Publication Type:Journal Article
Source:Journal of Geophysical Research: Atmospheres, Volume 101, Issue D7, p.12585 - 12599 (1996)
Keywords:Atmosphere, Troposphere: composition and chemistry, Troposphere: constituent transport and chemistry
Observations every two hours of CCl2FCClF2 at Mace Head, Ireland (February 1987–June 1994); Cape Meares, Oregon (April 1984–June 1989); Ragged Point, Barbados (October 1985–June 1994); Cape Matatula, Samoa (October 1985–June 1989 and January 1992–June 1994); and Cape Grim, Tasmania (June 1982–June 1994) are reported. The observations from Cape Grim have been extended back to 1978 using archived air samples. The global atmospheric abundance of CCl2FCClF2 is indicated to have been growing exponentially between 1978 and 1987 with an e-folding time of approximately 7.6 years; it has been growing less rapidly since that time. On January 1, 1994, the mean inferred northern hemispheric mixing ratio in the lower troposphere was 84.4 ± 0.4 ppt and the southern hemispheric 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 concentrations are calculated to be consistent with the almost entirely northern hemispheric release of this gas. The annual release estimates of CCl2FCClF2 by industry, which include estimates of eastern European emissions, fairly consistently exceed those deduced from the measurements by approximately 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 × 106 kg or 42 ± 15% of the 1985–1987 emissions.