The Scientific Assessment of Ozone Depletion 2022 has been published in the beginning of February 2023. The latest update of the Ozone Assessment, a report released by the World Meteorological Organization (WMO) every four years, was produced over the last two years with major contributions from scientists from DLR Institute of Atmospheric Physics. Dr. Birgit Hassler was a lead author of chapter 3 about global ozone distributions and Juniorprof. Dr. Hella Garny led chapter 4 about interactions of ozone and climate. Prof. Dr. Anja Schmidt contributed as an author to the newly added chapter 6 about the potential effects of “geoengineering” on the ozone layer.
Fig. 1: Ozone Assessment 2022 title page (Picture: CC0 , aus WMO 2022: Scientific Assessment of Ozone Depletion ).
One of the key findings of the Assessment is that recovery of the ozone layer from CFC-induced (chlorofluorocarbons) ozone depletion continues to be on track. The emission of these chemicals is regulated by the Montreal Protocol from 1987 and its amendments. Since the year 2000, concentrations of CFCs in the atmosphere decline. For the first time it could be shown in this latest assessment that the ozone layer is recovering at all latitudes. New modeling studies confirm previous expectations that the ozone layer will be fully recovered by mid of the century.
Montreal Protocol and its amendments also contribute substantially to the protection of climate as CFCs do not only destroy ozone, but are also potent greenhouse gases. If the emissions of CFCs would have continued with rates similar to the 1980s, CFCs would have added 0.1 to 0.2°C to global warming until now, and even up to 0.5°C until the mid of the century. Global temperatures are already about 1.2°C above pre-industrial levels today. If the additional warming by CFCs would not have been prevented, we would already be much closer to a warming of 1.5°C above preindustrial levels that was agreed upon as a maximum limit in the Paris agreement.
Fig. 2: Figure 1 of the Ozone Assessment Executive Summary. Timeline of: a) CFC-11-equivalent emissions, b) equivalent effective chlorine (EECl), c) global total ozone, and d) October Antarctic total ozone. (Graphics: CC0, aus WMO 2022: Scientific Assessment of Ozone Depletion).
Erstmals gab es in diesem Bericht auch ein Kapitel zu den potentiellen Effekten von künstlichen Maßnahmen zur For the first time, the Assessment contains a chapter that examines the potential effects of technological measures to reduce global warming (“geoengeneering“) on the ozone layer. One of these potential measures investigated is injections of aerosols into the stratosphere. This would lead to a cooling of the Earth’s surface similar to the effects of a strong volcanic eruption. Such additional aerosols, however, would also affect chemical ozone depletion and could therefore have negative effects on the ozone layer. Uncertainties and risks associated with such geoengineering measures are considered very high.
