The impact of the chlorocarbon industry on the ozone layer

Abstract

By means of calculations with a one‐dimensional photochemical‐diffusive model of the atmosphere a theoretical estimate is given of the present and the possible future impact of large sections of the chlorocarbon industry on the ozone layer. Our estimates for 1976 are that past chlorocarbon emissions may be responsible for a 1.5% reduction in the global total ozone content (0.8% by CFCl 3 and CF 2 Cl 2 , 0.5% by CCl 4 , and 0.2% by CH 3 CCl 3 ). This estimate was obtained by comparison with the ozone content of a model atmosphere without industrial chlorocarbon emissions. The effect of the nonindustrial gas CH 3 Cl can best be described by stating that without CH 3 Cl, there would be almost 1% more ozone in the atmosphere. Considerable attention should also be given to the atmospheric effects of expanding uses of CH 3 CCl 3 . The potential impact on the ozone layer of CHFCl 2 and CHF 2 Cl emissions is also discussed. However, there are too many uncertainties regarding the tropospheric concentrations of OH and its role as a scavenger to assess the effect of a number of chlorocarbon compounds reliably. The effect of other chlorocarbon compounds (C 2 Cl 4 , C 2 HCl 3 , C 2 H 5 Cl, C 2 H 4 Cl 2 , CHCl 3 ) on the ozone layer is estimated as being comparatively negligible. Model‐calculated vertical distributions of a large number of constituents are compared with observations. Substantial deviations between some theoretical and reported concentrations exist, especially for NO x , CO, and ClO. Uncertainties in our knowledge of stratospheric chemistry are discussed. It is concluded that these uncertainties are sufficiently numerous to take the given predictions of ozone reductions with some reservations.