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Permafrost soil thawing accelerates climate change despite more abundant vegetation

2013/03/13 - Global warming affects permafrost soils, for instance in Siberia, in two opposing ways. Their thawing accelerates decomposition processes in the soil, leading to higher CO2 emissions. On the other hand, enhanced vegetation growth due to higher temperatures leads to carbon intake by the plants, and consequently storage in the soil. However, the – often neglected – second effect in the long run cannot counter the first one, reveals a study now published by scientists of the Potsdam Institute for Climate Impact Research.
Permafrost soil thawing accelerates climate change despite more abundant vegetation

Permafrost soil thawing depth, according to a computer simulation. Graph: PIK

“Our study is the first to include the vegetation feedback on permafrost soils, as a reaction to climate change, in computer simulations,” says lead author Sibyll Schaphoff. “When thawing starts, contrary to some other studies at first a net uptake of CO2 happens, according to our projections.” This is due to the rapidly increasing vegetation growth. Vegetation benefits from higher temperatures in the high northern latitudes and more CO2 in the atmosphere, which directly stimulates plants.

Nonetheless, after a time lag of a few decades, the slowly thawing permafrost soil releases the carbon that before has been stored underground for millennia. This cannot be compensated for by vegetation growth – CO2 gets released, further contributing to climate change. “So plants will not avert us entering that vicious circle,” Schaphoff says.”Yet they are likely to somewhat reduce the additional greenhouse-gas emissions from permafrost soil melting.”

“Another important finding is that the effects of today`s climate change will continue to cause carbon release from permafrost soils for several centuries – there is a worrisome ‘long shadow’ of today’s warming into the far future,” says Wolfgang Lucht, co-chair of PIK’s research domain Earth System Analysis, who is also one of the authors. “Our study is the first to identify more precisely how much additional carbon would be lost from permafrost soils if the world were to warm by 4 or 5 degrees in the next hundred years, due to business as usual failing to lower greenhouse-gas emissions – rather than warming by not more than 2 degrees, the limit set by the international community, but requiring strong action.”

Despite much stronger plant growth in the Arctic regions at higher temperatures, Lucht says "strong climate protection would save us from around 150 billion tons of carbon emissions from those soils, or the equivalent of 15 years of human emissions at current levels.”

 

Article: Schaphoff, S., Heyder, U., Ostberg, S., Gerten, D., Heinke, J., Lucht., W. (2013): Contribution of permafrost soils to the global carbon budget. In: Environmental Research Letters [doi:10.1088/1748-9326/8/1/014026]

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