The clathrate gun hypothesis states that as sea temperatures rise the sudden release of methane from methane clathrate compounds buried in the seabeds will cause a drastic alteration of the ocean environment and the atmosphere of earth, as recent analysis concerning the Permian extinction event indicates may have happened in the past.
In 2002, a BBC2 'Horizon' documentary, 'The Day the Earth Nearly Died,' summarized some recent findings and speculation concerning the Permian extinction event. Paul Wignall examined Permian strata in Greenland, where the rock layers devoid of marine life are tens of meters thick. With such an expanded scale, he could judge the timing of deposition more accurately and ascertained that the entire extinction lasted merely 80,000 years and showed three distinctive phases in the plant and animal fossils they contained. The extinction appeared to kill land and marine life selectively at different times. Two periods of extinctions of terrestrial life were separated by a brief, sharp, almost total extinction of marine life. Such a process seemed too long, however, to be accounted for by a meteorite strike. His best clue was the carbon isotope balance in the rock, which showed an increase in carbon-12 over time. The standard explanation for such a spike – rotting vegetation – seemed insufficient.
Focusing on the Permian-Triassic boundary, Gregory Ryskin explores the possibility that mass extinction can be caused by an extremely fast, explosive release of dissolved methane (and other dissolved gases such as carbon dioxide and hydrogen sulfide) that accumulated in the oceanic water masses prone to stagnation and anoxia (e.g., in silled basins). As global CO2 levels head towards 450 ppm, the destabilisation of methane clathrates could become an uncontrollable feedback mechanism taking temperatures up alarmingly.
