Page 523 - Environment: The Science Behind the Stories

For the United States, potential impacts are analyzed Reduced Emissions Scenario
and summarized by the U.S. Global Change Research Projected Temperature Change (°F)
Program, which Congress created in 1990 to coordinate End-of-Century (2071–2099 average)
federal climate research. In 2013, this program issued a
comprehensive 1200-page report summarizing current
research, present trends, and future impacts of climate
change on the United States (Table 18.3). This report,
the National Climate Assessment, was produced by 240
scientists overseen by a 60-person staff. Released in draft
form online for public comment, it will be finalized and
presented to Congress, the president, and the American
people in 2014.
The report makes clear that some impacts are being felt
across the nation. Average temperatures across the United
States have already increased by 0.8°C (1.5°F) since record
keeping began in 1895, with over 80% of this rise occurring
just since 1980. Temperatures are predicted to rise by another Continued Emissions Scenario
2.1–6.2°C (4–11°F) by the end of this century (Figure 18.21). Projected Temperature Change (°F)
Extreme weather events have become more frequent and End-of-Century (2071–2099 average)
costly, and will continue to worsen, imposing escalating costs
on farmers, city-dwellers, coastal communities, and taxpayers
across the country.
Most impacts vary by region, and each region of the United
States will face its own challenges (Figure 18.22). For instance,
winter and spring precipitation is projected to decrease across
the South but increase across the North. Drought may strike in
some regions and flooding in others. Sea level rise will likely

Table 18.3 Some Predicted impacts of climate change Degrees F
in the united States
• Average temperatures will rise 2.1–6.2°C (4–11°F) further by 3 4 5 6 7 8 9 10 15
the year 2100.
Figure 18.21 Average temperatures across the United
• Droughts, flooding, and wildfire will worsen; dry areas will get States are predicted to rise by the end of this century. Even
drier and wet areas wetter. under a scenario of sharply reduced emissions (top), temperatures
• Extreme weather events will become more frequent. The are predicted to rise by 3–4°F. Under a scenario of business-as-
costs they impose on society will grow. usual emissions (bottom), temperatures are predicted to rise by
• Sea level will rise an additional 0.3–1.2 m (1–4 ft) by 2100. 7–11°F. Data from U.S. Global Change Research Program, 2013. National
climate assessment. Draft for public review.
• Storm surges will continue to erode beaches and coastal
wetlands, destroy real estate, and damage infrastructure.
• Health problems due to heat stress, disease, and pollution affect the Atlantic and Gulf Coasts more than the West Coast.
will rise. Some tropical diseases will spread north.
Agriculture, forests, wildlife, and human health may experience
• Drought, fire, and pest outbreaks will continue to alter forests. a wide array of impacts that will vary from one region to another.
• Marine ecosystems and fisheries will be affected by ocean You may learn more about the scientific predictions for your
acidification. own region by consulting this publicly accessible report online.
• Although enhanced CO and longer growing seasons favor All these impacts of climate change are projected conse-
2
crops, increased drought, heat stress, pests, and diseases quences of the warming effect of our greenhouse gas emis-
will decrease most yields. sions (Figure 18.23, see p. 524). We are bound to experience
• Snowpack will decrease in the West; water shortages will further consequences, but by addressing the root causes of
worsen in many areas. anthropogenic climate change now, we may still be able to
• Alpine ecosystems and barrier islands will begin to vanish. prevent the most severe future impacts.
• Northeast forests will lose sugar maples; Southwest
ecosystems will turn more desertlike. Are we responsible for climate change?
• Melting permafrost will undermine Alaskan buildings and
roads. Scientists agree that most or all of today’s global warm-
Adapted from U.S. Global Change Research Program, 2013. ing is due to the well-documented recent increase in green-
National climate assessment. Draft for public review. http://ncadac house gas concentrations in our atmosphere. They also
522 .globalchange.gov. agree that this rise in greenhouse gases results primarily

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