Scientists say there is good news for the ozone layer in the atmosphere that protects the earth from harmful ultraviolet solar rays. Global efforts to halt the effects of ozone-depleting chemicals are working.
The ozone hole isn't really a hole at all. It is a thinning of the protective ozone layer in the earth's atmosphere. In 1986 Susan Solomon, senior scientist with the National Oceanic Atmospheric Administration, led an expedition to Antarctica to check out what British scientists had detected the year before. "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," she says, adding that is about "twice the size of the continental United States."
Solomon's team put the blame on chlorofluorocarbons (or CFCs), industrially produced chemicals, which had been used since the 1930s as refrigerants and propellants in products like aerosol sprays. Solomon says these ozone-depleting chemicals do not cause global climate change, but DO have adverse effects on human health and ecosystems. "If we have a thinner ozone layer, we have a increased risk of skin cancer. If we have a thinner ozone layer, we have an increased risk of cataracts," she says. "There are [also] questions about the kinds of biological effects that can result. People in the Antarctic program in particular study things like whether changes in the ultraviolet [rays] due to the ozone hole can effect krill and other things in the southern oceans."
The international community acted quickly to address these problems. By 1989 a United Nations treaty was in place to phase out CFCs.
Ten years later, CFC production had dropped by 90 percent. David Hofman, who heads Global Monitoring for the National Oceanic and Atmospheric Administration, says the news is good. "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."
Susan Solomon says one obstacle is to contain CFC's from sources not anticipated by the U.N. treaty such as used refrigerators, air conditioning units and insulated foams from landfills and demolition sites. "They are continuing to leak to the atmosphere, actually in levels somewhat higher than we would have thought," she says.
Solomon expects a full recovery of the ozone hole by 2060. But, she cautions, a lot of work must be done to reach that goal. "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 internationally have been effective."
CFCs are long-lived and remain in the atmosphere for 50 to 100 years. But with global phase-out efforts, Solomon expects to see signs of a reduction in the ozone hole within a decade. Her job, she says, is to measure that process.