Scientists Optimistic About Ozone Recovery

WASHINGTON, DC, July 30, 2003 (ENS) - New observations show that the rate of ozone loss in the upper stratosphere is slowing and scientists credit the worldwide reduction in chlorofluorocarbon (CFCs) pollution.

The levels of ozone destroying chlorine in the upper stratosphere have peaked and are going down, scientists report in a study to be published in the American Geophysical Union's "Journal of Geophysical Research - Atmospheres."

"This is the beginning of a recovery of the ozone layer," said Michael Newchurch an atmospheric chemist at the University of Alabama in Huntsville, the scientist who led the ozone trend analysis research team. "We had a monumental problem of global scale that we have started to solve."

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Michael Newchurch is associate research professor in the Atmospheric Science Department University of Alabama in Huntsville, senior research scientist with the Earth System Science Center, and a scientist with the National Center for Atmospheric Research, Atmospheric Chemistry Division. (Photo courtesy NSSTC)
Ozone is a damaging pollutant in the lower atmosphere near the ground, but in the stratosphere, it shields the Earth from harmful ultraviolet solar radiation.

Some three decades ago scientists found that chlorine released into the stratosphere from CFCs - chemicals used as refrigerants and aerosol propellants - was destroying the protective ozone layer. An international ban on CFC-based products was signed in 1987 and Newchurch says "now, we can say that what we are doing is working, and we should continue the ban."

"We are not gaining ozone," Newchurch cautions, "we are just losing it less quickly."

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1997 hole in the Arctic ozone layer is shown by the dark blue color. (Photo courtesy NASA)
Using data from three National Aeronautics and Space Administration (NASA) satellites and three international ground stations, the team found that ozone depletion in the upper stratosphere - the layer of the atmosphere between 35 and 45 kilometers (22 and 28 miles) above the ground - has slowed since 1997.

The slowing of ozone destruction is seen only in the upper stratosphere, where ozone depletion is due primarily to chlorine pollution, Newchurch said.

"But there is not much ozone up there, and it has a small effect on the total ozone column," he said. "We do not see compelling evidence that the destruction of ozone is slowing in the lower stratosphere, where 80 percent of the protective ozone layer exists."

The trend line is flattening, Newchurch added, although the amount of chlorine in that layer of the stratosphere has not yet peaked.

But it has "slowed down significantly," he said.

Recovery of the ozone layer in the lower stratosphere requires more than just fixing the chlorine problem, according to Newchurch, because of the impact from the concentration of greenhouse gases, such as carbon dioxide and methane.