The impact of surface temperature variability on the climate change response in the Northern Hemisphere polar vortex

[1] This study investigates the importance of the timescales of variability of land and ocean surface temperatures in the stratospheric response to increased atmospheric greenhouse gas concentrations. We present results from five pairs of 100-year (timeslice) simulations – control and 2 × CO₂ – carried out with the coupled chemistry-climate model IGCM-FASTOC, in which land and/or sea surface temperatures are either calculated interactively, prescribed and interannually varying, or prescribed with a climatological seasonal cycle. The strongest response to CO₂-doubling in the Northern Hemisphere high-latitude winter stratosphere is found when surface temperatures are calculated interactively by a coupled slab ocean and a land surface scheme. Both the interannual variability in ocean and land temperatures, and the adjustment of oceans and lands to the atmosphere and to one another, are important in order to maintain realistic stratospheric forcing by planetary waves and to adequately capture the stratospheric response to global warming.