23 may 2008

By Richard Black
Environment correspondent, BBC News website

[This article has been edited by 4C Climate Change]

Higher atmospheric levels of the greenhouse gas methane noted last year are probably related to emissions from wetlands, especially around the Arctic.

Scientists have found indications that extra amounts of the gas in the Arctic region are of biological origin.

Global levels of methane had been roughly stable for almost a decade. Rising levels in the Arctic could mean that some of the methane stored away in permafrost is being released, which would have major climatic implications.

The gas is about 25 times more potent than carbon dioxide as a greenhouse gas, though it survives for a shorter time in the atmosphere before being broken down by natural chemical processes.

Indications that methane levels might be rising after almost a decade of stability came last month, when the US National Oceanic and Atmospheric Administration (Noaa) released a preliminary analysis of readings taken at monitoring stations worldwide. Noaa suggested that 2007 had seen a global rise of about 0.5%. Some stations around the Arctic showed rises of more than double that amount….

Warm and wet

Ed Dlugokencky, the scientist at Noaa's Earth System Research Laboratory (ESRL) who collates and analyses data from atmospheric monitoring stations, agrees that the 2007 rise has a biological cause...."In boreal regions it was warmer and wetter than usual, and microbes there produce methane faster at higher temperatures."

Dr Dlugokencky also suggested that the drastic reduction in summer sea ice around the Arctic between 2006 and 2007 could have increased release of methane from seawater into the atmosphere. A further possibility is that the gas is being released in increasing amounts from permafrost as temperatures rise. Researchers will be keeping a close eye on this year's data which will indicate whether 2007 was just a blip or the beginning of a sustained rise.

Methane concentrations had been more or less stable since about 1999 following years of rapid increases, with industrial reform in the former Soviet bloc, changes to rice farming methods and the capture of methane from landfill sites all contributing to the levelling off.
In the recent past, concentrations have risen during El Niño events, whereas the world is currently amid the opposite climatic pattern, La Niña.

An upturn in methane concentrations emissions could have significant implications for the Earth's climatic future.

A sustained release from Arctic regions or tropical wetlands could drive a feedback mechanism, whereby higher temperatures liberate more of the greenhouse gas which in turn forces temperatures still higher. …

(NOTE BY 4C CLIMATE CHANGE; While the scientists cited in the article attribute the dangerous rise in methane to "a biological cause", it is clear that the biological trigger is the result of warming induced by anthropogenic greenhouse gases, which have caused a temperature rise throughout the Arctic and Alaska that is twice the global average. See the article we cited in the fact sheet for our petition: “Warming hits 'tipping point'. Climate change alarm as Siberian permafrost melts for first time since ice age”, Ian Sample Guardian Weekly, August 19-25, 2005. [This report is based on an article in New Scientist of 11 August 2005: “Climate Warnings as Siberia Melts”, by Fred Pearce.])

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