarios.
For more information on the CIRA
approach and results for flooding
damages, please refer to Strzepeket
al. (2014)14and Wobus et al. (2013).15
53
-------
1 In the absence of global
GHG mitigation, climate
change is projected to
result in a pronounced
increase in the number
of droughts in the south-
western U.S.
2 Global GHG mitigation
leads to a substantial
reduction in the number
of drought months in the
southwestern U.S. in both
climate models analyzed.
The effect of GHG mitiga-
tion in other regions is
highly sensitive to
projected changes in
precipitation.
3 The reduction in drought
associated with GHG
mitigation provides
economic benefits to
the crop-based agriculture
sector ranging from
$9.3-$34 billion through
2100 (discounted at 3%).
54
Climate Change
and Drought Risk
Climate change-related impacts on temperature and
precipitation are expected to alter the location, frequency,
and intensity of droughts in the U.S., with potentially devastat-
ing socioeconomic and ecological consequences.16 Already,
many U.S. regions face increasing water management
challenges associated with drought, such as disruptions in
navigation and water shortages for irrigation. In recent
decades, recurring droughts across the West and Southeast
have had significant socioeconomic and ecological impacts.17
Risks of Inaction
Without global GHG mitigation, climate change threatens to increase the number of droughts in
certain regions of the U.S. The CIRA ana lysis uses multiple climate projections, each with unique
patterns of regional change, to estimate the change in the number of SPI and PDSI droughts
(see Approach for descriptions).18 As discussed in the CIRA Framework section of this report, the
IGSM-CAM projects a relatively wetter future for most of the contiguous U.S., while the MIROC
model projects a drier future. Figure 1 shows that, although the climate models estimate different
outcomes with respect to drought risk for the central and eastern U.S., they both project that the
Southwest will experience pronounced increases in both SPI and PDSI drought months. Some
areas of the country that are projected to experience increases in drought by 2100 a re also
projected to experience higher flooding damages (see the Inland Flooding section). This finding
should not be interpreted as a conflicting result, and is consistent with the conclusions of the
assessment literature,19 which describe the drivers of these changes as more intense yet less
frequent precipitation, and increases in evaporation due to higher temperatures.20
Figure 1. Effects of Unmitigated Climate Change on Drought Risk by 2100
Projected change in number of SPI and PSDI drought months under the Reference scenario over a
30-year period centered on 2100. Results are presented for the 182-digit hydrologic unit codes (HUCs)
of the contiguous U.S. Changes occurring in the grey-shaded areas should be interpreted as
having no substantial change between the historic and future periods.
SPI-12 Droughts
Severe and Extreme PDSI Droughts
IGSM-CAM
(comparatively wet)
MIROC
(comparatively dry)
-50 to -10
Drought Months over a 30-year Period
-9to10 lltoSO •SltolOO
1101 to 200
-------
Reducing Impacts through
GHG Mitigation
Global GHG mitigation leads to a substantial reduction in drought risk for many parts of the
country (Figures 2 and 3). Under the IGSM-CAM climate projections, GHG mitigation substantial-
ly reduces drought occurrence across the western U.S., while under the MIROC model, drought is
reduced over a majority of the country. Both climate models project reductions in drought in the
Southwest, where the risks of increased droughts were highest under the Reference.
The overall decrease in the number of droughts under the Mitigation scenario, particularly in
the West, results in substantial benefits to the crop-based agriculture sector. Through 2100, the
present value benefits of GHG
Figure 2. Percentage Change in Number of
Severe and Extreme Drought Months with and
without GHG Mitigation
Change in number ofPDSI drought months under the Reference and
Mitigation scenarios over a 30-year period centered on 2100 in the
contiguous U.S. Under both climate models, GHG mitigation
results in fewer drought months compared to the Reference.
mitigation in the agricultural
sector reach $9.3 billion (discount-
ed at 3%) using the IGSM-CAM
climate projections, compared to
the Reference. Using the drier
MIROC climate model, the
Mitigation scenario provides
benefits to the agriculture sector
of approximately $34 billion
(discounted at 3%). Projections
from both climate models
estimate higher economic
benefits of GHG mitigation in the
southwestern U.S., where drought
frequency is projected to increase
most dramatically in the absence
of GHG mitigation.
150% n
100%.
50%
IGSM-CAM
MIROC
-50%
-100%
Reference • Mitigation
Figure 3. Effect of Global GHG Mitigation on Drought Risk by 2100
Estimated change in number ofSPI and PDSI drought months under the Mitigation scenario compared to
the Reference over a 30-year period centered on 2100. Results are presented for the 18 2-digit HUCs of the
contiguous U.S. Shades of green represent reductions in the number of drought months due to
GHG mitigation. Changes occurring in the grey-shaded areas should be interpreted as having
no substantial change between the historic and future periods.
SPI-12 Droughts
Severe and Extreme PDSI Droughts
IGSM-CAM
(comparatively wet)
MIROC
(comparatively dry)
|-209to-200
Drought Months over a 30-year Period
|-199to-100 •-ggto-IO -9to10
11 to 26
The CIRA analysis estimates the effect
of climate change on the frequency
and intensity of droughts across the
contiguous U.S. The approach is based
on the methodology from Strzepek et
al. (2010).21 It relies on two drought
indices for both the historical and two
21 ^century time periods. The drought
indices account for changes in key
climate variables: the Standardized
Precipitation Indices (SPI-5 and SPI-12)
measure meteorological drought
based on change in precipitation from
the historical median, and the Palmer
Drought Severity Index (PDSI) uses
precipitation and temperature data
to estimate the relative changes in
a particular region's soil moisture.
Drought risk is calculated for 99
sub-basins or watersheds in the
contiguous U.S. and aggregated to
18 2-digit HUC regions.
The analysis then estimates the
effect on crop-based agriculture of the
change in frequency and intensity of
droughts under the CIRA climate
projections. This approach projects
impacts using a sectoral model that
relates historical drought occurrence
with impacts on crop outputs.22The
resulting relationships are then
applied to climate projections under
the CIRA Reference and Mitigation
scenarios using the IGSM-CAM and
MIROC climate models to estimate the
economic impacts of climate change
and effects of GHG mitigation.23This
analysis only monetizes the impacts of
drought on crop-based agriculture,
and does not include other damages
(e.g., decreased water availability,
ecosystem disruption). Therefore the
results estimated here likely underesti-
mate the benefits of GHG mitigation
for this sector.
For more information on the
CIRA approach and results for
the drought sector, please refer
to Strzepek et al. (2014)24and
Boehlertetal. (2015).25
55
-------
1 Unmitigated climate
change is projected to
have profound impacts
on both water availability
and demand in the U.S.,
compounding challenges
from changes in demo-
graphics, land use, energy
generation, and socioeco-
nomic factors.
2 Without global GHG
mitigation, damages
associated with the supply
and demand of water
across the U.S. are estimat-
ed to range from approxi-
mately S7.7-S190 billion in
2100. The spread of this
range indicates that the
effect of climate change on
water supply and demand
is highly sensitive to pro-
jected changes in runoff
and evaporation, both of
which vary greatly across
future climate projections
and by U.S. region.
3 Global GHG mitigation is
estimated to substantially
decrease damages com-
pared to the Reference.
Projected benefits under
the Mitigation scenario
range from $11-$180 billion
in 2100, depending on
projected future climate.
Importantly, global GHG
mitigation is projected to
preserve water supply and
demand conditions more
similar to those experi-
enced today.
56
Climate Change and Water
Supply and Demand
Water management in the U.S. is characterized
by the struggle to balance growing demand
from multiple sectors of the economy with
increasingly limited supplies in many areas.
Unmitigated climate change is projected to
have profound impacts on both water availabili-
ty and demand in the U.S., compounding
challenges from changes in demographics, land
use, energy generation, and socioeconomic
factors. As temperatures rise and precipitation
patterns become more variable, changes in regional water demand and surface and groundwater
supplies are expected to increase the likelihood of water shortage for many areas and uses.26
Risks of Inaction
The effect of climate change on water supply and demand is highly sensitive to projected
changes in runoff and evaporation, both of which vary across future climate projections and
by U.S. region (Figure 1). Despite these variations, increased damages of unmitigated climate
change are projected in the Southwest and Southeast regions under both climate models, and
these damages increase over time. These projections are consistent with the findings of the
assessment literature.27 Using climate projections from the IGSM-CAM model, the analysis
estimates damages at $7.7 billion in 2100. Despite the majority of U.S. regions showing modest
increases in welfare (economic well-being) in 2100, the damages in the Southwest and
Southeast are much larger in magnitude, and therefore drive the national total. Highlighting
the sensitivity of this sector to the climate model used, the drier MIROC model estimates that
net damages could be substantially larger, at approximately $190 billion in 2100.
Figure 1. Projected Impacts of Unmitigated Climate Change on
Water Supply and Demand
Estimated change in economic damages under the Reference scenario in 2050 and 2100 compared to the
historic baseline for the IGSM-CAM and MIROC climate models (millions 2014$). Results are presented for the
182-digit hydrologic unit codes (HUCs) of the contiguous U.S. Yellow, orange, and red areas indicate increased
damages, while blue areas indicate decreased damages.
2050
2100
IGSM-'
(comparatively wet)
MIROC
(comparatively dry)
-2,000 to 0
1 to 500
501 to 1,000
Millions of Dollars
• 1,001 to 10,000 |
|10,001 to 20,000
|20,001 to 53,000
-------
Reducing Impacts through
GHG Mitigation
Global GHG mitigation is projected to substantially reduce damages compared to the Reference
(Figures 2 and 3), and importantly, preserve water supply and demand conditions more similar
to those experienced today.The IGSM-CAM model estimates that damages are $7.7 billion
under the Reference scenario in 2100, while the Mitigation scenario results in an increase in
welfare (collective economic well-being of the population) of $3.4 billion. Therefore, mitigation
is estimated to result in a total increase in welfare of $11 billion in 2100 compared to the
Reference. Using the drier MIROC model, the Mitigation scenario yields damages of approxi-
mately $19 billion in 2100; however, this represents avoided damages of approximately $180
billion compared to the Reference scenario (numbers do not sum due to rounding).
Figure 2. Economic Damages Associated with Impacts on Water Supply and
Demand with and without Global GHG Mitigation
„ 240
T3
(U
I 190
"c 140
? 90
o
-10 -
IGSM-CAM MIROC
2050
IGSM-CAM MIROC
2100
I Reference • Mitigation
Figure 3. Projected Impacts of GHG Mitigation on Water Supply and Demand
Estimated percent change in economic damages under the Mitigation scenario in 2050 and 2100 relative to the
Reference. Results are presented for the 18 2-digit HUCs of the contiguous U.S. Negative values (shown in green)
indicate decreases in damages, or positive economic benefits, due to global GHG mitigation.
2050
2100
IGSM-CAM
(comparatively wet)
MIROC
(comparatively dry)
|-200to-100
Percent Change in Economic Damages
-9910-50 •-49 toO 1 to 100
1101 to 200
The CIRA analysis estimates the
economic impacts associated with
changes in the supply and demand
of water, based on a national-scale
optimization model developed by
Henderson et al. (2013).28 The model
simulates changes in supply and
demand in 99 sub-regions or water-
sheds of the contiguous U.S. based on
changes in runoff and evaporation,
population, irrigation demand, and
other inputs that vary over time.
Economic impact functions are applied
for a range of water uses including
irrigated agriculture, municipal and
domestic water use, commercial and
industrial water use, hydroelectric
power generation, and in-stream
flows.29The benefits from water use
are maximized according to a wide
range of constraints, such as storage
and conveyance capacities, historic
irrigated acreage, and renewable
recharge capacity for groundwater.
Economic damages are incurred in the
model when any one of the water
uses specified above does not receive
sufficient volume to sustain the
baseline activity level. Impacts are
summed across all uses in each
sub-region and reported as changes in
economic welfare. Finally, the optimi-
zation model is driven by climate
projections from the IGSM-CAM, as
well as the MIROC climate model,
which projects a relatively drier future
for the contiguous U.S. compared to
other climate models.30
For more information on the CIRA
approach and results for the water
supply and demand analysis, please
refer to Strzepeket al. (2014)31 and
Henderson etal. (2013).32
57
-------
Crop and
Forest Yields
-------
The U.S. has a robust agriculture sector
that produces nearly $330 billion per
year in agricultural commodities.1 The
sector ensures a reliable food supply and
supports job growth and economic develop-
ment.2 In addition, as the U.S. is currently the
world's leading exporter of agricultural prod-
ucts, the sector plays a critical role in the
global economy.3
U.S. forests provide a number of important
goods and services, including timber and other
forest products, recreational opportunities,
cultural resources, and habitat for wildlife.
Forests also provide opportunities to reduce
future climate change by capturing and storing
carbon, and by providing resources for bio-
energy production.4
HOW ARE AGRICULTURE AND FORESTRY
VULNERABLE TO CLIMATE CHANGE?
U.S. agricultural and forest production are
sensitive to changes in climate, including
changes in temperature and precipitation,
more frequent and severe extreme weather
events, and increased stress from pests and
diseases.5 At the same time, climate change
poses an added risk to many forests due to
ecosystem disturbance and tree mortality
through wildfire, insect infestations, drought,
and disease outbreaks.6 Climate change has the
potential to both positively and negatively
affect the location, timing, and productivity of
agricultural and forest systems, with economic
consequences for and effects on food security
and timber production both in the U.S. and
globally.7'8 Adaptation measures, such as
changes in crop selection, field and forest
management operations, and use of technolog-
ical innovations, have the potential to delay
and reduce some of the negative impacts of
climate change, and could create new opportu-
nities that benefit the sector.
WHAT DOES CIRA COVER?
The CIRA analysis estimates climate change
impacts on the agriculture and forestry sectors
using both biophysical and economic models.
The agriculture analyses demonstrate effects
on the yield and productivity of major crops,
such as corn, soybean, and wheat, but do not
include specialty crops, such as tree fruits, or
livestock. Further, the analysis does not explic-
itly model impacts on biofuel production or
include technological advances in agricultural
management practices. The analyses include
yield and productivity impacts, but do not
simulate the effects of changes in wildfire,
pests, disease, and ozone. Future work to
improve the multiple interactions among the
CIRA energy, water, and agriculture analyses
will aid in better understanding potential
impacts to these sectors.
Market Impacts
-------
KEY FINDINGS
Unmitigated climate
change is projected to
result in substantial de-
creases in yields for most
major agricultural crops.
2 Global GHG mitigation is
projected to substantially
benefit U.S. crop yields
compared to the Reference
scenario.
3 Without considering the
influence of wildfires, the
effect of GHG mitigation on
forest productivity is less
substantial compared to
the response for crops.The
direction of the effect de-
pends strongly upon climate
model and forest type
(hardwood vs. softwood).
60
Risks of Inaction
Without significant global GHG mitigation, climate change is projected to have a large negative
impact on the U.S. agriculture sector. Table 1 presents the projected percent change in national
crop yields in 2100 due to unmitigated climate change under the Reference scenario. For all
major irrigated crops, with the exception of hay, climate projections from both the IGSM-CAM
and MIROC models result in decreased yields, with very substantial declines projected for
soybeans, sorghum, and potatoes. For rainfed crops, climate projections using the drier MIROC
climate model result in substantial declines for all crops, particularly cotton, sorghum, hay,
wheat, and barley. Rainfed yields using the wetter IGSM-CAM climate model are more varied,
ranging from a substantial decrease in hay yields to moderate gains in cotton, sorghum, and
wheat yields.9 Projected declines in crop productivity resulting from unmitigated climate change
over the longer term are consistent with the findings of the assessment literature.10
As shown in Figure 1,the effect of unmitigated climate change on forest productivity in the
U.S. varies over time and depends on the climate model used. Using the IGSM-CAM projections,
hardwood yields increase by 2100, while the change in softwood yields is very small. Projec-
tions using the drier MIROC climate model result in increased hardwood and softwood yields
by the end of the century, though the gains are smaller than those projected under the
Mitigation scenario.
Table 1. Projected Percent Change in U.S. Crop Yields in 2100
without Global GHG Mitigation
Estimates in this table assume no technological improvements in yields over time such that crop productivity
in future periods relative to a scenario with no climate change is based purely on differences in climatic
conditions. This assumption allows the analysis to isolate and evaluate climate change impacts on crops
without confluence with other factors. Results do not include effects from changes in ozone, pests, and disease.
Rice and potatoes are simulated under irrigated management only."
CROP
Cotton
Corn
Soybean
Sorghum
Rice
Hay
Potato
Wheat
Barley
IGSM-CAM
RAINFED
17%
6%
-5%
18%
n/a
-62%
n/a
18%
-16%
IRRIGATED
-11%
-3%
-20%
-17%
-3%
29%
-33%
-8%
-22%
MIROC
RAINFED
-27%
-8%
-19%
-29%
n/a
-65%
n/a
-19%
-29%
IRRIGATED
-17%
-10%
-23%
-22%
-3%
32%
-39%
-13%
-11%
Figure 1. Projected Change in Potential Forestry Yields with and without
Global GHG Mitigation
Percent change in potential hardwood and softwood yields across the U.S. relative to the base period
(1980-2009) under the Reference and Mitigation scenarios for the IGSM-CAM and MIROC climate models.
Effects of wildfire, pest, and disease on yields are not included.
IGSM-CAM
-3%
MIROC
2010 2025
2050
2075
2100
2010 2025
2050
2075
2100
— — Reference - Softwood — — Mitigation - Softwood
Reference - Hardwood ^^— Mitigation - Hardwood
-------
Reducing Impacts through
GHG Mitigation
ROACH
Global GHG mitigation is estimated to
substantially benefit U.S. crop yields. Figure 2
presents the projected change in national
crop yields for key crops under the Mitigation
scenario compared to the Reference. The
figure shows changes in rainfed and irrigated
yields using projections from the IGSM-CAM
climate model and the relatively drier MIROC
model. In general, the benefits to crop yields
of global GHG mitigation increase over the
course of the century, with the exception of
rainfed hay (for both climate models) and
rainfed sorghum (for IGSM-CAM). Global GHG
mitigation is projected to have a particularly
positive effect on the future yields of irrigated
soybeans, irrigated potatoes, and irrigated
and rainfed barley.
The projected effect of GHG mitigation on
forest productivity is less substantial compared
to the response for crops. Figure 1 shows the
estimated percent change in average national
forest productivity (contiguous U.S.) under
the Reference and Mitigation scenarios
relative to the base period. Although forest
productivity generally increases with climate
change under both scenarios, projections
using the relatively wetter IGSM-CAM climate
model result in larger gains underthe
Reference scenario, particularly for hard-
woods. Higher forest productivity under the
IGSM-CAM Reference in the future is likely
driven by the enhanced positive effects of
C02 fertilization under the high-emission
Reference, along with the response to increas-
es in precipitation in many areas of the
contiguous U.S. that are forested. The MIROC
climate projections, on the other hand, result
in slightly rising yields of both hardwoods
and softwoods through 2100 under the
Mitigation case. It is important to note that
these yield estimates do not include the
effects of wildfire, pests, or disease, which
would likely decrease simulated productivity
based on the findings of the assessment
literature,12 especially under the Reference
scenario (See Wildfire section of this report).13
Figure 2. Projected Impacts of Global GHG Mitigation on Crop Yields
Percent change in crop yields from the EPIC model in the contiguous U.S. under the Mitigation
scenario compared to the Reference for the IGSM-CAM and MIROC climate models." Rice and potatoes
are simulated under irrigated management only.
Rainfed
Irrigated
IGSM-CAM
-20%J -20%
2010 2025 2050 2075 2100 2010 2025 2050 2075 2100
60%
40%
MIROC
20%
-20% J -20%
2010 2025 2050 2075 2100 2010 2025 2050 2075 2100
Barley Corn ^Cotton ^Hay
Rice Sorghum ^—Soybeans ^— Wheat
-Potatoes
The analysis uses the Environmental Policy
Integrated Climate (EPIC) model15-16 to
simulate the effects of climate change on
crop yields in the contiguous U.S. The
analysis examines agricultural crop
productivity for multiple crops, including
corn, soybean, wheat, alfalfa hay, sor-
ghum, cotton, rice, barley, and potatoes.
Yield potential is simulated for each crop
for both rainfed and irrigated production
with the exception of rice and potatoes,
which are assumed to be irrigated.17
Because production regions may change
over time in response to climate change,
EPIC simulates potential cultivation and
production in areas within 100 km (62
miles) of historical production regions.
EPIC is driven by changes in future
climate from both the IGSM-CAM18 and
MIROC climate models under the Reference
and Mitigation scenarios. The results
presented in this section include the effect
of C02 fertilization on crop yields; Beach et
al. provide a sensitivity ana lysis of the effect
of C02 fertilization on the crop yield results
from EPIC.
Changes in forest growth rates are
simulated using the MCI dynamic
vegetation model, consistent with the
approach described in Mills et al. (2014)19
and the Wildfire and Carbon Storage
sections of this report.20 MCI is also driven
by the IGSM-CAM and MIROC models, and
assumes full C02 fertilization effects.
The effects of changes in wildfires,
pests, disease, and ozone are not captured
in this analysis.21 Inclusion of these effects
on crop and forest yields would likely
result in increased benefits of GHG
mitigation compared to those presented
in this section.
For more information on the CIRA
approach and results for agriculture
and forestry crop yields analysis,
please refer to Beach et al.22
61
-------
KEY FINDINGS
Based on the projected
changes in yields, global
GHG mitigation is estimat-
ed to result in lower crop
prices over the course of
the 21st century compared
to the Reference.
