Ozone-climate interactions

The potential importance of the coupling between climate change and atmospheric ozone has been recognised for some time. However it is only recently that atmospheric scientists could even hope to start to capture the full complexity of the most important interactions in their models. In considering the role of atmospheric ozone it has been traditional largely to consider stratospheric ozone and tropospheric ozone separately, even though the importance for both regions of what happens in the upper troposphere and lower stratosphere (UTLS) has been well recognised. This approach is reflected, for example, in the respective scientific contents of the WMO-UNEP Scientific Assessments of Ozone and the assessments of the Intergovernmental Panel on Climate Change (IPCC), the essential scientific guides in the development of public policy on ozone depletion and climate change. These assessments have been based on available scientific knowledge and have been concerned, respectively, with how ozone-depleting substances affect stratospheric ozone and what chemical emissions cause tropospheric ozone to increase. Although these reports have recently included some aspects of the coupling between atmospheric ozone and climate, no thorough scientific overview of this problem is presently available. The aim of this European report is to present in a coherent way the present understanding of the interactions between ozone and climate, regardless of the atmospheric region where the processes are taking place and including their consequences for environmental problems such as climate change, ozone depletion and tropospheric pollution. In emphasising these interactions, the report will provide a framework for future strategies in the field of atmospheric research, and for further discussion involving scientists, research agencies and policy-makers on the necessary measures to be taken at the interface of the Kyoto Protocol and the Montreal Protocol.