The Trump administration on Monday formally notified the United Nations of its intention to withdraw from the Paris Agreement, a move that will leave the world’s second largest emitter of greenhouse gasses as the only nation to abandon the global effort to combat climate change.

The action, which came on the first possible day it could be issued under the accord’s complex rules on withdrawal, begins a yearlong countdown to America’s exit from the agreement, under which nearly 200 nations pledged to cut greenhouse emissions and help poorer countries cope with the worst effects of an already warming planet.

Under the rules of the Paris Accord, the Trump Administration’s withdrawal won’t become official for another year – the day after the next presidential election. Should Trump be defeated in November 2020, the next president could reenter the accord almost immediately.

The administration’s move comes as no surprise. Since before taking office in 2016, Trump has criticized the accord, often in crude terms, claiming that climate change is a hoax meant to dull American economic competitiveness. On the campaign trail, Trump’s promise to pull out of the accord became a ribald applause line for his supporters.

In June of 2017, when Trump announced his intention to withdraw from the agreement at the White House, he said the accord imposed “draconian financial and economic burdens” on the United States.

Secretary of State Mike Pompeo’s remarks on Monday, in which he announced the formal withdrawal, echoed these sentiments.

“President Trump made the decision to withdraw from the Paris Agreement because of the unfair economic burden imposed on American workers, businesses, and taxpayers by US pledges made under the agreement,” he said.

The announcement not only isolates the United States from the international community, but also highlights the stark divided between the Trump administration’s policies and the country it governs.

A 2018 survey by the Yale Programme on Climate Change Communication found that 77 percent of Americans believed the US should remain in the Paris Agreement, including 60 percent of Republicans. Among registered voters, 66 percent said they opposed Trump’s decision to pull out of the Paris deal.

Other recent polls have shown that nearly 4 in 10 Americans now define climate change as a “crisis,” up from less than a quarter five years ago.

Organizers of efforts in US cities and states to curb the effects of climate change say they are trying to play a role in fighting the climate crisis, despite the Trump administrations regressive policies.

Carl Pope, vice chair of the group America’s Pledge, told the Guardian newspaper that its members – who are vowing to keep fighting the climate emergency – produce more than half the country’s heat-trapping emissions and represent about 70 percent of the US gross domestic product. Another organization, the US Climate Alliance, includes the governors of 25 states, representing 55 percent of the US population.

Four major US automakers have likewise pledged to uphold fuel efficiency goals – holding to air standards demanded by the state of California – despite Trump’s efforts to weaken them.

Should a Democrat win the White House, the nation could reenter the agreement after a short absence — as numerous candidates have pledged they would do. But if Trump prevails, his reelection would probably cement the long-term withdrawal of the United States, which was a key force in helping forge the global effort under President Barack Obama.

Given this uncertainty, diplomats and climate negotiators the world over are preparing for a world in which US leadership on climate goals is nonexistent.

“Yes, there are conversations. It would be crazy not to have them,” Laurence Tubiana, who served as France’s climate change ambassador during the Paris negotiations, told the New York Times, adding, “We are preparing for Plan B.”

The timetable for withdrawal means the US will continue to be a legal party to the Paris Agreement during the climate talks hosted in Madrid next month, after Chile had to cancel the meeting due to social unrest. This will give the US administration a final say on how the Paris Agreement should be implemented

The talks are due to finalize the rulebook of the Paris accord and resolve contentious issues over how carbon credits can be traded between countries – technical discussions that are crucial to ensuring carbon markets encourage additional emissions cuts.

Once formally out of the agreement next year, the US will still be able to attend climate talks and sit in Paris-related discussions as an observer without the ability to make-decisions or block consensus but with the soft power to continue to shape global climate diplomacy.

But the official withdrawal is likely to further polarize a presidential election in which the stakes for the US population were already high. Monday’s announcement made them even higher ­– for the rest of the world as well.