A ciência no seu melhor

LUPER · 28 Set 2006 às 13:51

SUPER-COLD temperatures that may be a further indicator of global warming have helped produce an Antarctic ozone hole this year that rivals the largest.

Temperatures fell to minus 93 degrees Celsius in the upper atmosphere over the frozen continent in August, and the man-made hole expanded this week to nearly 28 million square kilometres.

The coldest air in 30 years of measurements was part of yearly weather variation over the South Pole which could also be linked to climate change, the CSIRO's Paul Fraser said yesterday

"Under climate change scenarios, there is global warming at the surface and increased cooling in the upper atmosphere," said Dr Fraser, the leader of the CSIRO's changing atmosphere research group.

"People are concerned about whether these extremely cold temperatures in the upper atmosphere are an indicator of that."

Ozone depletion is caused by man-made chemicals such as chlorofluorocarbons, which were used in spray cans and other consumer goods until the early 1980s. The chemicals eat the thin ozone layer that protects life on earth from harmful doses of the sun's ultraviolet radiation.

International bans have since been imposed on most ozone-depleting chemicals, but hopes of repair by 2050 were recently set back.

Scientists at NASA said in June that new models showed the ozone hole would not shrink significantly until about 2018, and the layer would not recover until about 2068 — a century after the damage was first done.

The World Meteorological Organisation reports show this year's hole grew rapidly in late August.

The largest hole yet measured, in 2000, was about 30 million square kilometres, Dr Fraser said.