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Global Climate Change Digest

A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999



Item #d98jul111

UNEP and the World Meteorological Organization released results of the latest assessment of ozone depletion in June 1998. It estimates that chlorine loading will peak around the year 2000, and complete recovery of the ozone layer is expected by the middle of the next century, providing the Montreal Protocol is fully implemented. The combined total abundance of ozone-depleting compounds in the troposphere peaked in 1994, as projected by the previous assessment (completed in 1994). That abundance is now slowly declining, although concentrations of bromine are still increasing. The importance of methyl bromide as an ozone-depleting compound is now thought to be less than estimated in the 1994 assessment, due to an increase in the estimated oceanic removal, and identification of the uptake potential of soils. Scientific Assessment of Ozone Depletion—1998 will be published as WMO Ozone Report No. 44 later this year. An executive summary is available from the WMO at 41 Ave. G. Motta, CP 2300, CH-1211 Geneva, Switz., and on its Web site ( Results and implications are discussed in Intl. Environ. Rptr., pp. 624-625, June 24, 1998; Eos, Trans. Amer. Geophys. Union, pp. 317-318, July 7; and Global Environ. Change Rep., pp. 1-3, June 26.

The UNEP/WMO assessment notes that in the northern polar latitudes, ozone has declined in six out of the last nine winter-spring seasons during some months by 25 to 30 percent below the 1960s average. In its Northern Hemisphere Winter Summary (1997-98), released in April, the National Oceanic and Atmospheric Administration reports that total column ozone values for February and March 1998 over much of the Arctic were about 10 percent lower than values observed in the early 1980s. Temperatures in the lower stratosphere over the north polar region in November and December 1997 reached record low levels, contributing to chemical destruction of ozone on polar stratospheric cloud particles. The annual NOAA summaries, issued in April for the Northern Hemisphere and December for the Southern Hemisphere, are available at

At a July working group meeting for the Montreal Protocol held in Geneva, delegates called on treaty parties to develop national strategies for reducing halon emissions and CFCs in metered dose inhalers. They also instituted an examination of the interdependence of actions under the Kyoto climate treaty and the Montreal Protocol. The Conference of Parties to the Montreal Protocol is slated for Nov. 17-27, 1998, in Cairo, Egypt.

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