Two weeks before President Trump was elected President in November 2016, then Secretary of State John Kerry held court in a hotel room in Kigali, Rwanda, to help secure one of the most important and little-known international climate agreements in history.

Durwood Zaelke, president of the Institute for Governance and Sustainable Development, recalled Kerry’s forthright approach and mastery of the process.

“He would summon a minister in and say, ‘You are not giving the right answer here, what’s wrong?’ Zaelke said, noting how the ministers stopped opposing the deal and began speaking in support of the agreement immediately after meeting with Kerry.

“He used every diplomatic skill that a seasoned diplomat has, including his ties with the heads of government,” Zaelke said.  “If he had a reluctant minister, as was the case sometimes, he could call the Prime Minister or the President and get that extra support that was needed. Without Kerry, we wouldn’t have gotten this in Kigali, he was instrumental.”

The agreement, known as the Kigali Amendment to the Montreal Protocol, has now begun to phase down the use of hydrofluorocarbon (HFC) refrigerants, climate super-pollutants that would otherwise have caused as much as 0.5 degrees Celsius of additional global warming by 2050.

President-elect Joe Biden’s announcement on Tuesday that Kerry—a former secretary of state, senator and presidential candidate—would serve in the newly created role of special presidential envoy for climate underscored the importance the Biden administration will place on international negotiations to address climate change, as illustrated by Kerry’s work in Kigali.

“Even the United States, for all of our industrial strength, is responsible for only 13% of global emissions,” Kerry said during a joint appearance in Wilmington, Delaware, with Biden and other newly announced members of his national security team. “To end this crisis, the whole world must come together. You’re right to rejoin Paris on day one, and you’re right to recognize that Paris alone is not enough.”

Kerry is likely to try to build on the success of the Kigali Amendment by taking swift action to work with other countries to reduce emissions from other sectors of the global economy, Zaelke said. 

One place he might look is the International Maritime Organization, a United Nations agency whose member states cooperate on regulations governing the international shipping industry. In 2018, the IMO agreed to cut greenhouse gas emissions from ships by 50 percent by 2050, but the organization later failed to approve any specific emissions reduction measures.

 Another is the International Civil Aviation Organization, a UN agency that is currently working to offset growth in carbon emissions from international flights after 2020.

A third possibility would be expanding the scope of the Montreal Protocol, an international agreement developed in the 1980s to phase out the production of ozone depleting chemicals. Some climate policy experts say the agreement should now be extended to reduce emissions of other greenhouse gases such as nitrous oxide, a greenhouse gas produced in chemical manufacturing that is nearly 300 times more potent at warming the planet than carbon dioxide, and also causes depletion of atmospheric ozone.

These lesser-known agreements and UN organizations have the ability to require mandatory emission reductions, giving them more teeth than the more well-known Paris climate agreement, which is voluntary.

“We have to have these sister agreements moving ahead to plug in and support the Paris Agreement,” Zaelke said.

Another place strong U.S. leadership could spur greater international action on climate change is the Climate and Clean Air Coalition, a voluntary U.N.-administered organization, formed in 2012 with support from the Obama administration.

The Coalition focuses on reducing emissions of “short-lived climate pollutants” including methane, HFCs, black carbon and ground level ozone, which are all climate super-pollutants that remain in the atmosphere for a relatively short period of time. Reducing these pollutants is widely seen as a way to quickly begin to address global warming.

The Coalition, in partnership with the United Nations Environment Programme, the European Commission, the Environmental Defense Fund and leading oil and gas companies, announced a new effort to report and reduce methane emissions from the oil and gas sector on Monday.

“Kerry can redouble the efforts and make it go twice as fast, and can also bring it to the highest level of government,” Zaelke said of the Coalition.

However, before the U.S. can seek to lead on any international climate agreement, it must first return to the Kigali Amendment, which the nation abandoned after Kerry had championed the agreement. 

More than 100 countries have signed the amendment, which the U.S., China and India have yet to ratify.  

U.S. ratification could come quickly. Legislation that would mandate the phase down of HFCs, a prerequisite for U.S. ratification of the Kigali Amendment, is now making its way through the U.S. Senate.

The legislation has rare, bipartisan support and is backed by a broad group of environmental organizations and business interests, including the Natural Resources Defense Council, the U.S. Chamber of Commerce and the National Association of Manufacturers.

The groups say it would both reduce greenhouse gas emissions and create jobs by stimulating the development of new, more climate friendly chemical refrigerants. In a Nov. 18 letter to Republican and Democratic leaders of the House and Senate, the groups called for swift passage of the bill during the current, “lame duck” session of Congress.

“There is a remarkable span of support for this among stakeholders and quite remarkable bipartisan sponsorship in the Senate,” said David Doniger, senior strategic director of the Natural Resources Defense Council’s Climate and Clean Energy Program. “I remain somewhere between hopeful and optimistic that this can succeed in this lame duck session.”