This bulletin on the state of the ozone over the Antarctic region was released August 25, 2000, by the Switzerland-based World Meteorological Organization (WMO). WMO Bulletins, released twice monthly between August and December, are based upon provisional data from the WMO Global Atmosphere Watch (GAW) stations. The purpose of these reports is to view changes in ozone over time. Averaged ground-based data from 1964 to 1976 (WMO Scientific Assessment of Ozone Depletion: 1998) are used to infer changes in current ozone amounts from pre-ozone hole conditions. The August 25 Bulletin is an update to that of August 11. This report shows an average decrease of about 30 percent in the total amount of ozone overhead when compared to the 1964-76 norms. This is double the fifteen percent reported August 11 and is unusual for this time of year.
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