For the past 20 years, the mayors of a widening circle of global cities have been convening regularly in an effort to leverage the political heft of municipal government to influence international climate policy. The group is called the C40, and its 97 members lobby, advocate, exchange ideas and, ideally, implement local programs that reduce emissions.
The C40 is one fairly robust example of subnational climate diplomacy, but it’s not the only one. The U.S. Climate Alliance, a league of more than 20 blue states, partners informally with European Union institutions and member states. The conjoined California-Quebec cap-and-trade market, which has been operating for about 12 years, shows how regional governments on different sides of a national border can create carbon markets. Earlier this year, in fact, California’s governor, Gavin Newsom, went one step further and pushed his state’s climate diplomacy all the way across the Atlantic, inking a memorandum of understanding with the United Kingdom’s Labour government to support decarbonization efforts, promote resilience, exchange technical expertise and “engage in mutually beneficial economic and innovation activities through increased research and academic cooperation.”
News of California’s deal with Westminster attracted, predictably, the ire of President Donald Trump, who first belittled Newsom and then stated that it is “inappropriate” for the United Kingdom to be dealing with a climate-minded governor. After all, the U.S. government’s national policy on climate change and the energy transition tacks in precisely the opposition direction, as evidenced by billions in stalled or cancelled clean-energy subsidies (although some offshore wind received reprieves in the courts), the declawing of the Environmental Protection Agency and the administration’s seemingly inexhaustible support for coal.
This latest clash between Trump and Newsom – hardly the first and unlikely the last – raises a tricky question: if international affairs is the natural purview of national governments, should subnational entities – states, regions, even cities – have the latitude to go their own way, especially when the climate stakes are so stark?
During Trump’s first term, the White House went to court to kill the California-Quebec cap-and-trade market, citing a provision in the U.S. Constitution that grants Washington the exclusive right to conduct international diplomacy unless Congress provides an exemption. But the Trump administration’s resulting lawsuit didn’t survive regime change, and the Biden administration dropped the case in 2021. A year later, Biden signed a law formalizing the role of subnational diplomacy, and even set up a dedicated division within the State Department, complete with its very own “special representative for city and state diplomacy.” That gesture, unsurprisingly, did not survive into Trump’s second term.
The case for a transatlantic framework
So now what? “In the absence of federal-level commitment and in the presence of federal contestation of climate change and energy security policy,” says Jakob Wiedekind, a professor of political science and international relations at the University of North Carolina at Chapel Hill, “it is clear that we are looking for other channels and avenues to cooperate across the Atlantic . . . This is not the first time we had to do that [because] American positions and climate change policy have fluctuated.”
In a recent article in the Georgetown Journal of International Affairs, Wiedekind laid out the case for creating what he dubs a “Transatlantic Subnational Resilience Framework” that could help sustain international dialogue on climate change and renewable energy in a period when Washington is very much not in the mood to engage, especially with the European Union.
The EU, of course, has plenty of its own experience with subnational diplomacy and what Wiedekind calls “multi-level governance.” For example, he cites the diverse ways in which EU member states sought to wean themselves off Russian natural gas after the 2022 invasion of Ukraine, with a heavy emphasis on renewables. That exercise, dubbed REPowerEU, originated with directives from the European Commission but “allowed member states specifically and regional actors to share expertise on how that would be done,” he says, adding there could be other such top-down/bottom-up efforts to confront issues such as the wildfires and flooding that have swept through much of Western Europe and the United States in recent years.
Wiedekind argues that a transatlantic framework for subnational climate diplomacy could work in a similarly flexible and decentralized way, through regular meetings, leveraging commercialized clean technologies, and shared commitments to achieve resilience goals. Wiedekind, however, stresses that any such group should not become part of the annual conference of the parties (COP) that have joined the UN Framework Convention on Climate Change, which, he says, has become too politicized.
Indeed, the whole point of the exercise Wiedekind envisions is to depoliticize those international conversations as much as possible so they don’t become a target. He also contends that shifting the focus to climate-adjacent topics like wildfires, flooding and profitable clean-energy ventures could evolve into a strategy for engaging state-level Republican lawmakers who might otherwise steer clear of climate policy per se.
Such ideas reveal both the desperation and opportunities of a moment when the world’s most powerful government has become consumed by climate denial. No matter how hard it tries, the Trump administration can project its philosophy only so far. Other nations and other jurisdictions are resisting. The resulting conversations around collaboration and work-arounds offer evidence, however slight, that climate diplomacy will persist until this storm passes.
John Lorinc is a Toronto journalist who writes about cities, climate and business.
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