Environmental effects of ozone depletion: 1998 Assessment

The Montreal Protocol on Substances that Deplete the Ozone Layer requires periodic assessments of available scientific, environmental, technical and economic information. The assessments shall be made at least every four years. Assessments were made in 1989, 1991, 1994, and the present one, in 1998. The 1998 assessment focuses on new information since 1994, but it includes some background of prior information, so that it can be read without having the earlier reports at hand. In 1994, the ozone layer was predicted to become thinner until about 1998, and to recover gradually thereafter. Taking into account new information, the Atmospheric Science Panel now expects that the most vulnerable period for ozone depletion will be extended into the coming two decades. Scientific studies are continuing on the most important effects, and on what can be done to prevent or mitigate these. The present assessment deals with the results of such investigations. These repeatedly give reasons for concern for potential effects, but relatively little progress has been made in quantifying these effects. The more the investigators look into the problems, the more the complexity becomes apparent. Nevertheless, the knowledge is accumulating. In comparison with the earlier assessments on effects of ozone depletion, the present report has a new section, Frequently Asked Questions.