New Zealand ozone researcher Greg Bodecker said Wednesday that 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.

Researcher Paul Fraser, of the Australian government-funded Commonwealth Scientific and Industrial Research Organization, or CSIRO, said the findings showed the value of international agreements aimed at protecting the climate.

Fraser said the recovery of the ozone layer was a result of international efforts to ban ozone-depleting chlorofluorocarbons in the mid-1990s.

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

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

The prohibition of CFCs - which were used in refrigerators, air conditioners and aerosol spray cans - came after it was found they were breaking up the earth's ozone, a thin layer of atmosphere that filters the sun's damaging ultraviolet rays and protects humans from skin cancer.

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

The CSIRO and Australia's Bureau of Meteorology have been monitoring and recording the level of chlorine in the troposphere over Australia's southern island state of Tasmania for several years.

Fraser, head of CSIRO's atmospheric research team, said while the ozone layer was yet to begin repairing itself the hole would probably start closing within five years, and should fully recover by 2050.

"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," Fraser told The Associated Press in a telephone interview on Tuesday.

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

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

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

Also 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, albeit slowly," the organizations said in a statement.