Over a decade of scientific research has supported the original 1970s predictions, which were that continued emissions of CFCs would eventually cause global ozone depletions of several percent by the middle of the next century. Science also, however, discovered some surprises, including observations of global ozone downward trends that were even larger than predicted and that losses as large as 60% were occurring in Antarctica. Direct measurements of the chemical species that control ozone allowed the link between this dramatic ozone depletion in Antarctica and emissions of CFCs and other human-made species to be established definitively. This overall sequence of research results, which extended from theory to observation to cause, was paralleled by governmental policies for reductions in and eventual phase-out of ozone-damaging compounds and by vigorous industrial development of safer substitutes.
Although recent atmospheric measurements are confirming that emissions of the major ozone- damaging compounds are now on the path to being largely eliminated, science and policy continue to address the key issues of managing the peak ozone depletions expected near the end of this decade, evaluating the success or failure of the hoped-for recovery of the ozone layer in the several decades thereafter, and understanding the emerging science/policy links between ozone depletion and surface climate change.
Adverse and fluctuating weather events on a large scale cause billions of dollars in crop losses and other economic impacts each year. Drought in the Sahara, delayed monsoons in India, and prolonged dry periods in food-growing and water resource regions create food and water shortages for large populations. Even in developed countries such as the United States, events such as the Great Plains droughts of 1988, the Mississippi River floods of 1993, and the California floods of 1995 cost millions of dollars in damages and crop losses.
El Nino affects weather from Australia to South and Central America, as well as into the western and southern United States. Although fluctuations in the weather cannot be prevented, the ability to predict extreme changes months in advance allows for agricultural yields to be protected by changing crops and planting schedules. Our improved forecasting ability is sufficiently accurate to also be applied to water resource planning in the southwestern United States. Water supplies can be protected by adjusting storage and management practices.