Global Warming as a Threat to Life on Earth

The greenhouse effect describes the accumulation of greenhouse gases which regulate the temperature on earth. A greenhouse gas is any molecule that absorbs radiation in the wavelength region at which the earth radiates heat to outer space. The greenhouse gases include carbon dioxide, methane, nitrous oxide, ozone (in the troposphere), and the chlorofluorocarbons CFC-11 and CFC-12. Although transparent to sunlight, greenhouse gases, along with water vapor, absorb infrared heat. The transparency of greenhouse gases permits the relatively unimpeded passage of sunlight through the atmosphere. By absorbing heat, greenhouse gases warm the lower atmosphere and global surface while cooling the upper atmosphere (the stratosphere). Carbon dioxide is the most important contributor to the greenhouse effect, an estimated 60 percent. Methane accounts for 15 percent, nitrous oxide 5 percent, tropospheric ozone 8 percent, CFC-11 4 percent, and CFC-12 8 percent (1:54).

The greenhouse effect is so named because it operate

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The earth's albedo, the measure of solar reflectivity, is influenced by cloud cover, the quantity of suspended particulates in the atmosphere, and by characteristics of the earth's surface. Human intervention has a profound effect on the earth's surface: "Cutting and burning forests, burning or plowing grasslands, blackening snow with dust, diverting the flow of rivers, impounding water with dams, building concrete cities and highways, and extensive agriculture--all these are modifications of the earth's surface and they, in turn, affect the weather and climate" (2:7). In general, the burning of fossil fuels (coal, oil, and natural gas) is a major factor in the increasing levels of carbon dioxide in the atmosphere. Approximately 90 percent of the world's energy needs are supplied by carbon-based fuels (9:11). Industrial nations currently account for 48 percent of the world's carbon dioxide (8:119). The ecological effects of the increase in atmospheric carbon dioxide are many and varied. Most of the direct effects of global warming would be experienced by plants. Animals would suffer from secondary impacts because of resultant changes in their habitat. Although few direct consequences would result from increases in air
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Approximate Word count = 2195
Approximate Pages = 9 (250 words per page)

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