The United States formally quit the Paris Climate Agreement at midnight Wednesday—but, if Joe Biden comes out on top at the end of the election count, it won’t be long until it rejoins. President Donald Trump served notice to pull the U.S.—the world’s second-biggest greenhouse-gas polluter—out of the global accord to fight the climate crisis on Nov. 4 last year, which then took one year to take effect. The U.S. is the only country of 197 signatories to have withdrawn from the agreement. However, Biden has promised to rejoin the agreement if he comes out on top from Tuesday’s presidential election.