par- 30 novembre 2011 - ( maj : 30 janvier 2012 )
As Arctic temperatures rise, the permafrost will thaw, releasing greenhouse gases that will accelerate the warming of the planet. But no one knows by how much or how quickly. Forty-one international experts seek to pin that down in a Comment piece in Nature. Permafrost thaw will release the same order of magnitude of carbon as deforestation, they calculate, but its effect on climate will be 2.5 times bigger.
Recent years have seen carbon being released from massive tundra fires and bubbling out of Arctic lakes. Northern soils are thought to hold around 1,700 billion tonnes of organic carbon — around four times more than all the carbon ever emitted by modern human activity and twice as much as is currently in the atmosphere. As the Arctic warms, microbes in the soil decompose this ancient carbon and spit out carbon dioxide and methane. Models aren’t very good at tracking this release : most project that the extent of permafrost warming will depend on the temperature of the air above, for example. But in reality, permafrost can warm much more quickly. If ice wedges melt, the ground can collapse, which accelerates permafrost thaw and causes trees to lean over as if drunk. Edward Schuur, Benjamin Abbott and the other members of the Vulnerability of Permafrost Carbon Research Coordination Network predicted how much of the permafrost is likely to thaw, how much carbon that will release, and how much of that carbon will be in the form of methane, which has a much greater effect on warming than carbon dioxide. Their collective estimate is that the amount of carbon released by 2100 will be 1.7–5.2 times greater than reported in several recent modelling studies. These levels “are cause for serious concern", they write. "The scientific community needs to collect more data and develop more sophisticated models to test the hypotheses presented by this survey."
*E.A.G. Schuur, B.W. Abbott, W.B. Bowden, V. Brovkin, P. Camill, J.P. Canadell, F.S. Chapin III, T.R. Christensen, J.P. Chanton, P. Ciais, P.M. Crill, B.T. Crosby, C.I. Czimczik, G. Grosse, D.J. Hayes, G. Hugelius, J.D. Jastrow, T. Kleinen, C.D. Koven, G. Krinner, P. Kuhry, D.M. Lawrence, S.M. Natali, C.L. Ping, A. Rinke, W.J. Riley, V.E. Romanovsky, A.B.K. Sannel, C. Schädel, K. Schaefer, Z.M. Subin, C. Tarnocai, M. Turetsky, K. M. Walter-Anthony, C.J. Wilson, and S.A. Zimov
Contact : G. Krinner
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