President Donald Trump is ordering the United States to withdraw from the landmark Paris Agreement, launching another retreat in the fight against climate change by the world’s wealthiest nation.

The move was widely expected since Trump pulled the U.S. from the emissions-cutting pact during his first term and had promised do to it again during his campaign. Nevertheless, the action, described in a White House fact sheet less than an hour after Trump was inaugurated, underscored the seriousness of the Republican’s commitments to rapidly overhaul U.S. energy and climate policy.

The planned exit from the Paris Agreement is just one of a number of changes Trump is set to initiate on his first day back in the White House, as he shifts U.S. policy toward promoting fossil fuel production and away from fighting climate change. In his inaugural address, Trump vowed that his actions Monday “will end the green new deal.”

The U.S.’s departure from the Paris Agreement isn’t expected to take effect immediately. Signatories to the 2015 accord must provide formal notice to the United Nations to initiate a withdrawal, then wait a year for it to take effect.

The spectre of the US leaving again has already shaken global climate diplomacy, casting a shadow over the last round of annual UN climate talks in Azerbaijan last November. The U.S. is the second-largest emitter of planet-warming gases and has been viewed as an important contributor to the fight to slow them. The U.S. exit revives long-simmering questions about whether a three-decades-long international framework for fighting climate change is up to the task.

Environmentalists excoriated Trump’s decision, saying the U.S. was shirking its responsibility to contend with climate change while ignoring the economic dividends tied to U.S. development of emission-free power and clean energy technology.

“The transition to a low-carbon economy is already underway,” said Ani Dasgupta, president of the World Resources Institute. “Walking away from the Paris Agreement won’t protect Americans from climate impacts, but it will hand China and the European Union a competitive edge in the booming clean energy economy and lead to fewer opportunities for American workers.”

European climate leaders have sounded a defiant note, insisting the U.S. withdrawal won’t impede global action.

“Multilateral climate action has proven resilient and is stronger than any single country’s politics and policies,” said Laurence Tubiana, a key architect of the Paris Agreement who is now chief executive officer of the European Climate Foundation.

Beyond jettisoning the Paris Agreement, Trump has vowed to undo a host of federal policies critical for the U.S. to meet its emission-cutting pledges, including a promised 50 per cent to 52 per cent reduction from 2005 levels by the end of the decade.

Business and local government leaders say they will continue to work toward cutting emissions and encourage carbon-free energy. But without robust federal action, analysts say private sector and subnational activity won’t be enough.

Opponents of U.S. participation in the Paris Agreement championed Trump’s move, saying the nation’s participation in the the pact drags down the economy. While most countries aren’t meeting their carbon-cutting targets under the pact, the U.S. can’t afford to let other nations dictate its energy future, they say.

Supporters — including business leaders and Republicans who encouraged Trump to stick with the accord in 2017 — say the U.S. can wield its leverage to better influence the talks, potentially helping propel American energy exports, including natural gas that burns more cleanly than coal when used to generate power.

Indeed, the Trump administration played a kind of spoiler role during the president’s first term, as the initial Paris exit was still pending, by championing fossil fuels in annual negotiations.

The actual U.S. exit last time was brief, only taking effect Nov. 4, 2020, because of a longer waiting period to make it official. Former President Joe Biden moved to reenter the accord immediately after his inauguration in January 2021.

Analysts, negotiators and veterans of climate diplomacy have predicted the latest U.S. departure could shift the balance of power to other countries and blocs. That includes emboldening China, which has installed renewable electricity capacity at a record scale — and is exporting emission-free energy tech to other nations — despite its long embrace of coal power.

It’s relatively easy for a U.S. president to unilaterally walk away from the Paris Agreement, which has been considered an executive agreement that relies on existing U.S. statutory authority, not a treaty. U.S. negotiators at the 2015 climate conference in Paris even worked to ensure the document referred to certain actions that “should” — not “shall” — be taken in order to ensure there’d be no need for a Senate vote to give advice and consent.