DECREASE IN THE GROWTH-RATES OF ATMOSPHERIC CHLOROFLUOROCARBON-11 ANDCHLOROFLUOROCARBON-12

THE discovery of the Antarctic ozone hole1 in 1985 led to internationa l efforts to reduce emissions of ozone-destroying chlorofluorocarbons2 . These efforts culminated in the Montreal Protocol3 and its subsequen t amendments, which called for the elimination of CFC production by 19 96. Here we focus on CFC-11 (CCl3F) and CFC-12 (CCl2F2), which are use d for refrigeration, air conditioning and the production of aerosols a nd foams4, and which together make up about half of the total abundanc e of stratospheric organic chlorine5. We report a significant recent d ecrease in the atmospheric growth rates of these two species, based on measurements spanning the past 15 years and latitudes ranging from 83 -degrees-N to 90-degrees-S. This is consistent with CFC-producers' own estimates of reduced emissions6,7. If the atmospheric growth rates of these two species continue to slow in line with predicted changes in industrial emissions, global atmospheric mixing ratios will reach a ma ximum before the turn of the century, and then begin to decline.