Impact of Chlorofluoromethanes on Stratospheric Ozone

Monthly averages of data on stratospheric total ozone and vertical distribution ozone profiles from a global collection of ground-based recording stations are analyzed for the detection of trend in ozone that may be associated with possible effects of the release of chlorofluoromethanes (CFM's). Regression time series models that include seasonal, trend, and other factors are estimated from the data at each individual station. A factor to explicitly account empirically for the effects of atmospheric aerosols due to volcanic activity on the ozone profile measurements is also included in the models. A random effects model for the individual station trend estimates is used to combine the individual trend estimates in the form of an overall global estimate of trend in ozone. Based on analysis of ozone data during the period 1960-1983, there is little evidence of any trend in total ozone. But a statistically significant negative trend of about −.3% change per year for the period 1970-1981 has been obtained for profile ozone data at about the 40 km altitude region. These empirical findings are in reasonably good agreement with current theoretical photochemical model predictions of ozone change.