BY SETH BORENSTEIN WASHINGTON (AP) – Earth's protective ozone layer is finally healing from damage caused by aerosol sprays and…
BY SETH BORENSTEIN
WASHINGTON (AP) – Earth’s protective ozone layer is finally healing from damage caused by aerosol sprays and coolants, a United Nations report said.
The ozone layer had been thinning since the late 1970s . Scientists 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 Monday at a conference in Quito, Ecuador. The Southern Hemisphere is 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. We stopped that. “
High in the atmosphere, ozone shields Earth from ultraviolet rays that cause skin cancer, crop damage and other problems. Gebruik van man-made chemicaliën genoemd chlorofluorocarbons (CFCs), which released chlorine and bromine, began eating away at the ozone. In 1
987, landen rond de wereld overeengekomen in het Montreal-protocol om CFC’s uit te vallen en bedrijven kwamen op met vervangingen voor spuitcans en andere toepassingen.
Op zijn ergst in de late jaren 1990 was ongeveer 10 procent van de bovenste ozonlaag depleted , said Newman. Since 2000, it has increased by about 1 to 3 percent per decade, the report said.
This year, the ozone hole across the South Pole peaked at nearly 9.6 million square miles. That’s about 16 percent less than the largest hole recorded – 11.4 million square miles in 2006.
The hole reaches its peak in September and October and disappears by late December until the next Southern Hemisphere jump, Newman said.
The ozone layer starts at about 6 miles (10 miles) above Earth and stretches for almost 25 miles (40 kilometers); ozone is a colorless 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, said University of Colorado’s Brian Toon, who was not part of the report.
“We are only at a point where recovery may have started,” said said, pointing to some ozone measurements that have not yet been increased.
Another problem is that new technology has found an increase in emissions of a banned CFC out of East Asia, the report noted.
On its own, the ozone hole has slightly shielded Antarctica from the much greater effects of global warming – It has heated up but not as much as it would likely without ozone depletion, said Ross Salawitch, a University of Maryland atmospheric scientist who co-authored the report.
So a healed ozone layer will worsen man-made climate change there a bit, newman said.
Scientists do not know how much a healed ozone hole will further warm Antarctica, but they do know the immediate effects of ozone depletion on the world and human health, so “it would be incredibly irresponsible not to do this,” Salawitch said.
And the replacements now being used to cool cars and refrigerators need to be replaced themselves with chemicals that do not worsen global warming, Newman said. An amendment to the Montreal Protocol that will go into effect next year would cut use of some of those gases.
“I do not think we can do a victory lap until 2060,” Newman said. “That will be for our grandchildren to do.”