T H E - C U L P R I T S

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.

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.