Given the recent controversy stirred up by the Whiteman et al. Commentary in Nature, it should be pointed out that this new paper by Gao et al. does not address methane release from thawing of permafrost on the submerged East Siberian Arctic Shelf. Therefore, its conclusions could easily be misinterpreted in a context that the authors had not intended when they submitted their paper for publication.
"...our model framework captures large-scale hydro-climate processes (i.e. precipitation, evaporation, sub-surface soil physics) that are highly relevant to large-scale saturated-area expansion, methane emissions, and resulting radiative forcing. Our intent here is not to provide a deterministic prediction of permafrost thaw and inundation, but rather to examine through an integrated assessment model framework the temperature feedback from a range of plausible CH4 emission responses that could occur as a result of human-induced climate warming and to examine a threshold of methane-emission increase for such temperature feedback to be salient. We assume any modeled inundation of thawed permafrost regions takes the form of wetlands and lakes. Using this simplified land-surface modeling approach coupled to an earth-system model (i.e. the IGSM), we are able to determine what threshold of methane-emission increase would result in a salient positive climate-warming feedback." I am not sending out this message in support of the Whiteman et al. Commentary; rather, I am simply pointing out that this particular study's conclusions are not relevant to resolving the controversy. Charles H. Greene, Director Ocean Resources and Ecosystems Program Department of Earth & Atmospheric Sciences 4120 Snee Hall, Cornell University Ithaca, NY 14853-2701 On Jul 28, 2013, at 1:28 PM, Andrew Lockley wrote: http://iopscience.iop.org/1748-9326/8/3/035014 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. Using an integrated earth-system model framework, we 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. We find 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. 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. Further, 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. Overall, this biogeochemical global climate-warming feedback is relatively small whether or not humans choose to constrain global emissions. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]<mailto:[email protected]>. To post to this group, send email to [email protected]<mailto:[email protected]>. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/geoengineering. For more options, visit https://groups.google.com/groups/opt_out.
