One explanation of rapid climate change at the end of the last glaciation, argues Dr Euan Nisbet of the University of Sakatchewan, is that it was initially driven by methane from natural gas fields and gas hydrates during a period of extreme insolation.
Methane hydrates are solids which lock methane gas up under pressure in an ice-like lattice of water molecules. They are present under the oceans and permafrost in vast quantities. In the offshore Arctic, the cold allows their formation at sufficiently shallow depths that warming can reach them and destabilize them.
Nisbet is one of a number of geologists who fear methane hydrates as a potentially major positive feedback. He wrote in a 1989 paper that "any slight warming of the Arctic water will release hydrate from the sea floor almost immediately. A temperature change of a few degrees will liberate methane from the uppermost sea-floor sediments at this depth within a few years." The worst- case analysis is grim indeed: "the danger of a thermal runaway caused by methane release from permafrost is minor, but real ...even if there is only a 1 per cent chance that such events will occur, the social implications are profound."
(E. Nisbet, "Climate change and methane," Nature, v. 347, p. 23, September 1990).
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