古老沼泽显示全球温室效应线索
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Analysis of sediments from a British bog suggest that methane emissions increased due to intense global warming around 55 million years ago.

The team from Royal Holloway, University of London, Bristol and other institutions analysed the geochemical composition of sediments taken from the Cobham Lignite wetland in southeast England, revealed when the Channel Tunnel rail link cut through it.

An article published today in Nature, the research team (which includes Professor Margaret Collinson and Professor Andrew Scott from the Geology Department at Royal Holloway) explains that carbon isotope values of hopanoids – compounds made by bacteria – suddenly decrease in a manner that can only be explained by switching to a diet of methane. This suggests that methane emissions must have increased at that time.

Methane is a very powerful greenhouse gas. So if the processes occurring at Cobham were widespread, then the increase in methane emissions could have caused further warming, amplifying the climate change at this time.

“We have been surprised at the amount of information that we could obtain from such a short section of a rail cutting and were fortunate that the rocks were of an age to help us unravel some of the secrets of a period of rapid global warming about fifty-five million years ago”, says Professor Scott.

Dr Pancost from Bristol University explains: “A massive release of carbon into the atmosphere caused significant global warming. It is likely that this warming and associated climate change caused a change in environmental conditions that brought about increased methane emissions. This in turn, may reflect an increase in methane production and subsequent release from the terrestrial biosphere.”

However, as Professor Scott cautions, “We can not use this section as an exact model for interpreting future global warming as the climate 55 million years ago was very much warmer than that of today.”

In such a scenario, not only will warming occur due to the carbon pumped into the atmosphere by our burning of oil and coal, but also due to the biological response of some ecosystems.

The team's research was sponsored by the Leverhulme Trust with Dr David Steart of the Geology Department at Royal Holloway as post-doctoral research assistant.

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