Climate Change Impacts in the United States

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Climate Change Impacts in the United States
This section is mainly from Global Climate
Change Impacts in the United States, U.S. Global
Change Research Program, Cambridge University
Press, 2009.
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General National Impacts
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Key National Climate Impacts

• U.S. average temperature has risen more than 2 F
  over the past 50 years and is projected to rise
  more in the future how much more depends on the
  amount of greenhouse gases emitted globally and
  how sensitive the climate is to those emissions.
• Precipitation has increased an average of about
  5 over the past 50 years. Projections of future
  precipitation generally indicate that northern
  areas will become wetter, and southern areas,
  particularly in the West, will become drier.
• The amount of rain falling in the heaviest
  downpours has increased about 20 on average in
  the past century, and this trend is very likely
  to continue, with the largest increases in the
  wettest places.
• Many types of extreme weather events, such as
  heat waves and regional droughts, have become
  more frequent and intense during the past 40 to
  50 years.
• The destructive energy of Atlantic hurricanes has
  increased in recent decades. The intensity of
  these storms is likely to increase in this
  century.
• In the eastern Pacific, the strongest hurricanes
  have become stronger since the 1980s, even while
  the total number of storms has decreased.
• Sea level has risen along most of the U.S. coast
  over the last 50 years, and will continue to rise
  in the future.
• Cold-season storms tracks are shifting northward
  and the strongest storms are likely to become
  stronger and more frequent.
• Arctic sea ice is declining rapidly and this will
  continue.

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Temperature Change between 1993-2008 (left), and
projected near term between 2010-2029 (right)
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Projected U.S. Temperature Increase (2040-2060)
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Projected temperature increases between 2040-2059
and 2080-2099 for higher emissions scenario (top)
and lower emissions scenario (bottom)
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U.S. Rainfall Anomaly Jan.-August 2007
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Increases in Amounts of Very Heavy Precipitation
(1958-2007)
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Change in Hadley Cell Circulation Could Decrease
Winter and Spring Precipitation in the Southwest

• The Hadley Effect The Hadley Cell circulation
  illustrates how rising air in the superheated
  tropics descends in the subtropics. This creates
  high-pressure zones in subtropical regions,
  including the U.S. Southwest.
• The area under the Hadley cells descending air
  is projected to widen in years to come. As a
  result, the jet stream that transports rain and
  snow during spring and winter is expected to move
  toward the North pole. Thus winter storms could
  enter the western United States in a more
  northerly position, bypassing the Southwest more
  often than it currently does.

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43 of U.S. in Drought Conditions in Oct. 2007
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Fires Are Increasing World-Wide
Wildfires in Western U.S. have increased 4-fold
in 30 years.
Western US area burned
Source Westerling et al. 2006
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Water Resources
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Key Water Resource Impacts

• Climate change has already altered, and will
  continue to alter, the water cycle, affecting
  where, when and how much water is available for
  all uses.
• Floods and droughts are likely to become more
  common and more intense as regional and seasonal
  precipitation patterns change, and rainfall
  becomes more concentrated into heavy events (with
  longer, hotter dry periods in between).
• Precipitation and runoff are likely to increase
  in the Northeast and Midwest in winter and
  spring, and decrease in the West especially the
  Southwest, in the spring and summer.
• In areas where snowpack dominates, the timing of
  runoff will continue to shift to earlier in the
  spring and flows will be lower in late summer.
• Surface water quality and groundwater quantity
  will be affected by a changing climate.
• Climate change will place additional burdens on
  already stressed water systems.
• The past century is no longer a reasonable guide
  to the future for water management.

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Observed Water-Related Changes During the Last
Century
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The Southwest Will Have Less Precipitation

• Using an "ensemble" of 18 global climate models
  and the moderate "A1B" emissions scenario,
  researchers at the NOAA Earth System Research
  Laboratory (ESRL) predict a reduction in
  precipitation across the Southwest by the end of
  the century.
• Credit Map produced by Jeremy Weiss of the
  University of Arizona, using data from Hoerling
  and Eischeid of NOAA ESRL. http//www.noaa.gov/

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Drought on the Southwest, U.S.
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Increases in Amounts of Very Heavy Precipitation
(1958-2007)
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Trends in Peak Streamflow Timing
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Potential Water Supply Conflicts by 2025
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Highlights of Water-related Impacts by Sector
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Energy Supply and Use
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Key Energy Supply and Use Impacts

• Warming will be accompanied decreases in demand
  for heating energy and increases in demand for
  cooling energy. The later will result in
  significant increases in electricity use and
  higher peak demand in most regions.
• Energy production is likely to be constrained by
  rising temperatures and limited water supplies in
  many regions.
• Energy production and delivery systems are
  exposed to disruption by sea level rise and
  extreme weather events in vulnerable regions.
• Climate change is likely to affect some renewable
  energy sources across the nation, such as
  hydroelectric power production in regions subject
  to changing patterns of precipitation or snowmelt.

