Friday, February 10, 2006

No evidence that methane releases triggered global warming at end of last ice age

Quirin Scheirmeier, Nature,  full article by subscription  comments on the study by Sowers published today in Science:  Sower abstract in Science

Methane escaping from the sea floor to the atmosphere has been a popular suspect for causing rapid climate changes during and at the end of the last ice age. But new data derived from a Greenland ice core have delivered a killer blow to the idea.

Methane (CH4) is a much stronger greenhouse gas than carbon dioxide. It is usually released from swamps or through biomass burning. But it is also trapped in huge amounts in some ocean-floor sediments, where it lies buried in a strange kind of ice known as 'methane clathrate'. These clathrates are stable only within a certain range of temperatures and pressures; when brought to the surface, they melt rapidly and release burnable gas to the air.

A catastrophic release of trillions of tonnes of methane is thought to have triggered a temperature jump some 55 million years ago in an already warm climate at the Palaeocene/Eocene boundary. But some scientists suspect that similar methane bursts, triggered perhaps by submarine landslides, sea-level drops or changes in water temperature, may also have caused a number of rapid warming episodes during and at the end of the last glacial period.

The theory has been popularized as the 'clathrate gun hypothesis' . But now an isotope analysis of methane trapped in bubbles of a Greenland ice core seems to disprove the idea. 

 

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Climate Change, Physical Science | Permalink

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