Unexplained strong methane rises raise concerns  
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來源: Carbon Commentary

Methane concentrations at the Mauna Loa observatory. The grey data points are preliminary. Graphic: NOAA.

Saturday 8 November 2008 in Newsletter #11 by Chris Goodall

We seem to know less about methane emissions than we thought. After a decade of stability, methane concentrations in the atmosphere have been rising strongly in the last 18 months.

Early research work suggested that this rise was concentrated in the northern latitudes of the northern hemisphere and was consistent with greater emissions from decaying organic matter in melting permafrost or from the melting of Arctic sea ice.

Now this result has been called into question by the publication of a new study showing the concentrations of methane are rising almost everywhere. Since methane takes some time to diffuse around the globe, the later work suggests that the rise in methane may not be directly due to enhanced emissions from biological sources.



he scientific debate about the cause of increased methane is important because it suggests that we do not yet have a good model for what determines changes in concentrations. One of the primary worries about global warming is that it will eventually trigger the eruption of untold millions of tonnes of methane from deep sea water. (This is usually known as the ‘clathrate gun’ hypothesis.)

The gas is currently locked into a stable bond with the extremely cold waters in the deep oceans. Continued world temperature increases will eventually cause the methane to burst from its chemical locks within the cold liquid and rise to the surface. This probably happened at times of rapid warming in the far-distant past.

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