[ad_1]
WASHINGTON – The Earth's protective ozone layer is finally healing aerosol and coolant damage, says a new UN report.
The ozone layer has cleared since the late 1970s. Scientists have sounded the alarm and ozone depleting chemicals have been eliminated worldwide.
As a result, the upper ozone layer over the northern hemisphere is expected to be fully repaired in the 2030s and the gaping hole of the Antarctic ozone layer is expected to disappear in the 2060s, according to a scientific badessment released Monday at a conference in Quito, Ecuador. The southern hemisphere is lagging behind and its ozone layer should be healed by the middle of the century.
"This is very good news," said Paul Newman, co-chair of the report, senior science scientist in Earth Sciences at NASA's Goddard Space Flight Center. "If ozone – depleting substances continued to increase, we would have had enormous effects. We stopped that. "
High in the atmosphere, ozone protects the Earth from ultraviolet rays that cause skin cancer, crop damage and other problems. The use of synthetic chemicals, called chlorofluorocarbons (CFCs), which give off chlorine and bromine, began to eat away at ozone. In 1987, countries around the world agreed in the Montreal Protocol to phased out CFCs and companies proposed alternatives for aerosol cans and other uses.
At the worst of the late 1990s, about 10 percent of the top ozone layer was depleted, Newman said. Since 2000, it has increased by about 1 to 3% per decade, the report says.
This year, the hole in the ozone layer above the South Pole has peaked at nearly 24.8 million square kilometers. That's about 16% less than the largest hole recorded – 29.6 million square kilometers (11.4 million square miles) in 2006.
The hole peaks in September and October and disappears in late December until next spring in the southern hemisphere, Newman said.
The ozone layer starts at about 10 km from the Earth and extends for nearly 40 km; Ozone is a colorless combination of three atoms of oxygen.
If nothing had been done to stop the thinning, the world would have destroyed two-thirds of its ozone layer by 2065, said Newman.
But it's not yet a complete success, said Brian Toon of the University of Colorado, which was not part of the report.
"We are only at a point where recovery may have begun," said Toon, noting that some ozone measurements have not yet increased.
Another problem is that new technology has seen an increase in emissions of a banned CFC from East Asia, the report noted.
And the alternatives currently used to cool cars and refrigerators must themselves be replaced by chemicals that do not worsen global warming, Newman said. An amendment to the Montreal Protocol, which will enter into force next year, would reduce the use of some of these gases.
"I do not think we can make a victory lap until 2060," Newman said. "It will be up to our grandchildren to do."
–
Follow Seth Borenstein on Twitter: @borenbears.
–
The Associated Press Science & Science Department is supported by the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content.
Source link
