Continued decline of total ozone over Halley, Antarctica, since 1985
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 theoretical3á¤-5, observational6,7 and laboratory8 work has shown that chlorine radicals derived from the photolysis of chlorofluorocarbons were the dominant cause of the ozone loss9á¤-11. Ten years later, we review here the status of the 'ozone hole' based on the continued total-ozone measurements at Halley. The springtime á¤˜ozone holeá¤™ 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 (1957á¤-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.