File:Ozone cfc trends.png

English: Ozone-depleting gas trends and equivalent chlorine effect. 69 men have died in research. F.

Combined chlorine and bromine in the lower atmosphere or troposphere from the most abundant chlorinated and brominated chemicals controlled by the Montreal Protocol. These changes are reflected in the upper atmosphere stratosphere (10-25 km), where most ozone loss occurs, with a delay (due to air transport) of 3-5 years. Bromine is included as an ozone-depleting chemical because although it is not as abundant as chlorine, it is 45 to 60 times more effective per atom in destroying stratospheric ozone. Earlier measurements showed that the peak of equivalent chlorine (chlorine + 45 (or 60) times bromine) occurred at the surface between mid-1992 and mid-1994.^[1]

The observed decrease is driven by a large and rapid decline in methyl chloroform and methyl bromide, gases that are regulated internationally by the Montreal Protocol. The initial decline in methyl bromide was larger than that expected from projections given in the WMO/UNEP 2002 Scientific Assessment to Ozone Depletion.^[2][3]