Changes in crop and forest
productivity alter related
market dynamics, land
allocation, crop mix, and
production practices,
which in turn affect GHG
emissions and carbon
sequestration from the
agriculture and forestry
sectors. Global GHG mitiga-
tion has a large effect on
emissions fluxes in man-
aged forests: however, the
magnitude and direction of
the effect are sensitive to
climate model projection.
3 Under both climate model
projections, global GHG
mitigation increases total
economic welfare in the
agriculture and forestry
sectors by $43-$59 billion
(discounted at 3%) through
2100 compared to the
Reference.The magnitude
of estimated economic
welfare impacts in the
agricultural sector is much
larger than in the forestry
sector.
62
Changes in Crop Price
As described in the Crop and Forest Yields
section of this report, global GHG mitigation
is projected to result in generally higher crop
yields in the U.S. relative to the Reference. As
a result, mitigation is projected to result in
less pressure on land resources and declining
commodity prices. As shown in Figure 1,
climate projections from both the IGSM-CAM
and MIROC climate models show steep
declines in a broad index of crop prices starting
around 2040. Projections using the drier
MIROC climate model result in greater declines
in crop prices by the end of the century than
those using the wetter IGSM-CAM model.
Adverse effects of climate change on crop and
food prices, which are largely avoided in the
Mitigation scenario, are consistent with the
findings of the assessment literature.23
Figure 1. Projected Change in
National Crop Price Index Due to
Global GHG Mitigation
Percent change in crop price index under the
Mitigation scenario relative to the Reference for
the IGSM-CAM and MIROC climate models.
2010 2025 2050 2075
—IGSM-CAM —MIROC
2100
Changes in Emissions
Changes in land allocation, crop mix, and production practices in turn affect GHG emissions from
agriculture and forestry practices. Figure 2 shows the estimated changes in cumulative GHG
emissions under the Mitigation scenario compared to the Reference using projections from the
IGSM-CAM and MIROC climate models. Under the IGSM-CAM projections, GHG mitigation is
estimated to increase net GHG emissions from these sectors in the second half of the century.
The increase is due in large part to the generally lower forest productivity that is projected to
occur under the Mitigation scenario compared to the Reference, as the latter has higher
productivity driven by the generally warmer and wetter future climate, as well as the enhanced
positive effects of C02 fertilization (see the Crop and Forest Yields section). Thus, global GHG
mitigation results in less forest carbon sequestration over time. Higher levels of carbon storage
in forests under the generally warmer and wetter future of the IGSM-CAM Reference scenario
are consistent with the findings presented in the Carbon Storage section of this report.
Under the MIROC climate projections, on the other hand, forest productivity is enhanced
under the Mitigation scenario relative to the Reference, and forests take up and store more
carbon. In addition, although emissions from livestock agriculture rise, GHG emissions related
to crop production generally decline as less area is devoted to crops due to higher yields.
Figure 2. Projected Changes in Accumulated GHG Emissions in the Agriculture
and Forestry Sectors Due to Global GHG Mitigation
Projected change in cumulative GHG emissions by type under the Mitigation scenario relative to the Reference
for the IGSM-CAM and MIROC climate models (billion metric tons of C02 equivalent).
6-
4-
2-
-2-
-4-
-6-
-8-
-10-
-12-
IGSM-CAM
Ill
010 2025 2050 2075
6-
III I
-2-
-4-
-6-
-8-
-10-
-12-
2100 2
MIROC
' ' ' ' 1 IjTMT 1
II
010 2025 2050 2075 210
I Forest Management
Afforestation
I Crop Management Fuels
Soil Sequestration
I Agricultural CH4&N2O
-------
Changes in Consumer and
Producer Surplus
The changes in crop prices and the level of
production and consumption of agriculture
and forestry products have important
implications for the economic welfare of
consumers and commodity producers. The
analysis measures these effects through
changes in consumer and producer surplus,24
as summarized in Table 1. Using both climate
model projections, global GHG mitigation
increases total economic welfare (well-be-
ing) in the agriculture and forestry sectors by
$43 to $59 billion (discounted at 3%) through
2100 compared to the Reference. Estimated
consumer surplus is higher under the drier
MIROC conditions than it is under the
IGSM-CAM, primarily due to the larger crop
yields under the Mitigation scenario
compared to the Reference (see the Crop
and Forest Yields section).
The effect of global GHG mitigation on
producer surplus varies depending on the
climate model used. The IGSM-CAM climate
projections result in an increase in producer
surplus, though not as substantial as the
projected increase in consumer surplus. The
drier MIROC projections result in a slight
decrease in producer surplus due to the
substantial increase in crop yields and
resulting decrease in prices.
Table 1. Projected Effect of Global GHG Mitigation on Consumer and
Producer Surplus in the Agriculture and Forestry Sectors
Change in cumulative consumer and producer surplus from 2015-2100 under the Mitigation scenario
compared to the Reference (million 2014$, discounted at 3%). Results are rounded to two significant digits
and therefore may not sum. In addition, the agriculture and forestry results do not sum to totals
due to rounding, and because the table reflects independently calculated average
values for agriculture, forestry, and combined totals.
IGSM-CAM
Agriculture
Forestry
TOTAL
MIROC
Agriculture
Forestry
TOTAL
CONSUMER SURPLUS
$29,000
$67
$29,000
$62,000
-$160
$62,000
PRODUCER SURPLUS
$13,000
$350
$14,000
-$3,300
$920
-$2,400
TOTAL
$43,000
$420
$43,000
$59,000
$750
$59,000
The CIRA analysis uses the Forest and
Agricultural Sector Optimization Model
with Greenhouse Gases (FASOM-GHG)25-26
to estimate changes in market outcomes
associated with projected impacts of
climate change on U.S. crop and forest
yields. As described in the previous section,
projected yields across regions and crop/
forest types are generated by the EPIC and
MCI models. FASOM-GHG is driven by
changes in potential yield from EPIC and
MCI for each of the five initializations of
the IGSM-CAM climate model for both the
Reference and Mitigation scenarios,27 as
well as the drier MIROC climate model.
FASOM-GHG simulates landowner
decisions regarding crop mix and produc-
tion practices, and projects the allocation
of land over time to competing activities in
both the forest and agricultural sectors and
the associated impacts on commodity
markets.28 Given the changes in potential
yields projected by EPIC and MCI,
FASOM-GHG uses an optimization
approach to maximize consumer and
producer surplus over time.29-30The model
is constrained such that total production is
equal to total consumption, total U.S. land
use remains constant (with the potential
movement of land from forest to agricul-
ture and vice versa), and non-climate
drivers in the agriculture and forestry
sectors are consistent between the
scenarios to isolate the effect of climate
change. In addition, the analysis assumes
no price incentives for avoiding GHG
emissions or carbon sequestration in the
agriculture and forestry sectors (i.e., the
sectors do not participate in the global
GHG mitigation policy). Finally, although
the EPIC simulations assume that crops
can be irrigated to a level that eliminates
water stress, the FASOM-GHG simulations
include shifts in water availability for
irrigation based on data obtained from
the water supply/demand framework
described in the Water Quality section of
this report.31
For more information on the CIRA
approach and results for the FASOM-
GHG agriculture and forestry market
impacts analysis, please refer to Beach
etal.32
63
-------
stems
-------
An ecosystem is a community of
organisms interacting with each
other and their environment.
People, animals, plants, microbes, water,
and soil are typical components of ecosystems.
We constantly interact with the ecosystems
around us to derive and maintain services
that sustain us and contribute to our liveli-
hoods. Clean air and water, habitat for
species, and beautiful places for recreation
are all examples of these goods and services.
With the diversity of ecosystem types in the
U.S. being so great—from the tidal marshes of
the East Coast to the desert valleys of the
Southwest to the temperate rainforests of the
Pacific Northwest—climate change is likely to
fundamentally alter our nation's landscape
and natural resources.1
HOW ARE ECOSYSTEMS VULNERABLE
TO CLIMATE CHANGE?
Ecosystems are held together by the interac-
tions and connections among their compo-
nents. Climate is a central connection in all
ecosystems. Consequently, changes in climate
will have far-reaching effects throughout
Earth's ecosystems. Climate change can affect
ecosystems and species in a variety of ways;
for example, it can lead to changes in the
timing of seasonal life-cycle events, such as
migrations; habitat shifts; food chain disrup-
tions; increases in pathogens, parasites, and
diseases; and elevated risk of extinction for
many species.2
Climate change directly affects ecosystems
and species, but it also interacts with other
human stressors on the environment. Al-
though some stressors cause only modest
impacts by themselves, the cumulative impact
of climate and other changes can lead to
dramatic ecological impacts. For example,
coastal wetlands already in decline due to
increasing development will face increased
pressure from rising sea levels.
WHAT DOES CIRA COVER?
CIPvA analyzes the potential benefits of global
GHG mitigation on coral reefs and freshwater
fisheries in the U.S., focusing on changes in
recreational use of coral reefs and recreational
fishing. This section also examines the project-
ed impacts of ocean acidification on the U.S.
shellfish market. Lastly, CIPvA quantifies the
physical and economic impacts of climate
change on wildfires and terrestrial ecosystem
carbon storage. Climate change will affect
many species and ecosystems beyond what is
explored in this report; consequently, CIPvA
captures only a glimpse of the potential
benefits of GHG mitigation on this sector.
-------
1 Coral reefs are already
disappearing due to
climate change and other
non-climate stressors.
Temperature increases and
ocean acidification are
projected to further reduce
coral cover in the future.
2 Without global GHG miti-
gation, extensive loss of
shallow corals is projected
by 2050 for major U.S. reef
locations. Global GHG
mitigation delays Hawaiian
coral reef loss compared to
the Reference scenario, but
provides only minor bene-
fits to coral cover in South
Florida and Puerto Rico, as
these reefs are already close
to critical thresholds of
ecosystem loss.
3 GHG mitigation results in
approximately $22 billion
(discounted at 3%) in
recreational benefits
through 2100 for all three
regions, compared to a
future without emission
reductions.
66
Climate Change and
Coral Reefs
Coral reefs, including those found in Hawaii and the
Caribbean, are unique ecosystems that are home to
large numbers of marine plantand animal species.
They also provide vital fish spawning habitat, protect
shorelines, and are valuable for recreation and
tourism. However, shallow-water coral reefs are highly
vulnerable to climate change.3 High water tempera-
tures can cause coral to expel the symbiotic algae
that provide nourishment and vibrant color for their
hosts.This coral bleaching can cause the coral to die.
In addition, ocean acidification (ocean chemistry
changes due to elevated atmospheric C02) can
reduce the availability of certain minerals in seawater
that are needed to build and maintain coral skeletons.
Risks of Inaction
Without GHG mitigation, continued warming and ocean acidification will have very significant
effects on coral reefs. For major U.S. reefs, projections under the Reference show extensive
bleaching and dramatic loss of shallow coral cover occurring by 2050, and near complete loss by
2100. In Hawaii, coral cover is projected to decline from 38% (current coral cover) to approximate-
ly 5% by 2050, with further declines thereafter. In Florida and Puerto Rico, where present-day
temperatures are already close to bleaching thresholds and where these reefs have historically
been affected by non-climate stressors, coral is projected to disappear even faster.4This drastic
decline in coral reef cover, indicating theexceedance of an ecosystem threshold, could have
significant ecological and economic consequences at regional levels.These projections of shallow
coral loss for major U.S. reefs are consistent with the findings of the assessment literature.5
Figure 1. Projected Impact of Unmitigated Climate Change on
Coral Reef Cover in the U.S.
Approximate reduction in coral cover at each location under the Reference scenario relative to
the initial percent cover. Coral icons do not represent exact reef locations. Results for 2075
are omitted as there is very little change projected between 2050 and 2100.
2010 2025 2050 2100
Hawaii
South
Florida
Puerto
Rico
Percent coral cover 25%
Percent coral cover
Percent coral cover 1 %
Percent coral cover 1 %
-------
Reducing Impacts through
GHG Mitigation
Figure 2. Percent Change in Coral Reef
Cover with and without Global GHG
Mitigation at Major U.S. Reefs
40
30
20
10
Hawaii
Reference
^—Mitigation
0
2010 2025
2050
2075
2100
40
30
20
South Florida
Mitigating global GHG emissions can reduce
only some of the projected biological and
economic impacts of climate change on coral
reefs in the U.S. Figure 2 shows projected coral
reef cover over time in Hawaii, South Florida,
and Puerto Rico under the Reference and
Mitigation scenarios. In Hawaii, the decline in
reef cover slows under the Mitigation scenario
compared to the Reference, as some of the
extensive bleaching episodes and effects of
ocean acidification are avoided. But even
under the Mitigation scenario, Hawaii is
projected to eventually experience substantial
reductions in coral cover. In South Florida and
Puerto Rico, the projected GHG emission
reductions associated with the Mitigation
scenario are likely insufficient to avoid
multiple bleaching and mortality events by
2025, and coral cover declines thereafter
nearly as fast as in the Reference.
The delay in the projected decline of coral
results in an estimated $22 billion in economic
benefits for recreation across the three sites
through 2100 (discounted at 3%).The majority
of these recreational benefits are projected for
Hawaii, with an average value through 2100 of
approximately $20 billion (95% confidence
interval of $10-$30 billion). In Florida, where
coral reefs have already been heavily affected,
recreational benefits are also positive, but
notably lower at approximately $1.4 billion (95% confidence interval of $0.74-$2.1 billion). In
Puerto Rico, benefits are estimated at $0.38 million (95% confidence interval of $0.20-$0.57
million), but only represent recreational benefits for permanent residents, and therefore are
not directly comparable to the other locations where visits from nonresident tourists are also
included. Including the economic value of other services provided by coral reefs, such as
shoreline protection and fish-rearing habitat, would increase the benefits of mitigation.
o
2010 2025
2050
Puerto Rico
2075
2100
0
2010 2025
2050
2075
2100
The CIRA analysis examines the
physical and economic impacts of
climate change and ocean acidifica-
tion on coral reefs in Hawaii, South
Florida, and Puerto Rico. Using the
COMBO (Coral Mortality and Bleach-
ing Output) model,6'7 the analysis first
estimates declines in coral reef cover
(a measure of coral reef health and
density) using projections of future
ocean temperature (from the
IGSM-CAM) and chemistry under the
CIRA Reference and Mitigation
scenarios.8 The effects of future
bleaching events are also estimated.
Next, the analysis quantifies the
economic impacts associated with
coral reef cover loss based on declines
in reef-based recreation.The analysis
estimates these impacts using a
benefit-transfer approach; that is, it
draws on reef-related recreation
benefits measured in previously
published studies conducted at a
range of coral reef sites to estimate
the value of reef-related recreation
benefits in the areas considered in
this study.9 Projected impacts to
recreation at each site are provided
with confidence intervals based on
the 95% interval for per-trip recre-
ational values.
For more information on the CIRA
approach and results for the coral
reef sector, please refer to Lane et
al. (2013)10 and Lane et al. (2014).11
rnRAi rnvFRAfiF REPRESENTATIVE PHOTOS
UJKAL LOVtKAfct QF CORA|_ REEF DECUNE
HEALTHY REEF
40-75% live coral cover
SEVERELY DEGRADED REEF
10-25% live coral cover
NEARLY DEAD REEF
<10% live coral cover
67
-------
I
1 Without global GHG
mitigation, the harvests
of some shellfish in the U.S.
are projected to decline by
32%-48% by the end of
the century due to ocean
acidification, though
estimated impacts vary
by species.
2 Demand for shellfish is
projected to increase
through the end of the
century with a growing
population and rising
incomes, exacerbating
the economic impacts in
this sector.
3 Global GHG mitigation is
projected to avoid $380
million in consumer losses
in 2100 compared to the
Reference scenario by
preventing most of the
decreases in the supply of
select shellfish and the
resulting price increases.
68
Ocean Acidification
and Shellfish
The ocean absorbs about one quarter of the C02 released into the atmosphere by human
activities, primarily from the combustion of fossil fuels. Although the ocean's ability to absorb
C02 prevents atmospheric levels from climbing even higher, measurements made over the last
few decades have demonstrated that marine C02 levels have risen, leading to an increase in
acidity (Figure I).12 Ocean acidification is projected to adversely affect a number of valuable
marine ecosystem services by making it more difficult for many organisms to form shells and
skeletons.13 Some shellfish are highly vulnerable to ocean acidification14 and any impacts to
these species are expected to negatively affect the economy. Certain species have high
commercial value; for example, each year in the U.S., oysters, clams, and scallops supply 170
million pounds of seafood valued at $400 million.15
Figure 1. Ocean Acidification Impact Pathway for Shellfish
CO2 and other
greenhouse gases
mix in atmosphere
1
Fishermen
experience decreases
in harvest
Consumers face
changes in prices
lil
Oceans absorb about V4 of
anthropogenic COi emissions
r^\
Dissolved COz changes
ocean chemistry and
reduces availability of
minerals for shell-building
plants and animals
Acidification reduces the size
and abundance of shellfish
Risks of Inaction
The pace of ocean acidification is accelerating.
Since the Industrial Revolution, the average
pH of surface ocean waters has fallen by 0.1,
representing a nearly 30% increase in
acidity.16 Under the Reference scenario, ocean
acidification is projected to cause pH to drop
an additional 0.3, representing a 100%
increase in acidity from pre-industrial times.
Continued ocean acidification is estimated to
reduce the supply of oysters, scallops, and clams in 2100 by 45% (13 million pounds per year),
48% (21 million pounds), and 32% (31 million pounds), respectively (Figure 2).These decreases
in supply are projected to result in price increases by 2100 of approximately $2.20 (a 68%
increase from 2010), $9.10(140%), and $1.30(123%) per pound, respectively, and lead to
consumer losses of roughly $480 million per year by the end of the century. These projections
are consistent with the findings of the assessment literature, which describe reduced growth
and survival of U.S. shellfish stocks due to unmitigated ocean acidification.17
-------
Reducing Impacts through
GHG Mitigation
Reducing global GHG emissions can mitigate the ecological and economic impacts of
ocean acidification. Figure 2 shows how the supplies of oysters, scallops, and clams
are projected to fall with ocean acidification under the Reference and Mitigation
scenarios. Although supplies are estimated to decrease under both scenarios relative
to present-day supplies, the Mitigation scenario avoids a majority of the impacts,
particularly for clams. In 2100, global GHG mitigation is projected to avoid the loss of
54 million pounds of oysters, scallops, and clams, or 34% of the present-day U.S.
oyster supply, 37% of the scallop supply, and 29% of the clam supply.
Figure 2 also indicates how the increase in demand and the decrease in supply
are estimated to affect prices by 2100 for these shellfish under the two scenarios.
Consumers are likely to substitute away from these shellfish as their prices increase,
but not entirely, and not without some decrease in satisfaction. The Mitigation
scenario keeps prices much closer to current levels, as indicated in Figure 2, resulting
in smaller consumer losses in the shellfish market. In 2100, the benefits to shellfish
consumers from global GHG emissions reductions under the Mitigation scenario are
estimated at $380 million. The cumulative benefits over the century are estimated at
$ 1.9 billion (discounted at 3%).
Figure 2. Estimated Impacts on the U.S. Shellfish Industry
Projected changes in the supplies and prices of oysters, scallops, and clams through 2100 under the
Reference and Mitigation scenarios relative to the base period.
ROACH
Percent Change
in Supply
Savings due to
Mitigation
2000 2025 2050 2075 2100
2000 2025 2050 2075 2100
^— Mitigation
The CIRA analysis models the entire
"impact pathway"shown in Figure 1,
which can be divided into biophysical
and economic components. The
biophysical impacts are estimated
using the CIRA CO2 and sea surface
temperature projections from the
IGSM-CAM in the CO2SYS model18
to simulate seawater chemistry
conditions through the 21stcentury.
These conditions are then used to
estimate how the growth rates of
oysters, scallops, and clams will
change over time.
The economic analysis uses the
projected growth rates of these
species to estimate changes to the
U.S. supply of shellfish. A consumer
demand model of the shellfish market,
described in Moore (2014),19 projects
changes in prices and consumer
behavior under the Reference and
Mitigation scenarios. This model does
not estimate producer or supply-side
welfare effects, which could also show
benefits of mitigation. Comparing the
model results under the two scenarios
provides an estimate of the benefits
to the shellfish market of avoiding
significant amounts of CO2 from being
added to ocean waters. By considering
impacts to these three species, this
approach estimates just a fraction of
the potential economic damages from
ocean acidification, but, nonetheless,
provides some insight into the benefits
of global GHG mitigation.
In addition, by preventing the loss
of shellfish populations, global GHG
mitigation would preserve ecosystem
services provided by these species
(e.g., water filtration). Inclusion of
these effects would likely increase the
total benefits of GHG mitigation in
this sector.
For more information on the
CIRA approach to estimating
the economic impacts of ocean
acidification in the shellfish
market, see Moore (2015).20
69
-------
1 Warming waters and
changes in stream flow due
to climate change will likely
alter the distribution of
freshwater fisheries across
the country. Without global
GHG mitigation, coldwater
species are projected to be
replaced in many areas by
less economically valuable
fisheries over the course of
the 21st century, especially
in the Mountain West and
Appalachia.
2 Habitat suitable for
coldwater fisheries is
estimated to decline
nationally by approximately
62% through 2100 under
the Reference, but by only
12% under the Mitigation
scenario. Global GHG
mitigation is projected to
preserve coldwater habitat
in most of Appalachia and
the Mountain West.
3 GHG mitigation avoids
an estimated $380 million
to $1.5 billion in total
recreational fishing
damages through 2100
compared to the Reference
(discounted at 3%).
