Alternatives to ozone-depleting chemicals in products like pesticides and aerosols are also contributing to climate change, according to a U.N. report released Monday.

Many of the more ozone-friendly chemicals were first put into products nearly a decade ago as part of a global accord on reducing the use of chlorofluorocarbons, or CFCs, that deplete the earth's protective ozone layer.

But since the Montreal Protocol went into effect in 1997, the less-harmful chemicals have accounted for about 5 percent of man-made greenhouse gas emissions, said the report from the United Nations Environment Program.

"There can be no trade-offs between saving the ozone layer and minimizing climate change," said UNEP Director Klaus Toepfer.

The UNEP's 31-page report outlined steps governments can take to curtail the use of these chemicals.

The agency suggests governments promote the containment of chemicals to prevent leaks, more recycling and the destruction of dangerous substances. It also suggests the use of alternatives such as ammonia and the development of new technologies that avoid harmful gasses.

Although there are few regulations for these types of chemicals under the Montreal Protocol or the Kyoto Protocol -- an international agreement to cut greenhouse gas emissions -- the UNEP believes that action on its proposals could halve the effect of these chemicals by 2015.

"When the CFCs were phased out, there was a preference for these new replacements," said Bert Metz, a climate change expert who contributed to the report. "But the (replacements) are strong greenhouse gases."

"Initially, it was thought these were an ideal solution -- obviously that was not the case if they were contributing to another problem."

While CFCs contribute more per unit to global warming, the rapid increase in the use of replacement chemicals makes them now the greater threat to climate stability, Metz told the AP in a telephone interview.

Governments should start thinking about how to replace these chemicals, he said, adding that a possible amendment to the Montreal Protocol setting reduction targets for them chemicals could serve as a starting point.

"These (chemicals) are rapidly growing right now," Metz said. "The amounts stored in equipment ten years from now will be a fivefold increase from today."

While it will take decades to purge the atmosphere, experts said last September that the ozone hole over Antarctica was markedly smaller for the second straight year, at 11 million square miles (28 million square kilometers), down from the huge 17 million square mile (44 million square kilometers) hole of 2002.

The Kyoto global warming pact, which went into force February, imposes legally binding requirements on 35 industrialized states to cut emissions of greenhouse gases an average of 5 percent below 1990 levels.

Average global temperatures rose about 1 degree in the 20th century, and scientists say that has contributed to the thawing of the permafrost, rising ocean levels and extreme weather. Experts say further increases could seriously disrupt ecosystems, agriculture and human lifestyles.

Source: Associated Press