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 phenomenon(2). Combined theoretical(3-5), observational(6,7) and laboratory(8) work has shown that chlorine radicals derived from the photolysis of chlorofluorocarbons were the dominant cause of the ozone loss(9-11). Ten years later, we review here the status of the 'ozone hole' based on the continued total-ozone measurements at Halley. The springtime 'ozone hole' 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 (1957-72) 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.