Environmental Engineering Reference
In-Depth Information
reliability of present-day electricity supply from hydropower and traditional
generation sources, such as coal, gas, and nuclear, that require cooling
water. {5.5}
Human Health
Heat-related illness and deaths occur as a direct result of sustained,
elevated levels of extreme temperatures during heat waves, which are pro-
jected to increase with increasing temperatures. The frequency and severity
of heat waves in Europe and North America are projected to increase under
climate change. Under a 2°C increase in global mean temperature, for ex-
ample, the average number of days per year with maximum temperatures
exceeding 38°C or 100°F across much of the south and central United States
could increase by a factor of 3 relative to the 1961-1990 average. Under a
3.5°C increase, the number of days is projected to increase by 5 to nearly
10 times. Some adaptation is inevitable as populations become accustomed
to permanently different conditions. However, most research indicates that
the public health impacts of climate change are likely to increase with
temperature extremes; and new research highlights the potential that heat
stress may impose hard limits on the inhabitability of some land areas under
global temperature changes on the order of 10°C or more. {5.5}
Climate change is likely to affect the geographic spread and transmis-
sion efficiency of illnesses and disease carried by hosts and vectors, but
complexity precludes any quantitative estimates of the relationship be-
tween incidence of a given disease and temperature change. Confounding
factors—involving viral, bacterial, plant, and animal physiology, as well as
sensitivity to changes in climate extremes, including precipitation intensity
and temperature variability—challenge attempts to resolve the influence of
temperature on observed trends in disease incidence. Most recent projec-
tions suggest that the ranges of malaria and other diseases may shift, but
increases in some areas will likely be accompanied by decreases in others.
{5.5}
Climate change may exacerbate existing stressors, such as air pollution,
water contamination, and pollen production. Warmer temperatures increase
production of ground-level ozone, which affects respiratory health. For a
given level of ozone precursor emissions, background ozone levels and days
with high ozone pollution levels above a defined safety standard (or “ozone
exceedances”) are projected to increase across much of the United States.
Where heavy precipitation increases, risk of water contamination could also
increase. Shifts in growing season, mean temperatures, and atmospheric
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