Would SETH BORENSTEIN
VASHINGTON (AP) – The protective ozone layer of the Earth has finally grown from damage due to aerosol sprays and coolants, according to a new report from the United Nations.
The ozone layer has been reduced since the late seventies. The scientists raised the alarm and the ozone-depleting chemicals were abolished around the world.
As a result, the upper layer of ozone above the northern hemisphere should be completely repaired during the 2030s, and the open Antarctic ozone hole should disappear in the 2060s, according to a scientific assessment released Monday at a conference in Kitou, Ecuador. The southern hemisphere is a bit lagging and its ozone layer needs to be healed by the middle of the century.
"It's really good news," said co-chairman Paul Nevman, chief Earth scientist at NASA's Goddard Flight Center. "If ozone-depleting substances continue to grow, we will see tremendous effects. We stopped this."
High in the atmosphere, ozone shield Earth from ultraviolet rays that cause skin cancer, damage to crops and other problems. The use of chemicals made from a human called chlorofluorocarbons (CFCs), released by chlorine and bromine, began to eat in ozone. In 1987, countries from all over the world agreed in the Montreal Protocol to abolish CFCs, and companies have replaced substitutes for spray cans and other purposes.
At the worst in the late nineties, about 10 percent of the upper ozone layer was exhausted, Nevman said. Since 2000, it has grown by about 1 to 3 percent per decade, the report said.
This year, the ozone hole on the southern pole reached almost 9.6 million square miles. That is about 16 percent less than the largest recorded hole – 11.4 million square miles in 2006.
The hole reached its peak in September and October and disappears in late December until the next spring of the Southern Hemisphere, said Nevman.
The ozone layer starts at about 6 miles (10 kilometers) above the Earth and stretches for almost 25 miles (40 kilometers); Ozone is a colorless combination of three oxygen atoms.
If nothing has been done to stop prosecutions, the world would have destroyed two-thirds of its ozone layer by 2065, Nevman said.
But this is not yet a complete success, said Brian Toon of the University of Colorado, who was not part of the report.
"We are only in a place where recovery may have begun," Toon said, pointing to some of the ozone measures that have not yet risen.
Another problem is that the new technology has found an increase in banned CFC emissions from East Asia, the report said.
By itself, the ozone hole has mildly protected Antarctica from the much larger effects of global warming – it has warmed up, but not as much as it would probably have been without ozone depletion, said Ross Salavitch, atmospheric science scientist at the University of Marilanda who co-authored the report .
So, the heaviest ozone layer will exacerbate climate change caused by humans, said Nevman.
Scientists do not know how much the infected ozone hole will further warm Antarctica, but know the immediate consequences of reducing ozone to the world and human health, and "it would be incredibly irresponsible not to do so," Salavitch said.
And replacements now used to cool cars and refrigerators have to be replaced by chemicals that do not deteriorate global warming, Nevman said. An amendment to the Montreal Protocol that comes into force next year would reduce the use of some of these gases.
"I do not think we can make a winning circuit by 2060," said Nevman. "That's what our grandsons will do."