Melting permafrost will be major driver of global warming

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Melting permafrost will be major driver of global warming
mongabay.com
September 1, 2008

The thawing of permafrost in northern latitudes will become a major source of greenhouse gas emissions, according to a new study that more than doubles previous estimates of the amount of carbon stored in the frozen soils of Alaska and Siberia.

Writing in the September 2008 issue of BioScience, Edward A. G. Schuur of the University of Florida and colleagues show that melting permafrost "could release as "could amount to roughly half those resulting from global land-use change during this century," according to a statement from the American Institute of Biological Sciences.

Reassessing how organic materials are stored during melting and freezing of permafrost, the authors estimate that frozen soils store more than a trillion metric tons of organic compounds. As these soils melt due to rapidly increasing temperatures, orgainc materials decompose, releasing methane and carbon dioxide into the atmosphere and thereby exacerbating warming.

Change in duration of snow-covered ground north of 50°N. The number of days in a year in which the ground is snow covered has decreased by an estimated average of 7.5 days from 1970 to 2000. Source: Euskirchen and others 2007, image courtesy of UNEP

The concern over the climate impact of sub-Arctic thaw is not new. The U.N. has called the melting of permafrost a "wild card" that could dramatically worsen global warming by releasing massive amounts of greenhouse gases.

"The balance of evidence suggests that Arctic feedbacks that amplify warming, globally and regionally, will dominate during the next 50 to 100 years," warned the UNEP Year Book 2008 when it was published earlier this year. "As warming continues, these feedbacks will likely intensify. We may be approaching thresholds that are difficult to predict precisely, but crossing such thresholds could have serious global consequences."

"It is already clear that the global climate is vulnerable to Arctic feedbacks and that the consequences of those feedbacks could be disastrous. The only way to reduce the magnitude of these consequences is to dramatically reduce and stabilize concentrations of GHGs in the atmosphere," the report continued. "The potential consequences of large amounts of methane entering the atmosphere, from thawing permafrost or destabilized ocean hydrates, would lead to abrupt changes in the climate that would likely be irreversible. We must not cross that threshold. Reversing current human induced warming will help us avoid such outcomes entirely."

Edward A. G. Schuur et al (2008) Vulnerability of Permafrost Carbon to Climate Change: Implications for the Global Carbon Cycle. Biosicence September 2008

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