GLOBAL TRENDS AND ANNUAL RELEASES OF CCL3F AND CCL2F2 ESTIMATED FROM ALE GAGE AND OTHER MEASUREMENTS FROM JULY 1978 TO JUNE 1991/

Thirteen years of Atmospheric Lifetime Experiment/Global Atmospheric G ases Experiment CCl3F and CCl2F2 measurements at five remote, surface, globally distributed sites are analyzed. Comparisons are made against shipboard measurements by the Scripps Institution of Oceanography gro up and archived air samples collected at Cape Grim, Tasmania, since 19 78. CCl3F in the lower troposphere was increasing at an average rate o f 9.2 ppt/yr over the period July 1978 to June 1988. CCl2F2 was increa sing at an average 17.3 ppt/yr in the lower troposphere over the same period. However, between July 1988 and June 1991 the increases of CCl3 F and CCl2F2 in this region have averaged just 7.0 ppt/yr and 15.7 ppt /yr, respectively. The rate of increase has been decreasing 2.4 ppt/yr and 2.9 ppt/yr(2) over this 3-year period. Based on a recent scenario of the global releases of these compounds and using the new calibrati on scale SIO 1993, the equilibrium lifetimes are estimated to be 44(-1 0)(+17) and 180(_81)(+820) years for CCl3F and CCl2F2, respectively. U sing these lifetime estimates and a two-dimensional model, it is estim ated that global releases of these two chlorofluorocarbons in 1990 wer e 249+/-28 x 10(6) kg for CCl3F and 366+/-30 x 10(6) kg for CCl2F2. It is also estimated that combined releases of these chlorofluorocarbons in 1990 were 21+/-5% less than those in 1986.