are best known as destroyers of ozone, however many are also powerful
greenhouse gases. Under the Montreal Protocol, emissions of halocarbons
are tightly controlled and concentrations of many dual 'ozone
depleting and global warming inducing' gases are now beginning
Three halocarbons, CFC-11, CFC-12 and CFC-113, stand out as having
the greatest potential as greenhouse gases. All three are produced
as a direct result of man's activity, with no known natural sources.
Due to the varying lifetimes of halocarbons in our atmosphere,
the impact of the Montreal Protocol has been more rapid for some
gases than others. Overall though, concentrations of most of these
gases are now declining or at least leveling off..
Man is completely responsible for emissions of the most important
greenhouse gas halocarbons. However, the effectiveness of the
Montreal Protocol stands out as an example of how emission of
atmospheric pollutants, like greenhouse gases, can be effectively
tackled on an global scale.
Though greenhouse gases may be be more diverse, and have many
more sources, the fact remains that political will can be effective
in dealing with such global threats. Where the situation of greenhouse
gas emission and global warming can be simplified to a level akin
to that of ozone depletion by CFCs, with cost effective remedies
and clear targets, even the most reluctant of governments can
be persuaded to act.
Potential for control
As described above, reduction in emissions of these halocarbon
greenhouse gases has largely been due to concern over ozone depletion
and compliance with the Montreal Protocol. The powerful greenhouse
gas status of some of these ozone depleting gases simply adds
further credence to the global cuts in emissions under the Montreal