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CO2 and Methane

(Clicking any of the underlined text in blue will take you to a reference on it.)

The natural gas we burn in our homes is primarily methane, the CH4 molecule; methane emissions are 25 times more potent atmospheric heaters than carbon dioxide emissions of equal mass. Science did not recognize methane’s effects on climate until the 1970s, but scientists now believe that methane’s increase from 700 parts per billion (ppb) in air in 1750, when the Industrial Revolution began, to 1,800 ppb by 2008 has warmed the atmosphere by almost half the amount credited to carbon dioxide increases for that period. The EPA estimates that for 2009 almost a third of “human-caused” methane emissions in the U.S. (helpfully pegged at 686 trillion grams of CO2 equivalents) came from “natural gas systems,” with another 40% from livestock and landfills.

Today’s news that natural gas’s replacing coal in power plants helped decrease U.S. carbon dioxide releases in 2011 (the EPA says 2011 CO2 emissions were about 9 percent lower than in 2005) is welcome, but equivocal. Burning natural gas generates less CO2 per unit of energy produced than burning coal does, but increased reliance on natural gas leads to incidental methane releases – in leaks, in mining procedures including hydraulic fracturing, in ordinary use such as when we turn on appliances. A broken, leaking natural gas pipeline can quickly equalize the global warming impacts of a dirty, coal-fired power plant and a new, “green” plant fueled by methane, just because atmospheric CH4 is so much better at capturing heat than is CO2.

Hey, we’re trying everything, but the bottom line is that high energy consumption, encouraged by cheap market prices, takes us into dangerous, uncharted waters.


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