Effects of Air Pollution 203© Frank Lukasseck/CorbisFor several years, climate scientists have noticed that
mountainous areas in the western United States are
receiving less precipitation than usual. The effect has been
particularly pronounced in mountains located downwind
from cities, leading scientists to speculate that air pollution
may be altering precipitation patterns. However, long-term
data to support this hypothesis were not available until
recently.
In 2007 climate scientists evaluated weather data taken
atop Mount Hua, a sacred mountain in China that overlooks a
EnviroDiscovery
Air Pollution May Affect Precipitation
A Taoist Temple on Mount Hua in China. Note the proximity of
the mountain to the plain where air pollution is produced.plain where several cities (which are a source of air pollution)
are located. The data, which include precipitation, visibility, and
humidity data, have been measured since 1954. By subtracting
the effect of humidity on visibility, scientists have been able
to estimate the amount of air pollution suspended in the air.
The scientists have correlated high visibility—that is, low air
pollution—with substantially more precipitation than when air
pollution levels were high. They caution, however, that the link
between air pollution and precipitation patterns is still tentative
and will require more research.