| The annual ozone layer remains important |
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| Monday, 28 April 2008 | |
 In the 1970's, scientists discovered that CFCs contribute to the depletion of the ozone layer. Since signing the Montreal Protocol in 1987, production and consumption of substances responsible for this loss decreased significantly. It will, however, expected between 2060 and 2075 so that the thickness of the ozone layer back to its level before 1980.Despite a massive reduction, thanks to the Montreal Protocol, production and consumption of chlorofluorocarbons (CFCs) and other harmful substances, the size of the "hole" in the annual ozone layer over the Antarctica remains important.
The lifetime in the atmosphere of different types of CFCs varies from 45 to 1,700 years, according to a report released in February and written by scientists on behalf of the World Meteorological Organization, the UN Programme for the Environment Programme (UNEP) and other agencies. "It will have to wait long for the concentration of CFCs in the atmosphere is reduced. We still need to wait for a good fifty years before seeing the direct effect of the Montreal Protocol. Today, we are seeing a slowdown in the formation of ozone "hole", which seems to have reached its maximum size, but there are still shrinking, he adds. In 1928, scientists are developing the first CFCs. In the years 1960, their consumption is increasing rapidly in industrialized countries. CFCs are used as refrigerants, cleaning solvents, aerosol propellants and blowing agents for the manufacture of foams.In 1974, two chemists, Sherwood Rowland and Mario Molina, publish an article in the journal Nature stating that CFCs can destroy ozone in the upper atmosphere, the stratosphere. In 1976, UNEP calls for the convening of an international conference on problems of ozone.The USA in 1978 prohibit the use of CFCs which are not considered essential. Canada, Norway and Sweden have followed suit.In 1982, 24 countries meet in Stockholm and agree to establish the Ad Hoc Working Group of Legal and Technical Experts entrusted with the elaboration of a global Framework Convention for the Protection of the Ozone Layer. In 1985, scientists from the British Antarctic Survey revealed the existence of a "hole in the ozone layer over Antarctica. It is since then observe a "hole" in ozone each spring in Antarctica during the autumn months of the northern hemisphere. "Once summer arrives, the" hole "closes and ozone reappears," says Bourqui. The formation of the "hole" in ozone requires very low temperatures, found in late winter. The Vienna Convention for the ozone layer was created in 1985. No protocol regulation is however expected. In 1987, 24 countries signed the Montreal Protocol on Substances that Deplete the Ozone Layer. At the end of 2005, the 191 countries that have so far signed the protocol were generally reduced by over 95% their consumption of substances that deplete the ozone layer - CFCs, halons, methyl bromide, HCFCs and others - compared to the reference levels set. Consequences The temperature in the stratosphere is currently less low in the Arctic and the Antarctic. Scientists have observed a depletion of ozone above the Arctic, but far less important than Antarctica. On the one hand, the reduction of the presence of CFCs should have a beneficial effect on the ozone layer over the Arctic, and the other, global warming could act in the opposite direction, said M . Bourqui. "At present, it is unclear for the next fifty years, what to expect. There is no real scientific consensus. " |
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| Last Updated ( Thursday, 03 July 2008 ) |
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