The Carbon Dioxide over Antarctica is most likely venting through one of the largest ozone holes ever recorded.
The hole over Antarctica's ozone layer is bigger than last year and is nearing the record 29-million-square-kilometre hole seen in 2000, the World Meteorological Organisation said.
Geir Braathen, the United Nations weather agency's top ozone expert, said ozone depletion had a late onset in this year's southern hemisphere winter, when low temperatures normally trigger chemical reactions that break down the atmospheric layer that filters dangerous solar radiation.
"The ozone depletion started quite late, but when it started it came quite rapidly," Braathen told journalists in Geneva on Friday.
"It (the hole) has now risen to a level that has passed last year's, and is very close to, if not equal to, the ozone hole size of 2003, and also approaching the size of 2000," he said.
The Antarctic ozone hole was at its second-largest in 2003.
While use of ozone-depleting chlorofluorocarbons (CFCs) has waned, Braathen said large amounts of chlorine and bromine remain in the atmosphere and would keep causing large reductions in the Antarctic ozone layer for many years to come.
"We will for the next couple of decades expect to see recurring ozone holes of the size that we see now," he said.
The WMO and the UN Environment Programme said in August that the protective layer would likely return to pre-1980 levels by 2049 over much of Europe, North America, Asia, Australasia, Latin America and Africa.
In Antarctica, the agencies said ozone layer recovery would likely be delayed until 2065.
