Publication Type:Journal Article
Source:Journal of Geophysical Research: Atmospheres, Volume 102, Issue D1, p.1259 - 1269 (1997)
Keywords:General or miscellaneous, Middle atmosphere: composition and chemistry, Troposphere: composition and chemistry
Global Atmospheric Gases Experiment/Advanced GAGE (GAGE/AGAGE) observations of CCl3F indicate that global concentrations of this compound reached a maximum in 1993 and decayed slightly in 1994; CCl2F2 concentrations increased approximately 7 ppt in both 1993 and 1994. The observations suggest that world emissions in these two years were smaller than industry production figures would suggest and have decreased faster than expected under the Montreal Protocol and its amendments. An analysis of regional pollution events at the Mace Head site suggest that industry may be underestimating the decline of emissions in Europe. It is argued, however, that the decline in European emissions is not biasing the background Mace Head measurements (or the GAGE global averages). Combining the chlorofluorocarbon measurements, including CCl2FCClF2, with GAGE/AGAGE measured global decreases in CH3CCl3 and CCl4 after 1992 and with Cape Grim archived air measurements of CHClF2, the measurements suggest that anthropogenic atmospheric chlorine loading from these six gases maximized in 1992 at 2.95±0.04 ppb and that it had decreased by 0.02±0.01 ppb by the beginning of 1995.