From: Nafeez Ahmed, The Ecologist, More from this Affiliate
Published July 31, 2013 08:50 AM

Arctic methane catastrophe scenario is based on new empirical observations

Last week, the journal Nature published a new paper warning of a $60 trillion price tag for a potential 50 Gigatonne methane pulse from the East Siberian Arctic Shelf (ESAS) over 10-50 years this century. The paper, however, prompted many to suggest that its core scenario - as Arctic permafrost thaws it could increasingly unleash dangerous quantities of methane from sub-ice methane hydrates in as quick as a decade - is implausible.

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The Washington Post's Jason Samenow argued that "almost everything known and published about methane indicates this scenario is very unlikely." Andrew Revkin of the New York Times (NYT) liberally quoted Samenow among others on "the lack of evidence that such an outburst is plausible." Similarly, Carbon Brief concluded: "The scientists we spoke to suggested the authors have chosen a scenario that's either implausible, or very much at the upper limit of what we can reasonably expect."

Both the Post and NYT quoted Prof David Archer, an expert on ocean sediments and methane at the University of Chicago:

"For methane to be a game-changer in the future of Earth's climate, it would have to degas to the atmosphere catastrophically, on a time scale that is faster than the decadal lifetime of methane in the air. So far no one has seen or proposed a mechanism to make that happen."

Dr Vincent Gauci, a methane expert at Open University, similarly argued:

"It's not a given that all the methane will end up in the atmosphere. Some could be oxidised [broken down] in the water by bacteria, and some could remain in the sediments on the seafloor."

The problem is that these reservations are based on outdated assumptions that sea floor released methane would not make it into the atmosphere - but all the new fieldwork on the levels of methane being released above the ESAS shows this assumption is just empirically wrong.

Atmospheric methane levels in the Arctic are currently at new record highs, averaging about 1900 parts per billion, 70 parts per billion higher than the global average. NASA researchers have found local methane plumes as large as 150 kilometres across - far higher than previously anticipated.

Dr Gavin Schmidt, climate modeller at NASA, was also cited claiming lack of evidence from ice cores of previous catastrophic methane pulses in the Earth's history in the Early Holocene or Eamian, when Arctic temperatures were warmer than today. But the blanket references to the past may well be irrelevant. In the Early Holocene, the ESAS was not an underwater shelf but a frozen landmass, illustrating the pointlessness of this past analogy with contemporary conditions.

Continue reading at ENN affiliate, The Ecologist.

Arctic aerial image via Shutterstock.

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