Scientists now say it will take until 2065 for the ozone layer to recover and the hole over the Antarctic to close.
The atmosphere will take up to 15 years longer than previously expected to recover from pollution and repair its ozone hole over the southern hemisphere, the United Nations' weather organization said Friday.
Thinning in the ozone layer -- due to chemical compounds leaked from refrigerators, air conditioners and other devices -- exposes the Earth to harmful solar rays. Too much ultraviolet radiation can cause skin cancer and destroy tiny plants at the beginning of the food chain.
Scientists said Friday it would take until 2065, instead of 2050 as previously expected, for the ozone layer to recover and the hole over the Antarctic to close.
"The Antarctic ozone hole has not become more severe since the late 1990s, but large ozone holes are expected to occur for decades to come," ozone specialist Geir Braathen told reporters in summarizing a new report by the World Meteorological Organization and the U.N. Environment Program. The report will be released next year.
The ozone hole, a thinner-than-normal area in the upper stratosphere's radiation-absorbing gases, has formed each year since the mid-1980s at the end of the Antarctic winter in August, and generally is at its biggest in late September.
Experts said they extended the projected recovery because chlorofluorocarbons, or CFCs, would continue to leak into the atmosphere from air conditioners, aerosol spray cans and other equipment for years to come.
But there was cause for celebration, they said, noting a decline in CFCs in the first two atmospheric layers above Earth.
"The level of ozone-depleting substances continues to decline from its 1992-1994 peak in the troposphere and the late 1990s peak in the stratosphere," WMO secretary-general Michel Jarraud said in a statement.
Less of these chemicals are used every year, he said, after 180 countries in 1997 committed to reducing CFCs under the Montreal Protocal.
"This shows that the Montreal Protocol is effective and is working," he said.
Last year, the ozone hole reached about 27 million square kilometers (10 million square miles) on September 20 -- just below its largest size in 2003 of about 29 million square kilometers (11.2 million square miles), WMO experts said.
