February 10, 2006
No evidence that methane releases triggered global warming at end of last ice age
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.
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