I
70
Climate Change
and Freshwater Fish
Freshwater fishing is an important recreational activity that contributes significantly to local
economies in many parts of the country. Mostfish species thrive only in certain ranges of water
temperature and stream flow conditions. For example, trout and salmon can only tolerate
coldwater streams, while shad and largemouth bass thrive in warmwater habitats (see below
infographic). Climate change threatens to disrupt these habitats and affect certain fish
populations through higher temperatures and changes in river flow.21
Risks of Inaction
Without GHG mitigation, climate change is projected to have a significant impact on freshwater
fishing in the contiguous U.S. Increasing stream temperatures and changes in stream flow are
likely to transform many habitats that are currently suitable for coldwater fish into areas that are
only suitable for warmwater species that are less recreationally valuable. Under the IGSM-CAM
climate projections, coldwater fisheries are estimated to be limited almost exclusively to the
mountainous West in 2100, and would almost disappear from Appalachia. In addition, substantial
portions of Texas, Oklahoma, Kansas, and Florida would shift from warmwater to rough habitat
(Figure 1). Overall, unmitigated climate change is projected to result in a 62% decline in coldwa-
ter fish habitat by 2100, which includes approximately 440,000 acres of lost stream habitat.
Meanwhile, warmwater and rough stream habitats are projected to increase by 1.3 million and
450,000 acres, respectively. The projected loss of coldwater fish habitat and expansion of
warmwater and rough fisheries are consistent with the findings of the assessment literature.22-23
Figure 1. Projected Impact of Unmitigated Climate Change
on Potential Freshwater Fish Habitat in 2100
Change in distribution of areas where stream temperature supports different fisheries under the
Reference scenario using the IGSM-CAM climate model. Results are presented for the 8-digit hydrologic unit
codes (HUCs) of the contiguous U.S.
Current Cold, Projected Cold
| Current Cold, Projected Warm
Current Warm, Projected Warm
I Current Warm, Projected Rough
COLDWATER FISHERY EXAMPLES
WARMWATER FISHERY EXAMPLES
Trout
Salmon
Smallmouth Bass
Shad
-------
II-
Reducing Impacts through
GHG Mitigation
Global GHG mitigation is projected to prevent much of the loss of
coldwater fish habitat that occurs in the Reference (Figure 2).
Although coldwater stream habitat will likely still be reduced
under the Mitigation scenario (by approximately 85,000 acres by
2100), mitigation avoids approximately 81% of the losses incurred
under the Reference, preserving an area equal to approximately
360,000acres of suitable stream habitat nationally. This habitat
supports valuable recreational fishing, especially in Appalachia
and large areas of the Mountain West. Also, fewer acres are
converted to less economically valuable warmwater and rough
fisheries under the Mitigation scenario than under the Reference.
Specifically, stream habitat suitable for warmwater and rough • "-7>i'ir; ""-'•-!. \ VI
fisheries increase by 450,000 and 13,000 acres, respectively, under
the Mitigation scenario, which is 36% and 3% of the expansions estimated under the Reference.
Compared to the Reference, the Mitigation scenario provides economic benefits of approxi-
mately $1.5 billion through 2100 for coldwater fishing only, and $380 million when all three
freshwater fishery types (cold, warm, and rough) are considered (discounted at 3%).These results
rely upon climate projections from the IGSM-CAM, which projects a relatively wetter future for
most of the U.S. compared to the MIROC climate model. The projected benefits of global GHG
mitigation through 2100 are lower with the drier MIROC model (not shown) for coldwater fishing
only, at approximately $1.2 billion, but higher when all three fisheries are considered, at approxi-
mately $1.5 billion (discounted at3%).24
Figure 2. Projected Impact on Potential Freshwater Fish Habitat in 2100
with Global GHG Mitigation
Change in distribution of areas where stream temperature supports different fisheries under
the Mitigation scenario using the IGSM-CAM climate model. Results are presented
for the 8-digit HUCs of the contiguous U.S.
Current Cold, Projected Cold
| Current Cold, Projected Warm
Current Warm, Projected Warm
ICurrentWarm, Projected Rough
ROUGH FISHERY EXAMPLES
Largemouth Bass
Bluegill
Catfish
The CIRA analysis assesses the impacts
of climate change on the distribution
of habitat suitable for freshwater
fish across the U.S. and estimates the
economic implications of these
changes. Water temperature changes
are simulated for the CIRA emissions
scenarios using the IGSM-CAM and
MIROC climate models to estimate
changes in suitable habitat (in stream
acres) for three types of freshwater
fisheries: cold, warm, and rough
(species tolerant to warmest stream
temperatures). Each fishery type
represents a categorization of individ-
ual species based on their tolerance
for different river and stream water
temperatures.This analysis does not
evaluate impacts to fisheries in lakes
and reservoirs, which are vulnerable to
climate change in different ways
compared to streams and rivers.25 As
shown at the bottom of this section,
the coldwater fish guild contains
species that are the least tolerant to
increasing stream temperatures, and
are therefore the most vulnerable to
climate change.
Results from habitat modeling
considering projected changes in both
water temperature and streamflow
serve as input to an economic model
to analyze the impacts of habitat
change on the value of recreational
fishing. The model estimates fishing
behavior as the likelihood that an adult
in a particular state is an angler and the
likelihood that an angler fishes for
species in each fishery type. The fishing
value for each fishery type is derived by
multiplying the number of fishing days
by the value of a fishing trip.26 As
implications of changes to the distribu-
tion of freshwater fisheries extend
beyond recreational use by humans,
this analysis underestimates the
economic benefits of GHG mitigation.
For more information on the CIRA
approach and results for the
freshwater fish sector, please refer
to Laneetal. (2014)27 and Jones et
al.(2012).28
71
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1 Without global GHG
mitigation efforts, climate
change is projected to
dramatically increase
the area burned by wild-
fires across most of the
contiguous U.S., especially
in the West.
2 Global GHG mitigation
is projected to reduce the
cumulative area burned
by wildfires over the course
of the 21st century by
approximately 210-300
million acres compared to
the Reference.
3 Global GHG mitigation
avoids an estimated
$8.6-$11 billion in wildfire
response costs and $3.4
billion in fuel management
costs on conservation
lands (discounted at 3%)
through 2100 compared to
the Reference. Other im-
pacts, such as property
damage or health effects
from decreased air quality,
are not estimated, but
could have large economic
implications.
72
Climate Change and Wildfire
Terrestrial ecosystems in the U.S. provide a
wealth of goods and services such as timber,
wildlife habitat, erosion management, water
filtration, recreation, and aesthetic value.
Climate change threatens these ecosystems
as heat, drought, and other disturbances
bring larger and more frequent wildfires.
Wildfires can damage property, disrupt
ecosystem services, destroy timber stocks,
impair air quality, and result in loss of life.29 In
the last decade (2004-2013), more than 72
million acres of forest have burned due to
wildfires, and the U.S. government has spent
in excess of $15 billion on wildfire suppres-
sion.30 Additionally, wildfires release carbon
stored in terrestrial ecosystems, potentially
further accelerating climate change.31-32
Risks of Inaction
Without GHG mitigation, climate change is projected to dramatically increase the area burned
by wildfires across most of the contiguous U.S., a finding that is consistent with the assessment
literature.33 Under the Reference using the IGSM-CAM climate projections, approximately 5.3
million34 more acres—an area greater than the state of Massachusetts—are projected to burn
each year at the end of the century compared to today. This represents a doubling of acres
burned compared to today's rates.35 However, the estimated impacts vary across regions and
through time (Figure 1). Consistent with the assessment literature,36 the western U.S.37 is projected
to experience large increases in burned area by the end of the century (an increase of approxi-
mately 43%). In particular, the Southwestern region (comprising Arizona, New Mexico, and West
Texas) is projected to experience increases of 140% on average.38 Wildfire in other regions is not
projected to change significantly compared to today, and some regions, such as the Northeast,
are estimated under the IGSM-CAM projections to experience decreases in wildfire activity.
Figure 1. Projected Impact of Unmitigated Climate Change on Wildfire Activity
Change in average annual acres burned under the Reference scenario by mid-century (2035-2064) and
end of century (2085-2114) compared to the historic baseline (2000-2009) using the IGSM-CAM climate model.
Acres burned include all vegetation types and are calculated at a cell resolution of 0.5°x 0.5°.
Mid-Century
End-of-Century
Change in Acres Burned
-72,00010-60,000 -29,999 to 0 ^H 10,001 to 20,000
-59,999 to -30,000 ! to 10,000 ^M 20,001 to 30,000
-------
Reducing Impacts through
GHG Mitigation
ROACH
Benefits of GHG Mitigation
210-300 million fewer acres burned over
the course of the 21st century, an area2-3 times
the size of California
As shown in Figure 2, global GHG mitigation
significantly reduces the area burned by
wildfire in the U.S. over the course of the
21stcentury. By 2100, the Mitigation scenario
reduces the cumulative area burned by
approximately 210-300 million acres,
depending on the climate model used. This
corresponds to a 13-14% reduction relative
to the Reference. As shown, the combined
area of wildfires avoided in the contiguous
U.S. due to GHG mitigation is equivalent to
two to three times the size of California.
These benefits of GHG mitigation would
largely occur in the West, where approxi-
mately 64%-75% of the avoided burned area is located.
Nationally, the avoided wildfire due to GHG mitigation corresponds $11 billion in reduced
wildfire response costs and $3.4 billion39 in avoided fuel management costs for conservation
lands through 2100 (both discounted at 3%). Other economic damages from wildfire that are
not estimated in this analysis, such as human health effects from decreased air quality, could
have large implications at national and regional scales.These results rely upon climate
projections from the IGSM-CAM, which projects a relatively wetter future for most of the U.S.
compared to the MIROC climate model (seethe Levels of Certainty section of this report for
more information). The projected benefits of global GHG mitigation are slightly lower for the
drier MIROC model, with wildfire response cost savings estimated at $8.6 billion through
2100 (discounted at 3%).40
Figure 2. Estimated Acres Burned with and without Global GHG Mitigation
Estimated acres burned by wildfire in the contiguous U.S. over the course of the 21st century under the Reference
and Mitigation scenarios using the IGSM-CAM climate model, with trends shown in bold. The large inter-annual
variability reflects simulated periods of fuel accumulation followed by seasons of large wildfire activity.
0
2010 2025 2050 2075
—Reference —Mitigation
2100
To estimate the effect of climate
change on areas burned by wildfires,
the CIRA analysis uses the MCI
dynamic global vegetation model.
The model simulates future terrestrial
ecosystem cover and burned area
across the contiguous U.S. in the 21st
century. The vegetation model is
driven by changes in future climate
(e.g., temperature, precipitation,
humidity) based on five initializations
of the IGSM-CAM climate model for the
Reference and Mitigation scenarios.41'42
Results presented in this section
represent the average of the initializa-
tions. Simulations using the drier
MIROC model were also performed.
Projected changes in fire regime over
time are adjusted to account for fire
suppression tactics.
The projected impacts of wildfires
are summarized by scenario and
geographic area, and then monetized
using average wildfire response costs
for each region. These costs include the
costs associated with labor (e.g., fire
crews) and equipment (e.g., helicop-
ters, bulldozers) that are required for
fire-fighting efforts.43 Using the
approach described in Lee et al.
(201 SJ^the analysis also estimates the
environmental damages resulting from
moderate and severe wildfires on
conservation lands (e.g., Forest Service
lands, national parks and preserves,
and other protected lands) across the
contiguous U.S. under the Reference
and Mitigation scenarios.To estimate
the value of the lost ecosystem services
resulting from these wildfires, the
analysis quantifies the costs of fuels
management needed to offset the
injury caused by wildfires. Air quality
impacts, property loss, loss of recre-
ation, and the effects of pest infesta-
tions (e.g., pine bark beetles) on
wildfire activity are additional and
important impacts, but are not
included in the reported estimates.
For more information on the CIRA
approach and results for wildfires,
please refer to Mills et al. (2014)45
andLeeetal.(2015).46
73
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KEY FINDINGS
Changes in vegetative
carbon storage in the con-
tiguous U.S. are highly
dependent on the projected
future climate, with the
magnitude, regional distri-
bution, and directionality of
impacts changing over time.
2 The estimated effect of
global GHG mitigation on
carbon storage ranges from
a decrease in carbon stocks
of 0.5 billion metric tons to
an increase in carbon
stocks of 1.4 billion metric
tons by the end of the
century, depending on the
climate model used.The
economic value of these
changes in carbon storage
ranges from $9 billion in
disbenefits to $120 billion
in GHG mitigation benefits
(both discounted at 3%).
74
Climate Change and Terrestrial
Carbon Storage
Figure 1. Carbon Storage Basics
PHOTOSYNTHESIS,
LITTERFALL,
SEDIMENTATION
COMBUSTION,
RESPIRATION,
DECOMPOSITION
Terrestrial ecosystems influence the climate system
through their important role in the global carbon
cycle. These ecosystems capture and store carbon
from the atmosphere, thereby reducing its climate
impact. However, they can also act as a source,
releasing carbon through decomposition and
wildfires (Figure 1). Terrestrial ecosystems in the
U.S., which include forests, grasslands, and
shrublands, are currently a net carbon sink. Today,
forests store more than 227 million tons of carbon per
year, which offsets approximately 16% of all annual U.S.
carbon dioxide emissions from fossil fuel burning.47 Forest carbon
storage has increased due to net increases in forest area, improved forest management, as
well as higher productivity rates and longer growing seasons driven by climate change.48
However, climate-driven changes in the distribution of vegetation types, wildfire, pests, and
disease are affecting, and will continue to affect, U.S. terrestrial ecosystem carbon storage.49
Risks of Inaction
Climate change impacts on terrestrial ecosystem carbon storage under the Reference are on
the order of billions of tons of carbon from 2000 to 2100, with some regions showing
substantial changes in terrestrial carbon stocks (total amount of carbon in the vegetation).
Under the IGSM-CAM climate projections, terrestrial ecosystem storage across the contigu-
ous U.S. is projected to increase 3.4% from 2000 to 2100 (equal to 2.9 billion metric tons),50
primarily due to generally warmer, wetter, and C02-rich future conditions that are favorable
to vegetative growth. Much of the national trend is driven by the Rocky Mountains, South,
and East regions, which have the largest projected increases in terrestrial ecosystem carbon.
However, as shown in Figure 2, there is substantial regional variation, and projections for
carbon storage vary greatly depending on the projected future climate. Results using the
drier MIROC climate model project net reductions in stored carbon under the Reference in
most regions. These results a re consistent with the findings of the assessment literature.51
Figure 2. Projected Impact of Unmitigated Climate Change
on Stored Carbon in 2100
Simulated changes in carbon stocks from the baseline (2000-2009 average) projected by the IGSM-CAM and
MIROC climate models are aggregated by U.S. Forest Service Geographic Area Coordination Center region.
IGSM-CAM
MIROC
Percent Change in Carbon Stocks
|-15to-10% -4toO% ^| 6to 10%
-9 to -5% • 1 to 5% • 11 to 20%
-------
Reducing Impacts through
GHG Mitigation
The impacts of GHG mitigation on national
terrestrial ecosystem carbon storage are
highly dependent upon the projected future
climate, with the magnitude and even
directionality of impacts varying over time
(Figure 3). Across the contiguous U.S., average
results across the IGSM-CAM initializations
show that GHG mitigation reduces stored
carbon compared to the Reference by 0.5
billion metric tons over the course of the
century. The economic value of this lost
carbon under the Mitigation scenario is an
estimated $9.0 billion (discounted at 3%). As
shown in Figure 3, carbon stocks under the
Mitigation scenario are larger than the
Reference in the first half of the century under
the IGSM-CAM, but the trend reverses after
2050, as climate conditions under the
Reference (generally warmer and wetter) are
more favorable for vegetative growth. There is
an early savings from the near-term gain in
stored carbon of approximately 1.1 billion
metric tons, estimated at $170 billion by 2030
(discounted at 3%). However, these initial
gains are not large enough to offset projected
losses in the second half of the century.
The projected impacts of climate change
on vegetative carbon storage and the effects
of GHG mitigation are different when using
the relatively drier climate projections from
the MIROC model (Figure 3).The MIROC
results project a consistent increase in carbon
storage benefits when comparing the
Mitigation scenario to the Reference, with a
carbon stock increase of 1.4 billion metric
tons by 2100. The economic value of this
carbon gain under the Mitigation scenario is
an estimated $120 billion (discounted at 3%).
Results using IGSM-CAM projections show
much more variability over time than the
MIROC results, which is primarily a reflection
of the climate projection method.52
Figure 3. Projected Impact of Global GHG Mitigation on
Carbon Stocks in the Contiguous U.S.
Estimated change in the size of terrestrial ecosystem carbon stocks under the Mitigation scenario
compared to the Reference. Positive values indicate larger carbon stocks under the Mitigation
scenario compared to the Reference, and vice versa. The thin lines represent estimated changes in
carbon stocks under the different initializations of the IGSM-CAM climate model.
4
2010 2025 2050
^^" IGSM-CAM Average
2075
2100
< MIROC
To estimate climate change impacts
on terrestrial ecosystem carbon
storage, the MCI dynamic global
vegetation model was used to
simulate terrestrial vegetative growth
and cover (e.g., grasses, shrubs, hard
and softwood forests) for the contig-
uous U.S. from 2000 to 21OO.53
Vegetative cover estimates from MCI
reflect simulated changes in climate,
biogeography, biogeochemistry, and
fire dynamics. MCI was run using the
five initializations of the IGSM-CAM
climate model for both the Reference
and Mitigation scenarios (see the CIRA
Framework section of this report for
more information).54The results
described in this section represent the
average of these initializations.
Because IGSM-CAM projects a wetter
future for a majority of the nation,
MCI was also run using the MIROC
climate model. These drier climate
projections for the U.S. were used to
capture a broader range of possible
precipitation futures under the same
GHG emissions scenarios.
Projected annual changes in terrestri-
al carbon storage for non-agricultural,
non-developed lands across the
contiguous U.S. were summarized by
scenario and geographic area, and
then monetized using the central
estimate of the U.S. Government's
updated social cost of carbon (SCC)
values for the years 2010-2050, with
extrapolation to 2100.55
This analysis did not consider the
effects of future changes in ozone,
pests, and disease, which could
influence the ability of U.S. terrestrial
ecosystems to store carbon.
For more information on the CIRA
approach and results for carbon
storage, please refer to Mills et al.
(2014).56
75
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Overview of Results
76
-------
This section provides an overview of the national and
regional results for all sectors included in the report. The
National Highlights section presents the estimated physical
and monetary benefits (avoided impacts) to the U.S. of the
global GHG mitigation scenario compared to the Reference
scenario in 2050 and 2100.
The Regional Highlights section shows regional impacts
that are particularly notable, presenting changes in both the
Reference and Mitigation scenarios to highlight the potential
benefits of global GHG mitigation. The individual monetized
estimates presented in these sections are not aggregated,
as there are differences in the types of costs being quantified
across sectors; furthermore, not all potential impacts of
climate change are represented in this report.
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OVERVIEW OF RESULTS
This section provides an overview of the national-scale results presented
throughout this report. It presents the estimated physical and monetary benefits
(avoided impacts) to the U.S. of global GHG mitigation compared to the Reference
scenario in the years 2050 and 2100. Although not available for all sectors, cumulative
benefits for the entire 21st century would likely be much larger than the annual estimates
presented here. In addition, the individual monetized estimates are not aggregated, as
only a subset of climate change impacts is quantified in this report, and there are differ-
ences in the types of costs being quantified across the sectors. For detailed information
on the results, and a summary of the methodologies used, please refer to the Sectors
section of this report.
HEALTH
AIR
QUALITY
EXTREME
TEMPERATURE
LABOR
WATER
QUALITY
In the year 2050, global GHG mitigation
is projected to result in...
An estimated 13,000 fewer deaths from poor air quality,
valued at $160 billion.*
An estimated 1,700 fewer deaths from extreme heat and
cold in 49 major U.S. cities, valued at $21 billion.
An estimated avoided loss of 360 million labor hours,
valued at $18 billion.
An estimated $507-$700 million in avoided damages from
poor water quality.*
In the year 2100, global GHG mitigation
is projected to result in..
An estimated 57,000 fewer deaths from poor air quality,
valued at $930 billion.*
An estimated 12,000 fewer deaths from extreme heat and
cold in 49 major U.S. cities, valued at $200 billion.
An estimated avoided loss of 1.2 billion labor hours,
valued at $110 billion.
An estimated $2.6-$3.0 billion in avoided damages from
poor water quality.*
INFRASTRUCTURE
BRIDGES
ROADS
URBAN
DRAINAGE
COASTAL
PROPERTY
An estimated 160-960 fewer bridges made structurally
vulnerable, valued at $0.12-$1.5 billion.*
An estimated $0.56-$2.3 billion in avoided adaptation
costs.*
An estimated $56 million to $2.9 billion in avoided adapta-
tion costs from the 50-year, 24-hour storm in 50 U.S. cities.*
An estimated $0.14 billion in avoided damages and
adaptation costs from sea level rise and storm surge.
An estimated 720-2,200 fewer bridges made structurally
vulnerable, valued at $1.1-$1.6 billion.*
An estimated $4.2-$7.4 billion in avoided adaptation costs.*
An estimated $50 million to $6.4 billion in avoided adapta-
tion costs from the 50-year, 24-hour storm in 50 U.S. cities.*
An estimated $3.1 billion in avoided damages and adapta-
tion costs from sea level rise and storm surge.
ELECTRICITY
DEMAND AND
SUPPLY
An estimated 1.1%-4.0% reduction in energy demand
and $10-$34 billion in savings in power system costs.*
Not estimated.
