Methane levels surge again after decade of stability

October 30th, 2008 - 3:21 pm ICT by IANS  

Washington, Oct 30 (IANS) The quantity of methane in the air surged last year, ending a decade of stability in levels of potent greenhouse gas, according to MIT team.Methane levels have more than doubled since pre-industrial times, accounting for around a fifth of the human contribution to greenhouse gas-driven global warming.

Given that, kilo for kilo, methane is 25 times more powerful as a greenhouse gas than carbon dioxide, the situation will require careful monitoring in the near future.

Until recently, the levelling off of methane levels had suggested that the rate of its emission from the earth’s surface was approximately balanced by the rate of its destruction in the atmosphere.

However, since early 2007 the balance has been upset, according to new findings. The paper’s co-authors, postdoctoral researcher Matthew Rigby and Ronald Prinn, professor of atmospheric chemistry in Massachusetts Institute of Technology (MIT), said this imbalance has resulted in several million tonnes of additional methane in the air.

Methane is produced by wetlands, rice paddies, cattle, and the gas and coal industries, and is destroyed by reaction with the hydroxyl free radical (OH), often referred to as the atmosphere’s “cleanser.”

One surprising feature of this recent growth is that it occurred almost simultaneously at all measurement locations across the globe. However, the majority of methane emissions are in the Northern Hemisphere, and it takes more than one year for gases to be mixed from the Northern Hemisphere to the Southern Hemisphere.

Hence, theoretical analysis of the measurements shows that if an increase in emissions is solely responsible, these emissions must have risen by a similar amount in both hemispheres at the same time, according to an MIT release.

These findings are being published this week in Geophysical Review Letters.

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