Evidence for a decline in the atmospheric accumulation rate of CHClF2 (CFC-22)

CHClF2 (CFC-22) is a promising substitute for atmospheric ozone damaging, fully halogenated hydrocarbons. Atmospheric CFC-22 measurements derived from ground-based solar spectra recorded between December 1980 and May 1988 are reported which show that the CFC-22 total column increased at an average annual exponential rate of 7.8 percent + or - 1.0 percent (2 sigma). Compared with other atmospheric data, these measurements indicate that CFC-22 is increasing at a more rapid rate than either CFC-11 or CFC-12, the two most abundant chlorofluorocarbons, but that the rate of CFC-22 increase is likely to have declined over the past few years.