Secretary of State John F. Kerry delivers a speech in October 2016 at the 28th Meeting of the parties to the 1987 Montreal Protocol in Kigali, Rwanda. (Cyril Ndegeya/AFP/Getty Images)

While it’s not the Paris climate agreement, hopes are rising that the Trump administration will not walk away from another international climate accord, one designed to limit emissions of super-polluting gases from air conditioners and refrigerators that could otherwise sharply warm the globe.

In Montreal this week, countries have assembled for the 29th meeting of the parties to the 1987 Montreal Protocol, a widely celebrated treaty to protect the planet’s ozone layer. And they’re welcoming an extension of the protocol, called the Kigali Amendment, which was negotiated last year and late last week crossed a key ratification threshold. Its formal acceptance now by 21 member countries will trigger its going into force in early 2019.

The amendment specifically targets a category of climate pollutants called hydrofluorocarbons, or HFCs, which are far more potent than leading greenhouse gases such as carbon dioxide or methane on a molecule per molecule basis. HFCs were originally a substitute for the chlorofluorocarbons (CFCs) that severely damage the ozone layer, but they’ve since been recognized as coming with their own significant problems.

The chemicals, which often leak from air conditioners, refrigerators and other industrial devices and then make their way into the atmosphere, have the potential to drive a half-degree Celsius (.9 degrees Fahrenheit) of global warming if not controlled in the early part of this century.

The Kigali Amendment, which would phase down HFCs, was strongly supported by the Obama administration. The Trump administration has not yet taken a position on it, other than perhaps one slight and murky signal: Over the summer, it refused to support a large climate change-related section of a G-7 communique that, among a long list of other matters, signaled support for the amendment. But it’s far from clear what that might really mean.

As the meeting proceeds in Montreal, with the U.S. representatives expected to speak later this week, there are positive signs.

“There are a number of steps in our domestic process that we would need to complete before reaching a final decision on joining the Kigali Amendment, and we have initiated that process,” a State Department statement sent from a spokesman said. “The Kigali Amendment represents a pragmatic and balanced approach to phasing down the production and consumption of hydrofluorocarbons, and we support the goals and approach.”

If there’s a reason the Trump administration could support the rather narrowly targeted amendment — yet still plan to exit the far more sweeping Paris agreement — it may have something to do with the Montreal Protocol itself. It’s an uncontroversial treaty with bipartisan domestic support and has traditionally been able to forge a cooperative, rather than adversarial, relationship with the companies making the chemicals subject to regulation.

“This is a Ronald Reagan-Margaret Thatcher agreement,” said Durwood Zaelke, president of the Institute for Governance and Sustainable Development, which tracks the protocol. “Bush used it successfully in 2007, and if the White House looks at it as a trade and competitiveness issue, it should be a slam dunk.”

U.S. companies that currently make products that use HFCs have supported the Kigali Amendment. Some of the most prominent, Honeywell and Chemours, already tout alternative chemicals with fewer environmental problems.

“We’re global companies and we operate in the global marketplace, and one of the advantages to ratification of the agreement is it avoids a patchwork of timelines and schedules globally,” said John Hurst, vice president for government affairs at Lennox International, which makes heating and cooling and refrigeration equipment. “So as any business would, we crave predictability and certainty. If ratified, it allows for research on the safe application of new alternative refrigerants, allows for more predictable product development decisions, allows companies to plan for R&D investments.”

Hurst is also chairman of the board of the Alliance for Responsible Atmospheric Policy, an industry group that has backed the Montreal Protocol and the Kigali Amendment.

U.S. manufacturers are looking at a massive business opportunity as the climate warms and developing nations expand their middle classes; huge swaths of the world, from Brazil to India, are expected to install enormous numbers of air conditioners in the coming decades. These companies want to build those products, but they also generally recognize that future air-conditioners will need to be more energy efficient and not reliant on HFCs.

“We’ve estimated the global market outside the U.S. in these technologies is probably over a trillion dollars over the next 10 years,” said Kevin Fay, the executive director of the alliance.

“The technology that we look to be replacing the high [global-warming potential] refrigerants will be predominantly North American-based technology, both refrigerants as well as systems,” added Stephen Yurek, president of the Air-Conditioning, Heating and Refrigeration Institute, an industry group.

If the United States doesn’t sign onto the amendment, companies could instead suffer damaging trade restrictions starting in the 2030s. “It’s not an environmental game at this point, it’s a competitiveness game,” Zaelke said.

Should the State Department signal its support, the amendment would be forwarded to the Senate for ratification, which requires a two-thirds vote.

“Historically, this has not been a partisan issue,” said Paul Bledsoe, a lecturer at American University’s Center for Environmental Policy and a former White House staffer on climate change in the Clinton administration. “So I think advocates are hopeful, both in industry and elsewhere, that the Senate would see this as a straight matter of economics and not have it be politicized as other agreements have been.”