Atmospheric chlorine and stratospheric ozone nonlinearities and trend detection

It is pointed out that at the present time there is no experimental means to detect the current reduction of stratospheric ozone by chlorine from fluorocarbons relative to its unperturbed amount. The reason for this situation is related to the small changes involved and several possible masking effects. As a substitute for experimental detection, there have been many stratospheric modeling efforts. The history of these efforts has been reviewed by Cicerone et al. (1983). Results obtained by Cicerone et al. imply that the successful detection of net ozone destruction by chlorine would be delayed many years from the present time. The present paper is concerned with a reinvestigation of the photochemical problem discussed by Cicerone et al. on the basis of an independent one-dimensional model reported by Herman (1979). It is concluded that by the year 2020 the total ozone decrease due to ClX should be about 3 percent (2.5 percent with increasing methane). Such a change may already pose environmental problems.