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The Culprits While the concentrations of almost all greenhouse gases have been increasing since the Industrial Revolution, carbon dioxide has had the greatest effect on changing the climate. During the 1980's humans released 5.5 billion tons of carbon dioxide into the atmosphere annually by burning fossil fuels (coal, oil, natural gas) for heat, transportation, and electricity. An additional 1.6 billion tons was released from anthropogenic (human-induced) changes in land-use (i.e. clearing land for agriculture, pastures, etc.) mostly through deforestation in the tropics. Where does that 7.2 billion tons of atmospheric carbon go? Ocean modelers find that the ocean takes up approximately 2 billion tons a year. Around 2 billion tons are taken up by a presently unidentified "sink" or reservoir of carbon (see The Missing Carbon Sink). This leaves a remainder of 3.2 billion tons of CO2, and global atmospheric measurements indicate that this amount is simply being added to existing concentrations already present in the atmosphere. The result is that the atmospheric concentration of carbon dioxide is increasing at a rate of approximately 1.5 ppm (parts per million) per year and overall it has increased about 30% since the beginning of the Industrial Revolution.

Human beings are causing the release of carbon dioxide and other greenhouse gases to the atmosphere at rates much faster than the earth can cycle them. Fossil fuels - oil, coal, natural gas, and their derivatives - are formed through the compression of organic (once living) material for millions of years, and we are burning billions of tons of these fuels per year. Why is this disconcerting? Because the CO2 expelled into the atmosphere through these activities does not disappear immediately or even over the course of a year. As a matter of fact, the residence times of greenhouse gases (how long they remain in the atmosphere) are on the order of decades to centuries. This means that the CO2 we emit today will likely be affecting the climate well into our children's future and likely into the futures of our grandchildren.

Despite the widespread recognition of this fact, worldwide emissions of fossil fuels continue to increase at a rate of about 1% per year (IPCC, 1995). Emissions will increase even further as the developing world moves towards greater industrialization. As of 1995 the industrialized world (the United States, Western Europe, Eastern Europe, and the Former Soviet Union) contributed more than 70% of the total world emissions. If use of fossil fuels continues to increase at present rates, by 2035 humans will annually be contributing 12 billion tons of CO2 to the atmosphere, about 50% of which will be due to developed nations and about 50% of which will be due to developing nations (IPCC 1995).

Source: www.whrc.org

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