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Monday, February 17, 2014

"Arctic amplification dominated by temperature feedbacks in contemporary climate models," by F. Pithan & T. Mauritsen, Nature Geosci., (2014); doi: 10.1038/ngeo2071

Nature Geoscience, (2014) ; doi:10.1038/ngeo2071

Arctic amplification dominated by temperature feedbacks in contemporary climate models

Felix Pithan and Thorsten Mauritsen


Climate change is amplified in the Arctic region. Arctic amplification has been found in past warm1 and glacial2 periods, as well as in historical observations3,4 and climate model experiments5,6. Feedback effects associated with temperature, water vapour and clouds have been suggested to contribute to amplified warming in the Arctic, but the surface albedo feedback—the increase in surface absorption of solar radiation when snow and ice retreat—is often cited as the main contributor7,8,9,10. However, Arctic amplification is also found in models without changes in snow and ice cover11,12. Here we analyse climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) archive to quantify the contributions of the various feedbacks. We find that in the simulations, the largest contribution to Arctic amplification comes from temperature feedbacks: as the surface warms, more energy is radiated back to space in low latitudes, compared with the Arctic. This effect can be attributed to both the different vertical structure of the warming in high and low latitudes, and a smaller increase in emitted blackbody radiation per unit warming at colder temperatures. We find that the surface albedo feedback is the second main contributor to Arctic amplification and that other contributions are substantially smaller or even oppose Arctic amplification.

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