Permafrost thaw accelerates global warming

Climate affected by positive feedback loop

Jorien Vonk

One of the consequences of global warming is the thawing of permafrost (frozen soil) in polar regions. Permafrost contains huge quantities of organic material, which, when thawed, are released and converted into greenhouse gases. The latter contribute in turn to accelerated global warming. That is the conclusion reached by climate researchers at Northern Arizona University and Utrecht University in an article published in Nature on 9 April.

The regions around the Arctic Ocean contain huge quantities of permafrost, which have sometimes been frozen for thousands of years. Around 1.5 billion tonnes of carbon are trapped in those soils, which is twice as much as is currently held in the atmosphere in the form of carbon dioxide. The thawing of those soils and large-scale composting will therefore release huge quantities of carbon into the atmosphere in the form of carbon dioxide and methane.

Not abruptly, but gradually

An international research group, including Dr Jorien Vonk of Utrecht University and led by Dr Ted Schuur of Northern Arizona University, concludes in this overview article that permafrost thaw will release greenhouse gases gradually, contrary to a previous theory that this would happen abruptly and over a much shorter period.

The researchers also predict that 5 to 15 per cent of the carbon now trapped in permafrost will be exposed to the atmosphere. In 2100, the contribution of greenhouse gases derived from permafrost thaw will amount to about a quarter of the current fossil fuel emissions,’ says Dr Vonk. ‘Although that does not seem much, once permafrost starts to thaw, the process can go on for centuries.’

Permafrost

Roles of humans and nature

Although current climate change is frequently attributed to human activity, including the use of fossil fuels and deforestation, natural ecosystems also play a major role in the global carbon cycle. Over the past thirty years, the temperature in the Arctic has risen twice as fast as in the rest of the world. As Dr Schuur explains, ‘People can trigger global warming by burning fossil fuels and through deforestation, but natural ecosystems, even in remote areas such as the Arctic, also contribute.’

Future research

‘The present article also considers future research angles,’ Vonk explains. ‘We are planning to improve existing climate models by incorporating various new databases and differentiating between the greenhouse gases: carbon and methane. And, of course, we are also planning to keep on improving our measurements of the amount of carbon released by permafrost, particularly in poorly studied Arctic Canada, Arctic Siberia and regions where permafrost occurs under the sea floor.’

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Publication

E.A.G. Schuur et al., Climate change and the permafrost carbon feedback, Nature, doi:10.1038/nature14338