And concentrations of the newer, ozone-friendly gases are also rising meteorically, because industrialized countries began switching to them a decade ago. New room air-conditioners in the United States now use an HFC coolant called 410a, labeled “environmentally friendly” because it spares the ozone. But its warming effect is 2,100 times that of carbon dioxide. And the treaty cannot control the rise of these coolants because it regulates only ozone-depleting gases.

The treaty timetable requires dozens of developing countries, including China and India, to also begin switching next year from HCFCs to gases with less impact on the ozone. But the United States and other wealthy nations are prodding them to choose ones that do not warm the planet. This week in Rio de Janeiro, Secretary of State Hillary Rodham Clinton is attending the United Nations Conference on Sustainable Development, also known as Rio+20, where proposals to gradually eliminate HFCs for their warming effect are on the provisional agenda.

But she faces resistance because the United States is essentially telling the other nations to do what it has not: to leapfrog this generation of coolants. The trouble is, there are currently no readily available commercial ozone-friendly alternatives for air-conditioners that do not also have a strong warming effect — though there are many on the horizon.

Nearly all chemical and air-conditioning companies — including DuPont, the American chemical giant, and Daikin, one of Japan’s leading appliance manufacturers — have developed air-conditioning appliances and gases that do not contribute to global warming. Companies have even erected factories to produce them.

But these products require regulatory approvals before they can be sold, and the development of new safety standards, because the gases in them are often flammable or toxic. And with profits booming from current cooling systems and no effective regulation of HFCs, there is little incentive for countries or companies to move the new designs to market.

“There are no good solutions right now — that’s why countries are grappling, tapping in the dark,” said Rajendra Shende, the recently retired head of the Paris-based United Nations ozone program, who now runs the Terre Policy Center in Pune, India.