Permafrost in northeastern Spitsbergen, Norway. Melting permafrost could eventually disgorge a billion tonnes a year of greenhouse gas into the atmosphere.
Credit: NASA Earth Observatory
Most of the 13 million square kilometres of permafrost remain frozen, but thawing is already under way around the region's southern fringes and is thought likely to expand this century.
In that scenario, the permafrost could release around a billion tonnes a year of carbon, roughly equivalent to the contribution to greenhouse emissions each year by deforestation in the tropics, the paper said.
Carbon source
Even as the Arctic greens, the rising loss of older carbon "could make permafrost a large biospheric carbon source in a warmer world," he said.
Burning fossil fuels adds about 8.5 gigatonnes of emissions each year, but it is a process that can theoretically be controlled. Permafrost thaw, though, would be self-reinforcing and could be almost impossible to brake.
"It's not an option to be putting insulation on top of the tundra," Schuur said. "If we address our own emissions either by reducing deforestation or controlling emissions from fossil fuels, that's the key to minimising the changes in the permafrost carbon pool."
