Geography Reference
In-Depth Information
Climate Change
Growing populations and increased human activity, rang-
ing from the burning of tropical forests to pollution of the
atmosphere by industry and automobiles, are having an
unprecedented impact on the atmosphere. The amounts of
key “greenhouse” gases, carbon dioxide (CO 2 ), methane,
and nitrous oxides in the atmosphere have been increas-
ing at a rate of about 2 percent per decade; automobiles,
steel mills, refi neries, and chemical plants account for a
large part of this increase. A simple experiment in a college
chemistry lab shows that an increase in the level of CO 2 in
the atmosphere traps more heat. Hence, it is not surprising
that an overwhelming majority of climate scientists have
concluded that
America, picked up millions of tons of pulverized rock
and deposited it in thick layers in what is today the U.S.
Midwest. Climatologists believe that the warming after
the Wisconsinan Glaciation included extraordinary tem-
perature swings and extreme weather events.
Extreme weather events have also accompanied
periods of global cooling. When the Little Ice Age cooled
Europe in the 1300s, some chroniclers described snow-
fall increasing so rapidly that glaciers fl owing from their
Alpine valleys “like white lava' onto neighboring plains as
rivers raged and crops withered.
Atmospheric scientists are investigating the relation-
ship between current changes in the climate and extreme
weather events. If you follow the news, you have read
headlines from around the world about cold snaps that
are the worst in the century, fl oods the highest in memory,
and droughts the longest on record. Many of the computer
models used to simulate these events show a link between
warming global temperatures and changing regional
weather systems.
tropospheric pollution from anthropogenic
(human) sources is causing the Earth to retain increasing
amounts of heat, with effects that will increase during the
course of the twenty-fi rst century and beyond.
While estimates of the degree of human-induced
climate change differ, climate records from recent decades
show that global temperatures are rising, which is why
climate change is sometimes called global warming.
Climate change is a more accurate term, however, because
while the global temperature is rising, the outcome will
vary greatly across regions of the world.
Sea-level rise is only one aspect of climate change.
While the rise in global temperatures will undoubtedly
be interrupted by occasional spurts of cooling, computer
models predict that warmer temperatures will melt polar
and glacial ice and that sea levels will rise as much as 50
centimeters or more over the next 90 years. Certain calcu-
lations project an even greater sea-level rise. Alarmed gov-
ernment leaders whose nations inhabit low-lying Pacifi c
and Indian Ocean islands talk of buying higher ground in
other countries and of suing the governments of polluting
states over lost real estate.
Changes in climate involve changes in the amount of
water vapor in the atmosphere, which affects patterns of
precipitation. Changes in precipitation affect where cer-
tain types of vegetation can grow, altering everything from
agricultural patterns to the location of animal hab
Acid Rain
A by-product of the enormous volume of pollutants
spewed into the atmosphere is acid rain . Acid rain forms
when sulfur dioxide and nitrogen oxides are released into
the atmosphere by the burning of fossil fuels (coal, oil, and
natural gas). These pollutants combine with water vapor
in the air to form dilute solutions of sulfuric and nitric
acids, which then are washed out of the atmosphere by
rain or other types of precipitation, such as fog and snow.
Although acid rain usually consists of relatively mild
acids, it is caustic enough to harm certain natural ecosys-
tems (the mutual interactions between groups of plant
and animal organisms and their environment). Already we
know that acid rain has acidifi ed lakes and streams (with
resultant fi sh kills), stunted growth of forests, and dam-
aged crops in affected areas. In cities, acid rain has acceler-
ated corrosion of buildings and monuments.
The geography of acid rain is most closely associated
with patterns of industrial concentration and middle- to
long-distance wind fl ows. The highest densities of coal
and oil burning are associated with large concentrations
of heavy manufacturing, such as those in Europe, the
United States, and China. As industrialization expanded
in these places during the second half of the twentieth
century, many countries (including the United States in
1970) enacted legislation establishing minimal clean-air
standards.
In the United States and western Europe, compli-
ance with legislated emission reductions is having posi-
tive results. In Canada as well as in Scandinavia, where
acid rain from neighboring industrial regions damaged
forests and acidifi ed lakes, recovery came faster than
most scientists had predicted. This evidence is now
itats.
While there is no doubt that sustained global warm-
ing would cause such changes, predicting exactly where,
and in what magnitude, these changes will occur is dif-
fi cult. What is clear is that those living on the margins of
sustainability are facing even riskier futures.
Extreme Weather Events
In recent years, climatologists have begun to focus on
abrupt weather events: a process that appears to be cou-
pled with “swings” in climate such as the Little Ice Age
and the current phase of climate change. Research has
already shown that the onset of the global warming that
led to the retreat of the Wisconsinan glaciers from north-
ern latitudes, gigantic storms swept across central North
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