By IANS,
Washington : An abrupt release of methane from ice sheets 635 million years ago triggered a spell of global warming, says a study that contends something similar is just waiting to happen.
Researchers believe the greenhouse gas was released gradually and then abruptly from clathrates – methane ice that forms beneath polar ice sheets. The release had resulted in a series of cataclysmic events and ended the last Ice Age.
These same methane clathrates are present today in the Arctic permafrost as well as below sea level at the continental margins of the ocean, and remain dormant until triggered by warming, the study said.
“Our findings document an abrupt and catastrophic means of global warming that abruptly led from a very cold, seemingly stable climate state to a very warm also stable climate state with no pause in between,” said Martin Kennedy of the University of California, Riverside, who led the research team.
“This tells us about the mechanism, which exists, but is dormant today, as well as the rate of change,” he added.
“What we now need to know is the sensitivity of the trigger: how much forcing does it take to move from one stable state to the other, and are we approaching something like that today with current carbon dioxide warming?”
The study said methane clathrate destabilisation acted as a runaway feedback to increased warming, and was the tipping point that ended the last Ice Age.
“Once methane was released at low latitudes, warming caused other clathrates to destabilise,” Kennedy said. “But not all the earth’s methane has been released as yet.”
Kennedy believes it’s possible that only a little warming will unleash this trapped methane.
“Such a violent, zipper-like opening of the clathrates could have triggered the catastrophic climate and biogeochemical reorganisation of the ocean around 635 million years ago,” he noted.
Also called marsh gas, methane is a colourless, odourless gas. As a greenhouse gas, it is about 30 times more potent than carbon dioxide.
The findings of the study are slated to appear in the latest issue of the journal Nature.