UNCERTAINTIES IN THE CALCULATION OF ATMOSPHERIC RELEASES OF CHLOROFLUOROCARBONS

Production and sales data for chlorofluorocarbons (CFCs) 11, 12, 113, 114, and 115 as well as for hydrochlorofluorocarbon (HCFC) 22 are available through 1991 from producer surveys. Global atmospheric emissions are estimated from these production data using estimates of the time pattern of release following production as well as estimates for nonreported production; each of these estimates has an associated level of uncertainty. This paper describes the uncertainties associated with emission estimates based on the industrial surveys and the associated uncertainties in lifetimes derived from analysis of the observed tropospheric trends of the key CFCs. For CFC 11 this analysis shows that the greatest uncertainty is associated with the release pattern for closed cell foam blowing agents, whereas for CFC 12 the greatest uncertainty involves estimates of nonreported production and use of material in that portion of the world not surveyed.