Amplified Arctic climate change: What does surface albedo feedback have to do with it?

Abstract

A group of twelve IPCC fourth assessment report (AR4) climate models have Arctic (60N–90N) warmings that are, on average, 1.9 times greater than their global warmings at the time of CO 2 doubling in 1%/year CO 2 increase experiments. Forcings and feedbacks that impact the warming response are estimated for both Arctic and global regions based on standard model diagnostics. Fitting a zero‐dimensional energy balance model to each region, an expression is derived that gives the Arctic amplification as a function of these forcings and feedbacks. Contributing to Arctic amplification are the Arctic‐global differences in surface albedo feedback (SAF), longwave feedback and the net top‐of‐atmosphere flux forcing (the sum of the surface flux and the atmospheric heat transport convergence). The doubled CO 2 forcing and non‐SAF shortwave feedback oppose Arctic amplification. SAF is shown to be a contributing, but not a dominating, factor in the simulated Arctic amplification and its intermodel variation.