Fractional change in near-surface permafrost extent (poleward of 45° N and in a nonglacier area) with respect to 2012 (around 1.02×1013 m2) under various climate projections
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Figure 1. Fractional change in near-surface permafrost extent (poleward of 45° N and in a nonglacier area) with respect to 2012 (around 1.02×1013 m2) under various climate projections. Thick lines represent the use of climatological geographic patterns in near-surface meteorology throughout the 21st century. Light thin lines represent the inclusion of additional geographic pattern shifts from the IPCC AR4 climate-model projections. The figure legend is detailed in table 1.
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.