CIESIN Reproduced, with permission, from: Tolba, M. K., O. A. El-Kholy, E. El-Hinnawi, M. W. Holdgate, D. F. McMichael, and R. E. Munn, eds. 1992. Ozone depletion. Chapter 2 in The world environment 1972-1992. New York: Chapman and Hall.

Implications of the Key Findings of the Scientific Assessment of Stratospheric Ozone: 1989

The findings and conclusions of the intensive and extensive ozone research over the past few years have several major implications as input to public policy regarding restrictions on man-made substances that lead to stratospheric ozone depletion:


The scientific basis for the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer was the theoretical prediction that, should CFC and halon abundances continue to grow for the next few decades, there would eventually be substantial ozone layer depletion.

The research of the last few years has demonstrated that actual ozone loss due to anthropogenic chlorine emissions (i.e. CFCs) and bromine has already occurred. i.e. the Antarctic ozone hole. Assuming that the atmospheric abundance of chlorine reaches about 9 ppbv by about 2050, ozone depletions of 0-4% in the tropics and 4-12% at high latitudes would be predicted, even without including the effects of heterogeneous chemical processes known to occur in polar regions.

The surface-induced, PSC-induced chemical reactions that cause the ozone depletion in Antarctica and that also occur in the Arctic represent additional ozone-depleting processes that were not included in the stratospheric ozone assessment models that were used to guide the Montreal Protocol. Recent laboratory studies suggest that similar reactions involving chlorine compounds may occur on sulphate particles present at lower latitudes, which could be particularly important immediately after a volcanic eruption.

Hence, future global ozone layer depletions could well be larger than originally predicted.


Large-scale ozone depletions in Antarctica appeared to have started in the late 1970s and were initiated by atmospheric chlorine abundance of about 1.5-2.0 ppbv, compared to today's level of about 3 ppbv.

To return the Antarctic ozone layer to levels approaching its natural state, and hence avoid the possible ozone dilution effect that the Antarctic ozone hole could have at other latitudes, one of a limited number of approaches to reduce the atmospheric abundance of chlorine and bromine is a complete phase-out of all fully halogenated CFCs, halons, carbon tetrachloride and methyl chloroform, as well as careful considerations of the HCFC substitutes. Otherwise, the Antarctic ozone hole is expected to recur seasonally, provided the present meteorological conditions continue.