Ozone layer making a recovery
Scientists caution it could take decades to restore
By Marsha Walton
ATLANTA, Georgia (CNN) -- Earth's ozone layer, which protects both humans and plant life from ultraviolet radiation from the sun, appears to be recovering.
A study just published by the Cooperative Institute for Research in Environmental Sciences shows declining ozone levels have leveled off from 1996 to 2002, and in some areas there even are small increases.
But scientists are cautious about the apparent recovery of the ozone layer, which they say has been thinning for many years because of the widespread use of several industrial chemicals.
"We will absolutely have to monitor for at least another decade before we can be confident," said Betsy Weatherhead, one of the researchers on the study published in the Journal of Geophysical Research.
In the mid-1970s scientists discovered that chlorine and bromine compounds, used widely for refrigeration and in aerosol products, was depleting the ozone layer in the stratosphere, from about 6 to 30 miles above Earth. When more UV rays reach Earth, people are more subject to skin cancer, cataracts and other diseases. There also may be consequences for plant life, including lower crop yields and an upset in the ocean's food chain.
The global effort to deal with the ozone problem gained momentum in the mid-1980s, when satellite evidence showed huge "ozone holes" over both the Arctic and Antarctic regions. Research indicated that ozone levels had declined by as much as 40 percent at the poles and about 10 percent over parts of North America, South America and Europe.
The 1987 Montreal Protocol, ratified by more than 180 nations, triggered changes in the manufacturing and design of products and processes that used chlorofluorocarbons, known as CFCs. The changes affected everything from cleaning products to deodorants to air conditioning.
"When I think of the project, there was just an amazing amount of collaboration, among chemical manufacturers, politicians, auto manufacturers, all realms of science and policy," Weatherhead said.
She said a team of statisticians and atmospheric scientists have been working together for 20 years to monitor and understand changes in the ozone layer. They have been collecting data from NASA and NOAA satellites and from ground stations in North America, Europe, Hawaii, Australia and New Zealand.
But even with indications of the beginning of an ozone recovery, Weatherhead said people still need to be conscious of the dangers of ultraviolet radiation. People should continue to use sunscreens and UV-blocking sunglasses to protect skin and eyes from the radiation that does make it to Earth's surface.
The worldwide effort now may seem like a fast-moving model of cooperation. But it did not seem that way for one of the scientists who identified the problem in 1974.
"Living through it did not seem so quick," said Sherwood Roland of the University of California at Irvine. Roland shared the 1995 Nobel Prize in Chemistry with Paul Crutzen and Mario Molina for their work in identifying the damage that CFCs could do to Earth's ozone layer.
"But the fact that we went from a two page paper in [the scientific journal] Nature in 1974 to worldwide control in 13 years; it does look quick," he said.
Roland says it could be another 40 years before there are significantly higher levels of atmospheric ozone. That's because the chemicals that reached Earth's atmosphere decades ago still are affecting ozone levels.
Both Roland and Weatherhead say there's another big unknown in understanding the ozone layer.
"The big question is, what role does climate change have in all of this?" Weatherhead said.
But the response to climate change issues already has been much different from reaction to the ozone problem.
"Changing from one style of refrigerator to another is a smaller and easier change than changing the way we all use fossil fuels," Weatherhead said.
"Everybody involved with the Montreal Protocol, the scientists, industry, government regulators, were all science oriented, and tended to believe science. That makes a difference. Most of the world call for action on global warming is more attuned to the science than the U.S. is," he said.