US secretary of state Michael Pompeo submitted the paperwork on 4 November to officially withdraw the United States from the 2015 Paris climate agreement.

The move came as little surprise: President Donald Trump had said he intended to pull the country out of the agreement in June 2017, arguing that remaining in the global pact it would harm the United States’ economic competitiveness. In announcing the decision on 4 November, Pompeo noted that US greenhouse gas emissions declined by 13% from 2005 to 2017, even as the economy grew 19%.

But the move to withdraw from the Paris agreement drew criticism from scientists and environmentalists . “President Trump’s decision to walk away from the Paris Agreement is irresponsible and shortsighted,” said Alden Meyer, director of strategy and policy at the Union of Concerned Scientists, an advocacy group in Cambridge, Massachusetts, in a statement.

Under the rules of the climate agreement, 4 November 2020 was the earliest a country could notify the United Nations Framework Convention on Climate Change (UNFCC) of its intent to withdraw from the pact, three years after it entered into force in 2016. The actual withdrawal will not take effect for another year, so the United States would formally exit the agreement on 4 November 2020 — one day after the presidential election that will determine whether Trump gets a second four-year term as president.

An uncertain future

Withdrawing from the Paris climate agreement will cost the United States in terms of political and economic influence, as other nations push forward to develop a low-carbon economy, says Andrew Light, who worked on the global pact at the US State Department under former President Barack Obama. But that could change if Trump doesn’t win re-election.

The Democratic presidential candidates are taking climate change seriously, and if one of them wins the 2020 election, they could direct the US back into the agreement once they take office in January 2021. Countries that leave the Paris agreement can rejoin the pact 30 days after notifying the UNFCC of their intentions, according to the World Resources Institute (WRI), an environmental think tank in Washington DC.

“The US will be under the gun to move as quickly as possible,” says Light, who is now a senior fellow at WRI. If Trump prevails, it will be up to US cities, states and businesses to maintain leadership on climate-change issues, he says.