Antarctica's ozone hole finally is starting to heal, a new study finds.
In a triumph of international cooperation over a man-made environmental problem, research from the United States and the United Kingdom shows that the September-October ozone hole is getting smaller and forming later in the year.
And the study in Thursday's journal Science also shows other indications that the ozone layer is improving after it was being eaten away by chemicals in aerosols and refrigerants.
Ozone is a combination of three oxygen atoms; high in the atmosphere, it shields Earth from ultraviolet rays.
The hole has shrunk by about 4.5 million square kilometres in the key month of September since the year 2000 - a decline of about one-fifth, the study found.
That difference is more than six times larger than the state of Texas.
It also is taking about 10 days longer to reach its largest size, according to the study.
The hole won't be completely closed until mid-century, but the healing is appearing earlier than scientists expected, said study lead author Susan Solomon of MIT.
"It isn't just that the patient is in remission," Solomon said.
"He's actually starting to get better. The patient got very sick in the '80s when we were pumping all that chlorine" into the atmosphere.
"I think it's a tremendous cause for hope" for fixing other environment problems, such as man-made climate change, said Solomon, who led two US Antarctic expeditions to measure the ozone layer in the 1980s and has also been a leader in studying global warming.
In the 1970s, scientists suggested that Earth's ozone layer - about 10 to 50 kilometres high in the stratosphere - was thinning because of chemicals called chlorofluorocarbons from aerosols and refrigerants.
The Montreal Protocol , a 1987 global treaty to phase out many of the ozone-depleting chemicals, led companies to develop new products that didn't eat away at the ozone layer.
Still, scientists said it would take time before the problem would heal.
Now it is actually getting better, not just stabilising, based on new observations using different methods to measure the ozone layer, Solomon said.
