The Greenhouse Effect Essay Research Paper 1What

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The Greenhouse Effect Essay, Research Paper 1.What are the Greenhouse Gases? Carbon dioxide (CO2) is responsible for more than half the human contribution to the greenhouse effect, and concentrations have climbed steadily from around 280 parts per million at the dawn of the industrial revolution meaning 0.028 percent of the air s volume is taken up by the gas to around 355 ppm today. As people burn oil, coal and natural gas, they release carbon that ancient plants in past geological ages absorbed and stored.6 As cement workers process limestone, carbon absorbed over millions of years by prehistoric marine organisms enters today s atmosphere as carbon dioxide. Each year human beings shift 6 billion metric tons of this fossil carbon from the earth to the air in the form of 22

billion tons of carbon dioxide. The destruction of forests and the degradation of soils adds an estimated 5.9 billion tons of CO2 to the atmosphere, although this estimate may be off in either direction by as much as 3.7 billion tons.7 About half of the CO2 released by human activities is quickly reabsorbed by the oceans and by immature trees, which store carbon in their expanding trunks and branches. But human-caused CO2 emissions exceed what the oceans and lands assimilate. Half the global emission total remains in the atmosphere indefinitely, contributing to the greenhouse effect. The annual human contribution of carbon dioxide seems small in comparison to the 2.75 trillion metric tons of the gas already in the air. The carbon cycle is so closely balanced under natural

conditions, however, that the 11 billion tons of carbon dioxide we add each year produces a continuous growth in the gas s atmospheric concentration of about 0.5 percent annually. Methane (CH5) is released as a result of the combustion of carbon and microbial decay in the absence of oxygen. This occurs in the cultivation of wetland rice, the burning of plant material (biomass), landfills and the digestive systems of livestock and termites. Methane also emanates from coal mines and the production and distribution networks of natural gas. Molecule for molecule, methane is 50 times more powerful in trapping heat than carbon dioxide, but there is less than one 200th as much of it in the atmosphere. Human activities have more than doubled its concentrations from 0.7 parts per million

in pre-industrial times to more than 1.7 ppm today. Methane accounts for 15 percent or more of the human intensification of the greenhouse effect. Because it is removed from the atmosphere relatively rapidly by chemical reactions in the air, emissions reductions of only about 15 to 20 percent would be required to stabilize methane at its current high concentrations. In recent years the rise of methane concentrations has slowed noticeably, perhaps largely as a result of reduced leakage from the natural gas pipeline network in Russia.8 Nitrous oxide (N20) is produced by a variety of biological processes in soils and water. Although its concentration increase of 8 percent since preindustrial times (from 288 to 310 parts per billion) is ascribed to human influence, its human sources

are not well understood. Soil cultivation, biomass burning, and fossil fuel combustion all play some role in nitrous oxide production. Bringing new land into cultivation may be the largest source of the gas. Two recently identified major sources are the production of nylon and nitrogen fertilizer. The uncertainty about this gas is especially troubling since the scientists advising the Intergovernmental Panel on Climate Change (IPCC) estimated that a 70 to 80 percent reduction in human emissions of nitrous oxide would be needed in order to stabilize concentrations at their present high level.9 Ozone (O3) is a powerful greenhouse gas with a split personality. In the upper atmosphere ozone protects living things from the sun s potentially harmful ultraviolet-B radiation. Near the