Unep ozone layer review : atmospheric ozone science

Abstract

Remarkable progress has been made in the past few years in understanding the physical and chemical processes that control the abundance of stratospheric ozone. In particular there have been highly significant advances in understanding the impact of human activities. Since the Montreal Protocol on Substances that Deplete the Ozone Layer was signed in 1987, there have been several major findings that each heighten the concern that chlorine and bromine containing chemicals can lead to a significant depletion of stratospheric ozone. These findings, which were discussed in the latest international scientific assessment, "Scientific Assessment of Stratospheric Ozone: 1989", which was co-sponsored by the United Nations Environment Programme, the World Meteorological Organization, U.K. Department of the Environment, U.S. National Aeronautics and Space Administration, and U.S. National Oceanic and Atmospheric Administration, include: 1. Chlorine and bromine species are the primary cause of the springtime Antarctic ozone hole. 2. The observed stratospheric ozone decrease in winter at mid-high northern latitudes cannot be explained by known natural processes. 3. The chemical composition in the Arctic stratosphere is highly perturbed in winter, similar to that observed in Antarctica. These findings suggest that: (a) There are major gaps in theoretical models used for assessment studies. (b) Protection of the ozone layer, specifically elimination of the Antarctic ozone hole, will require additional international regulations of the chemicals currently controlled by the Montreal Protocol (CFCs 11, 12, 113, 114, and 115, and halons 1211 and 1302) as well as international regulations on the emissions of carbon tetrachloride, methylchloroform and eventually, the proposed HCFC substitutes.