News in Science

Satellite finds ozone hole still shrinking

Shrinking hole The seasonal hole in the ozone layer above the Antarctic this year was the second smallest in two decades, but still covered an area three times the size of Australia, say US experts.

The average size of the hole in the Earth's protective shield was 17.9 million square kilometres, according to satellite measurements by the National Oceanic and Atmospheric Administration and NASA.

"It happened to be a bit warmer this year high in the atmosphere above Antarctica, and that meant we didn't see quite as much ozone depletion as we saw last year, when it was colder," says Jim Butler of NOAA's Earth System Research Laboratory.

The Antarctic ozone hole, which forms in September and October, reached its largest size for the season - 21 million square kilometres - on 22 September.

In comparison, the largest ozone hole recorded to date was one of 29.8 million square kilometres in the year 2000.

The ozone layer - which helps protect the Earth from potentially dangerous ultraviolet rays that can cause skin cancer and cataracts - began developing holes on an annual basis starting in the 1980s due to chlorofluorocarbons, or CFCs.

CFCs, once commonly used in refrigerators and aerosol cans, now are almost non-existent thanks to an international treaty signed on 16 September 1987, amid global concern over widening holes in the ozone layer.

Still, it could take another decade before scientists detect early signs that the ozone over the Antarctic is returning, says NOAA.

The ozone layer above Antarctica likely will not return to its early 1980s state until about 2060, according to NASA scientist Paul Newman.