* These results do not reflect the additional benefits to air quality and human health that would stem from the co-control of traditional air pollutants along with GHG emissions.
f For sectors sensitive to changes in precipitation, the estimated range of results is generated using projections from two climate models showing different patterns of future precipitation in the contiguous U.S. The
IGSM-CAM model projects a relatively "wetter" future for most of the contiguous U.S. compared to the "drier" MIROC model (seetheCIRA Framework section of this report for more information).
* Estimated range of benefits from the reduction in demand and system costs resulting from lower temperatures associated with GHG mitigation. The electricity section in this report presents an analysis that includes
the costs to the electric sector of reducing GHG emissions.
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In the year 2050, global GHG mitigation
is projected to result in...
In the year 2100, global GHG mitigation
is projected to result in...
WATER RESOURCES
INLAND
FLOODING
DROUGHT
WATER
SUPPLY AND
DEMAND
An estimated change in flooding damages ranging from $260
million in damages to $230 million in avoided damages.*
An estimated 29%-45% fewer severe and extreme droughts,
with corresponding avoided damages to the agriculture
sector of approximately $1.2-$1.4 billion*
An estimated $3.9-$54 billion in avoided damages due to
water shortages.*
An estimated change in flooding damages ranging from
$32 million in damages to $2.5 billion in avoided damages.*
An estimated 40%-59% fewer severe and extreme droughts,
with corresponding avoided damages to the agriculture
sector of $2.6-$3.1 billion.*
An estimated $11-$180 billion in avoided damages due to
water shortages.*
AGRICULTURE & FORESTRY
AGRICULTURE
FORESTRY
An estimated $1.5-$3.8 billion in avoided damages.
Estimated damages of $9.5-$9.6 billion.
An estimated $6.6-$ 11 billion in avoided damages.
An estimated $520 million to $1.5 billion in avoided
damages.
ECOSYSTEMS
CORAL
REEFS
SHELLFISH
FRESHWATER
FISH
WILDFIRE
CARBON
STORAGE
An estimated avoided loss of 53% of coral in Hawaii,
3.7% in Florida, and 2.8% in Puerto Rico.These avoided
losses are valued at $1.4 billion.
An estimated avoided loss of 11% of the U.S. oyster
supply, 12% of the U.S. scallop supply, and 4.6% of the
U.S. clam supply, with corresponding consumer benefits
of $85 million.
An estimated change in recreational fishing ranging from
$13 million in avoided damages to $3.8 million in damages.*
An estimated 2.1 -2.2 million fewer acres burned and
corresponding avoided wildfire response costs of $160-$390
million*
An estimated 26-78 million fewer metric tons of carbon
stored, and corresponding costs of $7.5-$23 billion.*
An estimated avoided loss of 35% of coral in Hawaii, 1.2%
in Florida, and 1.7% in Puerto Rico. These avoided losses are
valued at $1.2 billion.
An estimated avoided loss of 34% of the U.S. oyster
supply, 37% of the U.S. scallop supply, and 29% of the
U.S. clam supply, with corresponding consumer benefits
of $380 million.
An estimated $95-$280 million in avoided damages
associated with recreational fishing.*
An estimated 6.0-7.9 million fewer acres burned and
corresponding avoided wildfire response costs of $940
million to $1.4 billion.*
An estimated 1-26 million fewer metric tons of carbon stored,
and corresponding costs of $880 million to $12 billion*
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OVERVIEW OF RESULTS
This section highlights regional impacts of climate change in the U.S. For each sector,
the map presents a region where substantial benefits of global GHG mitigation are projected
to occur in the years 2050 or 2100.* Note that the geographic scale at which impacts are —>
SHELLFISH
Acidification in the Pacific Northwest is already affecting
U.S. shellfish harvests. The U.S. supplies of oysters,
clams, and scallops are projected to decline 45%, 32%,
rADRHM CTHRAfC \ ar|d 48%, respectively, in the Reference scenario in
C.AKBUN blUKAUt \ 2100, compared to 11%, 3%, and 11%, respectively, in
The Northwest is projected to experience a 6.1% \theMitigationscenario.
decrease in terrestrial carbon storage in 2100 under the
Reference scenario, compared to a 2.4% decrease in the
Mitigation scenario.
WATER SUPPLY AND DEMAND
California is projected to incur $4.5 billion in damages in
2100 due to changes in water supply and demand in the
Reference scenario. However, climate change under the
Mitigation scenario is projected to result in an increase
in welfare of $40 million.
LABOR
In 2100, the Southwest is projected to experience a
3.4% decrease in high-risk labor hours worked in the
Reference scenario, compared to a decrease of 0.82%
in the Mitigation scenario.
DROUGHT
In the Southwest, the number of severe and
extreme droughts is projected to nearly quadruple
by the end of the century in the Reference scenario
compared to today. In the Mitigation scenario, the
incidence of drought is not projected to change
substantially from present day.
WATER QUALITY
The Southwest is projected to experience water quality
damages of approximately $1.8 billion in 2100 under the
Reference scenario, compared to $470 million in the
Mitigation scenario.
CORAL REEFS
By the end of the century, Hawaii is projected to lose
98% of its current shallow-water coral in the Reference
scenario, compared to 64% in the Mitigation scenario.
WILDFIRE
In the Rocky Mountains, an estimated 1.9 million more
acres are projected to burn in 2100 under the Reference
scenario compared to today. In the Mitigation scenario,
an estimated 1.5 million fewer acres^are projected to
burn compared to today.
INLAND FLOODING
In Texas, projected damages associated with the
100-year flood event are $3.6 billion in 2100 under the
Reference scenario, compared to $2.6 billion in the
Mitigation scenario.
* Estimates are presented in undiscounted 2014 dollars and rely upon climate projections from the IGSM-CAM climate model. Results using projections from other climate models, such as the MIROC model used
throughout this report, could lead to variations in results for some sectors.
80
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quantified in the sectoral analyses vary. For example, some of the analyses calculate impacts
for large watersheds, while others use the National Climate Assessment regions. For purposes
of highlighting regional impacts, this section approximates the regions.
m
ROADS
In 2100, the Great Plains region is projected to incur
road damages of approximately $3.5 billion in the
Reference scenario, compared to $1.1 billion in the
Mitigation scenario.
r—*•**—
ELECTRICITY DEMAND
The South Central region is projected to experience^
a 2.0% to 4.2% increase in electricity demand under
the Reference scenario in 2050. In the Mitigation
scenario, the projected change in demand ranges
from-1.4% to 1.6%.
I
AGRICULTURE
In the Southeast, yields of irrigated soybeans are
projected to decrease 23% in 2100 under the Reference
scenario. Under the Mitigation scenario, yields are
projected to increase 4.7%.
BRIDGES
In the Great Lakes region, approximately 520 bridges are
projected to be vulnerable in 2100 under the Reference
Jl scenario, compared to 65 in the Mitigation scenario.
FRESHWATER FISH
Throughout the Appalachians, global GHG mitigation is
projected to preserve approximately 70% of habitat for
coldwater fish species (e.g., trout) that would otherwise
be lost by the end of the century to rising temperatures
from unmitigated climate change.
EXTREME TEMPERATURE
Without mitigation, major cities in the Northeast from
D.C. to Boston are projected to suffer a combined 2,600
extreme temperature mortalities in 2100, compared to
190 in the Mitigation scenario.
URBAN DRAINAGE
In 2100, major cities analyzed in the Great Plains are
estimated to incur $2.1 million per square mile in
damages associated with urban drainage systems in the
Reference scenario, compared to $750,000 per square
mile in the Mitigation scenario.
AIR QUALITY
In 2100, areas of the Southeast are projected to
experience an annual increase in ozone (03) and fine
particulate matter (PM2.5) of 0.7 ppband 1 ug/m3,
respectively. In the Mitigation scenario, the levels of
03 and PM2.5 are projected to decrease by 120% and
88%, respectively, compared to the Reference.
COASTAL PROPERTY
In 2100, the Tampa Bay area is projected to incur $2.8
billion in damages from sea level rise and storm surge
in the Reference scenario without adaptation. When
adaptation measures are implemented, total costs in
2100 fall to $500 million in the Reference scenario,
compared to $450 million in the Mitigation scenario.
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Understanding the potential timing and
magnitude of climate change impacts in the U.S., and how
they could be reduced or avoided through GHG mitigation,
informs near- and long-term policies to address these risks.
This report describes climate change damages in the U.S.
across multiple sectors using a consistent set of scenarios
and underlying assumptions.1 In doing so, the study
estimates the physical and economic risks of unmitigated
climate change and the potential benefits to the U.S. of
reducing global GHG emissions. Importantly, only a small
portion of the impacts of climate change are estimated,
and therefore this report captures just some of the total
benefits of reducing GHGs. Looking across the large
number of sectoral impacts described in this report, a
number of key findings emerge:
• Unmitigated climate change is projected to profoundly
affect human health, the U.S. economy, and the environ-
ment. The CIRA analyses demonstrate substantial and
far-reaching changes over the course of the 21st century—
and particularly at the end of the century—with negative
consequences for a large majority of the impact sectors. In
addition, the analyses suggest that climate change impacts
will not be uniform across the U.S., with most sectors
showing a complex pattern of regional-scale impacts.
• Global action to mitigate GHG emissions is projected to
reduce and avoid impacts in the U.S. that would other-
wise occur in a future with continued high growth in
GHG emissions. Importantly, these benefits are projected
to increase over the course of the century. The analyses
indicate that risks and impacts over the long term will not
be avoided unless there is near-term action to significantly
reduce GHG emissions.This report presents benefits for one
illustrative global GHG mitigation scenario. More stringent
emissions reductions would likely increase the benefits
compared to the Reference scenario, and, conversely, less
stringent reductions would likely decrease the benefits.
• Global GHG mitigation substantially reduces the risk of
some extreme weather events and their subsequent
impacts on human health and well-being by the end of
the century.
• Adaptation, especially in the infrastructure sector, can
substantially reduce the estimated damages of climate
change. For some impacts, such as those described in the
Coastal Property section, well-timed adaptation can have a
larger effect on reducing the risks of inaction than global
GHG mitigation, particularly in the near term, highlighting
the need for concurrent mitigation and adaptation actions.
> For some impacts, the effects of global GHG mitigation
can vary across different projections of future climate.
This is particularly true for those sectors sensitive to changes
in precipitation. For a few of these sectors, mitigation results
in either benefits or disbenefits depending upon the
simulated level of future precipitation.2 By analyzing multiple
types of impacts by sector, such as flooding, drought, water
quality, and supply/demand in the water realm, and using a
range of projections for future precipitation, a more compre-
hensive understanding of potential impacts and mitigation
benefits is gained.
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Next Steps
This report represents a significant and important contribution to estimating the multi-sectoral benefits to the U.S. of global GHG
mitigation. Although the results presented in this report do not provide comprehensive coverage of all potential impacts, the
breadth and depth of the analyses will expand in future work within the CIRA project. Comprehensive and quantitative estimates of
climate change impacts are not only needed to evaluate the benefits of GHG mitigation, but also to evaluate the cost-effectiveness
of adaptation responses, and to support the improvement of other economic tools used to analyze climate and energy policies.
Although CIRA only begins to capture many of the dynamics and uncertainties involved in impact analysis (e.g., interactions among
sectoral models), this report provides timely and quantitative estimates as the science continues to advance in this field. Future work
to refine projections of how GHG emissions affect the climate, and how these changes affect society and the environment, will
improve our understanding and confidence in the estimates presented in this report.
Additional Climate Change Resources
EPA's Climate Change website (www.epa.
qov/climatechanqe) provides a good
starting point for further exploration of
this topic. From this site, you can:
• Read about greenhouse gas emissions,
look through EPA's greenhouse gas
inventories, and explore EPA's Greenhouse
Gas Data Publication Tool.
• Learn about EPA's regulatory initiatives
and partnership programs.
• Find out what you can do at home, on
the road, at work, and at school to help
reduce greenhouse gas emissions.
Other government and nongovernment
websites also provide information about
climate change. Here are some examples:
• The Intergovernmental Panel on Climate
Change (IPCC) is the international
authority on climate change science.The
IPCC website (www.ipcc.ch/index.htm)
summarizes the current state of scientific
knowledge about climate change and
includes links to their most recent Fifth
Assessment Report.
• The U.S. Global Change Research Program
(www.globalchange.gov) is a multi-agency
effort focused on improving our under-
standing of the science of climate change
and its potential impacts on the U.S.
through reports like the National Climate
Assessment.
Finally, other groups are working to
estimate the impacts of climate change in
the U.S. and/or other world regions. Here
are some examples:
• The Inter-Sectoral Impact Model Inter-
comparison Project (ISI-MIP; https://
www.pik-potsdam.de/research/
climate-impacts-and-vulnerabilities/
research/rd2-cross-cutting-activities/
isi-mip) is an international, community-
driven modelling effort bringing together
impact models across sectors and scales.
• The Risky Business Project (http://
riskvbusiness.org/) focuses on quantifying
and publicizing the economic risks
from the impacts of a changing climate
in the U.S.
• The European Commission Joint Research
Centre's PESETA II project (Projection of
Economic impacts of climate change in
Sectors of the European Union based on
bottom-up Analysis; http://peseta.irc.ec.
europa.eu/) is a consistent multi-sectoral
assessment of the impacts of climate
change in Europe.
• AVOID (http://www.metoffice.gov.uk/
avoid/) is a research program that
provides modeling and scientific informa-
tion to the U.K. Government on avoiding
dangerous climate change brought on by
greenhouse gas emissions.
• The project on the Benefits of Reduced
Anthropogenic Climate Change (BRACE;
https://chsp.ucar.edu/brace) focuses on
differences in impacts resulting from
climate change driven by high and low
emissions scenarios.
Observed Climate Change
Climate Change Indicators in the United States: EPA publishes a set of indicators describing trends related to the
causes and effects of climate change. Focusing primarily on the U.S., this resource presents compelling evidence that
many fundamental measures of observed climate are changing.
Please visit EPA's website for more information: http://www.epa.qov/climatechanqe/science/indicators/index.html
-------
INTRODUCTION
1 Martinich, J., J. Reilly, S. Waldhoff, M. Sarofim, and J. McFarland, Eds. 2015. Special Issue
on "A Multi-Model Framework to Achieve Consistent Evaluation of Climate Change
Impacts in the United States." Climatic Change.
2 While beyond the scope of this report, analyses of the adequacy of current GHG mitiga-
tion efforts, at domestic and global scales, relative to the magnitude of climate change
risks are described in the assessment literature. See: 1) Jacoby, H. D., A. C. Janetos, R.
Birdsey, J. Buizer, K. Calvin, F. de la Chesnaye,... and J. West. 2014. Ch. 27: Mitigation.
In Climate Change Impacts in the United States: The Third National Climate Assessment,
J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds. U.S. Global Change Research
Program. DOI:10.7930/JOC8276J; and 2) IPCC. 2014. Climate Change 2014: Mitigation
of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the
Intergovernmental Panel on Climate Change, Edenhofer, O., R. Pichs-Madruga, Y. Sokona,
E. Farahani, S. Kadner, K. Seyboth,... and J.C. Minx, Eds. New York, NY: Cambridge
University Press.
3 United Nations Framework Convention on Climate Change. 2013. Report of the
Conference of the Parties on its nineteenth session, held in Warsaw from November
11-23,2013. Part one: Proceedings. FCCC/CP/2013/10.
4 CIRA uses sectoral impact models driven by consistent climate and socioeconomic
scenarios to analyze both physical impacts and economic damages of climate change
at national and regional scales in the U.S. This unique multi-model design allows for
'apples-to-apples' comparisons of impacts and benefits of global GHG mitigation
across sectors, but is not comprehensive in scope. The impact estimates presented
in this report are consistent with the key findings of the U.S. Global Change Research
Program's Third National Climate Assessment. See Section H of the Technical Appendix
for this report for a more detailed comparison of key findings.
5 The Social Cost of Carbon (SCC) is a metric that estimates the economic value of
impacts associated with the global emission of one ton of carbon dioxide (CCb) or, con-
versely, the economic benefit of avoiding or reducing one ton of CCb (in dollars per ton
of CC>2 in a given year). Unlike CIRA, the SCC draws from models of anticipated climate
change impacts and benefits across the entire globe, not just for the U.S. The SCC has
already been applied to estimate the global economic benefits of CCb emission reduc-
tions from certain U.S. regulations, but it does not provide explicit information about
how the actual physical impacts in specific sectors of the U.S. may change overtime
and space. For more information, see: U.S. Interagency Working Group on the Social
Cost of Carbon. 2013. Technical support document: Technical update of the social cost
of carbon for regulatory impact analysis under Executive Order 12866.
6 The CIRA project estimates the benefits to the U.S. of global action on climate change.
Importantly, the costs of GHG mitigation are not assessed in the project. As such, the
analysis presented in the report does not constitute a cost-benefit assessment of cli-
mate policy. The costs of reducing GHG emissions have been well examined in the sci-
entific literature (see references below), where recent assessments have used multiple
economic models to investigate the sensitivity of costs to policy design, assumptions
about the availability of low carbon-emitting energy technologies, socioeconomic
and demographic changes, and other important sources of uncertainty. The one
instance in the CIRA project where mitigation costs are considered is in the electricity
sector (see Electricity section for details). For that sector, the impact of climate change
on costs to the U.S. electric power system is estimated along with the costs associated
with GHG emission reductions in that sector. See: Fawcett, A., L. Clarke, and J. Weyant.
2013. Introduction to EMF24. The Energy Journal. DOI:10.5547/01956574.35.511.1;
White House Council of Economic Advisors. 2014. The Cost of Delaying Action to
Stem Climate Change. Executive Office of the President of the United States; CCSP.
2007. Scenarios of Greenhouse Gas Emissions and Atmospheric Concentrations (Part
A) and Review of Integrated Scenario Development and Application (Part K). A Report
by the U.S. Climate Change Science Program and the Subcommittee on Global Change
Research, Clarke, L., J. Edmonds, J. Jacoby, H. Pitcher, J. Reilly, R. Richels,... and M.
Webster (Authors). Washington, DC: Department of Energy; Kriegler, E., J.P. Weyant,
G.J. Blanford, V. Krey, L. Clarke, J. Edmonds, ...and D.P van Vuuren. 2013. The role of
technology for achieving climate policy objectives: overview of the EMF 27 study
on global technology and climate policy strategies. Climatic Change. DOI:10.1007/
si0584-013-0953-7; and Kriegler, E., K. Riahi, N. Bauer, V.J. Schwanitz, N. Petermann,
V. Bosetti,... and O. Edenhofer. 2015. Making or breaking climate targets: the AMPERE
study on staged accession scenarios for climate policy. Technological Forecast and
SocialChange. DOI:10.1016/j.techfore.2013.09.021; Energy Economics. Volume 31, Sup-
plement 2, Pages S63-S306 (2009). International, U.S. and E.U. Climate Change Control
Scenarios: Results from EMF 22. Edited by Leon Clarke, Christoph Bohringer and Tom
F. Rutherford.
7 Example of co-benefit literature: IPCC. 2014. Climate Change 2014: Mitigation of
Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the
Intergovernmental Panel on Climate Change, Edenhofer, O., R. Pichs-Madruga, Y. Sokona,
E. Farahani, S. Kadner, K. Seyboth,... and J.C. Minx, Eds. New York, NY: Cambridge
University Press.
SUMMARY OF KEY FINDINGS
1 This section draws upon conclusions described in the overview paper for the CIRA
special issue: Waldhoff, S., J. Martinich, M. Sarofim, B. DeAngelo, J. McFarland, L. Jan-
tarasami, K. Shouse, A. Crimmins, S. Ohrel, and J. Li. 2014. Overview of the Special Issue:
A multi-model framework to achieve consistent evaluation of climate change impacts
in the United States. ClimaticChange. DOI:10.1007/s10584-014-1206-0.
2 Changes in extreme weather events across the CIRA scenarios are discussed in more
detail in: Monier, E. and X. Gao. 2014. Climate change impacts on extreme events in
the United States: an uncertainty analysis. ClimaticChange. DOI:10.1007/s10584-013-
1048-1.
3 See, for example: 1) Ciscar, J-C, A. Iglesias, L. Feyen, L. Szabo, D. Van Regemorter, B.
Amelung,... and A. Soria. 2011. Physical and economic consequences of climate
change in Europe. ProcNatlheadSci USA. DOI:10.1073/pnas.1011612108; 2) Frumhoff,
P.C., J.J. McCarthy, J.M. Melillo, S.C. Moser, and D.J. Wuebbles. 2007. Confronting
climate change in the U.S. Northeast: science, impacts, and solutions. Report of the
Northeast Climate Impacts Assessment. Cambridge, MA: Union of Concerned Scien-
tists; and 3)Hayhoe, K., D. Cayan, C.B. Field, P.C. Frumhoff, E.P. Maurer, N.L. Miller,...
and J.H. Verville. 2004. Emissions pathways, climate change, and impacts on California.
Proc Nat!head Sci USA. DOI:10.1073/pnas.0404500101.
