Ozone Hole
The first global agreement to restrict CFCs came with the signing of the Montreal Protocol in 1987 which wanted to reduce the ozone depletion by half by 2000. Only two revisions have been made due to scientific advancements and the knowledge and understanding of ozone has been developed. Agreement has been reached on the control of the main CFCs will not be produced, except for a limited amount for essential uses, such as for medical sprays. These limitations were believed to lead to a recovery of the ozone layer within 50 years of 2000; the World Meteorological Organisation estimated 2045, but recent investigations suggest that no recovery has been made thus far.
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In the 1980's, researchers studying earths atmospheric conditions noticed a reduced concentration of ozone over Antarctica. In 1988, researchers stated that there was a hole in the ozone layer above Antarctica, and that it had been developing over a period of 15 years.
The hole over Antarctica caused by a number of atmospheric factors that destroy copious amounts of ozone. A polar vortex is formed around Antarctica, which is formed by the clockwise wind rotations. As a result, air over Antarctica does not mix with air in the rest of the earth's atmosphere. Often reaching -40 degrees Celsius, the formation of polar stratospheric clouds (PSC's) which are a mixture of frozen water and nitric acid occur. During the spring, PSC's melt, releasing the halogenated compounds trapped inside. High energy photons, that react with the CFC's, free the halogen radicals that break down O3. Due to the polar vortex, there is a concentration of halogens that begin to break down the ozone layer about the arctic. |