Abstract
Abstract. In a recent paper Hu et al. (2011) suggest that the recovery of stratospheric ozone during the first half of this century will significantly enhance free tropospheric and surface warming caused by the anthropogenic increase of greenhouse gases, with the effects being most pronounced in Northern Hemisphere middle and high latitudes. These surprising results are based on a multi-model analysis of CMIP3 model simulations with and without prescribed stratospheric ozone recovery. Hu et al. suggest that in order to properly quantify the tropospheric and surface temperature response to stratospheric ozone recovery, it is necessary to run coupled atmosphere-ocean climate models with stratospheric ozone chemistry. The results of such an experiment are presented here, using a state-of-the-art chemistry-climate model coupled to a three-dimensional ocean model. In contrast to Hu et al., we find a much smaller Northern Hemisphere tropospheric temperature response to ozone recovery, which is of opposite sign. We suggest that their result is an artifact of the incomplete removal of the large effect of greenhouse gas warming between the two different sets of models.
Highlights
Stratospheric ozone depletion has had a radiative effect on global mean surface climate, the sign of the effect is uncertain due to the large compensation between the shortwave warming due to increased penetration of solar radiation and the long-wave cooling due to reduced downwelling infrared radiation from the colder stratosphere (Intergovernmental Panel on Climate Change (IPCC), 2007; Chapter 10 of SPARC CCMVal, 2010)
The Antarctic ozone hole, which is a huge perturbation to the Southern Hemisphere (SH) stratosphere, has been the dominant driver of past changes in high-latitude SH tropospheric climate in summer (e.g. Arblaster and Meehl, 2006; Fogt et al, 2009), with ozone recovery expected to offset the effects of climate change over the half-century (e.g. Son et al, 2010)
We suggest that the enhanced tropospheric warming found ploys prescribed sea-surface temperatures and sea-ice disby H11 results from the comparison of groups of models hav- tributions generated using an earlier version of the Canadian Centre for Climate Modelling and Analysis (CCCma) ing different rates of greenhouse gas (GHG)-induced warming; coupled atmosphere-ocean model on which that version of that differencing the two groups of models does not remove Canadian Middle Atmosphere Model (CMAM) was based
Summary
Stratospheric ozone depletion has had a radiative effect on global mean surface climate, the sign of the effect is uncertain due to the large compensation between the shortwave warming due to increased penetration of solar radiation and the long-wave cooling due to reduced downwelling infrared radiation from the colder stratosphere (Intergovernmental Panel on Climate Change (IPCC), 2007; Chapter 10 of SPARC CCMVal, 2010). Arctic during the period of ozone recovery, and suggested spheric temperatures, consistent with the small estimated rathat the increasing ozone concentrations are somehow am- diative forcing of stratospheric ozone changes
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