August 2001 - -
One of planet earth's unique characteristics is a warm average temperature
of 57ºF that enables it to support the flourishing life that
exists today. A phenomenon known as the greenhouse effect is responsible
for maintaining this comfortable temperature. Unfortunately, human
activities over the last century have disrupted the earth's natural
balance by enhancing the greenhouse effect and initiating a frightening
trend of global warming.
Under normal conditions, a delicate balance exists between incoming
energy from the sun (solar radiation) and outgoing energy from the
earth in the form of reflected light and heat (infrared radiation).
Some heat is naturally trapped inside the atmosphere by naturally
occurring "greenhouse gases" such as carbon dioxide, water
vapor, nitrous oxide, methane, and ozone. This natural heat-trapping
process is known as the "greenhouse effect," and is essential
for maintaining the warm temperatures that support life on this planet.
Without it, the earth's temperature would be about 0ºF- too
cold for most life forms.
As mentioned above, most greenhouse gases (carbon dioxide, water
vapor, nitrous oxide, methane, and ozone) are naturally occurring
in certain amounts. Normally these gases are roughly balanced in
global cycles; atmospheric gases are emitted by sources such as wetlands
or decomposing biomass and absorbed by "sinks" such as
forests and oceans. Over the last century, however, human activities
have added abnormal amounts of these greenhouse gases into the atmosphere-
far more than the earth's sinks are capable of absorbing. As atmospheric
concentrations of these gases increase, the natural equilibrium is
disrupted and the greenhouse effect is enhanced. The result is global
warming, a gradual increase in the earth's overall average temperature.
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