The Montreal Protocol is an international agreement which was drawn up in September 1987. It originally aimed to half the use of CFCs by 1999. However, reviews of the protocol held in 1990 in London and 1992 in Copenhagen imposed more stringent controls, so that all production of CFCs, CCl4 and halons should cease by the year 2000. Many countries have even agreed to stop using CFCs before this deadline. Production of other ozone depleting gases is to stop in the early years of the 21st century. Unfortunately the ozone hole will not immediately disappear as CFCs are such stable gases that they will remain in the atmosphere for decades after release.

Independent reviews by panels of scientists (eg the UK Stratospheric Ozone Review Group reports) present conclusive evidence that CFCs are still increasing in the atmosphere and that chlorine from them is also increasing and is responsible for ozone depletion. Thanks to the provisions of the Montreal protocol and its subsequent amendments the level of ozone depleting gases in the atmosphere will start dropping by the end of the 1990s.