The Montreal Protocol on Substances That Deplete the Ozone Layer (a protocol to theVienna Convention for the Protection of the Ozone Layer) is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances believed to be responsible for ozone depletion. The treaty was opened for signature on September 16, 1987, and entered into force on January 1, 1989, followed by a first meeting in Helsinki, May 1989. Since then, it has undergone seven revisions, in 1990 (London), 1991 (Nairobi), 1992 (Copenhagen), 1993 (Bangkok), 1995 (Vienna), 1997 (Montreal), and 1999 (Beijing). It is believed that if the international agreement is adhered to, the ozone layer is expected to recover by 2050. Due to its widespread adoption and implementation it has been hailed as an example of exceptional international co-operation, with Kofi Annan quoted as saying that "perhaps the single most successful international agreement to date has been the Montreal Protocol". It has been ratified by 196 states.
Background
The origins of the Montreal Protocol trace back to a theory, published in 1974 by University of California researchers Sherwood Rowland and Mario Molina, that chlorine atoms released by the breakdown of chlorofluorocarbons (CFCs) in the upper atmosphere could precipitate a chemical chain reaction which would seriously damage the stratospheric ozone layer that protects all life from dangerous ultraviolet radiation (UV-B) emitted by the sun. The theory unleashed a firestorm of controversy, as CFCs, halons, and related chemicals were extremely useful substances—nontoxic, nonflammable, noncorrosive—that were finding continually new applications in thousands of products and processes. From construction, pharmaceuticals, and food processing, to telecommunications, aerospace, and computers, these chemicals seemed virtually synonymous with modern standards of living.
Several nations, including Canada, Denmark, Sweden, and the United States, voluntarily eliminated CFCs in aerosol spray cans in the late 1970s. Although many governments and the major chemical producers and CFC-using industries resisted strong actions, the United Nations Environment Programme organized efforts in 1982 to negotiate an international agreement. The discovery by a British research team in 1983 of an unexpected annual seasonal collapse in ozone concentrations over Antarctica (the “ozone hole”) sparked public interest, but scientists cautioned against basing the CFC negotiations on this phenomenon because there were other plausible causes for this occurrence. Rather, the scientific concern rested on theoretical computer models that predicted more gradual ozone depletion over the mid-latitudes – of which, however, there was no evidence. Indeed, at the time of the negotiations, measurements actually showed declines in UV-B radiation reaching Earth’s surface (a phenomenon that was later understood to be caused by high levels of pollution in the lower atmosphere that filtered out the radiation.)
According to research led by the Netherlands Environmental Assessment Agency, the Montreal Protocol has helped both to reduce global warming, and to protect the ozone layer. Research also reveals that the contribution of the ozone-depleting substances to radiative forcing would most likely have been much larger if the link of these substances to stratospheric ozone depletion had not been recognized in 1974 and followed by a series of regulations. Without the reductions achieved under the Montreal Protocol, the amount of heat trapped due to ozone-depleting substances would be about twice as high as present levels. The savings in trapped heat are equivalent to the current increase, built up during about 10 years of growth in carbon dioxide concentrations. The climate protection already achieved by the Montreal Protocol alone is far larger than the reduction target set for the first commitment period of the Kyoto Protocol. On the other hand, the effects of the Montreal Protocol on climate will become smaller in the future since the ozone-depleting gases are being phased out.
Sources:
www.eoearth.org/article/Montreal_Protocol_on_Substances_that_Deplete_the_Ozone_Layer
www.pbl.nl/en/publications/2007/The_importance_of_the_Montreal_Protocol_in_protecting_climate
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