The hole in the earth's protective ozone layer is stable. David Hofman with the National Oceanic and Atmospheric Administration (NOAA) made that assessment at a news conference this week in Washington.
"In Antarctica we say the patient is not getting any sicker, because the ozone hole is not getting any deeper or any broader. The data indicates that the reduction in ozone has stopped. It has come down and flattened out. It is not getting any worse. This is what has been called the first stage of ozone recovery."
Senior NOAA scientist Susan Solomon says recovery in human terms means fewer adverse health effects.
"If you have less ozone you have increased ultraviolet light at the surface and that can cause a variety of biological impacts. One of the most publicized ones is the increase in skin cancer in light skinned people. If we have a thinner ozone layer we have an increased risk of cataracts."
Solomon has followed these trends for more than 20 years. In 1986 she led an expedition to Antarctica to check the ozone hole. It had been detected the year before by British scientists.
"There were a lot of doubts in the scientific community at that time that the ozone hole was even real. But certainly there is not doubt anymore that the ozone hole is a real phenomenon, and that it covers essentially the entire Antarctic continent, which is something on the order of twice the size of the continental United States."
Solomon's team put the blame on chlorofluorocarbons or CFCs -- industrially produced chemicals found in aerosol sprays and refrigerants. The international community responded quickly. By 1989 a United Nations treaty was in place to phase out the harmful chemicals. CFC production had dropped by 90 percent by the late 1990s.
But CFC's still leak from sources not anticipated in the global agreement such as discarded refrigerators and air conditioners, along with insulated foam from landfills and demolition sites.
CFCs remain in the atmosphere for 50 to 100 years. But because of global eradication efforts, Solomon expects to see signs of a reduction in the ozone hole within a decade.
"I think that it is very important to make sure that we actually measure ozone - not only not getting any worse, but actually starting to improve to make sure that the actions that we have taken internationaly have been effective."
Solomon says she expects the ozone hole to be fully restored by 2060.
