Continued decline of total ozone over Halley, Antarctica, since 1985

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IN 1985, Farman et al.1 announced that a dramatic reduction in total ozone was occurring in the atmosphere over Halley, Antarctica, during the polar spring. Analysis of satellite data revealed that this ozone depletion was an Antarctic-wide phenomenon2. Combined theoretical3a¤-5, observational6,7 and laboratory8 work has shown that chlorine radicals derived from the photolysis of chlorofluorocarbons were the dominant cause of the ozone loss9a¤-11. Ten years later, we review here the status of the 'ozone hole' based on the continued total-ozone measurements at Halley. The springtime a¤˜ozone holea¤™ continues to deepen, with both the October mean and minimum total ozone persistently decreasing. The ozone loss extends into January and February, so that significant increases in ultraviolet-B radiation can be expected at the surface over Antarctica during the summer. A signal of ozone loss is now apparent in the spring and summer temperature records, with recent temperatures at the 100-mbar level consistently close to, or colder than, the historical (1957a¤-72) minima for the period October to January. These low temperatures may well enable the maintenance of springtime ozone-loss mechanisms until later in the year.