A new paper suggests permafrost may be in danger of thawing much faster than previously estimated.
The study, published in the journal Nature Climate Change, looked at the rate at which permafrost disappeared between 1960 and 1990 instead of relying on models, and found that it is 20 per cent more sensitive to warming than models predict.
"Previous estimates could range from a really very large permafrost loss to a very small permafrost loss in the future," says lead author Sarah Chadburn.
"What we've done is reduced that range, and we've ended up with something that's towards the high end of what was estimated from previous studies."
The paper concluded that for every degree Celsius of warming, about four million square kilometres of permafrost is lost. Over the baseline period from 1960 to 1990, there was around 15 million square kilometres of permafrost worldwide.
For an optimistic climate scenario in which warming is maintained at 1.5 C above pre-industrial levels, Chadburn estimates 4.8 million square kilometres would be lost, with the ice generally moving north. A darker, business-as-usual scenario and associated warming of 5 C would leave the world with a maximum of 1.5 million square kilometres, an area about the size of Mongolia.
That could mean disaster for the landscape and hydrology of the North, putting cities and roads at risk across the high-latitude regions of the Northern Hemisphere.
"It is very urgent," says Hugues Lantuit, a French geomorphologist who was not involved in the paper. Lantuit specializes in the erosion effects of thawing permafrost, working out of a field station on Herschel Island in the Beaufort Sea.
"When the ice melts in the permafrost, it leads to dramatic changes in the landscape… Basically, the ice is what's holding the coast together," he says.
Warming permafrost would also dump methane into the atmosphere, further accelerating warming and causing feedback loops as more and more of the remaining permafrost begins to decompose.
Chadburn's paper has been submitted to a special report of the Intergovernmental Panel on Climate Change that will address the 1.5 — 2 C warming scenario.
"Hopefully it will somehow help," she says.