Emissions from incinerators, waste treatment plants, electric power plants, factories, household furnaces, cars and buses are all contributors to this problem. (Stegar/Bowermaster 1990) Carbon dioxide is recovered from the atmosphere in photosynthesis and reused. After excretion, waste products are broken down and reconstituted as foods in the soil. Water, minerals and other chemicals pass out of living organisms into the environment, and are then taken up again as inputs. (Jacobs 1991) METHANE, also marsh gas, is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from the decomposition of organic wastes in municipal solid waste landfills, and the raising of livestock. It is lighter than air, colorless, odorless, and flammable. NITROUS OXIDE is emitted during agricultural and industrial activities, as well as during combustion so solid waste and fossil fuels. (www.epa.gov) Other very powerful greenhouse gases that are not naturally occurring include hydro fluorocarbons (HFC's), perfluorocarbons (PFC's), and sulfur hexafluoride (SF6), which are generated in a variety of industrial processes. Each greenhouse gas differs in its ability to absorb heat in the atmosphere. HFC's and PFC's are the most heat-absorbent. Methane traps over 21 times more heat per molecule than carbon dioxide, and nitrous oxide absorbs 270 times more heat per molecule than carbon dioxide. Often, estimates of greenhouse gas emissions are presented in units of millions of metric tons of carbon equivalents, which weigh each gas by its Global Warming Potential (GWP). (www.epa.gov).
The Greenhouse Effect and Climate.
Weather stations, balloons, ocean buoys, and satellites tell us the Earth's temperature today. Ice cores, sediment layers and tree rings tell us about what the Earth's climate has been like in the past. With this evidence, scientists are learning how climate changes over time.