More Extreme Heat Waves:
Global Warming’s Wake Up Call
N A T I O N A L W I L D L I F E F E D E R A T I O N
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C O N F R O N T I N G G L O B A L W A R M I N G
Global warming will bring more extreme heat waves. As the United States
warms another 4 to 11°F on average over the next century, we will have
more extremely hot summer days. Every part of the country will be
affected. Urban areas will feel the heat more acutely because asphalt,
concrete, and other structures absorb and reradiate heat, causing
temperature to be as much as 10°F higher than nearby rural areas.
Urban air pollution will be exacerbated by more extreme heat. Warm,
sunny conditions accelerate the formation of ground-level ozone,
a major component of smog. Even if air pollution is improved, as required
by the Clean Air Act, global warming could mean an extra 10 parts per
billion (ppb) of ozone during heat waves in the Midwest and Northeast,
forcing some cities to take even more aggressive steps to meet the 75
ppb ozone standard.
Heat waves disproportionately impact the very old and very young, as
well as people who are poor, have asthma or heart disease, or live in big
cities. With often diminished health and a greater likelihood of living
alone, the elderly are especially vulnerable. As the U.S. demographics
shift toward an older and more urban population, efforts to protect these
at-risk communities from extreme heat will become increasingly
Natural habitats and agriculture are also vulnerable to extreme heat.
More extreme temperatures are already pushing wildlife and their
habitats beyond their normal tolerance levels. Heat-related declines have
been documented for wild salmon and trout, moose, and pika. Livestock
and crops have lower productivity and increased mortality associated
with heat stress and drought.
We can reduce the severity of heat waves and their impacts on vulnerable
people. Curbing global warming pollution as much and as quickly as
possible is an essential first step. Shifting to clean solar energy is an