PARIS – Massive leakage of methane from thawing shorelines in the Arctic would devastate the world’s climate and economy, three scientists warned Wednesday.
Billions of tons of the potent greenhouse gas are locked in the shallow frozen shelf of the Arctic Ocean, which warms when summer sea ice retreats as a result of the greenhouse gas effect, they said in a contribution to Nature.
The team modeled what would happen if 50 gigatons of methane escaped over a decade from the floor of the East Siberian Sea, covering 2 million sq. km of the Arctic Ocean off northeastern Russia.
“The methane release would bring forward the date at which the global mean temperature rise exceeds 2 degrees Celsius by between 15 and 35 years,” said Chris Hope of Cambridge Judge Business School, part of England’s University of Cambridge.
Gail Whiteman, a professor of sustainability, management and climate change at Erasmus University in Rotterdam, the Netherlands, described the threat as an “invisible time bomb.”
“The mean impacts of just this one effect — $60 trillion — approaches the $70 trillion value of the world economy in 2012,” Whiteman said.
The high cost is explained by damage to the climate system, reflected in worse floods, droughts, storms and heat stress, she said.
Eighty percent of the effects would occur in poorer nations in Africa, Asia and South America, according to the scientists’ model, called PAGE09.
The estimates are based on how the added methane would affect two trends: one for existing greenhouse gas emissions, which are very high, and the other for lower emissions giving a more than 1 in 2 chance of meeting the United Nations’ 2 degree warming target.
In an email exchange, Hope said that if the 50 gigatons were released over 20 years, from 2015 to 2035, the cost would come to around $64.5 trillion. If the release were spread over 30 years from 2015, it would be $66.2 trillion. If 25 gigatons were released, the cost in all scenarios would be roughly halved.
Scientists have long worried about methane locked up in shoreline sediments and also in permafrost on land. The gas is 25 times more effective than carbon dioxide in trapping solar heat.
The big concern is that the methane, if released, will add to global warming and thus accelerates the thaw, creating more gas and amplifying the temperature rise — a “positive feedback,” or vicious circle in climate terms.
But evidence for such a threat is sketchy, research into it is meager and the conclusions often contested. Some experts also say there could be as yet unknown mechanisms in permafrost thaw that may limit the methane leakage.
In 2008, Russian scientists writing in the journal Geophysical Research estimated that 540 gigatons of methane are stored in the Siberian Arctic shelf. Of this, up to 50 gigatons could be considered as being “highly possible for abrupt release at any time.”
In 2010, another Russian team, reporting in Science, said they had found large amounts of leakage from perforated permafrost on the shelf.