Global Warming: The Truth


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English 101


3rd Draft of MP# 4


According to the National Academy of Sciences, with accelerated global warming during the past two decades, there is now new and stronger evidence that most of the warming over the last 50 years is due to human activities (U.S. EPA 1). These activities have altered the chemical composition of the atmosphere through the buildup of greenhouse gases.


Greenhouse gasses occur naturally with in our atmosphere. Energy from the sun drives the earth\'s weather and climate, and heats the earth\'s surface; in turn, the earth radiates energy, in the form of heat, back into space. Natural atmospheric greenhouse gases such as water vapor, methane, and carbon dioxide trap some of the outgoing energy, retaining heat somewhat like the glass panels of a greenhouse (U.S. EPA 3). Without this natural "greenhouse effect”, temperatures would be much lower than they are now, and life as we know it today would not be possible.


Since the Industrial Revolution, human activities have increased the levels of most naturally occurring gases through transportation and industry. Carbon dioxide is released into the atmosphere when solid waste, fossil fuels, wood and wood products are burned. Methane is emitted during the production and transport of coal, natural gas, and oil. Emissions from methane also result from the decomposition of organic wastes in


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municipal solid waste landfills, and the raising of livestock. Nitrous oxide is emitted into the atmosphere during agricultural and industrial activities as well as during combustion of solid waste and fossil fuels.


Very powerful greenhouse gases that are not naturally occurring within the Earth’s atmospheres are known as CFC’s or chlorofluorocarbons and sulfates. Sulfates and CFC’s are generated in a variety of industrial processes mostly used in the production of propellants, aerosol cans, and freon for cooling systems (U.S. EPA 2). Problems may arise when the atmospheric concentration of greenhouse gases becomes too high. Since the beginning of the industrial revolution, atmospheric concentrations of carbon dioxide have increased nearly 30%. Methane concentrations have more than doubled while nitrous oxide concentrations have risen by about 15%. These increases have enhanced the heat-trapping capability of the earth\'s atmosphere. This build up of gasses, primarily carbon dioxide, methane, and nitrous oxide, ultimately cause global warming.


But why the sudden increase greenhouse gas concentrations? Scientists generally believe that what has changed in the last few hundred years is the additional release of carbon dioxide by human activities. Fossil fuels burned power factories, to run cars and trucks and to heat homes and businesses are responsible for about 98% of U.S. carbon dioxide emissions, 24% of methane emissions, and 18% of nitrous oxide emissions. Increased agriculture, deforestation, landfills, industrial production, and mining also contribute a significant share of harmful emissions.


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In 1997, the United States emitted about one-fifth of total global greenhouse gases (Global Warming Impacts 2). Recent studies have shown that the Earth\'s surface temperature has risen by about 1 degree Fahrenheit in the past century. Changing regional climate could alter forests, crop yields, and water supplies (U.S. EPA 3).


This rise in surface temperature also causes the temperature of the sea to increase as well, altimetry causing an increase in evaporation and a more vigorous hydrological cycle leading to increased precipitation. Other effects of global warming are: an increase in the north-south gradient in salinity, a decrease in the thickness and extent of ice cover in the arctic, a reduction of the north-south temperature gradient and possibly a reduction in average wind stress over the whole of the north Atlantic which could lead to a decrease in the strength of wind-driven currents such as the Gulf Stream (U.S.EPA 3).


Over the past forty years, the ozone layer has depleted from 330 ppm (parts per million) to only 131 ppm in 2001. Eye cataracts, ocular cancer, lowered resistance to tumors and infectious disease, accelerated photo aging of the skin and various types of skin cancers may alter human health due to prolonged exposure to ultraviolet radiation resulting from ozone depletion (U.S. EPA 3). Deserts may expand into existing rangelands, and features of some of our National Parks may be permanently altered. Most of the United States is expected to warm, although sulfates may limit warming in some areas. Scientists currently are unable to determine which parts