The US is expected to withdraw once again from the Paris Agreement on climate change if Donald Trump is reelected president in November, bringing more policy uncertainty to a world enduring what scientists believe will be another record-hot year.

Conservative activists are also pushing for a US retreat from the United Nations Framework Convention on Climate Change (UNFCCC), the underlying 1992 agreement to stabilize greenhouse gas emissions that was ratified by 198 nations. Such a move, if successful, would cut US diplomats from all global negotiations related to transitioning away from fossil fuels.

The extent to which those reversals would damage international climate efforts — and US attempts to shrink its large carbon footprint — is uncertain, experts and political activists told S&P Global Commodity Insights.

A potential Trump administration might have less of an impact on international climate efforts if it were to withdraw the US from the Paris accord and the UNFCCC than if the country were to stay in, suggested David Victor, a climate expert and professor at the University of California San Diego's School of Global Policy and Strategy.

As formal treaty members, US diplomats under Trump could obstruct and slow-walk initiatives to cut emissions as the US did with the Kyoto Protocol, Victor explained. Politically appointed diplomats under then-President George W. Bush caused an upheaval around the Kyoto Protocol before the US abandoned that climate treaty in 2001, he noted.

Moreover, if Trump is in power, "the Europeans will double down on climate, states will double down on climate," Victor said. "What we observed last time is that a lot of other folks are willing to step into the breach, and this time it will happen faster."

The US is the largest cumulative emitter of greenhouse gases since industrialization began around 1850 and still has a larger carbon footprint than any other nation after China.

'A massive failure'

Former Trump administration officials, while pushing for US disengagement on climate under a second Trump term, said they have better solutions.

"I would argue the UNFCCC has been a massive failure," said Mandy Gunasekara, who as a senior policy adviser for the US Environmental Protection Agency under Trump pushed for and crafted the US withdrawal from the Paris Agreement in 2017.

The UNFCCC "was instituted in 1992 and emissions across the globe have gone up exponentially," Gunasekara said. "So why continue to spend resources on a failed process when it would be better to focus on spurring innovation here in the United States and then sharing those technologies with countries that are serious about actually reducing their overall emissions?"

Gunasekara said she has not discussed a UNFCCC departure with the former president or his campaign. The Project 2025 policy blueprint, which the Heritage Foundation think tank released earlier this year for the next Republican presidency, said a UNFCCC exit would be one of the next administration's priorities. Gunasekara was among two dozen officials from Trump's first administration who contributed to the report, together accounting for 25 of its 30 chapters, according to a tally by the Revolving Door Project.

Still, whether a president can take executive action to leave the UNFCCC without Senate approval is disputed and will likely be litigated, Gunasekara and other observers across the political spectrum agreed.

"It'll be mired in controversy and be dragged through the courts, and then there'll be no clear answer to that question," Victor predicted. "And while there's no clear answer to that question for at least four years, we'll still be in the treaty."

Janos Pasztor, a top UN climate adviser in the leadup to the Paris Agreement nine years ago, acknowledged that a Trump win could slow down overall global efforts at a time when emission reductions must accelerate. But he said on-again-off-again climate actions by the US matter less to other nations today than they once did.

"China is not engaging seriously on climate because the US is pressing it, they are doing it because they are a highly vulnerable country," Pasztor said. "In all these countries — China, India, EU — there are plenty of good reasons why they are engaging."

Battle over cars

Perhaps the most consequential step Trump might take domestically on the climate front if elected is rolling back President Joe Biden's fuel economy and emissions reduction standards for cars. Such measures are seen as critical for the administration's Paris Agreement pledge to cut US economywide emissions in half by 2030.

The rules, together with massive clean car investments under the 2022 Inflation Reduction Act (IRA), were designed to push automakers to produce more electric vehicles and tackle the nation's largest source of greenhouse gas emissions. Pollution from internal combustion engines is the largest source of US emissions today, and passenger cars make up 57% of the sector's carbon footprint.

Trump and other critics of the rules say the focus on electric cars hampers consumer choice and wastes tax dollars.

"We have subsidies and auto companies are pricing their EVs artificially lower and pricing their SUVs and minivans artificially higher to encourage people to buy the EVs, but they're still not selling in the requisite amounts," said Diana Furchtgott-Roth, a senior official with the US Department of Transportation under the first Trump administration and a critic of the rules.

GOP lawmakers want EV plants

The GOP 2024 platform pledges to "revive the US auto industry by reversing harmful regulations, canceling Biden's electric vehicle and other mandates." While there is no EV mandate, any effort to cancel incentives for EV development could face bipartisan resistance.

Republican strategists say there is little appetite on Capitol Hill, even among fiscal conservatives, to stymie the nation's emerging EV market or the EV production credits made possible by the IRA.

Many GOP lawmakers are seeing billions in EV and battery investment flow into their districts and want the economic growth, noted Heather Reams, president of the center-right nonprofit Citizens for Responsible Energy Solutions (CRES). Instead, their conversation centers around the $7,500 federal tax credit for EV buyers and whether such policies help drive down emissions, she said.

"I hear many members of Congress … saying 'You know, I want to have a discussion about the consumer tax credits. I'm less interested in having a discussion about the electric vehicle production tax credits,'" Reams said.

CRES has been urging lawmakers to tread carefully with any revisions to the IRA tax benefits, most of which have so far benefited the EV supply chain. In conversations with lawmakers, Reams is also making a case for the US staying in the UNFCCC and "at the international table."

"We think the United States has a good story to tell about our emission reductions and what we can offer the developing world to help lower their emissions," Reams said. "There's a great case for staying in."