Former President Barack Obama recently expressed disappointment in the US being the only country not supporting the Paris climate agreement.

 Former President Barack Obama recently expressed disappointment over the U.S. being the only country not supporting the Paris climate agreement.  During a town hall in Berlin, he did admit that he wasn't fully satisfied with the goals outlined in the accord, as, even if they are met, they won't meet the planet-saving minimum requirements outlined by scientists.  "But, if I had held out for us getting to where we needed to be in the science, we wouldn't have gotten the accord," Obama continued. After noting that initially there were only "one or two countries that didn't sign up," he commented, "Now it's only mine—but that's a whole other question."  President Trump announced his intention to withdraw the US from the climate agreement in June of 2017, stating: "As of today, the United States will cease all implementation of the non-binding Paris Accord and the draconian financial and economic burdens the agreement imposes on our country."  It turns out, the agreement is more binding than he suggested. The Washington Post reports it "specifies that after joining the agreement, a country can't leave for three years, after which there is a one-year waiting period for the leave to be fully in effect." 
That means the earliest the U.S. can exit is the day after the 2020 election.