40 Years with the "Ozone Hole": What's in the Future?

In 1985, a massive depletion of the ozone layer was discovered and attributed to the emission of halogen-containing species. Similar phenomena, but on a smaller scale, were subsequently recorded in other regions, particularly in the Arctic. The subsequent efforts by the science community and policymakers made it possible to identify the physical processes behind this phenomenonand define the way to prevent a disastrous future. Implemented in 1987, by Montreal Protocol limitations on the ozone-depleting substances helped to slow down the ozone depletion and even stabilize the situation.The use of modern chemistry-climate models of the Earth System made it possible to reproduce the formation of ozone anomalies and to estimate the relative contribution of various physical and chemical processes to their development. The report presents the results of numerical modeling of ozone anomaly formation in different regions of the globe and estimates the relative contribution of halogenated compounds, as well as such phenomena as polar vortex stability, denitrification, and dehydration, to the development of ozone holes in Antarctica and mini-holes in the Arctic. The report devotes considerable attention to the analysis of ozone depletion in the tropical and mid-latitude stratosphere discovered in 2018, which has not yet received a convincing explanation. The absence of some chemical reactions in modern chemical-climate models and the use of an inaccurate scheme of chemical species transport may be responsible for the inability to correctly reproduce this negative trend.

Despite the efforts of the global community to limit the emission of ozone-depleting substances into the atmosphere, the full recovery of the ozone layer in the future is not yet a foregone conclusion. The paper discusses how the simultaneous change in climate and atmospheric chemistry in the future may affect the state of the ozone layer under different scenarios of greenhouse gas and ozone-depleting substances evolution. It also discusses other problems that threaten the future recovery of the ozone layer, which may be associated with a huge increase in the number of space rocket launches, large-scale forest fires, powerful volcanic eruptions, or widely discussed climate intervention measures based on the release of sulfur-containing compounds into the stratosphere.

The work was supported by the St. Petersburg State University within the framework of research grant 116234986, as well as the project of the state assignment of the Ministry of Science and Higher Education to the Russian State Hydrometeorological University (project FSZU-2023-0002) and the RSF grant 24-17-00230.