| Summary: | Stratospheric ozone is expected to recover by the end of this century due to the regulation of ozone depleting substances by the Montreal Protocol. Targeted modeling studies have suggested that the climate response to ozone recovery will greatly oppose the climate response to rising greenhouse-gas (GHG) emissions. However, the extent of this cancellation remains unclear since only a few such studies are available. Here, we analyze a much larger set of simulations performed for the Coupled Model Intercomparison Project, phase 5, all of which include ozone recovery. We show that the closing of the ozone hole will cause a delay in summer-time (DJF) Southern Hemisphere climate change, between now and 2045. Specifically, we find that the position of the jet stream, the width of the subtropical dry-zones, the seasonality of surface temperatures, and sea ice concentrations all exhibit significantly reduced summer-time trends over the first half of the 21st Century as a consequence of ozone recovery. After 2045, forcing from GHG emissions begins to dominate the climate response. Finally, comparing the relative influences of future GHG emissions and historic ozone depletion, we find that the simulated DJF tropospheric circulation changes between 1965-2005 (driven primarily by ozone depletion) are larger than the projected changes in any future scenario over the entire 21st Century.
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