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Risk of Warming via Methane Release by Permafrost Degradation
Reference
Gao, X., Schlosser, C.A., Sokolov, A., Anthony, K.W., Zhuang, Q. and Kicklighter, D. 2013. Permafrost degradation and methane: low risk of biogeochemical climate-warming feedback. Environmental Research Letters 8: 10.1088/1748-9326/8/3/035014.

Background
The authors write that "climate change and permafrost thaw have been suggested to increase high-latitude methane emissions that could potentially represent a strong feedback to the climate system," noting that "of particular concern is the permafrost in near-surface, carbon-rich, ice-rich soils," where "increased thawing of these soils can transform the hydrologic landscape to aid in the formation/expansion of saturated areas such as lakes and wetlands (Zimov et al., 1997; Shindell et al., 2004)," and where "anaerobic decomposition of thawed organic carbon results in emission of methane, a potent greenhouse gas, which could constitute a positive feedback to the climate system (Walter et al., 2006; Anisimov, 2007)" with - one need hardly add - extremely undesirable consequences.

What was done
To better evaluate this line of reasoning, Gao et al. used an integrated earth-system model framework to "examine the degradation of near-surface permafrost, temporal dynamics of inundation (lakes and wetlands) induced by hydro-climatic change, subsequent methane emission, and potential climate feedback."

What was learned
The six scientists found that "increases in atmospheric CH4 and its radiative forcing, which result from the thawed, inundated emission sources, are small, particularly when weighed against human emissions," and that "the additional warming, across the range of climate policy and uncertainties in the climate-system response, would be no greater than 0.1°C by 2100." What is more, they calculated that "for this temperature feedback to be doubled (to approximately 0.2°C) by 2100, at least a 25-fold increase in the methane emission that results from the estimated permafrost degradation would be required."

What it means
In light of the findings reported above, it would appear that the so-called methane problem is actually no problem at all.

References
Anisimov, O.A. 2007. Potential feedback of thawing permafrost to the global climate system through methane emission. Environmental Research Letters 2: 10.1088/1748-9326/2/4/045016.

Shindell, D., Walter, B.P. and Faluvegi, G. 2004. Impacts of climate change on methane emissions from wetlands. Geophysical Research Letters 31: 10.1088/1748-9326/8/3/035014.

Walter, K.M., Zimov, S.A., Chanton, J.P., Verbyla, D. and Chapin III, F.S. 2006. Methane bubbling from Siberian thaw lakes as positive feedback to climate warming. Nature 443: 71-75.

Zimov, S.A., Voropaev, Y.V., Semiletov, I.P., Davidov, S.P., Prosiannikov, S.F., Chapin, F.S., Chapin, M.C., Trumbore, S. and Tyler, S. 1997. North Siberian lakes: a methane source fuelled by Pleistocene carbon. Science 277: 800-802.

Reviewed 19 February 2014