Up to two-thirds of Earth's permafrost will probably disappear by 2200, say scientists, unleashing vast quantities of carbon into the atmosphere.
The carbon comes from plant material, primarily roots trapped and frozen in soil during the last glacial period that ended roughly 12,000 years ago.
A study by the University of Colorado Boulder is the first to make actual estimates of future carbon release from permafrost. "This gives us a starting point, and something more solid to work from in future studies," says the university's Kevin Schaefer. "We now have some estimated numbers and dates to work with."
The team ran multiple Arctic simulations assuming different rates of temperature increases to forecast how much carbon could be released globally from permafrost in the next two centuries.
They came up with a figure of roughly 190 billion tons, most of it in the next 100 years. The team used Intergovernmental Panel on Climate Change scenarios and land-surface models for the study.
"The amount we expect to be released by permafrost is equivalent to half of the amount of carbon released since the dawn of the Industrial Age," said Schaefer.
Using data from all climate simulations, the team estimated that about 30 to 60 percent of Earth's permafrost will disappear by 2200.
Fossil fuel emissions should be slashed even further to take account for carbon released by the permafrost, says Schaefer.
"The problem is getting more and more difficult all the time," he said. "It is hard enough to reduce the emissions in any case, but now we have to reduce emissions even more. We think it is important to get that message out now."