Ozone hole looms large, but not as big as it was
Commonwealth of Australia Bureau of Meteorology
26 September 2007
The Antarctic ozone hole is back and although it’s almost as big as previous years, the long term outlook for a return to better ozone levels remains good.
Over the past ten years the destruction of ozone has resulted in large ozone holes appearing over the Antarctic each spring with almost all growing to an area of more than 25 million square kilometres (about three times the size of Australia). This year, the Bureau of Meteorology reports that the hole has already reached that size but has not grown as large as the record 28 million square kilometre holes that developed during 2000, 2003 and 2006.
Ozone holes develop during spring because sunlight returning to the polar regions trigger chemical reactions that have remained dormant during the darkness of winter. The size and depth of the hole is determined by factors including the concentrations of ozone-depleting chemicals such as Chlorofluorocarbons (CFCs), as well as the temperature of the lower stratosphere. It is also influenced by broad scale atmospheric circulation patterns which vary significantly from year to year.
Though recent Antarctic ozone holes have been very large, measurements show that the concentrations of ozone-depleting substances in the lower atmosphere, such as CFCs, have peaked and are now slowly declining. In its most recent assessment of ozone depletion, compiled last year, the World Meteorological Organization stated that ozone levels are expected to return to pre-ozone-hole conditions between 2060 and 2075.
More information is available
from the World Meteorological Organization: