Halocarbons 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 to decline.

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..

Human Impact

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 Protocol.