Potential of future stratospheric ozone loss in the mid-latitudes under climate change and sulfate geoengineering

Abstract

Abstract. The potential of heterogeneous chlorine activation in the mid-latitude lowermost stratosphere during summer is a matter of debate. The occurrence of heterogeneous chlorine activation through the presence of aerosol particles could cause ozone destruction. This chemical process requires low temperatures and is accelerated by an enhancement of the stratospheric water vapour and sulfate amount. In particular, the conditions present in the lowermost stratosphere during the North American Summer Monsoon season (NAM) are expected to be cold and moist enough for causing the occurrence of heterogeneous chlorine activation. Furthermore, the temperatures, the water vapour mixing ratio and the sulfate aerosol abundance are affected by future climate change and by the potential application of sulfate geoengineering. Hence, both future scenarios could promote this ozone destruction process. We investigate the likelihood for the occurrence of heterogeneous chlorine activation and its impact on ozone in the lowermost stratospheric mixing layer between tropospheric and stratospheric air above central North America (30.6–49.6° N, 72.25–124.75° W) in summer for conditions today, at the mid and at the end of the 21st century. Therefore, the results of the Geoengineering Large Ensemble Simulations (GLENS) for the lowermost stratospheric mixing layer between tropospheric and stratospheric air are considered together with 10 day box-model simulations performed with the Chemical Lagrangian Model of the Stratosphere (CLaMS). In GLENS two future scenarios are simulated: the RCP8.5 climate change scenario and a geoengineering scenario, where sulfur is additionally injected in the stratosphere to keep the global mean surface temperature from changing. In the GLENS simulations, the mixing layer will warm and moisten in both future scenarios with a larger effect in the geoengineering scenario. The likelihood for chlorine activation to occur in the mixing layer is highest in the years 2040–2050 if geoengineering is applied, accounting for 3.3 %. In comparison, the likelihood for conditions today is 1.0 %. At the end of the 21st century, the likelihood of this ozone destruction process to occur decreases. We found that 0.1 % of the ozone mixing ratios in the mixing layer above central North America is destroyed for conditions today. A maximum ozone destruction of 0.3 % in the mixing layer occurs in the years 2040–2050 if geoengineering is applied. Comparing the southernmost latitude band (30–35° N) and the northernmost latitude band (44–49° N) of the considered region, we found a higher likelihood for the occurrence of heterogeneous chlorine activation in the southernmost latitude band, causing a higher impact on ozone as well. However, the ozone loss process is found to have a minor impact on the mid-latitude ozone column with not more than 0.1 DU today or in the future scenarios.

High‐Latitude Stratospheric Aerosol Geoengineering Can Be More Effective if Injection Is Limited to Spring

“…We also observe that despite differences in SSI, winter sea ice extents for MAM-60 and ANN-60 are comparable (Figure 2d). In addition to surface cooling, stratospheric sulfate aerosols will warm the stratosphere (Ferraro et al, 2015) and contribute to high-latitude ozone loss (Robrecht et al, 2020). In Figure 4, we present annual mean increases in stratospheric sulfate mixing ratio and its effect on air temperature and ozone concentration for MAM-60 and ANN-60; all changes presented are normalized by the extent of SSI restored, which allows us to evaluate the effects of both strategies relative to their efficacy.…”

International Debates and Reflections on the Successful Case of Montreal Protocol

“…In addition, excessive ultraviolet radiation has a great impact on aquatic organisms. Ultraviolet radiation can lead to the imperfect development of aquatic organisms and the decline of fecundity, which greatly impacts the marine biological chain, ecological balance, and water self-purification [8][9][10]. This article will deeply analyze the mechanism, conflict, and success factors of the protocol.…”

Comment on acp-2021-749

“…Anderson et al (2012) have hypothesized that the moistening of the lowermost stratosphere by convective overshooting can lead to severe ozone depletion in summer in the mid-latitudes through heterogeneous chlorine activation. However, in a detailed analysis of the relevant chemical processes, Robrecht et al (2019Robrecht et al ( , 2020 conclude that convective moistening only has a minor impact on stratospheric ozone and the mid-latitude ozone column.…”