Sunday, September 23, 2007

Climate change: British bog holds clue to ancient global warming

Around 55 million years ago, the Earth underwent a period of intense global warming. An analysis of sediments from a British bog now suggests that methane levels increased during this time, indicating that the greenhouse gas may have contributed to global warming as part of a positive feedback loop.

Richard D. Pancost and colleagues analysed the geochemical composition of sediments spanning the onset of this warm period, taken from the Cobham Lignite wetland in southeast England. Their results are reported in this week’s Nature. Carbon isotope values of hopanoids, a biomarker derived from bacteria, decreased, suggesting that methane-munching bacteria increased during this time. This in turn, may reflect an increase in methane production and release from the terrestrial biosphere.

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