With United Nations climate talks underway in Germany, scientists are warning of dire results if action is not taken to defuse a "time bomb" of greenhouse gas lurking in Arctic permafrost.
Permafrost, which is thawing with the warming climate, holds about 1,500 billion tons of heat-trapping carbon gases, they say. If released from the perennially frozen ground making up around a quarter of the Northern Hemisphere's exposed land, it could unleash a vicious cycle in the planet's global-warming threat, according to Susan Natali of the Woods Hole Research Center in Massachusetts.
"Emissions from permafrost could lead to out-of-control global warming," scientists said in a presentation at the 11-day climate talks being held in Bonn.
The amount of carbon entrapped in permafrost is around twice that currently found in Earth's atmosphere, explained Natali, who co-authored a paper on the climate threat of thawing permafrost published in the journal Nature in April.
"By 2100, we expect 130 to 160 gigatons of carbon [to be] released into the atmosphere," she said in Bonn.
The Nature study came too late to be included in the most recent warming projections issued by the U.N.'s Intergovernmental Panel on Climate Change.
Negotiators from many nations are at the Bonn talks intended to create a draft for a global climate pact to be considered at a full United Nations climate summit in Paris this December.
However, little progress has been made toward that draft, with national delegates reporting the talks are becoming bogged down in procedural and technical side issues.
Carbon release from thawing permafrost will only add to the problem of soaring emissions from the burning of fossil fuels, Natali and other researchers warn. The thaw and release are interlocked, they explain, as the thawing is being accelerated by climate warming already occurring as a result greenhouse gas emissions from human activities.
In the Nature study, the researchers estimated that the world could see a global loss of permafrost between 30 and 70 percent by 2100, tied to the rate of emissions.
The lower figure is based on successful attainment of the U.N.'s stated goal of limiting global warming to 2 degrees Celsius (3.6 degrees Fahrenheit) above pre-Industrial levels; the higher figure would be the result of unrestrained emission.
"The actions that we take now in terms of our fossil fuel emissions are going to have a significant impact on how much permafrost is lost and in turn how much carbon is released from permafrost," Natali said. "While there is some uncertainty, we know that permafrost carbon losses will be substantial, [and] they will be irreversible."