Scientists had shown in 1974 that chlorofluorocarbons, used in aerosol sprays, refrigerators and foam, could break down stratospheric ozone, which shields life from ultraviolet radiation. The discovery of an ozone "hole" over Antarctica in 1985 added urgency. The Montreal Protocol, signed by 24 countries and the European Community, set limits that later amendments tightened into bans. Every UN member state eventually ratified it. The ozone layer is now slowly recovering.
In 1974 the chemists Mario Molina and F. Sherwood Rowland published a paper warning that chlorine from chlorofluorocarbons, or CFCs, would drift into the stratosphere and destroy ozone molecules. Industry groups disputed the science for years. Then in 1985, scientists of the British Antarctic Survey reported that springtime ozone levels over Antarctica had fallen dramatically, and satellite data confirmed a vast area of depleted ozone.
Negotiations under the UN Environment Programme, led by its executive director Mostafa Tolba, moved fast. The agreement signed on September 16, 1987, required developed countries to cut CFC production in half by 1999. Developing countries were given extra time, and a fund was later created to help them switch to substitutes.
The protocol entered into force on January 1, 1989, and was strengthened repeatedly as the science became clearer. In 1995 Molina, Rowland and the Dutch scientist Paul Crutzen received the Nobel Prize in Chemistry. The former UN Secretary-General Kofi Annan called the protocol perhaps the single most successful international agreement. Scientists expect the ozone layer over most of the world to return to 1980 levels around the middle of this century.
Key people: Mostafa Tolba, Mario Molina, F. Sherwood Rowland