An abrupt release of methane, a powerful greenhouse gas, from ice sheets that extended to Earth’s low latitudes some 635 million years ago caused a dramatic shift in climate, scientists funded by the National Science Foundation (NSF) report in this week’s issue of the journal Nature.

The shift triggered events that resulted in global warming and an ending of the last “snowball” ice age.

The researchers believe that the methane was released gradually at first and then very quickly from clathrates–methane ice that forms and stabilizes beneath ice sheets.

When the ice sheets became unstable, they collapsed, releasing pressure on the clathrates. The clathrates then began to de-gas.

“Our findings document an abrupt and catastrophic global warming that led from a very cold, seemingly stable climate state to a very warm, also stable, climate state–with no pause in between,” said geologist Martin Kennedy of the University of California at Riverside (UCR), who led the research team.

“What we now need to know is the sensitivity of the trigger,” he said. “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”

This transition from ‘snowball Earth‘ into a warmer period shows the compelling need for research on abrupt climate change in Earth’s history,” said H. Richard Lane, program director in NSF’s Division of Earth Sciences. “These changes have much to tell us about the modern human-induced threat of rapid climate change.”

According to Kennedy and colleagues, methane clathrate destabilization acted as a runaway feedback to increased global warming, and was the tipping point that ended the last snowball Earth.

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