Permafrost, the soils in polar regions that are normally frozen year-round, hold twice as much carbon as there is in the atmosphere. Temperatures have risen twice as fast in permafrost regions relative to the rest of the globe, and many fear that as permafrost thaws large amounts of greenhouse gases will be rapidly released into the atmosphere, potentially accelerating climate change. Predicting the climate change effects of thawing permafrost, however, depends on understanding how quickly greenhouse gases will be released, a topic which has been debated for some time. A recent synthesis of new data on the thawing permafrost problem by Schuur and colleagues sheds valuable light on this debate.
The authors examined the newly expanded permafrost soil carbon database and confirmed that carbon storage in global permafrost is immense. They also synthesized data from laboratory incubations of permafrost soils and found that a large proportion of permafrost carbon can be slowly mineralized by microbes, thereby releasing it into the atmosphere. A synthesis of field observations shows that abrupt thaws of permafrost are common, but that current climate change models do not account for rapid thaw events. The authors conclude that greenhouse gas emissions from thawing permafrost in the near future will be only a small fraction of the emissions produced by burning fossil fuels, and insignificant over a sub-decade timescale. They will, however, significantly contribute to climate change over many decades and centuries. While thawing permafrost is not expected to accelerate climate change immediately, it needs to be accounted for in long term climate change policy planning.
Schuur, E., AD McGuire, C Schadel, G Grosse, JW Harden, DJ Hayes, G Hugelius, CD Koven, P Kuhry, DM Lawrence, SM Natali, D Olefeldt, VE Romanovsky, K Schaefer, MR Turetsky, CC Treat, JE Vonk (2015) Climate change and the permafrost carbon feedback. Nature, 520, 171-179.