Image:Ozone cfc trends.png

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Chloroflourocarbon (CFC) gas trends and equivalent chlorine effect. The concentration of chlorine and bromine in the atmosphere is key to the process of ozone depletion and the creation of the ozone hole

Combined chlorine and bromine in the lower stratosphere (10-25 km), where most ozone loss occurs, leveled off around 1999. Bromine, although much less abundant than chlorine, is 45 times more effective per atom in destroying stratospheric ozone. Earlier measurements showed that the peak of equivalent chlorine (chlorine + 45 times bromine) had already occurred at the surface between circa 1993.

The observed decrease is driven by a large and rapid decline in methyl bromide, a brominated gas that is regulated internationally by the Montreal Protocol. The rate of decline exceeds that expected from model calculations in the WMO/UNEP 2002 Scientific Assessment to Ozone Depletion.

References

"News Release Feb 6, 2001". Climate Monitoring and Data Laboratory. URL accessed on March 17, 2005.
"CMDL Scientists find that ozone-depleting bromine is now on the decline". Climate Monitoring and Data Laboratory. URL accessed on June 9, 2005.
"Halocarbons and other Atmospheric Trace Species". Climate Monitoring and Data Laboratory Summary Report #27. URL accessed on March 17, 2005.

Source

This image is a work of the National Oceanic and Atmospheric Administration, taken or made during the course of an employee's official duties. As works of the U.S. federal government, all NOAA images are in the public domain.

Source: ftp://140.172.192.211/hats/Total_Cl_Br/totCl_2004.ps from CMDL Data Archive: http://www.cmdl.noaa.gov/info/ftpdata.html