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Global methane levels on the rise again

30 Oct, 2008 01:18 PM
After eight years of near-zero growth in atmospheric methane concentrations, levels have again started to rise.

“This is not good news for future global warming,” says CSIRO’s Dr Paul Fraser, who co-authored a paper to be published in Geophysical Research Letters, a journal of the American Geophysical Union.

“Over recent years, the growth of important greenhouse gases, namely methane and the CFCs, had slowed.

"This tended to offset the increasing growth rate of carbon dioxide that results mainly from large increases in the consumption of fossil fuels, particularly in the developing world.

“Now that methane levels have resumed their growth, global warming may accelerate.”

Methane is the second most important greenhouse gas in the atmosphere after carbon dioxide, accounting for nearly 20pc of global warming since the industrial revolution.

Methane is emitted to the atmosphere from natural wetlands, rice fields, cattle, forest and grassland fires, coal mines, natural gas leakage and use, and other sources.

“Over the past decade these methane sources have been close to balancing the absorption of methane through atmospheric oxidation and into dry soil,” Dr Fraser says.

“This fragile balance has resulted in little growth of methane in the atmosphere.

"Apparently some sources have been increasing, such as from fossil fuel use, cattle, and rice, while others have been decreasing, particularly natural tropical wetlands.

"However, over the past year, the total sources have overwhelmed the total sinks, and methane has again started to rise.”

Dr Fraser says that recent analyses of global data by CSIRO and collaborators at the Massachusetts Institute of Technology, Scripps Institution of Oceanography and the University of Bristol suggest that the methane increase is, at least in part, due to methane releases in the high latitudes of the Northern Hemisphere.

“Such increases have been predicted as rapid Arctic ice melting creates more high latitude wetland sources,” says Dr Fraser.

“A possible additional cause of the methane increase is that atmospheric oxidation may be weakening, for reasons as yet unknown, although recovery from ozone depletion, which is predicted to have commenced, may be involved.”

The Intergovernmental Panel on Climate Change (IPCC) has identified the need to understand causes of the variations of methane growth rates as a priority area of research.

“The reality is that scientists have only a very basic understanding of these methane variations,” Dr Fraser says.

“In order to predict the future contribution of methane to climate change, continuing high-quality observations, in particular in tropical and boreal locations, are required as input to, and verification of, sophisticated climate models.”

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A frozen peat bog in western Siberia the size of France and Germany put together contains about 500 billion tons of carbon. Western Siberia has warmed faster than almost anywhere else on the Earth, with an increase in average temperature of about 3C in the last 40 years. Even more Siberian permafrost is under the ocean, an area six times the size of Germany containing about 540 billion tons of carbon. That submarine permafrost is perilously close to thawing. Three to 12 kilometers from the coast the sea sediment is just below freezing. The permafrost has grown porous, there is a loss of rigor in the frozen sea floor, and the surrounding seawater is highly oversaturated with solute methane. “If the Siberian (submarine) permafrost-seal thaws completely and all the stored gas escapes, the methane content of the planet's atmosphere would increase twelve fold. The result would be catastrophic global warming.” --"A Storehouse of Greenhouse Gases Is Opening in Siberia," Spiegel, 17 April '08
Posted by dobermanmacleod, 30/10/2008 10:16:12 PM
And here we were believing that it was all to do with cows farting. Well that's what ''they'' told us previously. Lying bums
Posted by aarjaay, 1/11/2008 7:59:04 PM
Meh, not much we can do about methane gas - it comes from animals, trees and plants. When you pass wind you're adding methane into the atmosphere. Only way to stop it is to pretty much kill nearly every natural substance on land that includes us.
Posted by budman, 1/11/2008 9:35:17 PM
After a few beers and a day at the footy me and me mates punch out more gas than any paddock full of cows ever will, according to the woman.
Posted by Mr Methane, 3/11/2008 11:30:18 AM

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