The Science Behind Global Warming Theories
Sunday, Feb. 01, 2004 at 12:57 AM
Section 4 of Perspectives on Global Warming: A Primer
The Science Behind Global Warming Theories
Scientists who study climate change have noted that global warming is not a distant possibility, but may be under way
right now. Global mean surface temperature has increased about 1.1°F (0.6°C) since the beginning of the 20th century,
there has been a significant loss of glacial and polar ice, global sea level has risen between 3.9 and 10 in.
(10 - 25 cm), and more frequent, persistent and intense El Ninos have been observed in recent decades. While some
scientists claim that this is natural fluctuation in temperature, or it is due to the earth getting closer to the sun,
there is increasingly clear evidence that this increase in temperature is directly related to human activities, namely
the burning of fossil fuels. This article will give a succinct explanation of the science behind the global
warming debate. For those interested in reading more detailed analysis, with charts and tables, please visit the
The "greenhouse effect" is actually natural, to some degree. Large amounts of carbon dioxide, water vapor, and
other "greenhouse gases" exist in the atmosphere naturally, and they keep the earth at a relatively stable temperature by
allowing sunlight in, but preventing a great deal of heat from escaping into space. If the greenhouse effect did
not exist here
on earth, the planet would be inhospitable. A problem, however, arises when the greenhouse effect becomes accelerated.
Plant respiration and other natural processes release large amounts of carbon dioxide into the atmosphere constantly,
but for millions of years, the carbon dioxide has been reabsorbed at the same rate by other natural processes
and the greenhouse effect has stayed
in a state of balance. Since the industrial revolution, however, humans' burning of fossil fuels and other
activities, such as production of chemicals like aerosols and massive deforestation, has tipped that
Climate scientists try to predict what will happen now that this balance has been disrupted. Their method is
complicated, and involves a great deal of uncertainty. They chart the current temperature trends, then compare
them with estimations
of global temperature changes in the past. They also measure the amount of emissions released into the air, as
well as the amount of deforestation and other significant changes in the atmosphere and oceans, and they
compare those changes with the current changes in temperature. This becomes very difficult, as the number of
factors that must be
considered is gigantic. Once they have some idea of how the earth's temperature has tended to naturally
change, and how it is changing now with the human acceleration of the greenhouse effect, they make computer models
in order to predict future temperatures. Generally, a collection of scientists with differing ideas of which data
is important independently create about two dozen computer models,
then predict a range of possible changes. Though there are dissenters, most of the prominent scientific community
is very concerned about the results of these
models. While some have come to the conclusion that humans actually have very little impact on climate, most of the
computer models employed thus far have given predictions from minor discomfort to global catastrophe. But because
the calculations are extremely complicated, and we do not yet have enough proven facts about the combined effects
of these various factors, all scientists
agree that these models are still unrefined, and more research will be necessary if more accurate predictions are expected.
Climate scientists are also able to determine, to a very high degree of accuracy, the sources of all the greenhouse
gases. They also know of methods creating "carbon sinks," which are places to which carbon from the atmosphere can be
transferred. These range from very simple, like planting trees, to complex and expensive, like ocean sequestering.
These parts of climate science are very important in determining the most effective ways of preventing and reversing global
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