Combined Effects of Global Warming and Ozone Depletion/Recovery on Southern Hemisphere Atmospheric Circulation and Regional Precipitation

Abstract

Ozone depletion led to a positive trend in the summertime Southern Annular Mode (SAM) during the last decades of the 20th century. During the present century, global warming (GW) is expected to contribute to a positive SAM trend while ozone recovery is expected to act in the opposite direction. Here, Southern Hemisphere (SH) circulation and regional precipitation change are studied with a methodology that separates the effects from GW and ozone depletion/recovery. Our results show that a “tug‐of‐war” between ozone and GW occurs in the summertime stratosphere, propagating to the troposphere where it is manifest in the SAM. However, at the regional scale this “tug‐of‐war” is not as relevant as the combined effects of other remote drivers of circulation change, which force different kinds of precipitation changes in the SH. For regional precipitation changes, the uncertainty in future circulation change is as important as the uncertainty in the GW level.

Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2021

“…However, stratospheric warming events, such as that observed in 2019, are less likely in a future climate [ 6 ] as increasing concentrations of greenhouse gases (GHG) will cool the stratosphere. Furthermore, modelling studies suggest that summertime precipitation in the Southern Hemisphere, with some regions projected to get drier and others wetter, will be more affected by future increases in the concentration of GHGs and warming of the tropical upper troposphere than by stratospheric ozone recovery resulting from the implementation of the Montreal Protocol [ 7 ].…”

“…In Polar Regions, variability and trends in the downward coupling from the stratosphere to the troposphere have contributed to changes in climate patterns on seasonal and interannual time scales [4,7,94,95]. In Antarctica, interaction between stratospheric ozone change and the strength of the dynamical coupling from the stratosphere may be partially responsible at a regional scale for trends in surface temperature and precipitation, placing the stability of these fragile ecosystems at risk [96][97][98][99][100][101].…”

Stratospheric ozone depletion and tropospheric ozone increases drive Southern Ocean interior warming

“…Such an assumption is justified given that the climate response, for example, the response of the polar vortex breakdown to equivalent effective stratospheric chlorine, does not show a systematic difference between models with prescribed and interactive ozone 47 .…”

Can southern Australian rainfall decline be explained? A review of possible drivers

“…Combining more lines of evidence, such as from paleo‐records, extended reanalyses, or improved model projections will help address these knowledge gaps. Future research avenues include: Using advanced statistical methods and appropriate definitions to better understand the spatial and temporal interactions of the climate drivers and large‐scale circulation, and their impacts on rainfall. Applying detection and attribution modeling techniques to, for example, identify the relative roles of stratospheric ozone recovery and greenhouse gases on the SAM and rain‐bearing weather systems; and explicitly link changes in rainfall‐producing weather systems. Following a storyline approach to better constrain model projections of southern Australian rainfall (Mindlin et al, 2020, 2021; Shepherd et al, 2018). …”

“…However, while this winter rainfall decline is linked to a poleward shift in the storm tracks (Frederiksen & Frederiksen, 2007), ozone depletion is unlikely to be an important factor outside of summer (Karoly, 2014). Further, the autumn decline in southeast Australian rainfall is not related to changes in the SAM (Mindlin et al, 2021; Purich et al, 2013). Conversely, central Chilean autumn rainfall decline from the 1970s has been linked with the positive SAM trend (Boisier et al, 2016).…”