With rare, bipartisan support including a phalanx of Republican lawmakers, the U.S. Senate voted 69-27 Wednesday in favor of ratifying a key international climate agreement that will significantly curb global warming and, climate advocates say, could serve as a springboard for further emissions reductions.

The Kigali Amendment to the Montreal Protocol is a binding agreement to reduce production and use of hydrofluorocarbons (HFCs), chemicals used in refrigeration and air conditioning that are also potent, short-lived greenhouse gases. President Joe Biden is expected to soon sign the agreement, something he has called for since his inauguration. The United States would join 137 other countries in an agreement that is projected to prevent substantial additional warming by the end of the century.

“I am thrilled to see the U.S. rally to the support of this vital agreement,” John Kerry, the U.S. special presidential envoy for climate, who, as U.S. Secretary of State, helped forge the initial agreement in 2016, said in a written statement.

“Businesses supported it because it drives American exports; climate advocates championed it because it will avoid up to half a degree of global warming by the end of the century; and world leaders backed it because it ensures strong international cooperation,” Kerry said.

The U.S Chamber of Commerce sent a letter to members of the U.S. Senate earlier in the week urging individual members to vote in support of the treaty and noting that they “will consider including votes related to this legislation in our annual ‘How They Voted’ scorecard.” The Senate had to give its “advice and consent” with a two-thirds majority vote in favor of ratification before President Biden could ratify the agreement.

A 2018 report by the U.S. air conditioning and refrigeration industry found that by 2027, the Kigali amendment would increase U.S. manufacturing jobs by 33,000, increase U.S. exports by $5 billion, and reduce imports by nearly $7 billion.

The United States began phasing down the production and use of HFCs after Congress passed the American Innovation and Manufacturing (AIM) Act, legislation that was signed by then President Donald Trump in 2020. Subsequent regulations released by the EPA in 2021 are compliant with the Kigali Amendment, which requires the U.S. and other developed countries to reduce production and use of HFCs by 85 percent by 2036.

Officially ratifying the Kigali Amendment further solidifies the United States commitment to reducing HFC emissions and protects U.S. industry. Failure to ratify would close segments of the chemical and manufacturing industries to U.S. producers after 2023 because the Montreal Protocol “prohibits trade with countries not party to [it] or its amendments” according to the Air-Conditioning, Heating, and Refrigeration Institute and the Alliance for Responsible Atmospheric Policy, industry groups that support ratification.

U.S. ratification also shows that the country is committed to climate action, Avipsa Mahapatra, the climate campaign lead at the Environmental Investigation Agency, said.

“This is the first time the Senate has, in a bipartisan way, signed on to a climate treaty in the last 30 years,” Mahapatra said of those who voted for the agreement, including Senate minority leader Mitch McConnell (R-Ky.), who for years had mocked and criticized Democrats’ efforts to do anything about climate change. “I think it does infuse a little bit of hope in our ability to make climate action possible in this country.”

Phasing down HFCs is of particular importance because the chemicals are “short-lived climate pollutants.” HFCs remain in the atmosphere for 15 years on average, far shorter than carbon dioxide which remains in the atmosphere for 300 to 1000 years. Any effort to curb HFC emissions or other short-lived climate pollutants such as methane will have a near-instantaneous impact on slowing global warming.

A study published earlier this year in the Proceedings of the National Academy of Sciences (PNAS) found curbing HFCs and other short-lived climate pollutants along with carbon dioxide and nitrous oxide, a greenhouse gas with an atmospheric lifetime of 109 years, slows the rate of warming a decade or two earlier than decarbonization alone and can avoid altogether the 2 degree Celsius threshold of warming that the Paris Agreement cites as the maximum allowable to avoid catastrophic environmental impacts. 

 “That is the only way to slow near term warming,” said Durwood Zaelke, president of the Institute for Governance & Sustainable Development in Washington, and a co-author of the PNAS study.  

Zaelke said the Kigali Amendment to the Montreal Protocol is the first step in tackling short-lived climate pollutants. The next step is to focus on methane, the second leading driver of climate change after carbon dioxide, he said.  

“You can use the Montreal Protocol as your inspiration for creating a new agreement on methane,” Zaelke said. Last year more than 100 nations led by the U.S. and the European Union pledged to curb methane emissions; however, the existing agreement, the Global Methane Pledge, is non-binding.

Mahapatra said more can also be done with the Kigali Amendment to further reduce HFC emissions.

“It has always operated on the principle of start and strengthen,” Mahapatra said of the Montreal Protocol. “From here, we hope that there will be deeper cuts in HFC production… to totally eliminate the use of these gases.”