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Sources of U.S Greenhouse Gas Emissions (2003)
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Primary Energy Consumption by Major Source
(1949-2007)
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U. S. Electricity Sources (2007)
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Population Change (1970-2008)
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Shifting Energy Demand in the U. S. by 2080-2099.
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Significant Weather-related U.S. Electric Grid
Disturbances
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Transportation
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Key Transportation Impacts

• Sea level rise and storm surge will increase the
  risk of major coastal impacts, including both
  temporary and permanent flooding of airports,
  roads, rail lines, and tunnels.
• Flooding from increasingly intense downpours will
  increase the risk of disruptions and delays in
  air, rail and road transportation, and damage
  from mudslides in some areas.
• The increase in extreme heat will limit some
  transportation operations and cause pavement and
  track damage. Decreased extreme cold will provide
  some benefits such as reduced snow and ice
  removal costs in some areas.
• Increased intensity of strong hurricanes would
  lead to more evacuations, infrastructure damage
  and failure, and transportations disruptions.
• Arctic warming will continue to reduce sea ice,
  lengthening the ocean transport season, but also
  resulting in greater coastal erosion due to
  waves. Permafrost thaw in Alaska will damage
  infrastructure. The ice road season will become
  shorter.

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Agriculture
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Key Agriculture Impacts

• Many crops show positive responses to elevated
  CO2 and low levels of warming, but higher levels
  of warming often negatively affect growth and
  yields.
• Extreme events such as heavy downpours and
  droughts are likely to reduce crop yields because
  excesses or deficits of water have negative
  impacts on plant growth.
• Weeds, diseases, and insect pests benefit from
  warming, and weeds also benefit from a higher CO2
  concentrations, increasing stress on crop plants
  and requiring more attention to pest and weed
  control.
• Forage quality in pastures and rangelands
  generally declines with increasing CO2
  concentration because of the effects on plant
  nitrogen and protein content, reducing the lands
  ability to supply adequate livestock feed.
• Increased heat, disease, and weather extremes are
  likely to reduce livestock and agricultural
  productivity.

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Ecosystems
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Key Ecosystem Impacts

• Ecosystem processes, such as those that control
  growth and decomposition, have been affected by
  climate change.
• Large-scale shifts have occurred in the ranges of
  species and the timing of the seasons and animal
  migration, and are very likely to continue.
• Fires, insect pests, disease pathogens, and
  invasive weed species have increased, and these
  trends are likely to continue.
• Deserts and drylands are likely to become hotter
  and drier, feeding a self-reinforcing cycle of
  invasive plants, fire, and erosion.
• Coastal and near-shore ecosystems are already
  under multiple stresses. Climate change and ocean
  acidification will exacerbate these stresses.
• Arctic sea ice ecosystems are already being
  adversely affected by the loss of summer sea ice
  and further changes are expected.
• The habitats of some mountain species and
  coldwater fish, such as salmon and trout, are
  very likely to contract in response to warming.
• Some of the benefits ecosystems provide to
  society will be threatened by climate change,
  while others will be enhanced.

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Butterfly Range Shifts Northward

• As the climate warms, many species in the United
  States are shifting their ranges northward and to
  higher elevations. The map show the response of
  Ediths Checkerspot butterfly populations to a
  warming climate over the past 136 years in the
  American West. Over 70 of the southernmost
  populations (shown in yellow) have gone extinct.
  The northernmost populations and those above
  8,000 feet elevation in the cooler climate of
  Californias Sierra Nevada (shown in green) are
  still thriving. These differences in numbers of
  population extinctions across the geographic
  range of the butterfly have resulted in the
  average location shifting northward and to higher
  elevations over the past century, illustrating
  how climate change is altering the ranges of many
  species. Because their change in range is slow,
  most species are not expected to be able to keep
  up with the rapid climate change projected in the
  coming decades.

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Human Health
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Key Health Impacts

• Increases in the risk of illness and death
  related to extreme heat and heat waves are very
  likely. Some reduction in the risk of death
  related to extreme cold is expected.
• Warming is likely to make it more challenging to
  meet air quality standards necessary to protect
  public health.
• Extreme weather events cause physical and mental
  health problems. Some of these events are
  projected to increase.
• Some diseases transmitted by food, water, and
  insects are likely to increase.
• Rising temperature and CO2 concentrations
  increase pollen production and prolong the pollen
  season in a number of plants with highly
  allergenic pollen, presenting a health risk.
• Certain groups, including children, the elderly,
  and the poor, are most vulnerable to a range of
  climate-related health effects.

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Number of Days Over 100 F

• The number of days in which the temperature
  exceeds 100 F by late this century, compared to
  the 1960s and 1970s, is projected to increase
  strongly across the United States. For example,
  parts of Texas that recently experienced about 10
  to 20 days per year over 100 F are expected to
  experience more than 100 days per year in which
  the temperature exceeds 100 F by the end of the
  century under the higher emissions scenario.

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Occurrence of the Dengue Fever Vector Mosquito
and Number of Suspected Cases in Each State
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Society
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Key Society Impacts

• Population shifts and development choices are
  making more Americans vulnerable to the expected
  impacts of climate change.
• Vulnerability is greater for those who have few
  resources and few choices.
• City residents and city infrastructure have
  unique vulnerabilities to climate change.
• Climate change affects communities through
  changes in climate-sensitive resources that occur
  both locally and at great distances.
• Insurance is one of the industries particularly
  vulnerable to increasing extreme weather events
  such as severe storms, but it can also help
  society mange the risks.
• The United States is connected to a world that is
  unevenly vulnerable to climate change and thus
  will be affected by impacts in other parts of the
  world.

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