One tonne of methane has the same global warming effect as 21 tonnes of carbon dioxide, and, on this basis, methane is known to be responsible for approximately 20% of the greenhouse gas effect. And yet one rarely, if ever, hears environmentalists lobbying for political action to control atmospheric methane levels. The arguments of environmentalists appear to focus, almost exclusively, upon carbon dioxide, and the release of carbon dioxide into the atmosphere as a result of the burning of fossil fuels to power cars, aircraft, and the industrial economy in general.
A couple of interesting facts about methane have emerged in the past year, which have received little attention from the media. Firstly, it was discovered that trees and plants actually release large amounts of methane during their normal lifetime. "This effect is completely missing from climate change and biogeochemical models," according to Peter Cox of the Centre for Ecology and Hydrology, at Winfrith in Dorset, UK. (http://news.bbc.co.uk/1/hi/sci/tech/4604332.stm, http://www.newscientist.com/channel/life/mg18925343.900-the-lungs-of-the-planet-are-belching-methane.html). It had been understood for some time that dead trees and plants release methane into the atmosphere as bacteria consume the dead plant matter. At any one time, a certain proportion of a forest will consist of decaying plant matter, so it was known that a forest is a source of atmospheric methane. The latest research suggests that the methane released by trees and plants during their normal lifetime could be responsible for 10-30% of atmospheric methane production. David Lowe of New Zealand's National Institute of Water and Atmospheric Research points out that "We now have the spectre that new forests might increase greenhouse warming through methane emissions rather than decrease it by sequestering carbon dioxide."
One can well understand why environmentalists do not want to publicise such a possibility. Moreover, it has recently been discovered that the growth-rate of atmospheric methane was at its greatest in the 1980s, and there has been no increase at all in the past seven years. (http://environment.newscientist.com/channel/earth/dn10643-emissions-of-key-greenhouse-gas-stabilise.html, http://news.bbc.co.uk/1/hi/sci/tech/6170736.stm). As the BBC article states "some scientists and policymakers...suggest that cutting emissions of methane could be a more effective way of curbing climate change than focusing on carbon dioxide."
The lack of attention devoted by environmentalists to methane, and their obsession with carbon dioxide, supports the following hypothesis: most 'environmentalists' are fundamentally motivated by political and economic beliefs, rather than environmental principles alone; a large proportion of 'environmentalists' are anti-capitalists, who see environmentalism as a tool for attacking the industrial, capitalist world economy. The global capitalist economy is largely built upon the burning of fossil fuels, so the anti-capitalists are seeking to bring down the system by attacking its foundation. Hence, many environmentalists argue that the only way to avoid catastrophic climate change is to reduce economic growth, and perhaps to even accept economic contraction. The rational alternative, to transform the efficiency with which we expend our energy resources, seems to receive scant consideration as the overall solution.
Of course, the truth-value of a proposition, and the validity of an argument, is independent of the person expressing that proposition or argument, and independent of the motives they may or may not possess. However, understanding the motives of environmentalists helps one to assess the credibility of their science, and the credibility of their economic proposals.