Methane Climate Shock Unlikely, Study Suggests

April 24, 2009 -- Catastrophic climate change due to a massive release of underwater and underground stores of methane is less likely than previously thought, suggests new research.

CSIRO atmospheric scientist David Etheridge and colleagues report their findings in today's issue of the journal Science.

"It think [the study] helps us have some confidence to narrow down the range of possible future methane levels," said Etheridge.

Methane is a potent greenhouse gas with current atmospheric levels close to 1800 parts per billion and increasing, says Etheridge.

He says the most common natural source of atmospheric methane is anaerobic decomposition of organic material in wetlands.

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But a much greater potential source is trapped in methane hydrates, or clathrates, deep on the ocean floor or under permafrost.

Clathrates are ice-like lattices that can release methane gas as the temperature warms, pressure decreases, or land slips.

Some scientists have worried that catastrophic global warming could occur if warming triggers vast releases of methane from clathrates.

"If they were unstable, clathrates have the potential to overwhelm the atmospheric carbon cycle," said Etheridge.