Ozone hole expected to close within 50 years

New finding of decreased airborne CFCs creates optimism that atmosphere will start to heal soon.

From staff and wire reports

September 19, 2002

SYDNEY, AUSTRALIA-Chlorine-based chemical levels in the atmosphere are falling, and the hole in the ozone layer over Antarctica should close within 50 years, an Australian government-funded study says.

The finding offers the latest strong support for the work of University of California, Irvine, scientists, including F. Sherwood Rowland, who first warned that chemicals called cholorofluorocarbons, or CFCs, were destroying the ozone layer. They were ridiculed for their work for years before being vindicated by the discovery of a massive hole in the ozone layer over Antarctica.

Rowland, along with Mario Molina and Paul Crutzen, won a Nobel Prize in 1995 for their work.

Although the ozone layer has not yet begun to repair itself, the hole will probably start closing within five-years, and should fully recover by 2050, said Paul Fraser, of the Australian government-funded Commonwealth Scientific and Industrial Research Organization.

Fraser credited the ozone layer's recovery to international efforts to ban ozone-depleting chlorofluorocarbons in the mid-1990s.

In a telephone interview with the Associated Press this week, Fraser said, "Once CFCs have been phased out of the developing world by about 2005, the most persistent ozone-depleting chemicals in the atmosphere will no longer be released in any significant amounts.

"That means that the atmosphere can work its magic and start to destroy these chemicals at a rate faster than they're being released."

Fraser and UCI researchers said the discovery proved that direct action taken by the international community on environmental issues could make a difference.

"This is an amazing story," said UCI Chancellor Ralph Cicerone, one of two researchers who discovered that chlorine destorys ozone before Molina and Rowland independently reached the same conclusion. "I hope we can do the same thing with anything else that develops in the future."

Before they were banned, CFCs were widely used in aerosol spray cans, air conditioners and refrigerators.

Depletion of ozone is a matter of global concern because it allows dangerous ultraviolet radiation to reach the Earth's surface, causing health problems such as increased rates of skin cancer.

The Australian researchers' atmospheric monitoring has found that chlorine from CFCs leveled off in the troposphere-the lower atmosphere-two years ago, and is falling for the first time in more than 20 years.

The ozone layer over Antarctica has suffered the most damage from CFCs, which have eaten a hole about 10 million square miles in size-about three times the size of Australia.

CFCs were banned in the developed world in the mid-1990s after a pact signed at a 1989 international conference in Montreal. They are still being phased out in developing countries.

Scientists expect the chlorine decrease to lead to a gradual recovery of the ozone layer during the next half century. In turn, the ozone recovery will decrease the risk of skin cancer and similar ailments in the far Southern Hemisphere, where damage to the protective layer of gas is most serious.

The ozone recovery will not alleviate projected problems related to global- warming woes. Those problems are caused by the release of other heat-trapping gases into the atmosphere.

The Australian findings match the expectations of UCI researchers, who first sounded the alarm in 1974. Rowland, as the most visible of the scientists, took the most heat for showing that civilization was harming the planet, his colleagues said.

"He got it from Joe Citzen, from the big shots at DuPont," said Don Blake, an atmospheric researcher at UCI who still works with Rowland, now 75. "He got it from wherever."

But Rowland, who was in Italy on Wednesday and could not be reached, persevered, even campaigning for a ban on CFCs.

Blake, who came to UCI as a graduate student under Rowland in 1978, said the attacks continued until the mid-1980s. Even President Ronald Reagan, he said, declined to regulate CFCs, demanding proof that they were causing harm.

That came in 1985, when other researchers discovered a gaping hole in the ozone layer over Antarctica.

Since then, measurements have shown that the hole fluctuates seasonally.

When Rowland won his Nobel Prize, he predicted that it would be several decades before ozone damage leveled off and the ozone layer began to repair itself.

The Australian researchers' findings back up that prediction.

New Zealand ozone researcher Greg Bodecker, when asked about the Australian findings Wednesday, said measurements from a number of sites around the world by several research groups" have confirmed that stratospheric chlorine levels have indeed peaked."

Measurements at one site in New Zealand have confirmed that stratospheric chlorine levels "are probably now decreasing." Bodecker said.

On Monday, scientists meeting in Utah said it would take 50 years for the hole in the ozone layer to disappear.

The "world is making steady progress toward the recovery of the ozone layer with the total amount of ozone-depleting chemicals in the lower atmosphere continuing to decline, albeith slowly, "the organizations said in a statement.

Also Monday, the U.N. Environmental Program and World Meteorological Organization said the ozone layer remains at risk despite signs of recovery.

UCI's Blake agreed, saying the prediction of recovery would hold only if there were no major atmosphere or climate changes in the years to come.