THE ROLE OF OZONE IN GLOBAL CHANGE

Over recent years convincing evidence has emerged of both a decrease in stratospheric ozone concentrations and an increase in tropospheric ozone concentration. These trends can be attributed primarily to increased global emissions of chlorofluorocarbons and of nitrogen oxides, respectively. Ozone plays an important role in the earth's atmosphere and changes in its concentration are of concern for several reasons: increased penetration of ultraviolet (UV) radiation, a contribution to global warming, perturbations in atmospheric chemistry, and direct toxic effects on the terrestrial biosphere. Concern over the direct toxic effects arises both from the expansion of the global area affected by regional episodes of elevated ozone concentrations, and an increased concentration in the background troposphere. Tropospheric ozone concentrations will continue to rise, in the absence of effective emission control measures, because of increased energy consumption and motor vehicle use, and any increase in concentrations will have detrimental effects on sensitive terrestrial ecosystems. Ozone should be considered as a component of global change, and priority be given to understanding its interaction with other, more important, factors such as CO2 concentration, water availability and temperature. Other important interactions may arise from the fact that ozone alters the performance of herbivorous insect pests and of plant pathogens, which will themselves be influenced by climate change. © 1991.