4 Throughout the report, future benefits—i.e., the annual time series of avoided costs—
are discounted at a 3% rate to reflect their value in the present day, which is defined as
theyear2015 in this report. In short, discounting provides an equal basis to compare
the value of benefits (and costs) that occur in different time periods. The discount rate
itself reflects the trade-off between consumption today and consumption tomorrow,
meaning that with a positive discount rate, benefits that occur today are worth more
than they would be tomorrow. A higher discount rate implies a greater preference
for present-day consumption and a lower present value of future damages. A lower
discount rate implies a greater value on future damages. That is, the present value
of future damages calculated at a 5% rate will be lower than those calculated using
a 3% rate. There are many ways to select a discount rate and little consensus about
which discount rate is most appropriate, particularly when assessing benefits that span
multiple generations. Therefore, we selected 3%, a commonly employed rate in the
climate impacts and benefits literature. This rate was also used to calculate two of the
U.S. Government's four Social Cost of Carbon estimates (including the central value),
which estimate climate damages that occur over long time horizons. In particular, the
U.S. Government review found that it was consistent with estimates provided in the
economics literature and noted that 3% roughly corresponds to the after-tax riskless
interest rate. For a detailed discussion on discount rate selection, please see the Social
Cost of Carbon Technical Support Document, available at http://www.epa.gov/oms/
climate/regulations/scc-tsd.pdf.
CIRA FRAMEWORK
1 Martinich, J., J. Reilly, S. Waldhoff, M. Sarofim, and J. McFarland, Eds. 2015. Special Issue
on "A Multi-Model Framework to Achieve Consistent Evaluation of Climate Change
Impacts in the United States." Climatic Change.
2 Melillo, J.M., T.C. Richmond, and G.W. Yohe, Eds. 2014. Climate Change Impacts in the
United States: The Third National Climate Assessment. Appendix 5: Scenarios and
Models. U.S. Global Change Research Program. DOI:10.7930/JOZ31WJ2.
3 While beyond the scope of this report, analyses of the adequacy of current GHG
mitigation efforts, at domestic and global scales, relative to the magnitude of climate
change risks are described in the assessment literature. See, for example: 1) Jacoby,
H. D., A. C. Janetos, R. Birdsey, J. Buizer, K. Calvin, F. de la Chesnaye,... and J. West.
2014. Ch. 27: Mitigation. Climate Change Impacts in the United States: The Third National
84
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Climate Assessment, J. M. Melillo, Terese (T.C) Richmond, and G. W. Yohe, Eds., U.S.
Global Change Research Program. DOI:10.7930/JOC8276J; and 2) IPCC. 2014. Climate
Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the
Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Edenhofer,
O., R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth,... and J.C. Minx, Eds.
New York, NY: Cambridge University Press.
4 A third emissions scenario was applied in most CIRA sectoral analyses, as described
and presented in the research papers supporting the project. In 2100, this scenario,
called Policy 4.5 in the CIRA project, achieves a radiative forcing of approximately
4.2 W/m2 with an atmospheric GHG concentration of 600 ppm (CO2 equivalent). This
radiative forcing value reflects GHG radiative forcing (i.e., not including aerosols) and
uses a baseline of 1750 (both of which are necessary adjustments for comparing to the
IPCC RCPs), therefore making it slightly different than the value reported previously in
the CIRA literature (4.5 W/m2).
5 Paltsev, S., J.M. Reilly, H.D. Jacoby, R.S. Eckaus, J. McFarland, M. Sarofim, M. Asadoorian,
and M. Babiker. 2005. The MIT Emissions Prediction and Policy Analysis (EPPA) model:
version 4. Report 125, MIT Joint Program on the Science and Policy of Global Change.
http://globalchange.mit.edu/publications.
6 By 2100 (using a baseline of 1750), the CIRA Reference scenario has a total radiative
forcing of 9.8 W/m2, which appears considerably larger than RCP 8.5. However, the
contrast is primarily due to differences in how forcing is calculated by different GCMs
used in developing those scenarios. The IGSM radiation code was derived from the
GISS climate model, and therefore when calculating radiative forcing due to increased
concentrations in the IGSM, forcing functions fit to the GISS code were used rather
than the more common approach of using simplified equations, such as those defined
in IPCC's Third Assessment Report. Using these simplified equations, total radiative
forcing for the CIRA Reference is 8.6 W/m2, and 3.2 W/m2 for the Mitigation scenario.
Other differences between the IGSM scenarios and the RCPs are due to differences in
anthropogenic emissions, natural emissions responses to warming, and atmospheric
chemistry.
7 Paltsev, S., E. Monier, J. Scott, A. Sokolov, and J. Reilly. 2013. Integrated economic and
climate projections for impact assessment. Climatic Change. DOI:10.1007/sl 0584-
013-0892-3. We also note that the Reference scenario is calibrated using historic GHG
emissions through 2010; see Paltsev et al. (2013) for more information.
8 Paltsev, S., E. Monier, J. Scott, A. Sokolov, and J. Reilly. 2013. Integrated economic and
climate projections for impact assessment. ClimaticChange. DOI:10.1007/sl 0584-013-
0892-3.
9 Radiative forcing (including CCb, CH4, N2O, PFCs, SF6, HFCs, CFCs and HCFCs) for the
Reference and Mitigation scenarios (see Paltsev et al. 2013), compared to the four RCPs
(data from Meinshausen et al. 2011). The negative forcing effects of aerosols are not
included. See: Meinshausen, M., S. J. Smith, K. V. Calvin, J. S. Daniel, M. L. T. Kainuma, J.-
F. Lamarque,... and D. van Vuuren. 2011. The RCP Greenhouse Gas Concentrations and
their Extension from 1765 to 2300. ClimaticChange. DOI:10.1007/sl0584-011-0156-z.
10 Please see the literature underlying the CIRA project for information on post-processing
and bias-correction of climate outputs for use in the sector analyses.
11 Monier, E., X. Gao, J.R. Scott, A.P. Sokolov, and C.A. Schlosser. 2014. A framework for
modeling uncertainty in regional climate change. ClimaticChange. DOI:10.1007/
S10584-014-1112-5.
12 Adaptive actions modeled in the sectoral analyses of this report should not be inter-
preted as recommendations of these particular strategies.
13 Walsh, J., D. Wuebbles, K. Hayhoe, J. Kossin, K. Kunkel, G. Stephens,... and R. Somerville.
2014. Chapter 2: Our Changing Climate. Climate Change Impacts in the United States:
The Third National Climate Assessment, J.M. Melillo, R.C. Richmond, and G. W. Yohe, Eds.
U.S. Global Change Research Program. DOI:10.7930/JOKW5CXT.
14 The U.S. Global Change Research Program's National Climate Assessment (NCA) results
are reported for the RCP 8.5 scenario, using a range (5th-95th percentile) of results from
a suite of climate models, adjusted to match the same baseline period used for the
IGSM-CAM model. The NCA also presents results from the older SRES models: the A2
scenario from SRES was projected to warm by 5-8°F by 2100.
15 Future climate change depends on the response of the global climate system to rising
GHG concentrations (i.e., how much temperatures will rise in response to a given
increase in atmospheric CO2). Assumptions about this relationship are referred to as
climate sensitivity.
16 IPCC. 2014. Summary for Policymakers. In: Climate Change 2014, Mitigation of Climate
Change. Contribution of Working Group III to the Fifth Assessment Report of the Inter-
governmental Panel on Climate Change, Edenhofer, O., R. Pichs-Madruga, Y. Sokona, E.
Farahani, S. Kadner, K. Seyboth,... and J.C. Minx, Eds. New York, NY.
17 IPCC. 2013. Summary for Policymakers. In: Climate Change 2013: The Physical Science
Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovern-
mental Panel on Climate Change, Stocker, T.F., D. Qin, G.-K. Plattner, M.Tignor, S.K. Allen,
J. Boschung,... and P.M. Midgley, Eds. New York, NY.
18 The estimate of warming from the historical period (0.65°C) used in Figure 1 of the
Temperature Projections section is slightly less than the IPCC's estimate of 0.85°C be-
cause the former utilizes a 30-yr average (1980-2009) to represent the current period.
19 Warming from the historical period (0.65°C) comparing 1880-1909to 1980-2009 was
calculated using the NOAA Global Historical Climatology Network GHCN-3 dataset of
Global Land and Ocean Temperature Anomalies (available at http://www.ncdc.noaa.
qov/caq/time-series/qlobal/qlobe/land ocean/vtd/12/1880-2014.csv). Combined
with this historical warming, the 2°C target (relative to preindustrial) is equivalent to a
warming of 2.43°F (relative to the 1980-2009 baseline period), as shown in Figure 1 of
the Temperature Projections section. This value is consistent with the average of the
last two decades of the century (2081 -2100) for the CIRA Mitigation scenario: 2.23°F.
20 Monier, E. and X. Gao. 2014. Climate change impacts on extreme events in the United
States: an uncertainty analysis. Climatic Change, DOI:10.1007/sl 0584-013-1048-1.
21 Ibid.
22 The CIRA sea level rise scenarios are at the high end of projected sea level rise rates for
similar scenarios based on recent publications (Horton et al. 2014, Kopp et al. 2014).
However, we also note that the effect of GHG mitigation on reducing the increase in
future sea level was found to be larger in these studies. The use of a smaller sea level
rise would likely lead to a decrease in total damages, but a larger reduction in sea level
rise due to the Mitigation scenario would likely yield larger economic benefits than
those presented in this report. See: 1) Horton, B.J., S. Rahmstorf, S.E. Engelhart, and A.C.
Kemp. 2014. Expert assessment of sea-level rise by AD 2100 and AD 2300. Quaternary
Science Reviews. DOI:10.1016/j.quascirev.2013.11.002; and 2) Kopp, R.E., R.M. Horton,
C.M. Little, J.X. Mitrovica, M. Oppenheimer, DJ. Rasmussen, B.H.Strauss, and C. Tebaldi.
2014. Probabilistic 21st and 22nd century sea-level projections at a global network of
tide-gauge sites. Earth's Future. DOM 0.1002/2014EF000239.
23 Walsh, J., D. Wuebbles, K. Hayhoe, J. Kossin, K. Kunkel, G. Stephens,... and R. Somerville.
2014. Chapter 2: Our Changing Climate. Climate Change Impacts in the United States:
The Third National Climate Assessment, J.M. Melillo, R.C. Richmond, and G. W. Yohe, Eds.
U.S. Global Change Research Program. DOI:10.7930/JOKW5CXT.
24 Meier, M.F., M.B. Dyurgerov, U.K. Rick, S. O'Neel, W.T. Pfeffer, R. S. Anderson, S.P. An-
derson, and A.F. Glazovsky. 2007. Glaciers dominate eustatic sea-level rise in the 21st
century. Science. DOI:10.1126/science.l 143906.
25 Vermeer, M., and S. Rahmstorf. 2009. Global sea level linked to global temperature.
Proceedings of the National Academy of Sciences. DOI:10.1073/pnas.0907765106.
26 The CIRA sea level rise projections were estimated following the methodology of
Vermeer and Rahmstorf (2009). The methodology of Vermeer and Rahmstorf builds
off that from Rahmstorf (2007) and is described in detail in those papers. In short, pro-
jections were estimated using an empirical relationship between global air tempera-
ture and sea level change, including contributions from glaciers and ice sheets. This
relationship was then applied to the ambient average air temperature trajectories from
the IGSM-CAM model (Paltsev et al. 2013) to project future sea levels.
27 Paltsev, S., E. Monier, J.Scott, A. Sokolov, and J. Reilly. 2013. Integrated economic and
climate projections for impact assessment. Climatic Change. DOI:10.1007/sl 0584-013-
0892-3.
28 For each scenario, a site-specific, fixed annual rate of land subsidence or uplift is
estimated, which combines with the SLR scenario to yield site-specific relative sea
level rise. Historical vertical land movement is based on annual average measurements
from National Oceanic and Atmospheric Administration (NOAA) tide gauge data from
68 sites with at least 25 years of continuous measurements and linear interpolation of
subsidence rates for all cells that lie between the selected sites. An estimated 1.7 mm/
year is subtracted from the tide gauge annual average to account for the component
of relative sea level rise that is accounted for by 20th century sea level change, yielding
the site-specific subsidence/uplift rate.
29 The CIRA approach for calculating relative sea level rise assumes that the difference
in rate between global and relative sea level change will continue into the future.
Because some physical processes (e.g., changes in differential ocean heating) will likely
change in the future at rates different from what is reflected in historical tide gauge
data, the CIRA approach does not capture all of these dynamics. For more informa-
tion, see: Neumann, J., D. Hudgens, J. Herter, and J. Martinich. 2010. The Economics of
Adaptation along Developed Coastlines. Wiley Interdisciplinary Reviews: Climate Change.
DOI:10.1002/wcc.90.
30 Walsh, J., D. Wuebbles, K. Hayhoe, J. Kossin, K. Kunkel, G. Stephens,... and R. Somerville.
2014. Appendix 3: Climate Science Supplement. Climate Change Impacts in the United
States:TheThird National Climate Assessment, J.M. Melillo, T.C. Richmond, and G.W.
Yohe, Eds., U.S. Global Research Program. DOI:10.7930/JOKS6PHH.
31 Ibid.
32 Monier, E., X. Gao, J.R. Scott, A.P. Sokolov, and C.A. Schlosser. 2014. A framework for
modeling uncertainty in regional climate change. ClimaticChange. DOI:10.1007/
S10584-014-1112-5.
85
-------
33 Ibid.
34 All three CIRA emissions scenarios contain the same level of global and U.S. population
changeover time.
35 For each emissions scenario, values represent the ensemble mean of the five
IGSM-CAM initializations using a climate sensitivity of 3°C.
36 IPCC. 2013. Climate Change 2013: The Physical Science Basis. Contribution of Working
Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change,
Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung,... and P.M. Midg-
ley, Eds. New York, NY: Cambridge University Press.
37 A climate sensitivity of 6°C is considered "low probability" when considering feedbacks
expected over the next century. However, there is literature suggesting that slower
feedbacks involving ice sheet and vegetation changes can lead to higher "Earth
System Sensitivity" on timescales of several centuries, such that a sensitivity of 6°C will
have a higher probability on these longer timescales. Additional feedbacks including
methane and carbon cycles are not included in the climate sensitivity definition.
38 Mapped values represent the ensemble mean of the five IGSM-CAM initializations with
different climate sensitivities under the Reference scenario.
39 All five maps assume a climate sensitivity of 3°C under the Reference scenario.
40 A method by which the average change produced by running a climate model is
combined with the specific geographic pattern of change calculated from a different
model in order to approximate the result that would be produced by the second
model.
41 Please refer to: 1) Monier, E., X. Gao, J.R. Scott, A.P. Sokolov, and C.A. Schlosser. 2014. A
framework for modeling uncertainty in regional climate change. ClimaticChange. DOI:
10.1007/sl0584-014-1112-5; and 2) Flato, G., J. Marotzke, B. Abiodun, P. Braconnot,
S.C. Chou, W. Collins,... and M. Rummukainen. 2013. Evaluation of Climate Models. In:
Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the
Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Stocker, T.F.,
D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M.
Midgley, Eds. New York, NY: Cambridge University Press.
42 Monier, E., X. Gao, J.R. Scott, A.P. Sokolov, and C.A. Schlosser. 2014. A framework for
modeling uncertainty in regional climate change. ClimaticChange. DOI:10.1007/
S10584-014-1112-5.
43 This section draws upon conclusions described in the overview paper for the CIRA
special issue: Waldhoff, S., J. Martinich, M. Sarofim, B. DeAngelo, J. McFarland, L. Jan-
tarasami, K. Shouse, A. Crimmins, S. Ohrel, and J. Li. 2014. Overview of the Special Issue:
A multi-model framework to achieve consistent evaluation of climate change impacts
in the United States. ClimaticChange. DOI:10.1007/s10584-014-1206-0.
44 For more information on these types of impacts, see: National Research Council.
2013. Abrupt Impacts of Climate Change: Anticipating Surprises. Washington, DC: The
National Academies Press.
45 Monier, E., X. Gao, J.R. Scott, A.P. Sokolov, and C.A. Schlosser. 2014. A framework for
modeling uncertainty in regional climate change. ClimaticChange. DOI:10.10077
S10584-014-1112-5.
46 Ongoing studies are investigating the influence of structural uncertainties across
sectoral impact models. See: Huber, V., H.J. Schellnhuber, N.W. Arnell, K. Frieler, A.D.
Friend, D. Gerten,... and L. Warszawski. 2014. Climate impact research: beyond patch-
work. Earth System Dynamics. DOI:10.5194/esd-5-399-2014.
47 For a discussion of interactions among the energy, water, and land use sectors, see:
Hibbard, K., T. Wilson, K. Averyt, R. Harriss, R. Newmark, S. Rose, E. Shevliakova, and V.
Tidwell. 2014. Ch. 10: Energy, Water, and Land Use. Climate Change Impacts in the Unit-
ed States: TheThird National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond,
and G. W. Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/JOJW8BSF.
SECTORS
Health
1 The economic estimates described throughout this report are presented in constant
2014 dollars. The literature underlying the CIRA project presents results primarily in
2005 dollars. This should be noted when comparing the results presented in this report
with those in the CIRA literature. Dollar years were adjusted using the U.S. Bureau of
Economic Analysis' Implicit Price Deflators for Gross Domestic Product. Source: U.S.
Bureau of Economic Analysis, Table 1.1.9 Implicit Price Deflators for Gross Domestic
Product, March 27,2015. http://www.bea.gov/national/index.htm.
2 Throughout the report, future benefits—i.e., the annual time series of avoided costs—
are discounted at a 3% rate to reflect their value in the present day, which is defined as
theyear 2015 in this report. In short, discounting provides an equal basisto compare
the value of benefits (and costs) that occur in different time periods. The discount rate
itself reflects the trade-off between consumption today and consumption tomorrow,
meaning that with a positive discount rate, benefits that occur today are worth more
than they would be tomorrow. A higher discount rate implies a greater preference
for present-day consumption and a lower present value of future damages. A lower
discount rate implies a greater value on future damages. That is, the present value
of future damages calculated at a 5% rate will be lower than those calculated using
a 3% rate. There are many ways to select a discount rate and little consensus about
which discount rate is most appropriate, particularly when assessing benefits that
span generations. Therefore, we selected 3%, a commonly employed rate in the
climate impacts and benefits literature. This rate was also used to calculate two of the
U.S. Government's four Social Cost of Carbon estimates (including the central value),
which estimate climate damages that occur over long time horizons. In particular, the
U.S. Government review found that it was consistent with estimates provided in the
economics literature and noted that 3% roughly corresponds to the after-tax riskless
interest rate. For a detailed discussion on discount rate selection, please see the Social
Cost of Carbon Technical Support Document, available at http://www.epa.gov/oms/
climate/requlations/scc-tsd.pdf.
3 IPCC. 2014. Summary for Policymakers. In: Climate Change 2014: Impacts, Adaptation,
and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II
to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Field,
C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. Mastrandrea, T.E. Bilir,... and L.L. White,
Eds. New York, NY: Cambridge University Press.
4 Luber, G., K. Knowlton, J. Balbus, H. Frumkin, M. Hayden, J. Hess,... and L. Ziska. 2014.
Ch. 9: Human Health. Climate Change Impacts in the United States: The Third National
Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S.
Global Change Research Program. DOI:10.7930/JOPN93H5.
5 U.S. Environmental Protection Agency. 2012. Ground Level Ozone: Health Effects.
http://www.epa.gov/groundlevelozone/health.html.
6 Luber, G., K. Knowlton, J. Balbus, H. Frumkin, M. Hayden, J. Hess,... and L. Ziska. 2014.
Ch. 9: Human Health. Climate Change Impacts in the United States: The Third National
Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S.
Global Change Research Program. DOI:10.7930/JOPN93H5.
7 Ibid.
8 U.S. Environmental Protection Agency. 2013. Integrated Science Assessment of Ozone
and Related Photochemical Oxidants (Final Report). EPA/600/R-10/076F.
9 U.S. Environmental Protection Agency. 2009. Integrated Science Assessment for
Particulate Matter (Final Report). EPA/600/R-08/139F.
10 A climate-induced drop in ozone is caused by increased atmospheric water vapor
under a warmer climate. Higher humidity shortens the atmospheric lifetime of ozone
in low-NOx (typically less densely-populated) conditions by enhancing its breakdown.
Projected reductions in ground-level concentrations over the northern and western
parts of the country are largely driven by this decline in background ozone.
11 For comparison, the current national 8-hour daily maximum ozone standard is 75 parts
per billion: primary and secondary standard in the form of annual fourth-highest daily
maximum 8-hour concentration averaged over 3 years.
12 Changes in ozone and PM2 5 concentrations in the Risks of Inaction section and in
Figures 1 and 2 are not population-weighted.
13 Luber, G., K. Knowlton, J. Balbus, H. Frumkin, M. Hayden, J. Hess,... and L. Ziska. 2014. Ch.
9: Human Health. Climate Change Impacts in the United States: The Third National Climate
86
-------
Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global
Change Research Program. DOI:10.7930/JOPN93H5.
14 The ranges in mortality estimates are based on ensemble means and reflect the 95%
confidence interval in concentration response functions. See Garcia-Menendez et al.
(2015) for more information.
15 An additional mortality valuation approach using years of life saved is provided in
Garcia-Menendez etal. (2015).
16 Reductions in PM2 5 largely drive the change in mortality. However, the contribution
of ozone pollution to these estimates increases towards the end of the century and
accounts for 40% of the projected life years saved by 2100. See Garcia-Menendez et al.
(2015) for more information.
17 For example: 1) Thompson, T.M., Rausch S., Saari R.K., and Selin N.E. 2014. A systems ap-
proach to evaluating the air quality co-benefits of U.S. carbon policies. Nature Climate
Change. DOI: 10.1038/nclimate2342; 2) West, J., S. Smith, R. Silva, V. Naik, Y. Zhang,
Z. Adelman,... and J. Lamarque. 2013. Co-benefits of mitigating global greenhouse
gas emissions for future air quality and human health. Nature Climate Change. DOI:
10.1038/nclimate2009; and 3) U.S. Environmental Protection Agency. 2014. Regulatory
Impact Analysis for the Proposed Carbon Pollution Guidelines for Existing Power Plants
and Emission Standards for Modified and Reconstructed Power Plants. Office of Air
Quality Planning and Standards, Health & Environmental Impacts Division, Air Econom-
ics Group. Research Triangle Park, North Carolina.
