| As
carbon dioxide and certain other gases increase in the atmosphere,
more and more of the heat that should escape and radiate into
space remains trapped. This trapped heat is the subject of debate
within the scientific community. Scientists, lined up on each side
of the issue disagree as to whether this heat may cause a rise in
global temperatures.
According to the late Carl
Sagan, a world-renowned environmental author, the typical global
temperature difference between an ice age and an interglacial
period is three to six degrees Celsius (5 degrees to 11 degree
Fahrenheit). Sagan theorized that if global temperatures were to
rise three to six degrees C, water would become warmer and expand,
melt polar ice caps and raise sea levels. Under these conditions,
many islands would disappear and the oceans would flood such
coastal cities as New York, Los Angles and Tokyo. Just a
three-foot rise in sea level would triple the size of San
Francisco Bay.
Global warming may change
precipitation patterns as well. Rainfall could decrease in some
areas, causing water shortages and failing crops, while increasing
in other areas with attendant flooding and soil erosion. Plants
and animals that do not adapt quickly to the changing environment
could become endangered species.
Some scientists, however,
believe that an increase in global temperature could result in
increased crop yields. Higher carbon dioxide levels associated
with global warming could be beneficial for plants. If carbon
dioxide levels doubled, it is theorized that plants could improve
productivity by as much as one-third. Some evidence shows that a
rise in carbon dioxide could increase a plant's optimal
temperature and allow plants to thrive in warmer temperatures.
Those that subscribe to the
greenhouse theory and global warming believe the primary cause of
global warming is high emissions of carbon dioxide from industrial
processes and the burning of fossil fuels. The U.S. is the world's
largest carbon dioxide emitter. The greatest amount of carbon
dioxide emitted comes from burning oil, coal and natural gas to
produce the electricity that maintains the American standard of
living. Transportation is the second largest contributor to the
problem. Each car in the United State emits more carbon dioxide
per year than the weight of the car.
Some models used by scientists
support the theory that an increase in atmospheric carbon dioxide
produces global warming. Scientists have been making attempts to
measure any difference in global temperature. Researchers at NASA
as well as other scientists believe there has been a 0.5 degree C
(0.9 degree F) increase in the average global temperature over the
last 100 years. Other scientists remain unconvinced. Researchers
using the TIROS-N weather satellite to measure the temperature of
the lower portions of the atmosphere during the 1980s did not find
any detectable warming.
Despite the controversy over
whether the global temperature is rising, the greenhouse effect is
a well-established theory in atmospheric science. For example,
Venus has a dense carbon dioxide atmosphere that could account for
its surface temperatures of 426 degrees C (800 degrees F). Mars,
with a thin carbon dioxide atmosphere, has an average temperature
of -53 degrees C (-63 degrees F). This temperature difference,
however, may also be partially explained by the distance of these
planets from the sun.
More on the greenhouse effect here: |
