This seminar will summarize key points of our present scientific understanding of ozone depletion, what research results they are based upon, and the outlook for the future of our ozone layer. In the early 1970's chemists Paul Crutzen and Harold Johnston described the effects of nitrogen oxides on stratospheric ozone chemistry. In 1974 chemists Mario Molina and Sherwood Rowland realized that human-produced chlorine compounds, particularly CFC's, could deplete the Earth's ozone layer. These scientists, together with Paul Crutzen, were recently awarded Nobel Prizes for their research. Although the phenomenon is not yet fully understood, the weight of evidence indicates that these losses are due in large part to human-produced chemicals.
Ozone depletion is observed to cause an increase in UV-B radiation at the Earth's surface.
Monitoring data show that the growth in concentrations of ozone-depleting chemicals in the atmosphere is slowing, consistent with the declining production required by international agreements. The amount of UV-B radiation in natural sunlight is dependent upon the concentration of ozone molecules in the atmosphere. Any reduction in stratospheric ozone concentration will result in increased amounts of UV-B radiation reaching the surface. Even a small increase in UV-B radiation is likely to have important consequences for plant and animal life, and will almost certainly jeopardize human health. The best understood harmful effects of UV-B radiation on human health are basal and squamous cell cancers of the skin and eye damage, including cataracts, which can lead to blindness.