While carbon dioxide receives most attention in discussions of global warming, methane, another greenhouse gas, is also building up rapidly in the atmosphere as a result of various human activities.
USEFUL FACTS:
Sources of methane: rice paddies, termites, coal mines, land fills, and digestive tracts of animals. Estimated shares:
Tundra, bogs, swamps 26%
Rice 20
Livestock 15
Burning of vegetation 10
Oil and natural gas 8
Landfills 7
Coal mining 6
Wild animals and termites 4
Animal waste 3
Oceans 1
Concentration of methane in the atmosphere has more than doubled in the last 300 years, from 650 ppb (parts per billion) to 1,700, and is increasing at a rate of 1% per year.
Methane is 20-30 times as effective in trapping heat as CO2. While its atmospheric concentration is much lower, therefore, it makes up about 20-25% of the global warming problem, while CO2 is 50-55% and another 20-25% is CFCs (chlorofluorocarbons).
Environmental Protection Agency (EPA) today [11/22/89] is publishing report on prospects for reducing methane.
Methane may be easier to control than CO2 or CFCs, because its lifetime in the atmosphere is short (~10 years). A cut in emissions of 10-20%, the report says, would stabilize atmospheric levels.
Of that amount, 50-75% can be achieved by cutting emissions from farm animals by 50%. Among techniques to do this: improved feed and nutrition, hormone treatments to improve productivity.
Total yearly emissions are placed at 425-675 million tons by scientists. Of that amount, “human-induced sources” are 60%, natural 40%.
One fear: global warming may cause the release of “methane locked in frozen tundra and in permafrost in the sediments at the bottom of arctic seas…releasing vast new amounts of methane that would further promote atmospheric warming.”
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