For their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone, the Royal Swedish Academy of Sciences awarded the 1995 Nobel Prize in Chemistry to:
The announcement by the Royal Swedish Academy of Sciences stated that these three scientists "...have all made pioneering contributions in explaining how ozone is formed and decomposes through chemical processes in the atmosphere. Most importantly, they have in this way showed how sensitive the ozone layer is to the influence of anthropogenic emissions of certain compounds. The thin ozone layer has proved to be an Achilles heel that may be seriously injured by apparently moderate changes in the composition of the atmosphere."
In 1970, Dr. Paul Crutzen "...showed that the nitrogen oxides NO and NO2 react catalytically (without themselves being consumed) with ozone, thus accelerating the rate of reduction of the ozone content....These nitrogen oxides are formed in the atmosphere through the decay of the chemically stable nitrous oxide (N2O), which originates from microbiological transformations at the ground. The connection demonstrated by Crutzen between microorganisms in the soil and the thickness of the ozone layer is one of the motives for the recent rapid development of research on global biogeochemical cycles....This was also the start of intensive research into the chemistry of the atmosphere which has made great progress during the past several years."
"The next leap in our knowledge of ozone chemistry was in 1974, when Mario Molina and Sherwood Rowland published their widely noted Nature article on the threat to the ozone layer from CFC gases- 'freons'-used in spray bottles, as the cooling medium in refrigerators and elsewhere, and plastic foams....Molina and Rowland realized that the chemically inert CFC could gradually be transported up to the ozone layer, there to be met by such intensive ultraviolet light that they would be separated into their constituents, notably chlorine atoms. They calculated that, if human use of CFC gases was to continue at an unaltered rate, the ozone layer would be depleted by many percent after some decades....Many were critical of Molina and Rowland's calculations but yet more were seriously concerned by the possibility of a depleted ozone layer. Today, we know that they were right in all essentials. It was to turn out that they had even underestimated the risk."
Thanks to the good scientific understanding of the ozone problem achieved by Crutzen, Molina, and Rowland, as well as others who have made crucial contributions, it has been possible to make far- reaching decisions on regulating the release of gases that destroy ozone. A protocol on the protection of the ozone layer was negotiated under the auspices of the United Nations and signed in Montreal, Canada, in 1987. "Since it takes some time for the ozone-destroying gases to reach the ozone layer, we must expect the depletion, not only over Antarctica but also over parts of the Northern Hemisphere, to worsen for some years to come. Given compliance with the [Montreal Protocol], the ozone layer should gradually begin to heal after the turn of the century. Yet it will take at least 100 years before it has fully recovered."