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  • Saturday, December 9, 2006
    The earth’s climate and weather is driven by energy from the sun. This energy heats the planet, which in turn radiates that heat back into space. However, much of this heat is retained by various greenhouse gases in our atmosphere, such as carbon dioxide (CO2), methane and nitrous oxide—and this is a good thing. Without such gases contributing to this natural greenhouse effect, life as we know it would not exist. Temperatures would be similar to our airless moon, ranging wildly from 225°F during the day to negative 243°F at night. Obviously, this would not be an environment conducive for life.

    But due to greenhouse gases, the earth’s average temperature is a hospitable 60°F. However, problems arise when the concentration of these gases increase.

    Huge amounts of carbon have been captured by plants and buried in the ground in the form of coal, oil and natural gas, called fossil fuels. (In contrast to human beings, plants take in CO2 and expel oxygen.) These fuels have accumulated over the course of perhaps millions of years. With the advent of the Industrial Revolution, mankind began extracting and burning earth’s vast reservoirs of these fuels. This released millions of tons of carbon, in the form of CO2, into the atmosphere, thus increasing the levels of greenhouse gases beyond what the earth can safely handle. Since then, atmospheric concentrations of CO2 have increased nearly 30%, methane concentrations have more than doubled, and nitrous oxide concentrations have risen roughly 15%. These increases have enhanced the heat-trapping capability of earth’s atmosphere, and will continue to do so for years to come.

    Fossil fuels burned to power cars and trucks, heat homes and businesses, and power factories are responsible for about 98% of U.S. CO2 emissions, 24% of methane emissions and 18% of nitrous oxide emissions.

    AT RISK: On the frozen Beaufort Sea outside the Inupiat village of Kaktovik, Alaska, a polar bear pauses from a meal of whale meat. The 3,800 polar bears along the Alaskan coast face an uncertain future as global warming melts more summer sea ice each year.

    Photo: KRT
    Also contributing a significant share of emissions are increased agriculture, deforestation, landfills, industrial production and mining. In 1997, the United States discharged roughly one-fifth of the world’s total greenhouse gases.

    Estimating how much of these gases will be emitted in the future is difficult, as it depends on demographic, economic, technological, policy and institutional developments. Based on differing projections of these principal factors, several scenarios have been developed.

    For example, in the absence of emissions control policies, by the year 2100, CO2 concentrations are projected to be 30 to 150% higher than today’s levels. However, even if human beings were to cease emitting heat-trapping gases into the atmosphere, the climate still would not stabilize for quite some time, as the gases that are already there will remain for decades, even centuries.
     
    posted by sasikala at 12:39 PM |


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