Increases in decadal averaged (2091–2100) annual CH<sub>4</sub> emission (Tgyr<sup>−1</sup>, poleward of 45° N) with respect to 2011–20 as a result of the warming and expansion of yedoma lakes (Y), non-yedoma (NY) lakes, wetlands (W), and total inundated areas for the low and high TCR under the UCE and GST scenarios, respectively

<p><strong>Figure 3.</strong> Increases in decadal averaged (2091–2100) annual CH<sub>4</sub> emission (Tgyr<sup>−1</sup>, poleward of 45° N) with respect to 2011–20 as a result of the warming and expansion of yedoma lakes (Y), non-yedoma (NY) lakes, wetlands (W), and total inundated areas for the low and high TCR under the UCE and GST scenarios, respectively. Each scenario contains 18 ensemble members (17 members of model-based pattern shifts and one member of climatological pattern). Whisker plots show the minimum, maximum, and plus/minus one standard deviation about the ensemble mean.</p> <p><strong>Abstract</strong></p> <p>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 CH<sub>4</sub> 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.</p>