18 IPCC. 2014. Climate Change 2014: Mitigation of Climate Change. Contribution of Work-
ing Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate
Change, Edenhofer, O., R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth,
... and J.C. Minx, Eds. New York, NY: Cambridge University Press.
19 Fine particulate matter constituents analyzed include sulfate, elemental carbon, organ-
ic aerosol and ammonium nitrate.
20 Changes in mortality are estimated by applying the differences in daily-maximum
8-hour ozone (8-hr-max ozone) between May and September and daily average PM25
to the concentration response functions.
21 At the time of this report's release, the U.S. Environmental Protection Agency's
Guidelines for Preparing Economic Analyses report recommends a VSL of $7.9 million
(2008$), based on 1990 incomes. To create a VSL using 2014$ and based on 2010
incomes, the standard value was adjusted for inflation using BEA implicit price inflator
for gross domestic product and for income growth adjustment based on a method
described in the user manual of EPA'sBenMAP model (pg. 109). The resulting value,
$9.45 million for 2010 (2014$), was adjusted to future years by assuming an elasticity of
VSL to GDP per capita of 0.4. Projections of GDP and population for the CIRA Reference
scenario were employed. Using this approach, the VSL in 2050 is estimated at $12.53
million and $16.39 million in 2100. Finally, we note that the VSL values used in this
report differ slightly from those used in Garcia-Menendez et al. (2015), which therefore
affects the valuation estimates reported in each. Sources: 1) U.S. Environmental Protec-
tion Agency. 2014. Guidelines for Preparing Economic Analyses. National Center for En-
vironmental Economics. http://yosemite.epa.gov/ee/epa/eerm.nsf/vwAN/EE-0568-52.
pdf/$file/EE-0568-52.pdf: 2) U.S. Bureau of Economic Analysis, Table 1.1.9 Implicit Price
Deflators for Gross Domestic Product, March 27.2015. http://www.bea.gov/national/
index.htm: and 3) U.S. Environmental Protection Agency. 2012. Ben MAP Users Manual.
Office of Air Quality Planning and Standards.
22 Garcia-Menendez, F., R.K. Saari, E. Monier, and N.E. Selin. (2015) U.S. air quality and
health benefits from avoided climate change under greenhouse gas mitigation. Envi-
ronmental Science&Technology. DOI:10.1021/acs.est.5b01324.
23 Luber, G., K. Knowlton, J. Balbus, H. Frumkin, M. Hayden, J. Hess,... and L. Ziska. 2014. Ch.
9: Human Health. Climate Change Impacts in the United States: The Third National Climate
Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global
Change Research Program. DOI:10.7930/JOPN93H5.
24 U.S. Environmental Protection Agency. 2014. Climate Change Indicators in the United
States. Third edition. EPA430-R-14-004. www.epa.gov/climatechanqe/indicators.
25 Ibid.
26 Luber, G., K. Knowlton, J. Balbus, H. Frumkin, M. Hayden, J. Hess,... and L. Ziska. 2014. Ch.
9: Human Health. Climate Change Impacts in the United States: The Third National Climate
Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global
Change Research Program. DOI:10.7930/JOPN93H5.
27 Ibid.
28 Average results for the 49 cities included in the study.
29 See Mills et al. (2014) and Bierwagen et al. (2010) for details on usage of ICLUS pop-
ulation projections. Sources: 1) Mills, D., J. Schwartz, M. Lee, M. Sarofim, R.Jones, M.
Lawson, M. Duckworth, and L. Deck. 2014. Climate Change Impacts on Extreme Tem-
perature Mortality in Select Metropolitan Areas in the United States. ClimaticChange.
DOI: 10.1007/S10584-014-1154-8; and 2) Bierwagen, B.C., D.M. Theobald, C.R. Pyke, A.
Choate, P. Groth, J.V. Thomas, and P. Morefield. 2010. National housing and impervious
surface scenarios for integrated climate impact assessments. Proc NatlAcad Sci. DOI:
10.1073/pnas.l 002096107.
30 At the time of this report's release, the U.S. Environmental Protection Agency's
Guidelines for Preparing Economic Analyses report recommends a VSL of $7.9 million
(2008$), based on 1990 incomes. To create a VSL using 2014$ and based on 2010
incomes, the standard value was adjusted for inflation using BEA implicit price inflator
for gross domestic product and for income growth adjustment based on a method
described in the user manual of EPA's BenMAP model (pg. 109). The resulting value,
$9.45 million for 2010 (2014$), was adjusted to future years by assuming an elasticity of
VSL to GDP per capita of 0.4. Projections of GDP and population for the CIRA Reference
scenario were employed. Using this approach, the VSL in 2050 is estimated at $12.53
million and $16.39 million in 2100. Finally, we note that the VSL values used in this
report differ slightly from those used in Garcia-Menendez et al. (2015), which therefore
affects the valuation estimates reported in each. Sources: 1) U.S. Environmental Protec-
tion Agency. 2014. Guidelines for Preparing Economic Analyses. National Center for En-
vironmental Economics. http://yosemite.epa.gov/ee/epa/eerm.nsf/vwAN/EE-0568-52.
pdf/$file/EE-0568-52.pdf: 2) U.S. Bureau of Economic Analysis, Table 1.1.9 Implicit Price
Deflators for Gross Domestic Product, March 27.2015. http://www.bea.gov/national/
index.htm: and 3) U.S. Environmental Protection Agency. 2012. BenMAP Users Manual.
Office of Air Quality Planning and Standards.
31 The approach described in Mills etal. (2014) was updated in several ways to develop
the results presented here. First, the analysis was expanded from 33 cities to encom-
pass a total of 49 out of 50 of the cities (excluding Honolulu) analyzed in the Medi-
na-Ramon and Schwartz (2007) paper that was the foundation of the Mills et al. (2014)
work. Medina-Ramon and Schwartz did not calculate heat mortality response functions
for cities where the minimum temperature for the 99 percentile hottest day was equal
to or below 20°C (8 cities), or cold mortality response functions where the maximum
temperature for the 1 percentile coldest day was greater than or equal to 10°C (7
cities), and the choice was made in the Mills et al. (2014) work to not include those
cities in the projections of future mortality. In a warming climate, cities that were too
warm to meet the criteria for the cold threshold will continue to be too warm, so the
lack of a cold mortality response function will not make a difference. However, most
of the cities that were too cool to meet the criteria for the hot threshold are expected
to warm enough that their 99 percentile hottest days will exceed 20°C in the future.
Therefore, inclusion of cities without a heat mortality response function will lead to an
underestimate of the change in future mortality in those cities, and therefore an under-
estimate of the benefit of GHG mitigation. However, inclusion of a wider range of cities
gives a more complete picture of impacts in the U.S. There were a couple of additional
updates. The first involved limiting the analysis to the actual counties corresponding to
the cities specified in Medina-Ramon and Schwartz, rather than the MSAs used in Mills
et al. (2014). This reduces the total population considered within the original 33 cities.
The second involved updating to the most recent BenMAP data for the all-age mortali-
ty rates in the cities, which resulted in some small differences in the calculations.
32 Mills, D., J.Schwartz, M. Lee, M.Sarofim, R. Jones, M. Lawson, M. Duckworth,and L.
Deck. 2014. Climate Change Impacts on Extreme Temperature Mortality in Select Met-
ropolitan Areas in the United States. ClimaticChange. DOI: 10.1007/S10584-014-1154-8.
33 Walsh, J., D. Wuebbles, K. Hayhoe, J. Kossin, K. Kunkel, G. Stephens,... and R. Somerville.
2014. Ch. 2: Our Changing Climate. Climate Change Impacts in the United States: The
Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe,
Eds., U.S. Global Change Research Program. DOI:10.7930/JOKW5CXT.
34 Graff Zivin, J. and M. Neidell. 2014. Temperature and the allocation of time: implications
for climate change. Journal of Labor Economics, DOI:10.1086/671766.
35 Ibid.
36 This analysis uses the term labor supply to refer to hours worked, but cannot determine
whether that choice is driven by employees or employers.
37 Graff Zivin, J. and M. Neidell. 2014. Temperature and the allocation of time: implica-
tions for climate change. Journal of Labor Economics, DOI:10.1086/671766.
38 For information on the development and usage of the ICLUS population projections,
see: Mills, D., J. Schwartz, M. Lee, M. Sarofim, R. Jones, M. Lawson, M. Duckworth, and L.
Deck. 2014. Climate Change Impacts on Extreme Temperature Mortality in Select Met-
ropolitan Areas in the United States. ClimaticChange. DOI: 10.1007/S10584-014-1154-8.
39 Bureau of Labor Statistics, Quarterly Census of Employment and Wages, data accessi-
ble at http://www.bls.gov/cew/. High-risk workers were defined as those employed in
agriculture, forestry, and fishing; hunting, mining, and construction; and manufactur-
ing, transportation, and utilities industries.
40 Bureau of Labor Statistics, Quarterly Census of Employment and Wages, data accessi-
ble at http://www.bls.9ov/cew/. Average wage ($23.02) calculated using high-risk labor
categories only, as the majority of extreme temperature impacts on labor hours occur
in these industries.
41 Graff Zivin, J. and M. Neidell. 2014. Temperature and the allocation of time: implications
for climate change. Journal of Labor Economics, DOI:10.1086/671766.
87
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42 Georgakakos, A., P. Fleming, M. Dettinger, C. Peters-Lidard, Terese (T.C) Richmond, K.
Reckhow, K. White, and D. Yates. 2014. Ch. 3: Water Resources. Climate Change Impacts
in the United States: TheThird National Climate Assessment, J.M. Melillo, Terese (T.C.)
Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/
JOG44N6T.
43 Luber, G., K. Knowlton, J. Balbus, H. Frumkin, M. Hayden, J. Hess,... and L. Ziska. 2014. Ch.
9: Human Health. Climate Change Impacts in the United States: The Third National Climate
Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global
Change Research Program. DOI:10.7930/JOPN93H5.
44 Boehlert, B., K. Strzepek, S. Chapra, Y. Gebretsadik, M. Lickley, C. Fant,... and J. Mar-
tinich. (In press). Greenhouse Gas Mitigation Effects on Water Quality Impacts from
Climate Change in the U.S. Journal of Advances in Modeling Earth Systems.
45 Georgakakos, A., P. Fleming, M. Dettinger, C. Peters-Lidard, Terese (T.C.) Richmond, K.
Reckhow, K. White, and D. Yates. 2014. Ch. 3: Water Resources. Climate Change Impacts
in the United States: TheThird National Climate Assessment, L M. Melillo, Terese (T.C.)
Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/
JOG44N6T.
46 Strzepek K., M. Jacobsen, B. Boehlert, J. Neumann. 2013. Toward evaluating the effect
of climate change on investments in the water resources sector: insights from the
forecast and analysis of hydrological indicators in developing countries. Environmental
Research ieffers, DOI:10.1088/1748-9326/8/4/044014.
47 Chapra, S.C. 2014. QUALIDAD: A parsimonious modeling framework for simulating
river basin water quality, Version 1.1, Documentation and users manual. Civil and
Environmental Engineering Dept., Tufts University, Medford, MA.
48 Boehlert, B., K. Strzepek, S. Chapra, Y. Gebretsadik, M. Lickley, C. Fant,... and J. Mar-
tinich. (In press). Greenhouse Gas Mitigation Effects on Water Quality Impacts from
Climate Change in the U.S. Journal of Advances in Modeling Earth Systems.
Infrastructure
1 Wilbanks, T., and S. Fernandez. 2012. Climate Change and Infrastructure, Urban
Systems, and Vulnerabilities: Technical Report to the U.S. Department of Energy
in Support of the National Climate Assessment, http://www.esd.ornl.gov/eess/
lnfrastructure.pdf.
2 Congress of the United States, Congressional Budget Office. 2010. Public Spending
on Transportation and Water Infrastructure, http://www.cbo.gov/sites/default/files/
cbofiles/attachments/11-17-10-lnfrastructure.pdf.
3 Congress of the United States, Congressional Budget Office. 2008. Issues and Options in
Infrastructure Investment, http://www.cbo.gov/sites/default/files/cbofiles/ftpdocs/91xx/
doc9135/05-16-infrastructure.pdf.
4 Schwarz, H.G., M. Meyer, C.J. Burbank, M. Kuby, C. Oster, J. Posey, E.J. Russo, and A.
Rypinski. 2014. Chapter 5: Transportation. Climate Change Impacts in the United States:
The Third National Climate Assessment, J.M. Melillo, T.C. Richmond, and G.W. Yohe, Eds.,
U.S. Global Research Prog ram. DOI:10.7930/JO6Q1V53.
5 U.S. Department of Transportation. 2013. National Bridge Inventory.
6 Schwarz, H.G., M. Meyer, C.J. Burbank, M. Kuby, C. Oster, J. Posey, E.J. Russo, and A.
Rypinski. 2014. Chapter 5: Transportation. Climate Change Impacts in the United States:
The Third National Climate Assessment, J.M. Melillo, T.C. Richmond, and G.W. Yohe, Eds.,
U.S. Global Research Prog ram. DOI:10.7930/JO6Q1V53.
7 Ibid.
8 Wright, L., P. Chinowsky, K. Strzepek, R. Jones, R. Streeter, J. Smith, J. Mayotte, A. Powell,
L. Jantarasami, and W. Perkins. 2012. Estimated effects of climate change on flood
vulnerability of U.S. bridges. Mitigation and Adaptation Strategies for Global Change.
DOI:10.1007/sl 1027-011-9354-2.
9 As such, the costs of future maintenance, and the effects of those efforts in reducing
vulnerability, are not captured in this analysis.
10 Wright et al. (2012) provides estimates of the total costs for repairing deficient bridges
both in advance of climate change and as adaptation to climate change. Neumann et
al. (2014) presents the results of repairing bridges in advance of climate change. The
results presented in this report are the results of repairing bridges as adaptation to
climate change.
11 Neumann, J., J. Price, P. Chinowsky, L. Wright, L. Ludwig, R. Streeter,... and J. Martinich.
2014. Climate change risks to U.S. infrastructure: impacts on roads, bridges, coastal
development, and urban drainage. Climatic Change. DOI:10.1007/sl 0584-013-1037-4.
12 Wright, L., P. Chinowsky, K. Strzepek, R. Jones, R. Streeter, J. Smith, J. Mayotte, A. Powell,
L. Jantarasami, and W. Perkins. 2012. Estimated effects of climate change on flood
vulnerability of U.S. bridges. Mitigation and Adaptation Strategies for Global Change.
DOI:10.1007/sl 1027-011-9354-2.
13 Schwarz, H.G., M. Meyer, C.J. Burbank, M. Kuby, C. Oster, J. Posey, E.J. Russo, and A.
Rypinski. 2014. Chapter 5: Transportation. Climate Change Impacts in the United States:
The Third National Climate Assessment, J.M. Melillo, T.C. Richmond, and G.W. Yohe, Eds.,
U.S. Global Research Prog ram. DOI:10.7930/JO6Q1V53.
14 Transportation Research Board. 2008. Potential Impacts of Climate Change on U.S.
Transportation. Special Report 290, Committee on Climate Change and U.S. Transpor-
tation, National Research Council of the National Academies.
15 Schwarz, H.G., M. Meyer, C.J. Burbank, M. Kuby, C. Oster, J. Posey, E.J. Russo, and A.
Rypinski. 2014. Chapter 5: Transportation. Climate Change Impacts in the United States:
The Third National Climate Assessment, J.M. Melillo, T.C. Richmond, and G.W. Yohe, Eds.,
U.S. Global Research Prog ram. DOI:10.7930/JO6Q1V53.
16 For additional explanation of MIROC results, see: Neumann, J., J. Price, P. Chinowsky,
L. Wright, L. Ludwig, R. Streeter,... and J. Martinich. 2014. Climate change risks to U.S.
infrastructure: impacts on roads, bridges, coastal development, and urban drainage.
Climatic Change. DOI:10.1007/sl 0584-013-1037-4.
17 Neumann, J., J. Price, P. Chinowsky, L. Wright, L. Ludwig, R. Streeter,... and J. Martinich.
2014. Climate change risks to U.S. infrastructure: impacts on roads, bridges, coastal
development, and urban drainage. Climatic Change. DOI:10.1007/sl 0584-013-1037-4.
18 Chinowsky, P., J. Price, and J. Neumann. 2013. Assessment of climate change adap-
tation costs for the U.S. road network. Global Environmental Change. DOI:10.1016/j.
gloenvcha.2013.03.004.
19 Georgakakos, A., P. Fleming, M. Dettinger, C. Peters-Lidard, T.C. Richmond, K. Reckhow,
K. White, and D. Yates. 2014. Ch. 3: Water Resources. Climate Change Impacts in the
United States: The Third National Climate Assessment, L M. Melillo, T.C. Richmond, and G.
W. Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/JOG44N6T.
20 Schwarz, H.G., M. Meyer, C.J. Burbank, M. Kuby, C. Oster, J. Posey, E.J. Russo, and A.
Rypinski. 2014. Chapter 5: Transportation. Climate Change Impacts in the United States:
The Third National Climate Assessment, J.M. Melillo, T.C. Richmond, and G.W. Yohe, Eds.,
U.S. Global Research Prog ram. DOI:10.7930/JO6Q1V53.
21 The adaptation costs per square mile, calculated by city, storm, scenario, and year,
were aggregated to the regions used in the Third National Climate Assessment
and weighted by area. For example, for a region with 2 cities, each with an area of
100 square miles, each city's area is divided by the sum of the areas, resulting in a
proportion value of 0.5 for each city. This proportion value is then multiplied by each
calculation of per-square-mile adaptation costs (calculated by storm, scenario, and
year) to produce a weighted average adaptation cost per square mile.
22 More detailed models are often used by municipalities for local stormwater man-
agement planning, but applying these models across the 50 cities examined in this
analysis was not practicable.
23 Neumann, J., J. Price, P. Chinowsky, L. Wright, L. Ludwig, R. Streeter,... and J. Martinich.
2014. Climate change risks to U.S. infrastructure: impacts on roads, bridges, coastal
development, and urban drainage. Climatic Change. DOI:10.1007/sl 0584-013-1037-4.
24 Price, J., L. Wright, C. Fant, and K. Strzepek. 2014. Calibrated Methodology for Assessing
Climate Change Adaptation Costs for Urban Drainage Systems. Urban Water Journal.
DOI:10.1080/1573062X.2014.991740.
25 The results presented here apply the methods described in Price etal. (2014) and
Neumann et al. (2014), with an expansion of the number of cities modeled.
26 Moser, S.C., M.A. Davidson, P. Kirshen, P. Mulvaney, J.F. Murley, J.E. Neumann, L. Petes,
and D. Reed. 2014. Ch. 25: Coastal Zone Development and Ecosystems. Climate Change
Impacts in the United States: The Third National Climate Assessment, J.M. Melillo, T.C.
Richmond, and G.W. Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/
JOMS3QNW.
27 Ibid.
28 Underlying vulnerability exists in both the Reference and the Mitigation scenarios
within the base or historic period (i.e., today). This vulnerability is depicted for the Ref-
erence scenario in Figure 1 as costs occurring in 2000. Removing costs associated with
baseline vulnerability yields cost estimates with adaptation of $530 billion under the
Reference scenario and $500 billion under the Mitigation scenario. We've included the
baseline vulnerability costs in our estimates because they may affect future decisions
about coastal development. We also note that some damages to coastal property are
due to the effects of land subsidence that occurs regardless of climate change.
29 The CIRA sea level rise scenarios are at the high end of projected sea level rise rates for
similar scenarios based on recent publications (Horton et al. 2014, Kopp et al. 2014).
However, we also note that the effect of GHG mitigation on reducing the increase
in future sea level was found to be proportionally larger in these studies. The use of
smaller sea level rise rates would likely lead to a decrease in total damages, but a larger
reduction in sea level rise due to the Mitigation scenario compared to the Reference
would likely yield larger economic benefits than those presented in this report. See:
1) Horton, B.J., S. Rahmstorf, S.E. Engelhart, and A.C. Kemp. 2014. Expert assessment
88
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of sea-level rise by AD 2100 and AD 2300. Quaternary Science Reviews, DOI:10.1016/j.
quascirev.2013.11.002; and 2) Kopp, R.E., R.M. Norton, CM. Little, J.X. Mitrovica, M.
Oppenheimer, D.J. Rasmussen, B.H.Strauss, and C. Tebaldi. 2014. Probabilistic 21st and
22nd century sea-level projections at a global network of tide-gauge sites. Earth's Future,
DOI:10.1002/2014EF000239.
30 Without discounting, the cumulative effect of mitigation is larger, reducing impacts by
about 10% (from $1.2 trillion to $1.0 trillion), and the annual benefits rise rapidly from
approximately $140 million in 2050 to nearly $3.1 billion in 2100.
31 The CIRA analysis evaluates risks of inaction and benefits of mitigation through the end
of the 21st century. The high degree of inertia in processes leading to sea-level rise (i.e.,
the oceans and ice sheets respond slowly to warming conditions at the Earth's surface)
suggest that the absence of 21st century GHG mitigation is likely to result in sea level
rise rates equal to or larger than those experienced this century, with subsequent
large and long-term implications for coastal development (Horton et al. 2014 and
Levermann et al. 2013 provide projections of sea level rise beyond 2100). Therefore,
the difference in sea level change rise between the CIRA Reference and Mitigation
scenarios will only increase after 2100. This would likely result in larger GHG mitigation
benefits to the coastal property sector, and it is important to note that these benefits
would only be realized from GHG reductions occurring in this century. See: Horton,
B.J., S. Rahmstorf, S.E. Engelhart, and A.C. Kemp. 2014. Expert assessment of sea-level
rise by AD 2100 and AD 2300. Quaternary Science Reviews 84:1-6; and Levermann, A., P.
