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Energy, environment and sustainable development

Case Study

Environment & Climate

The Diminishing Ozone Layer

Global environmental problems such as ozone depletion require global scientific co-operation. EU research programmes play a leading international role.



The 'Ozone Hole' - a thinning of the stratospheric layer of ozone which shields all living organisms from solar ultra-violet (UV) radiation - may well be one of the first global environmental problems to be widely understood by the general public. It has led to the Montreal protocol, effectively banning significant emissions of chlorofluorocarbons, historically widely used in aerosol propellants, air conditioning systems and insulation foams.

The phenomenon itself, however, is only partly understood. The European Commission has funded research in this field for many years, from an array of small projects to major international flagship campaigns like the Third European Stratospheric Experiment on Ozone (Theseo) 1998-2000. Theseo is a truly international study, involving over 500 participants from 20 different European countries, as well as Canada, Japan, Russia and the United States. Using high-altitude balloons and aircraft, ground stations and satellites, Theseo shed light on the chemical processes in the stratosphere that control the ozone layer. For example, it studied local polar stratospheric clouds, which, when chlorine and bromine compounds are present, are responsible for reducing the ozone layer's thickness over the Arctic and Europe by up to 60%. Theseo reinforced concerns that, due to global climate change, Arctic ozone levels may continue to decline despite the reduction in stratospheric chlorine levels resulting from the Montreal Protocol.

As the ozone layer is thinning, the levels of particularly harmful UV-B radiation are increasing over populated regions of Europe. Other projects have therefore investigated the climatology of atmospheric UV radiation and its possible effects on agriculture, the ecosystems and human health, particularly in relation to immune system problems and cancer.

Although our understanding of the critical atmospheric processes has increased dramatically, we still do not know enough. New numerical models, for example, have correctly calculated the relative variations in ozone loss observed over the Arctic, but consistently underestimate the actual amount of ozone lost. More research is therefore vital in order to predict how ozone levels could recover in the future.

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