Nearly six years after the United States helped negotiate it, the Senate has ratified a global climate treaty that would formally phase down the use of hydrofluorocarbons, or HFCs, industrial chemicals commonly found in air conditioners and refrigerators, insulating foams and pharmaceutical inhalers.

The Kigali Amendment, an addition to the Montreal Protocol climate treaty, aims to drastically reduce the global use of the compounds.

"This measure will go a long way to lowering global temperatures while also creating tens of thousands of American jobs," Senate Majority Leader Chuck Schumer said before Wednesday's vote, which passed 69-27.

HFCs were widely adopted in the 1980s and 1990s to replace another family of chemicals, chlorofluorocarbon, or CFCs, which damage the Earth's ozone layer. But after the switch, HFCs emerged as some of the most potent greenhouse gases, hundreds to thousands of times more potent than carbon dioxide.

Successfully phasing out HFCs around the globe could reduce warming by up to 0.5 degrees Celsius (or about 1 degree Fahrenheit) by the end of the century, according to the Environmental Protection Agency. As the world struggles to limit warming this century to 1.5 degrees Celsius to try to avoid several catastrophic tipping points, half a degree can make a major difference, said scientists.

The U.S. is already taking steps to eliminate HFCs

Reducing HFCs is one area of climate policy where environmentalists, manufacturers and politicians tend to agree.

"Stakeholders, from business to environmental groups, have urged the Senate to ratify the strongly bipartisan Kigali Amendment," said Stephen Yurek, president and CEO of the Air-Conditioning, Heating, and Refrigeration Institute, a trade organization.

Republicans have supported the phase-down as being good for business, while Democrats and climate activists praise it as good climate policy. The United States was involved in negotiating the terms of the amendment, which was signed in Kigali, Rwanda, in 2016, but never ratified it. More than 130 countries have signed on in some fashion, according to the United Nations.

The United States has already taken steps to adhere to provisions of the amendment before actually ratifying it. In December 2020, Congress passed the American Innovation and Manufacturing (AIM) Act as part of an appropriations bill. It empowers the EPA to enforce a phase-down of 85% of the production and consumption of HFCs over 15 years.

Industry groups such as the Alliance for Responsible Atmospheric Policy said the AIM Act is important, but that ratifying the amendment was still necessary to make American companies truly competitive.

"It's an enhancement of your market access. These are very competitive industries on a global basis, China being the fiercest," said executive director Kevin Fay.

His group estimated that ratifying the amendment would "increase U.S. manufacturing jobs by 33,000 by 2027, increase exports by $5 billion, reduce imports by nearly $7 billion, and improve the HVACR [Heating, Ventilation, Air Conditioning, and Refrigeration] balance of trade," by guaranteeing that U.S. companies will be adopting standards needed to sell products in countries that already ratified the measure.

On the climate side, there is some evidence that commitments to cut back on the use of HFCs are not being followed. A study published in Nature Communications in 2021 found that atmospheric levels of the most potent HFC, HFC-23, should have been much lower than what scientists detected if China and India, countries responsible for manufacturing the majority of the compound that turns into HFC-23, had accurately reported their reductions.