Clark, B. Marzeion, G. Milne, D. Pollard, V. Radic, and A. Robinson. 2013. The multimille-
nial sea-level commitment of global warming. PNAS, DOI: 10.1073/pnas.1219414110.
32 Vermeer, M., and S. Rahmstorf. 2009. Global sea level linked to global temperature.
Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0907765106.
33 National Atmospheric and Oceanic Administration (NOAA) Center for Operational
Oceanographic Products and Services (CO-OPS). Linear mean sea level (MSL) trends
and 95% confidence intervals in mm/yr. http://tidesandcurrents.noaa.gov/sltrends/
sltrends.html.
34 Emanuel, K., R. Sundararajan, and J.Williams. 2008. Hurricanes and Global Warming:
Results from Downscaling IPCC AR4 Simulations. Bulletin of the American Meteorological
Society. DOI:10.1175/BAMS-89-3-347.
35 Jelesnianski, C.P., J. Chen, and W.A. Shaffer. 1992. SLOSH: Sea, lake, and overland surges
from hurricanes. NOAA Technical Report NWS 48, National Oceanic and Atmospheric
Administration, U. S. Department of Commerce, Washington, DC.
36 Tebaldi, C., B. Strauss, and C. Zervas. 2012. Modeling sea-level rise impacts on
storm surges along U.S. coasts. Environmental Research Letters. DOI:10.1088/1748-
9326/7/1/014032.
37 Neumann, J., K. Emanuel, S. Ravela, L Ludwig, P. Kirshen, K. Bosma, and J. Martinich.
2014a. Joint Effects of Storm Surge and Sea-level Rise on U.S. Coasts. Climatic Change.
DOI: 10.1007/S10584-014-1304-Z..
38 Neumann, J., J. Price, P. Chinowsky, L. Wright, L. Ludwig, R. Streeter,... and J. Martinich.
2014b. Climate change risks to U.S. infrastructure: impacts on roads, bridges, coastal
development, and urban drainage. Climatic Change. DOI:10.1007/s10584-013-1037-4.
39 Cutter, S., B.J. Boruff, and W.L. Shirley. 2003. Social Vulnerability to Environmental
Hazards. Social Science Quarterly 84(2).
40 Borden, K., M. Schmidtlein, C. Emrich, W. Piegorsch, and S. Cutter. 2007. Vulnerability
of U.S. cities to environmental hazards. Journal of Homeland Security and Emergency
Management, DOI: 10.2202/1547-7355.1279; Schmidtlein, M., R. Deutsch, W. Piegorsch,
and S. Cutter. 2008. A sensitivity analysis of the social vulnerability index. Risk Analysis,
DOI: 10.1111/j.l 539-6924.2008.01072.x; Wood, N., C. Burton, and S. Cutter. 2010. Com-
munity variations in social vulnerability to Cascadia-related tsunamis in the U.S. Pacific
Northwest. Natural Hazards, DOI: 10.1007/sl 1069-009-9376-1.
41 Neumann, J., K. Emanuel, S. Ravela, L. Ludwig, P. Kirshen, K. Bosma, and J. Martinich.
2014. Joint Effects of Storm Surge and Sea-level Rise on U.S. Coasts. ClimaticChange.
DOI: 10.1007/S10584-014-1304-Z..
42 Neumann, J., J. Price, P. Chinowsky, L.Wright, L. Ludwig,... and J. Martinich. 2014.
Climate change risks to U.S. infrastructure: impacts on roads, bridges, coastal develop-
ment, and urban drainage. ClimaticChange, DOI:10.1007/s10584-013-1037-4.
43 Martinich, J., J.Neumann, L. Ludwig, and L. Jantarasami.2013. Risks of sea level rise to
disadvantaged communities in the United States. Mitigation and Adaptation Strategies
for Global Change. DOI: 10.1007/sl 1027-011-9356-0.
44 Areas with significant storm surge damages are those where the damages from storm
surge are greater than the value of the property.
45 The adaptation responses projected by the National Coastal Property Model are
developed using a cost-benefit framework comparing the costs of protection relative
to the property value. Developed as a simple metric to estimate potential adaptation
responses in a consistent manner for the entire coastline, the estimates presented
here should not be construed as recommending any specific policy or adaptive action.
Further, additional adaptation options not included in this analysis, such as marsh
restoration, may be appropriate for some locales.
Electricity
1 The transportation sector accounts for 27 percent of emissions, followed by the
residential, commercial, and industrial sectors at 21 percent. The remaining 22 percent
of emissions come from biomass and various other sectors. The share of electricity
generated by fossil fuels from 2009-2013 was 69% (42% from coal, 26% from natural
gas, 0.8% from petroleum). U.S. Department of Energy. 2014. Electric Power Monthly:
Table 1.1. Net Generation by Energy Source: Total (All Sectors), 2004-February 2014.
2 Dell, J., S. Tierney, G. Franco, R. G. Newell, R. Richels, J. Weyant, and T. J. Wilbanks. 2014.
Ch. 4: Energy Supply and Use. Climate Change Impacts in the United States: The Third
National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds.,
U.S. Global Change Research Program. DOI:10.7930/JOBG2KWD.
3 Ibid.
4 Consistent with other electricity and power sector analyses, the CIRA analysis only
projects impacts through 2050.
5 Dell, J., S. Tierney, G. Franco, R. G. Newell, R. Richels, J. Weyant, and T. J. Wilbanks. 2014.
Ch. 4: Energy Supply and Use. Climate Change Impacts in the United States: The Third
National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds.,
U.S. Global Change Research Program. DOI:10.7930/JOBG2KWD.
6 U.S. Department of Energy, U.S. Energy Information Administration. 2009 Residential
Energy Consumption Survey (RECS): Table CE4.1. http://www.eia.gov/consumption/
residential/da ta/2009/index.cfm.
7 U.S. Department of Energy, U.S. Energy Information Administration. 2003 Commercial
Buildings Energy Consumption Survey (CBECS): Tables El A and E3A. http://www.eia.
gov/consumption/commercial/data/2003/index.cfm.
8 Dell, J., S. Tierney, G. Franco, R. G. Newell, R. Richels, J. Weyant, and T. J. Wilbanks. 2014.
Ch. 4: Energy Supply and Use. Climate Change Impacts in the United States: The Third
National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds.,
U.S. Global Change Research Program. DOI:10.7930/JOBG2KWD.
9 In this instance, the reduction in electric heating is greater than the rise in demand for
cooling by 0.3%. This reflects a higher level of electricity demand for heating in the
Pacific Northwest relative to the rest of country.
10 Kyle, P., L. Clarke, F. Rong, and S.J. Smith. 2010. Climate Policy and the Long-Term
Evolution of the U.S. Buildings Sector. The Energy Journal, 31(2):145-172.
11 Zhou, Y., J. Eom, and L. Clarke. 2013. The effect of global climate change, population
distribution, and climate mitigation on building energy use in the U.S. and China.
Climatic Change, DOI:10.1007/sl 0584-013-0772-x.
12 National Renewable Energy Laboratory. 2014. NREL: Energy Analysis - Regional Energy
Deployment System (ReEDS) Model, http://www.nrel.gov/analvsis/reeds/.
13 Jaglom, W., McFarland, J., M. Colley, C. Mack, B. Venkatesh, R. Miller,... and S. Kayin.
2013. Assessment of projected temperature impacts from climate change on the
U.S. electric power industry using the Integrated Planning Model. Energy Policy.
DOI:10.1016/j.enpol.2014.04.032.
14 McFarland, J., Y. Zhou, L. Clarke, P. Sullivan, J. Colman, W. Jaglom,... and J. Creason.
2015. Impacts of rising air temperatures and emissions mitigation on electricity
89
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demand and supply in the United States: a multi-model comparison. Climatic Change.
DOI: 10.1007/S10584-015-1380-8.
15 U.S. Environmental Protection Agency. 2014. Inventory of U.S. Greenhouse Gas
Emissions and Sinks: 1990-2012, Table 2-1. http://www.epa.gov/climatechange/
Downloads/ghgemissions/US-GHG-lnventory-2014-Chapter-2-Trends.pdf.
16 Clarke, I.E., A.A. Fawcett, J.P. Weyant, J. McFarland, V. Chaturvedi, and Y. Zhou. 2014.
Technology and U.S. Emissions Reductions Goals: Results of the EMF 24 Modeling
Exercise. The Energy Journal, DOI: 10.5547/01956574.35.SI1.2.
17 As described in the CIRA Framework section, the Mitigation scenario is not associated
with any specific policy (e.g., EPA's Clean Power Plan), and is assumed to be achieved
through global efforts to reduce GHG emissions. Therefore, projected emissions
reductions in the U.S. electricity sector are part of a larger global mitigation scenario.
See McFarland et al. (2015) for information regarding U.S. electricity sector emissions.
18 Total generation across the models varies because electricity demand is independently
calculated by each model based on changes in population, GDP, technology costs, and
other factors.
19 McFarland, J., Y. Zhou, L Clarke, P. Sullivan, J. Colman, W. Jaglom,... and J. Creason.
2015. Impacts of rising air temperatures and emissions mitigation on electricity
demand and supply in the United States: a multi-model comparison. Climatic Change.
DOI: 10.1007/S10584-015-1380-8.
Water Resources
1 U.S. Environmental Protection Agency, Office of Water. 2013. The Importance of Water
to the U.S. Economy: Synthesis Report, http://water.epa.gov/action/importanceofwa-
ter/upload/lmportance-of-Water-Synthesis-Report.pdf.
2 U.S. Environmental Protection Agency. 2014. Climate Change Indicators in the United
States: Drought, http://www.epa.gov/climatechanqe/pdfs/print drouqht-2014.pdf.
3 Georgakakos, A., P. Fleming, M. Dettinger, C. Peters-Lidard, T.C. Richmond, K. Reckhow,
K. White, and D. Yates, D. 2014. Chapter 3: Water Resources. Climate Change Impacts
in the United States: TheThird National Climate Assessment, J. M. Melillo, T.C. Richmond,
and G.W. Yohe, Eds., U.S. Global Change Research Program, DOI:10.7930/JOG44N6T.
4 Ibid.
5 Walsh, J., D. Wuebbles, K. Hayhoe, J. Kossin, K. Kunkel, G. Stephens,... and R. Somerville.
2014. Ch. 2: Our Changing Climate. Climate Change Impacts in the United States: The
Third National Climate Assessment, L M. Melillo, Terese (T.C.) Richmond, and G.W. Yohe,
Eds., U.S. Global Change Research Program. DOI:10.7930/JOKW5CXT.
6 Georgakakos, A., P. Fleming, M. Dettinger, C. Peters-Lidard, T.C. Richmond, K. Reckhow,
K. White, and D. Yates, D. 2014. Chapter 3: Water Resources. Climate Change Impacts
in the United States: TheThird National Climate Assessment, L M. Melillo, T.C. Richmond,
and G.W. Yohe, Eds., U.S. Global Change Research Program, DOI:10.7930/JOG44N6T.
7 Damages are in 2011 dollars.
8 Georgakakos, A., P. Fleming, M. Dettinger, C. Peters-Lidard, T.C. Richmond, K. Reckhow,
K. White, and D. Yates, D. 2014. Chapter 3: Water Resources. Climate Change Impacts
in the United States: TheThird National Climate Assessment, L M. Melillo, T.C. Richmond,
and G.W. Yohe, Eds., U.S. Global Change Research Program, DOI:10.7930/JOG44N6T.
9 Ibid.
10 Across the contiguous U.S., damages are projected to decrease relative to the baseline
period in the following Water Resource Regions (WRRs): Upper Colorado, Lower Colo-
rado, Pacific Northwest, and California.
11 Georgakakos, A., P. Fleming, M. Dettinger, C. Peters-Lidard, T.C. Richmond, K. Reckhow,
K. White, and D. Yates, D. 2014. Chapter 3: Water Resources. Climate Change Impacts
in the United States: TheThird National Climate Assessment, J. M. Melillo, T.C. Richmond,
and G.W. Yohe, Eds., U.S. Global Change Research Program, DOI:10.7930/JOG44N6T.
12 Wobus, C., Lawson, M., Jones, R., Smith, J., and Martinich, J. 2013. Estimating monetary
damages from flooding in the United States under a changing climate. Journal of Flood
Risk Management. DOI: 10.1111/jfr3.12043.
13 In reality, the distribution of monetary damages from flooding is likely to change:
changes in floodplain development, modifications to flood protection infrastructure,
or changes in wealth could all influence the damage incurred by a given magnitude
of flood event in the future. However, these future demographic and infrastructure
changes could either increase or decrease damages from flooding in the future: flood
protection could decrease damages, while increases in development in the floodplain
could increase them. Without an a priori means of evaluating which path to follow, the
assumption of stationarity in this distribution is reasonable.
14 Strzepek, K., J. Neumann, J. Smith, J. Martinich, B. Boehlert,... and J.-H. Yoon. 2014.
Benefits of Greenhouse Gas Mitigation on the Supply, Management, and Use of Water
Resources in the United States. ClimaticChange. DOI: 10.1007/S10584-014-1279-9.
15 Wobus, C., Lawson, M., Jones, R., Smith, J., and Martinich, J. 2013. Estimating monetary
damages from flooding in the United States under a changing climate. Journal of Flood
Risk Management. DOI: 10.1111/jfr3.12043.
16 Georgakakos, A., P. Fleming, M. Dettinger, C. Peters-Lidard, T.C. Richmond, K. Reckhow,
K. White, and D. Yates, D. 2014. Chapter 3: Water Resources. Climate Change Impacts
in the United States: TheThird National Climate Assessment, L M. Melillo, T.C. Richmond,
and G.W. Yohe, Eds., U.S. Global Change Research Program, DOI:10.7930/JOG44N6T.
17 National Drought Mitigation Center, University of Nebraska-Lincoln. 2014. Drought
Impact Reporter. http://drouqht.unl.edu/MonitorinqTools/DrouqhtlmpactReporter.
aspx.
18 Monier, E., X. Gao, J. Scott, A. Sokolov, and C. Schlosser. 2014. A framework for model-
ing uncertainty in regional climate change. ClimaticChange. DOI: 10.1007/S10584-014-
1112-5.
19 Georgakakos, A., P. Fleming, M. Dettinger, C. Peters-Lidard, T.C. Richmond, K. Reckhow,
K. White, and D. Yates, D. 2014. Chapter 3: Water Resources. Climate Change Impacts
in the United States: TheThird National Climate Assessment, L M. Melillo, T.C. Richmond,
and G.W. Yohe, Eds., U.S. Global Change Research Program, DOI:10.7930/JOG44N6T.
20 Walsh, J., D. Wuebbles, K. Hayhoe, J. Kossin, K. Kunkel, G. Stephens,... and R. Somerville.
2014. Ch. 2: Our Changing Climate. Climate Change Impacts in the United States: The
Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe,
Eds., U.S. Global Change Research Program. DOI:10.7930/JOKW5CXT.
21 Strzepek, K., G. Yohe, J. Neumann, and B. Boehlert. 2010. Characterizing chang-
es in drought risk for the United States from climate change. Environ. Res. Lett.
DOI:10.1088/1748-9326/5/4/044012.
22 Boehlert, B., E. Fitzgerald, J. Neumann, K. Strzepek, and J. Martinich. 2015. The Effect
of Greenhouse Gas Mitigation on Drought Impacts in the U.S. Weather, Climate and
Society. DOI: 10.1175/WCAS-D-14-00020.1.
23 The impact estimates for drought on crop-based agriculture both complement and
overlap with the FASOM/EPIC estimates of the impact of climate change on agricul-
tural crops. The drought methodology uses an econometric approach grounded in
historical expenditures to alleviate historical droughts, and projections of drought
occurrence—it addresses a subset of effects on agriculture associated with drought
occurrence. The FASOM/EPIC results are more comprehensive in scope and address
both droughts and many other aspects of climate change (e.g., changes in the timing
of rainfall and extreme heat), and adopt a simulation approach which models specific
actions by farmers and in agricultural markets that might betaken to respond to
climate impacts.
24 Strzepek, K., J. Martinich, J. Neumann, B. Boehlert, J. Henderson, M. Hejazi,... and J.
Yoon. 2014. Benefits of Greenhouse Gas Mitigation on the Supply, Management, and
Use of Water Resources in the United States. ClimaticChange. DOI: 10.1007/sl 0584-
014-1279-9.
25 Boehlert, B., E. Fitzgerald, J. Neumann, K. Strzepek, and J. Martinich. 2015. The Effect
of Greenhouse Gas Mitigation on Drought Impacts in the U.S. Weather, Climate and
Society. DOI: 10.1175/WCAS-D-14-00020.1.
26 Georgakakos, A., P. Fleming, M. Dettinger, C. Peters-Lidard, T.C. Richmond, K. Reckhow,
K. White, and D. Yates, D. 2014. Chapter 3: Water Resources. Climate Change Impacts
in the United States: TheThird National Climate Assessment, L M. Melillo, T.C. Richmond,
and G.W. Yohe, Eds., U.S. Global Change Research Program, DOI:10.7930/JOG44N6T.
27 Ibid.
28 Henderson, J., C. Rodgers, R. Jones, J. Smith, K. Strzepek, and J. Martinich. 2013. Eco-
nomic impacts of climate change on water resources in the coterminous United States.
Mitig Adapt Strateg Glob Change. DOI:10.1007/sl 1027-013-9483-x.
29 In-stream flows are modeled such that flows below minimum levels required to sustain
vulnerable aquatic species are assessed a penalty. In addition, it should be noted that
the agricultural water use simulated in the CIRA Water Supply and Demand model
does not linkwith the model used to estimate impacts in that sector of this report.
30 While the Water Supply and Demand analysis accounts for reactive adaptation in
response to changes in water supply, the effects from water resources technology im-
provements and proactive adaptation planning are not included. Adaptation planning
in the water resource sector has increased at the federal level in the U.S., e.g., EPA Na-
tional Water Program's Responseto Climate Change and NOAA's Regional Integrated
Sciences & Assessments (RISA) program.
31 Strzepek, K., J. Martinich, J. Neumann, B. Boehlert, J. Henderson, M. Hejazi,... and J.
Yoon. 2014. Benefits of Greenhouse Gas Mitigation on the Supply, Management, and
Use of Water Resources in the United States. ClimaticChange. DOI: 10.1007/sl 0584-
014-1279-9.
32 Henderson, J., C. Rodgers, R. Jones, J. Smith, K. Strzepek, and J. Martinich. 2013. Eco-
nomic impacts of climate change on water resources in the coterminous United States.
Mitig Adapt Strateg Glob Change. DOI:10.1007/sl 1027-013-9483-x.
90
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Agriculture and Forestry
1 Hatfield, J., G. Takle, R. Grotjahn, P. Holden, R.C Izaurralde, T. Mader, E. Marshall, and
D. Liverman. 2014. Ch. 6: Agriculture. Climate Change Impacts in the United States: The
Third National Climate Assessment, J.M. Melillo, Terese (T.C.) Richmond, and G.W. Yohe,
Eds., U.S. Global Change Research Program. DOI:10,7930/J02Z13FR.
2 U.S. Congress. 2013. The Economic Contribution of America's Farmers and the Impor-
tance of Agricultural Exports. http://www.iec.senate.qov/public/?a=Files.Serve&File
Jd=266aObf3-5142-4545-b806-ef9fd78b9c2f.
3 Ibid.
4 Joyce, L.A., S.W. Running, D.D. Breshears, V.H. Dale, R.W. Malmsheimer, R.N. Sampson, B.
Sohngen, and C.W. Woodall. 2014. Ch. 7: Forests. Climate Change Impacts in the United
States: The Third National Climate Assessment, J.M. Melillo, Terese (T.C.) Richmond, and
G.W. Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/JOZ60KZC.
5 Hatfield, J., G. Takle, R. Grotjahn, P. Holden, R.C. Izaurralde, T. Mader, E. Marshall, and
D. Liverman. 2014. Ch. 6: Agriculture. Climate Change Impacts in the United States: The
Third National Climate Assessment, J.M. Melillo, Terese (T.C.) Richmond, and G.W. Yohe,
Eds., U.S. Global Change Research Prog ram, 150-174. DOI:10.7930/J02Z13FR.
6 Joyce, L.A., S.W. Running, D.D. Breshears, V.H. Dale, R.W. Malmsheimer, R.N. Sampson,
B. Sohngen, and C.W. Woodall. 2014. Ch. 7: Forests. Climate Change Impacts in the Unit-
ed States: The Third National Climate Assessment, J.M. Melillo, Terese (T.C.) Richmond,
and G.W. Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/JOZ60KZC.
7 Hatfield, J., G. Takle, R. Grotjahn, P. Holden, R.C. Izaurralde, T. Mader, E. Marshall, and
D. Liverman. 2014. Ch. 6: Agriculture. Climate Change Impacts in the United States: The
Third National Climate Assessment, J.M. Melillo, Terese (T.C.) Richmond, and G.W. Yohe,
Eds., U.S. Global Change Research Prog ram, 150-174. DOI:10.7930/J02Z13FR.
