Feedback effects associated with the amount of energy radiated back to space per unit of surface warming are the dominant reason why the Arctic is warming much faster than Earth’s average. This conclusion, published online in Nature Geoscience, is in contrast to previous suggestions that amplified warming in northern high latitudes is caused mainly by the more efficient absorption of sunlight by the dark ocean or land surface once sea ice or snow have melted.
Felix Pithan and Thorsten Mauritsen analysed a suite of state-of-the-art climate model simulations to quantify the contributions of a number of previously suggested feedback mechanisms - associated with temperature, water vapour and clouds - to the amplified warming in the Arctic region. They find that temperature feedbacks associated with the vertical temperature structure of the atmosphere, and with cooler initial surface temperatures in the Arctic than at lower latitudes, make the largest contribution to the amplification of warming in the Arctic. Changes in surface reflectivity as a result of melting ice and snow are identified as the second largest factor.