Scientists estimate that an increase in average global temperatures of three degrees Fahrenheit could tip the planet into a dangerous future of rising sea levels, devastating droughts, extreme storms and shortages of food and water. Studies show that banning HFCs worldwide could prevent an increase of nearly one degree over the next century.
“Amending the Montreal Protocol to phase down HFCs is one of the single most important unitary steps that we could possibly take at this moment to stave off the worst impacts of climate change and to protect the future for people in every single corner of the globe,” Secretary of State John Kerry said in a speech to negotiators in Vienna on Friday.
An amendment to the Montreal Protocol would have the force of law in almost every country, which could give it more potency than the Paris Agreement, a legal hybrid that lacks the binding force of a treaty. While some portions of the Paris Agreement are legally binding, the specific actions taken by countries to reduce their emissions are voluntary. And there are already questions about whether some countries will follow through on their Paris pledges.
In Brazil, the impeachment proceedings against President Dilma Rousseff have thrown the fate of her Paris promise into question. Rodrigo Duterte, the new president of the Philippines, said this month that he would not honor the Paris agreement. And in the United States, Donald J. Trump, the Republican presidential nominee, has vowed to “cancel” the Paris accord.
Most countries support some form of a deal to phase out HFCs, but some with developing economies, led by India, are pushing for a slow timeline. While the United States wants a deal that would phase out production of the chemicals in five years, Indian diplomats are pushing for 15. They say the costs of new substitute coolants will disproportionately affect the residents of developing countries in warm climates, where the use of air conditioning is expected to soar in coming decades.
“An earlier date would impose economywide costs on India,” said Arunabha Ghosh, the chief executive of the Council on Energy, Environment and Water in New Delhi. “The cost of alternative refrigerants are eight to 10 times what is available.”
President Obama, who has sought to make climate change prevention a cornerstone of his legacy, has spoken at length with Prime Minister Narendra Modi of India about reaching a deal, and Mr. Kerry flew to Vienna on Friday to personally engage in the negotiations. In his speech on Friday, he pledged that a final deal would include assistance from rich countries to help poorer ones deal with the cost of transitioning to the new chemicals, although he did not specify a dollar amount.
Final details of timing and financial aid are expected to be established at the October meeting in Kigali.
Many large American chemical companies are pushing hard for the amendment. Final passage of the deal could create a new market for their coolants in refrigerators and air-conditioners around the world.
“Our member companies pushed for this amendment for years,” said Francis Dietz, a vice president of the Air-Conditioning, Heating and Refrigeration Institute, a lobbying group. “It’s sort of unusual for industry to spend a lot of time trying to get regulated. But we knew regulations of HFCs were coming down the pike, and we’re ready.”
Honeywell, the New Jersey-based multinational company that produces everything from aerospace systems to home thermostats, has already invested $900 million in developing and patenting an HFC substitute, now being made in two recently built plants in Baton Rouge, La. A third plant in Louisiana is planned for next year, in anticipation of a booming demand for the products after passage of the Montreal Protocol amendment.
“We began developing replacements for HFCs years ago,” said Ken Gayer, a vice president with Honeywell. Mr. Gayer said the company was already planning to make the new cooling products in India and China.
The deal’s support from major businesses has blunted much of the criticism that many Republicans in the United States typically bring to debates about efforts to control global warming. Obama administration officials have pointed out that the Montreal Protocol itself, which was largely negotiated by President Ronald Reagan, has long enjoyed bipartisan support. Those circumstances, and the relatively low profile of the Vienna talks, appear to have kept the HFC amendment out of the political fray that often surrounds climate change policy.
Gina McCarthy, the Environmental Protection Agency administrator, who has led the United States delegation in Vienna, noted the change.
“It’s very different from the Paris climate meetings,” she said. “It’s not been the same political dynamics as in that world.”
An earlier version of this article misstated proposals by the United States and India for limiting hydrofluorocarbons. The United States wants a deal that would phase out production in five years, not “within 10 years,” and India is pushing for a timeline of 15 years, not 15 to 20 years.