By SETH BORENSTEIN
WASHINGTON (AP) – Earth's protective ozone layer eventually heals from damage caused by aerosol sprays and refrigerants, according to a new United Nations report.
The ozone layer had become thinner since the late 1970s. Scientists have raised the alarm and ozone-depleting chemicals have been abolished worldwide.
Therefore, the upper ozone layer over the northern hemisphere should be completely repaired in the 2030s, and the gaping ozone hole of the Antarctic should disappear in the 2060s. A scientific assessment was released on Monday at a conference in Quito (Ecuador). The southern hemisphere has lagged slightly and its ozone layer should be healed by the middle of the century.
"It's really good news," said Paul Newman, co-chair of the report, senior Earth scientist at the Goddard Space Flight Center at NASA. "If ozone depleting substances had continued to increase, we would have seen tremendous effects. We stopped it. "
Ozone protects the earth high in the atmosphere from ultraviolet rays that cause skin cancer, crop damage and other problems. The use of artificial chemicals, the so-called chlorofluorocarbons (CFCs), which release chlorine and bromine, began to dissolve in ozone. In 1
In the worst case of the late 1990s, about 10 percent of the upper ozone layer was depleted, Newman said. Since 2000, it has risen by about 1 to 3 percent per decade.
This year, the ozone hole at the South Pole reached nearly 9.6 million square kilometers. This is about 16 percent less than the largest recorded hole – 11.4 million square miles in 2006.
The hole reaches its peak in September and October and disappears in late December until the next spring of the Southern Hemisphere, Newman said.
The Ozone The layer begins about 10 km above the earth and stretches for almost 40 km. Ozone is a colorless combination of three oxygen atoms.
If nothing had stopped the thinning out, the world would have destroyed two-thirds of its ozone layer by 2065, Newman said.
But it's not a complete success Yet, Brian Toon of the University of Colorado, who was not part of the report, said.
"We are only at a point where recovery could have started," Toon said, pointing to some ozone measurements that have not yet risen.
Another problem is that the new technology has detected an increase in the emissions of a banned CFC from East Asia.
The ozone hole alone has easily shielded the Antarctic from the much larger effects of global warming. "It's getting hot, but not as much as it would without ozone depletion," said Ross Salawitch, an atmospheric scientist at the University of Maryland. who wrote the report.
A healed ozone layer will therefore worsen the man-made climate change there a bit, Newman said.
Scientists do not know how much a healed ozone hole will keep the Antarctic warming, but they know the immediate impact of ozone depletion on the world and human health. Therefore, it would be "irresponsible not to do that," Salawitch said.
And the replacement now being used to cool cars and refrigerators needs to be replaced with chemicals that will not exacerbate global warming, Newman said. An amendment to the Montreal Protocol, which will come into force next year, would restrict the use of some of these gases.
"I do not think we can drive a winning round by 2060," Newman said. "That will be for our grandchildren."