LIFETIME AND EMISSION ESTIMATES OF 1,1,2-TRICHLOROTRIFLUORETHANE (CFC-113) FROM DAILY GLOBAL BACKGROUND OBSERVATIONS JUNE 1982 JUNE 1994

Observations every two hours of CCl2FCClF2 at Mace Head, Ireland (Febr uary 1987-June 1994); Cape Meares, Oregon (April 1984-June 1989); Ragg ed Point, Barbados (October 1985-June 1994); Cape Matatula, Samoa (Oct ober 1985-June 1989 and January 1992-June 1994); and Cape Grim, Tasman ia (June 1982-June 1994) are reported, The observations from Cape Grim have been extended back to 1978 using archived air samples. The globa l atmospheric abundance of CCl2FCClF2 is indicated to have been growin g exponentially between 1978 and 1987 with an e-folding time of approx imately 7.6 years; it has been growing less rapidly since that time. O n January 1, 1994, the mean inferred northern hemispheric mixing ratio in the lower troposphere was 84.4 +/- 0.4 ppt and the southern hemisp heric value was 80.6 +/- 0.4 ppt; the global growth rate in 1991-1993 is estimated to have averaged approximately 3.1 +/- 0.1 ppt/year. The differences between the northern and southern hemispheric concentratio ns are calculated to be consistent with the almost entirely northern h emispheric release of this gas. The annual release estimates of CCl2FC ClF2 by industry, which include estimates of eastern European emission s, fairly consistently exceed those deduced from the measurements by a pproximately 10% from 1980 to 1993. The uncertainties in each estimate is approximately 5%. This difference suggests that up to 10% of past production might not yet have been released. The measurements indicate that atmospheric releases of CCl2FCClF2 have been decreasing rapidly since 1989 and in 1993 amounted to 78 +/- 27 x 10(6) kg or 42 +/- 15% of the 1985-1987 emissions.