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The importance of the Montreal Protocol in protecting climate

Article | 01-03-2007
Photo showing a Hole in the ozone layer over Antartica

The 1987 Montreal Protocol - restricting the use of ozone-depleting substances - has helped both to reduce global warming and to protect the ozone layer. The benefit to climate achieved by the Montreal Protocol alone at present greatly exceeds the initial target of the Kyoto Protocol. The effects of the Montreal Protocol on climate will become smaller in the future, while emission reductions after 2012 under the Kyoto Protocol will potentially have much larger effects on climate.

Dual benefits ozone protocol: ozone layer and climate change

Ozone layer and the Montreal Protocol

Chlorofluorocarbons (CFCs) and other ozone-depleting substances are now globally recognised as the main cause of the observed depletion of the ozone layer. Molina and Rowland’s recognition of the potential of CFCs in depleting stratospheric ozone for the first time in 1974 provided an ‘early warning’. Concern was further heightened by the discovery of the ozone hole over Antarctica in 1985. The 1987 Montreal Protocol on Substances that Deplete the Ozone Layer formally recognised the significant threat of ozone-depleting substances to the ozone layer and provided a mechanism to reduce and phase out the global production and use of these compounds. This ozone protocol represents a landmark in the successful reduction of global production, use and emissions of ozone-depleting substances. According to research the ozone layer is now starting to recover.

Greenhouse gases and Kyoto Protocol

Ozone-depleting substances are also greenhouse gases that contribute to the radiative forcing of climate change. Their current contribution to the radiative forcing is about 20% of that of carbon dioxide, CO2. The Kyoto Protocol of 1997 is a global treaty to reduce the emissions CO2, the leading greenhouse gas, and five other gases. These gases do not deplete the ozone layer. The ozone-depleting gases are not included in the Climate Convention and its Kyoto Protocol.

Dual benefit

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 recognised 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.

Future benefits

Additional climate benefits of significance in comparison to the Kyoto Protocol reduction target could be achieved by new actions under the Montreal Protocol. These actions are destroying CFCs present in existing applications (refrigerators, foams), limiting the production of not fully halogenated fluorocarbons (HCFCs), and/or implementing alternative gases with lower global warming potentials. Additional emission reductions after 2012 are being negotiated in the framework of the Kyoto Protocol. Such reductions have potentially much larger effects on climate than the additional climate benefits of the Montreal Protocol.

Author(s)Velders GJM ; Anderson SO ; Daniel JS ; Fahey DW ; McFarland M
Publication date01-03-2007
PublicationProc Nat Acad Sci 2007; 104(12):4814-9