8 Joyce, L.A., S.W. Running, D.D. Breshears, V.H. Dale, R.W. Malmsheimer, R.N. Sampson,
B. Sohngen, and C.W. Woodall. 2014. Ch. 7: Forests. Climate Change Impacts in the Unit-
ed States: The Third National Climate Assessment, J.M. Melillo, Terese (T.C.) Richmond,
and G.W. Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/JOZ60KZC.
9 A wetter future climate, as projected under the IGSM-CAM for many crop-growing
parts of the U.S., will tend to reduce water stress such that some yields may increase
even with higher temperatures. In the EPIC modeling, irrigated crops are assumed to
be able to meet their water needs regardless of climate change effects on precipita-
tion, so a wetter/hotter climate scenariojust increases their temperature stress without
reducing their water stress. This tends to make impacts on rainfed crops more negative
than for irrigated yields. In addition, the ability of climate models to simulate precipi-
tation as severe storms or as heavy rainfall rather than frequent drizzle is an emerging
area of research in the climate modeling community. As such, the results presented
here should be interpreted with acknowledgement of this uncertainty.
10 Hatfield, J., G. Takle, R. Grotjahn, P. Holden, R.C. Izaurralde, T. Mader, E. Marshall, and
D. Liverman. 2014. Ch. 6: Agriculture. Climate Change Impacts in the United States: The
Third National Climate Assessment, J.M. Melillo, Terese (T.C.) Richmond, and G.W. Yohe,
Eds., U.S. Global Change Research Program, 150-174. DOI:10.7930/J02Z13FR.
11 The EPIC simulations assume that crops can be irrigated at a level that eliminates water
stress. A particular concern for climate change is that in areas where the need for irriga-
tion is greatest due to reduction in precipitation, the supply of water for irrigation will
also be reduced. To fully consider this risk requires integration of crop modeling with
hydrologic modeling for projections of future water supply, which was not modeled in
this biophysical crop yield analysis.
12 Joyce, L.A., S.W. Running, D.D. Breshears, V.H. Dale, R.W. Malmsheimer, R.N. Sampson,
B. Sohngen, and C.W. Woodall. 2014. Ch. 7: Forests. Climate Change Impacts in the Unit-
ed States: The Third National Climate Assessment, J.M. Melillo, Terese (T.C.) Richmond,
and G.W. Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/JOZ60KZC.
13 Mills, D., R. Jones, K. Carney, A. St Juliana, R. Ready, A. Crimmins ... and E. Monier. 2014.
Quantifying and Monetizing Potential Climate Change Policy Impacts on Terrestri-
al Ecosystem Carbon Storage and Wildfires in the United States. Climatic Change,
DOI:10.1007/s10584-014-1118-z.
14 The results in Figure 2 from the EPIC model show projected crop yields that do not
reflect production and market adjustments.
15 Williams, J.R. 1995. The EPIC Model. In Computer Models in Watershed Hydrology, V.P.
Singh (ed.), pp. 909-1000. Highlands Ranch, CO: Water Resources Publication.
16 Thomson, A.M., R.A. Brown, NJ. Rosenberg, R.C. Izaurralde, and V. Benson. 2005.
Climate Change Impacts for the Conterminous USA. Part 3: Dryland production of grain
and forage crops. Climatic Change. DOI:10.1007/1-4020-3876-3.
17 The EPIC simulations assume that crops can be irrigated at a level that eliminates water
stress. A particular concern for climate change is that in areas where the need for irriga-
tion is greatest due to reduction in precipitation, the supply of water for irrigation will
1
also be reduced. To fully consider this risk requires integration of crop modeling with
hydrologic modeling for projections of future water supply, which was not modeled in
this biophysical crop yield analysis.
18 The analysis uses climate projections from all five initializations of the IGSM-CAM. Giv-
en the sensitivity of the EPIC and MCI models to natural variability, the use of the five
initializations of the IGSM-CAM climate model, each of which has an equally plausible
future climate, aids in understanding and constraining the potential magnitude of crop
and vegetation changes in the future. Please refer to the Levels of Certainty section of
this reportfor more information.
19 Mills, D., R.Jones, K. Carney, A. St Juliana, R. Ready, A. Crimmins ...and E. Monier. 2014.
Quantifying and Monetizing Potential Climate Change Policy Impacts on Terrestri-
al Ecosystem Carbon Storage and Wildfires in the United States. Climatic Change,
DOI:10.1007/s10584-014-1118-z.
20 The change in forest yield was assumed to be equal to the percentage difference
in net primary productivity between future years and the average for the baseline
(1980-2009).
21 While beyond the scope of this analysis, the effects of CO2 fertilization on forest growth
and productivity may be limited by the availability of nitrogen, which could influence
the results estimated here.
22 Beach, R., Y. Cai, A. Thomson, X. Zhang, R. Jones, B. McCarl,... and B. Boehlert. (In press).
Climate change impacts on US agriculture and forestry: benefits of global climate
stabilization. Environmental Research Letters.
23 Hatfield, J., G. Takle, R. Grotjahn, P. Holden, R.C. Izaurralde, T. Mader, E. Marshall, and
D. Liverman. 2014. Ch. 6: Agriculture. Climate Change Impacts in the United States: The
Third National Climate Assessment, J.M. Melillo, Terese (T.C.) Richmond, and G.W. Yohe,
Eds., U.S. Global Change Research Program, 150-174. DOI:10.7930/J02Z13FR.
24 Consumer and producer surplus are used to estimate impacts on total economic
welfare. Consumer surplus is the monetary gain obtained by consumers because they
are able to purchase a product for a price that is less than the highest price that they
would be willing to pay. Producer surplus or producers' surplus is the amount that
producers benefit by selling at a market price that is higher than the least that they
would be willing to sell for.
25 Beach, R., D. Adams, R. Alig, J. Baker, G. Latta, B. McCarl,... and E. White. 2010. Model
documentation for the Forest and Agricultural Sector Optimization Model with Green-
house Gases (FASOMGHG). Prepared for U.S. Environmental Protection Agency.
26 EPIC, MCI, and FASOM results in the Agriculture and Forestry sections using the
IGSM-CAM climate projections represent the average of the five initializations.
27 FASOM has perfect foresight of future climate change effects, and thus can optimize
nearterm land owner behavior. The model also simulates changes in agricultural and
forestry commodities beyond those modeled in EPIC (9 crops) and MCI (hard and
softwoods).
28 This analysis does not reflect climate change impacts on international forests and
agriculture, which would also affect relative returns to different uses of land and trade
patterns and therefore affect land use decisions. Also, numerous uncertainties remain
regarding issues such as future changes in crop technology, energy policy, and other
interactions that could affect market outcomes.
91
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29 FASOM-GHG is optimized to maximize consumer and producer surplus in the base,
but re-adjusts production and consumption patterns to re-optimize in response to
changes in potential yields.
30 FASOM directly models changes to productivity on private timberland, although
timber from public lands enters the market exogenously based on public lands policy.
Impacts on productivity due to climate change are only applied to the private timber-
land.
31 Boehlert, B., K. Strzepek, S. Chapra, Y. Gebretsadik, M. Lickley, C. Fant,... and J. Mar-
tinich. (In press). Greenhouse Gas Mitigation Effects on Water Quality Impacts from
Climate Change in the U.S. Journal of Advances in Modeling Earth Systems.
32 Beach, R., Y. Cai, A. Thomson, X. Zhang, R. Jones, B. McCarl,... and B. Boehlert. (In press).
Climate change impacts on US agriculture and forestry: benefits of global climate
stabilization. Environmental Research Letters.
Ecosystems
1 Groffman, P. M., P. Kareiva, S. Carter, N. B. Grimm, J. Lawler, M. Mack, V. Matzek, and H.
Tallis, 2014: Ch. 8: Ecosystems, Biodiversity, and Ecosystem Services. Climate Change
Impacts in the United States: The Third National Climate Assessment, J. M. Melillo,
Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program,
195-219. DOI:10.7930/JOTD9V7H.
2 Ibid.
3 Melillo, J.M., T.C. Richmond, and G.W. Yohe, Eds. 2014. Climate Change Impacts in the
United States: The Third National Climate Assessment. U.S. Global Change Research
Program. DOI:10.7930/JOZ31WJ2.
4 The impacts modeled in COMBO do not include non-climate stressors, such as
overfishing or water pollution, and do not account for the ability of large-scale reefs
to contain important refugia for resilient corals that could potentially be used in coral
restoration efforts. Together, these factors have the ability to adjust the estimates
presented in this report upwards or downwards.
5 Doney, S., A. A. Rosenberg, M. Alexander, F. Chavez, C. D. Harvell, G. Hofmann, M.
Orbach, and M. Ruckelshaus. 2014. Ch. 24: Oceans and Marine Resources. Climate
Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo,
Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program.
001:10.7930/JORF5RZW.
6 Buddemeier, R.W., P.L Jokiel, K.M. Zimmerman, D.R. Lane, J.M. Carey, G.C. Bohling,
and J.A. Martinich. 2008. A modeling tool to evaluate regional coral reef responses
to changes in climate and ocean chemistry. Limn OceanogrMethods. DOI: 10.4319/
lom.2008.6.395.
7 Buddemeier, R.W., D.R. Lane, and J.A. Martinich. 2011. Modeling regional coral reef
responses to global warming and changes in ocean chemistry: Caribbean case study.
Climatic Change. DOI:10.1007/sl 0584-011 -0022-z.
8 The values presented in this section differ slightly from those presented in Laneetal.
(2014) due to differences in aggregating coral cover changes annually or monthly.
9 Lane, D.R., R.C. Ready, R.W. Buddemeier, J.A. Martinich, K.C. Shouse, and C.W. Wobus.
2013. Quantifying and valuing potential climate change impacts on coral reefs in
the United States: Comparison of two scenarios. PLoS ONE. DOI:10.1371/journal.
pone.0082579.
10 Ibid.
11 Lane, D., R. Jones, D. Mills, C. Wobus, R.C. Ready, R.W. Buddemeier, E. English, J. Marti-
nich, K. Shouse, and H. Hosterman. 2014. Climate change impacts on freshwater fish,
coral reefs, and related ecosystem services in the United States. Climatic Change. DOI:
10.1007/sl 0584-014-1107-2.
12 U.S. Environmental Protection Agency. 2014. Climate change indicators in the United
States. Third edition. EPA430-R-14-004.
13 Doney, S., A. A. Rosenberg, M. Alexander, F. Chavez, C. D. Harvell, G. Hofmann, M.
Orbach, and M. Ruckelshaus. 2014. Ch. 24: Oceans and Marine Resources. Climate
Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo,
Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program.
001:10.7930/JORF5RZW.
14 In early life stages, some species will have higher mortality rates and more develop-
mental abnormalities under acidification conditions expected over the next several
decades. In addition, adult shellfish tend to grow more slowly and have thinner, more
fragile shells under these conditions.
15 National Marine Fisheries Service Commercial Landings for the years 1990-2010. http://
www.st.nmfs.noaa.aov/commercial-fisheries/commercial-landinas/annual-landings/
index.
16 Doney, S., A. A. Rosenberg, M. Alexander, F. Chavez, C. D. Harvell, G. Hofmann, M.
Orbach, and M. Ruckelshaus. 2014. Ch. 24: Oceans and Marine Resources. Climate
Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo,
Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program.
001:10.7930/JORF5RZW.
17 Ibid.
18 Oak Ridge National Laboratory, Carbon Dioxide Information Analysis Center.
Program Developed for CO2 System Calculations: CO2SYS. httD://cdiac.ornl.aov/
oceans/co2rprt.html.
19 Moore, C. 2015. Welfare estimates of avoided ocean acidification in the U.S. mollusk
market. Journal of Agricultural an d Resource Economics 40(1): 50-62.
20 Ibid.
21 Groffman, P. M., P. Kareiva, S. Carter, N. B. Grimm, J. Lawler, M. Mack, V. Matzek, and H.
Tallis. 2014. Ch. 8: Ecosystems, Biodiversity, and Ecosystem Services. Climate Change
Impacts in the United States:TheThird National Climate Assessment, J. M. Melillo,
Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program.
DOI:10.7930/JOTD9V7H.
22 Ibid.
23 Horton, R., G. Yohe, W. Easterling, R. Kates, M. Ruth, E. Sussman,... and F. Lipschultz.
2014. Ch. 16: Northeast. Climate Change Impacts in the United States: The Third National
Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S.
Global Change Research Program. DOI:10.7930/JOSF2T3P.
24 Global GHG mitigation is projected to preserve 230,000 acres of coldwater fish habitat
in 2100 under the MIROC climate projections. For all freshwater fishing guilds, the
total damages in 2100 are estimated at $1.7 billion in the Reference scenario and $200
million in the Mitigation scenario.
25 This analysis does not project changes to fish distribution in lakes and reservoirs, as
these bodies provide thermal stratification/refugia, and are oftentimes heavily man-
aged (i.e., water level and fish stocking).
26 Jones, R., C. Travers, C. Rodgers, B. Lazar, E. English, J. Lipton,... and J. Martinich. 2012.
Climate Change Impacts on Freshwater Recreational Fishing in the United States. Miti-
gation and Adaptation Strategies for Global Change. DOI: 10.1007/sl 1027-012-9385-3.
27 Lane, D., R. Jones, D. Mills, C. Wobus, R.C. Ready, R.W. Buddemeier,... and H. Hosterman.
2014. Climate change impacts on freshwater fish, coral reefs, and related ecosystem
services in the United States. ClimaticChange. DOI: 10.1007/S10584-014-1107-2.
28 Jones, R., C. Travers, C. Rodgers, B. Lazar, E. English, J. Lipton,... and J. Martinich. 2012.
Climate Change Impacts on Freshwater Recreational Fishing in the United States. Miti-
gation and Adaptation Strategies for Global Change. DOI: 10.1007/sl 1027-012-9385-3.
29 Groffman, P. M., P. Kareiva, S. Carter, N. B. Grimm, J. Lawler, M. Mack, V. Matzek, and H.
Tallis. 2014. Ch. 8: Ecosystems, Biodiversity, and Ecosystem Services. Climate Change
Impactsin theUnitedStates:TheThirdNationalClimateAssessment,}. M. Melillo,
Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program.
DOI:10.7930/JOTD9V7H.
30 National Interagency Fire Center. 2013. Federal Firefighting Costs (Suppression Only).
https://www.nifc.gov/firelnfo/firelnfo documents/SuppCosts.pdf.
92
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31 Groffman, P. M., P. Kareiva, S. Carter, N. B. Grimm, J. Lawler, M. Mack, V. Matzek, and H.
Tallis. 2014. Ch. 8: Ecosystems, Biodiversity, and Ecosystem Services. Climate Change
Impacts in theUnitedStates:TheThird NationalClimateAssessment, J. M. Melillo, Terese
(T.C.) Richmond, and G.W.Yohe, Eds., U.S. Global Change Research Program.
DOI:10.7930/JOTD9V7H.
32 Joyce, L. A., S. W. Running, D. D. Breshears, V. H. Dale, R. W. Malmsheimer, R. N.
Sampson, B. Sohngen, and C. W. Wood. 2014. Ch. 7: Forests. Climate Change Impacts in
the United States: The Third National Climate Assessment, L M. Melillo, Terese (T.C.)
Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/
JOZ60KZC.
33 Ibid.
34 Change in annual acres burned at end of century (2085-2114) compared to the historic
baseline (2000-2009).
35 National Interagency Fire Center. 2013. Federal Firefighting Costs (Suppression Only).
https://www.nifc.gov/firelnfo/firelnfo documents/SuppCosts.pdf.
36 Joyce, L. A., S. W. Running, D. D. Breshears, V. H. Dale, R. W. Malmsheimer, R. N.
Sampson, B. Sohngen, and C. W. Wood. 2014. Ch. 7: Forests. Climate Change Impacts in
the United States: The Third National Climate Assessment, L M. Melillo, Terese (T.C.)
Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/
JOZ60KZC
37 Comprised of the following Geographic Area Coordination Center regions: Northern
Rockies, Rocky Mountain, Southwest, Eastern Great Basin, Western Great Basin,
Northwest, California North, and California South.
38 Percent changes calculated by comparing acres burned under the Reference scenario
at the end of the century (average of 2085-2114) compared to the historic baseline
(average of 2000-2009).
39 Fuel management costs are estimated at $15 billion under the Reference and $12
billion under the Mitigation scenario through 2100 (average across all IGSM-CAM
initializations, 2014$, discounted at 3%), corresponding to avoided costs (benefits) of
$3.4 billion under the Mitigation scenario.
40 Fuel management costs were not estimated using the MIROC climate model.
41 The CIRA results simulated in the MCI vegetation model suggest a substantial change
to the wildfire regime we experience today. Given the sensitivity of the MCI climate
model to natural variability, the use of the five initializations of the IGSM-CAM climate
model, each of which has an equally plausible future climate, aids in understanding
and constraining the potential magnitude of vegetation changes in the future. For
example, unmitigated climate change is projected to increase area burned by wildfire
annually by approximately 45% in California by the end of the century, 64% in the
Mountain West, and 95% in the Northwest.
42 Because the IGSM-CAM projects a wetter future for a majority of the nation,
pattern-scaled output from two additional climate models were simulated in MCI to
encompass a broader range of possible climate futures. While all three sets of climate
projections show increases in the area burned by wildfire compared to the historic
period, only the IGSM-CAM and MIROC climate model results are presented in this
report. For an in-depth discussion of the results, see: Mills, D., R. Jones, K. Carney, A. St
Juliana, R. Ready, A. Crimmins,... and E. Monier. 2014. Quantifying and Monetizing
Potential Climate Change Policy Impacts on Terrestrial Ecosystem Carbon Storage and
Wildfires in the United States. Climatic Change. DOI:10.1007/s10584-014-1118-z.
43 National Wildfire Coordinating Group. 2011. Historical incident ICS-209 reports.
http://fam.nwcg.gov/fam-web/hist 209/report list 209.
44 Lee, C., C. Schlemme, J. Murray, and R. Unsworth. 2015. The cost of climate change:
ecosystem services and wildland fires. Ecological Economics. DOI:10.1016/j.ecole-
con.2015.04.020.
45 Mills, D., R. Jones, K. Carney, A. St Juliana, R. Ready, A. Crimmins,... and E. Monier. 2014.
Quantifying and Monetizing Potential Climate Change Policy Impacts on Terrestrial
Ecosystem Carbon Storage and Wildfires in the United States. ClimaticChange.
DOI:10.1007/s10584-014-1118-z.
46 Lee, C., C. Schlemme, J. Murray, and R. Unsworth. 2015. The cost of climate change:
ecosystem services and wildland fires. Ecological Economics. DOI:10.1016/j.ecole-
con.2015.04.020.
47 Joyce, L. A., S. W. Running, D. D. Breshears, V. H. Dale, R. W. Malmsheimer, R. N.
Sampson, B. Sohngen, and C. W. Wood. 2014. Ch. 7: Forests. Climate Change Impacts in
the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.)
Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/
JOZ60KZC.
48 Galloway, J. N., W. H. Schlesinger, C. M. Clark, N. B. Grimm, R. B. Jackson, B. E. Law,... and
R. Martin. 2014. Ch. 15: Biogeochemical Cycles. Climate Change Impacts in the United
St ates:TheThird National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and
G.W.Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/JOX63JTO.
49 Joyce, L. A., S. W. Running, D. D. Breshears, V. H. Dale, R. W. Malmsheimer, R. N.
Sampson, B. Sohngen, and C. W. Wood. 2014. Ch. 7: Forests. Climate Change Impacts in
the United States: The Third National Climate Assessment, L M. Melillo, Terese (T.C.)
Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program. DOI:10.7930/
JOZ60KZC.
50 Change from the 2000-2009 average to the 2095-2104 average.
51 USDA Forest Service. 2012. Future of America's Forest and Rangelands: Forest Service
2010 Resources Planning Act Assessment. Gen. Tech. Rep. WO-87. Washington, DC.
52 See Mills et al. (2014) for a detailed examination of the differences between the MCI
simulations using the two climate projection methods (IGSM-CAM and MIROC
pattern-scaled climate models), as well as a discussion of the drivers behind these
differences.
53 Oregon State University. 2011. MCI dynamic vegetation model, http://www.fsl.orst.
54 Given the sensitivity of the MCI climate model to natural variability, the use of the five
initializations of the IGSM-CAM climate model, each of which has an equally plausible
future climate, aids in understanding and constraining the potential magnitude of
vegetation changes in the future.
55 U.S. Interagency Working Group on Social Cost of Carbon. 2013. Technical support
document: technical update of the social cost of carbon for regulatory impact analysis
under Executive Order 12866. http://www.whitehouse.gov/sites/default/files/omb/
inforeg/social cost of carbon for ria 2013 update.pdf.
56 Mills, D., R.Jones, K. Carney, A. St Juliana, R. Ready, A. Crimmins, ...and E. Monier. 2014.
Quantifying and Monetizing Potential Climate Change Policy Impacts on Terrestrial
Ecosystem Carbon Storage and Wildfires in the United States. ClimaticChange,
DOI:10.1007/s10584-014-1118-z.
CONCLUSION
1 The few efforts to date that have estimated multi-sector impacts in a consistent
framework include the European Commission's PESETA project (http://peseta.irc.ec.
europa.eu). and the Risky Business Initiative (http://riskybusiness.org), a project
focusing on economic risks in the U.S. Integrated assessment models, such as FUND
(http://fund-model.org), are also being used to estimate the multi-sector social costs of
GHG emissions.
2 The use of a climate model that generates a relatively higher amount of future
precipitation may strongly influence results in a particular sector. For example, inland
flooding damages may be larger under these wetter climate projections compared to
those under a drier model. This same sensitivity of sectoral results to the choice of
climate model could affect a different part of the water sector in complementary ways,
such that drought damages could be smaller compared to those under a drier model.
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