“Now comes the first news that levels of methane in the atmosphere, which began rising in 2007 when an unprecedented heatwave in the Arctic caused a record shrinking of the sea ice, have continued to rise significantly through 2008 and 2009.
Although researchers cannot yet be certain, and there may be non-threatening explanations, there is a fear that rising temperatures may have started to activate the positive feedback mechanism. This would see higher atmospheric levels of the gas producing more warming, which in turn would release more methane, which would produce even further warming, and so on into an uncontrollable “runaway” warming effect. This is believed to have happened at the end of the last Ice Age, causing a very rapid temperature rise in a matter of decades. …
In a presentation on “Global atmospheric methane in 2010: budget, changes and dangers”, the two scientists will reveal that, after a decade of near-zero growth, “globally averaged atmospheric methane increased by [approximately] 7ppb (parts per billion) per year during 2007 and 2008.”
They go on: “During the first half of 2009, globally averaged atmospheric CH4 was [approximately] 7ppb greater than it was in 2008, suggesting that the increase will continue in 2009. There is the potential for increased CH4 emissions from strong positive climate feedbacks in the Arctic where there are unstable stores of carbon in permafrost … so the causes of these recent increases must be understood.”
Professor Nisbet said at the weekend that the new figures did not necessarily mark a new excursion from the trend. “It may just be a couple of years of high growth, and it may drop back to what it was,” he said. “But there is a concern that things are beginning to change towards renewed growth from feedbacks.”
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