WASHINGTON » With energy legislation shelved in the United States and little hope for a global climate change agreement this year, some policy experts are proposing a novel approach to curbing global warming: including greenhouse gases under an existing and highly successful international treaty ratified more than 20 years ago.

The treaty, the Montreal Protocol, was adopted in 1987 for a completely different purpose, to eliminate aerosols and other chemicals that were blowing a hole in the Earth’s protective ozone layer.

But as the signers of the protocol convened the 22nd annual meeting in Bangkok on Monday, negotiators are considering a proposed expansion in the ozone treaty to phase out the production and use of the industrial chemicals known as hydrofluorocarbons or HFCs. The chemicals have thousands of times the global warming potential of carbon dioxide, the most prevalent greenhouse gas.

HFCs are used as refrigerants in air conditioners and cooling systems. They are manufactured mostly in China and India, but appliances containing the substance are in use in every corner of the world. HFCs replaced even more dangerous ozone-depleting chemicals known as HCFCs, themselves a substitute for the chlorofluorocarbons that were the first big target of the Montreal process.

"Eliminating HFCs under the Montreal Protocol is the single biggest chunk of climate protection we can get in the next few years," said Durwood Zaelke, president of the Institute for Governance and Sustainable Development, a non-government organization based in Washington. He noted that the ozone protection effort had begun under former President Ronald Reagan and continues to enjoy bipartisan support.

The United States has thrown its support behind the proposal and negotiators said there was a strong current of support for the move at the meeting on Monday. All the signatories to the Montreal Protocol would have to agree to the expansion, but no further approval from Congress would be needed. So far, there has been no congressional or industry opposition to the idea.

But the plan is not expected to be adopted this year. Large developing countries, including China, India and Brazil, object that the timetable is too rapid and that payments for eliminating the refrigerant are not high enough.

One advantage to using the Montreal protocol as a vehicle, supporters say, is that negotiations over the treaty have been utterly unlike the contentious U.N. climate talks that foundered in Copenhagen last year. Negotiators say that without legislative action on curbing greenhouse gases by the United States, little progress will be made when countries gather in Cancun, Mexico, late this month for another round of climate talks.

In a post-election news conference, President Barack Obama noted that it was doubtful that Congress would do anything to address global warming "this year or next year or the year after."

Unlike the Kyoto Protocol, the Montreal treaty has been signed by all nations. They conduct their business with little drama and with broad scientific and technical input from governments and industry. The financing mechanisms, while occasionally contentious, are generally quickly resolved and seen as equitable.

The ozone treaty was unanimously ratified in 1988 by the U.S. Senate, which a decade later unanimously voted against adopting the Kyoto Protocol to address climate change. Montreal’s pollution reduction targets are mandatory, universally accepted and readily measurable. None of that is true of the climate process.

The Montreal Protocol has phased out nearly 97 percent of 100 ozone-depleting chemicals, some of which are also potent climate-altering gases. The net effect has been the elimination of the equivalent of more than 200 billion metric tons of global-warming gases, five years’ worth of total global emissions, far more than has been accomplished by the Kyoto process.

It has been, according to the former U.N. secretary-general Kofi Annan, "perhaps the most successful international agreement to date."

The proposal to eliminate HFCs was advanced several years ago by the tiny island nation of Micronesia, one of the places on Earth most vulnerable to sea-level rise and other global warming effects.

The United States quickly signed on. Along with Mexico and Canada, the Obama administration has proposed a rapid series of steps to reduce HFC production, with rich countries meeting a faster timetable than developing nations and helping to pay the poorer countries to find substitutes. But the Environmental Protection Agency estimates that adopting the HFC proposal could eliminate the equivalent of 88 billion metric tons of carbon dioxide by 2050, and slow global warming by a decade.

Daniel A. Reifsnyder, the deputy assistant secretary of state for environment and the nation’s chief Montreal Protocol negotiator, said that it might take several years to persuade the ozone treaty countries to back the plan.

In addition to pace and cost issues, some countries say that HFCs have little impact on the ozone layer and thus should be handled under the U.N. climate change talks. Reifsnyder dismissed that as a legalistic argument and said that the ozone treaty could and should be used to achieve broader environmental objectives.

"What we’ve found is that the Montreal Protocol has been a very effective instrument for addressing global environmental problems," Reifsnyder said in an interview. "It was created to deal with the ozone layer, but it also has tremendous ability to solve the climate problem if people are willing to use it that way."

Mario Molina, the Mexican scientist who shared the Nobel Prize in chemistry for his groundbreaking work in identifying the role of chlorofluorocarbon gases in the breach of the stratospheric ozone layer, said that it might take two or three years for other countries to see the virtues of the HFC reduction.

"My hope is that everybody will agree with this proposal from the United States and Mexico and a few other countries because the Montreal Protocol has been so successful at controlling these industrial chemicals," he said in an interview from his institute in Mexico City.

Molina said that extending the protocol to include HFCs could reduce the threat of climate change by several times what the Kyoto Protocol proposes. He noted that the climate treaty had fallen far short of its goals, and that there was no agreement on what should replace it when its major provisions expired in 2012.

"We understand it’s a stretch to use an international agreement designed for another purpose," he said. "But dealing with these chemicals and using this treaty to protect the planet makes a lot of sense."

© 2010 The New York Times Company