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 si