Mass Extinction And Climate Change
...greenhouse theory of climate change postulates that Earth's average temperature will rise over time due to the increased concentrations of certain gases within the atmosphere. Earth derives its energy from the sun, but much of the sun's radiation bounces back after reaching Earth. Some of this "bounced" radiation strikes molecules of carbon dioxide, water vapor, and other gases within the atmosphere, which results in the retention of some of this energy within the atmosphere. Without this effect, life on Earth would not be possible, since the planet would be too cold to support life.
Fossil records indicate that variances in temperature correspond significantly with the presence of greenhouse gases. Although the cause and effect cycle of the past is not completely understood, there is some indication that the gases act as a feedback mechanism, exacerbating other climatic changes.
Atmospheric concentrations of green house gases have risen significantly since the pre-industrial period, primarily due to the use of fossil fuels, destruction of forests, and agricultural practices. Climate scientists have prepared models predicting temperature change based upon different levels of fossil fuel consumption.
The model for the "high" scenario presented in this graph assumes that consumption of fossil fuels continues until cheap new technologies are developed to replace these energy sources. Under this scenario, atmospheric carbon dioxide concentrations would peak at about 1200 ppm, more than four times the pre-industrial levels. The global average temperature would rise 10 degrees.
In the medium scenario, no significant action is taken to replace fossil fuels until 2100. Carbon dioxide concentrations would rise to 850 ppm, and average temperatures could reach six degrees above the current mean.
The low scenario assumes significant action immediately....
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