Ozone layer is healing: UN

The Associated Press
Seth Borenstein

WASHINGTON–Earth’s protective ozone layer finally is healing from damage caused by aerosol sprays and coolants, a new United Nations report said.
The ozone layer had been thinning since the late 1970s.
Scientist raised the alarm and ozone-depleting chemicals were phased out worldwide.
As a result, the upper ozone layer above the Northern Hemisphere should be completely repaired in the 2030s and the gaping Antarctic ozone hole should disappear in the 2060s, according to a scientific assessment released today at a conference in Quito, Ecuador.
The Southern Hemisphere lags a bit and its ozone layer should be healed by mid-century.
“It’s really good news,” said report co-chairman Paul Newman, chief Earth scientist at NASA’s Goddard Space Flight Center.
“If ozone-depleting substances had continued to increase, we would have seen huge effects,” he noted.
“We stopped that.”
High in the atmosphere, ozone shields Earth from ultraviolet rays that cause skin cancer, crop damage, and other problems.
Use of man-made chemicals called chlorofluorocarbons (CFCs), which release chlorine and bromine, began eating away at the ozone.
In 1987, countries around the world agreed in the Montreal Protocol to phase out CFCs and businesses came up with replacements for spray cans and other uses.
At its worst in the late 1990s, about 10 percent of the upper ozone layer was depleted, Newman said.
Since 2000, it has increased by about one-three percent per decade, the report noted.
This year, the ozone hole over the South Pole peaked at nearly 24.8 million square km. That’s about 16 percent smaller than the biggest hole recorded–29.6 million square km–in 2006.
The hole reaches its peak in September and October, then disappears by late December until the next Southern Hemisphere spring, Newman said.
The ozone layer starts at about 10 km above Earth and stretches for nearly 40 km.
Ozone is a colourless combination of three oxygen atoms.
If nothing had been done to stop the thinning, the world would have destroyed two-thirds of its ozone layer by 2065, Newman said.
But it’s not a complete success yet, warned University of Colorado’s Brian Toon, who wasn’t part of the report.
“We are only at a point where recovery may have started,” Toon said, pointing to some ozone measurements that haven’t increased yet.
“I don’t think we can do a victory lap until 2060,” Newman conceded.
“That will be for our grandchildren to do.”