1.2　Restatement of the problem

In the face of the benefits and severe situation of ozone layer,people realized the necessity and importance of protection for it.In 1985,20 nations signed the Vienna Convention for the Protection of the Ozone Layer.In 1987,representatives from 43 nations signed the Montreal Protocol,which is in agreement to freeze production of CFCs at 1986 levels and to reduce production by 50 percent by 1999.Apparently,since the adoption and strengthening of the Montreal Protocol has contributed to reductions in the emissions of CFCs,atmospheric concentrations of the most-significant compounds have been declining.

Considering the importance of forecasting changes in total ozone for human survival,we need to develop a predictive model that reliably predicts future ozone levels over the next 50 years.This model is supposed to take into account the uncertainties of the factors affecting the total amount of ozone,the temporal and spatial characteristics of ozone distribution,and the changes in human activity patterns after 1987.