Abstract
Abstract. Recent simulations predicted that the stratospheric ozone layer will likely return to pre-1980 levels in the middle of the 21st century, as a result of the decline of ozone depleting substances under the Montreal Protocol. Since the ozone layer is an important component in determining stratospheric and tropospheric-surface energy balance, the recovery of stratospheric ozone may have significant impact on tropospheric-surface climate. Here, using multi-model results from both the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC-AR4) models and coupled chemistry-climate models, we show that as ozone recovery is considered, the troposphere is warmed more than that without considering ozone recovery, suggesting an enhancement of tropospheric warming due to ozone recovery. It is found that the enhanced tropospheric warming is mostly significant in the upper troposphere, with a global and annual mean magnitude of ~0.41 K for 2001–2050. We also find that relatively large enhanced warming occurs in the extratropics and polar regions in summer and autumn in both hemispheres, while the enhanced warming is stronger in the Northern Hemisphere than in the Southern Hemisphere. Enhanced warming is also found at the surface. The global and annual mean enhancement of surface warming is about 0.16 K for 2001–2050, with maximum enhancement in the winter Arctic.
Highlights
After about 20 yr of severe depletion from the late 1970s to late 1990s (Solomon, 1999), the stratospheric ozone layer shows a stabilization or a weak increase in the past decade, consistent with the observed decline in ozone depleting substances (ODSs) that peaked in the middle 1990s (Weatherhead and Andersen, 2006; WMO, 2007)
By comparing multimodel ensemble simulation results, we have demonstrated that tropospheric and surface temperatures have robust responses to stratospheric ozone recovery in the first half of the 21st century
Relatively large enhanced warming occurs in polar regions and middle latitudes in summer for both hemispheres
Summary
After about 20 yr of severe depletion from the late 1970s to late 1990s (Solomon, 1999), the stratospheric ozone layer shows a stabilization or a weak increase in the past decade, consistent with the observed decline in ozone depleting substances (ODSs) that peaked in the middle 1990s (Weatherhead and Andersen, 2006; WMO, 2007). The recovery of the ozone layer will help reduce ultraviolet transmission, which benefits ecosystems on the Earth’s surface, and have important impacts on troposphere and surface climate throughout its radiative effect. The radiative effect of the ozone layer is an important component in determining the energy balance in the troposphere and surface (Ramanathan and Dickinson, 1979). While ozone warms the stratosphere by absorbing solar radiation and thermal infrared radiation emitted from the troposphere and surface, its emission in the 9.6 μm band cools the stratosphere, but warms the troposphere. Because the ozone layer absorbs more radiative energy than it emits, an increase (decrease) of stratospheric ozone increases (decreases) stratospheric temperatures, and increases (decreases) the downward infrared radiation to the troposphere, causing tropospheric warming (cooling)
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