President Trump is about to be a party of one.

Earlier this week, Syria announced during an international conference in Bonn, Germany, that it would add its name to the historic 2015 Paris climate agreement, in which nearly 200 countries pledged their best efforts to reduce greenhouse gas emissions. This would leave the United States as the only country to have rejected the Paris deal, which Mr. Trump did in a Rose Garden rant on June 1 that was notable, even by Trumpian standards, for its dishonesty.

Our advice to the delegates in Bonn is this: Ignore Mr. Trump, who seems, on this issue anyway, to be beyond persuasion. Honor your pledges. Get on with the talks, which are supposed to build on the Paris agreement by establishing benchmarks to measure how well you’re doing now and to lay the groundwork for even more ambitious targets in 2020. And hope, as we do, that efforts now underway by state and local governments and by private businesses to control emissions and move the United States to a cleaner energy future will make up for Mr. Trump’s indifference.

That Mr. Trump wants out of Paris is only one measure of that indifference. A better measure is provided by policies that would move exactly in the wrong direction, policies aimed at overturning greenhouse gas regulations on power plants, repealing limits on methane emissions, weakening automobile efficiency standards, enlarging subsidies for coal plants and increasing oil drilling in the Arctic.

Meanwhile, the hacks, industry careerists and global warming deniers he has appointed to run agencies responsible for climate policy are mostly a joke, the latest howler being Kathleen Hartnett White, a former Texas regulator whom Mr. Trump has named to run the White House Council on Environmental Quality. Mrs. White, who, if approved, would coordinate the administration’s environmental policy, has dismissed carbon dioxide as a “harmless trace gas” (but a useful “plant food”) and described as “paganism” the belief that man-made pollutants are warming the atmosphere.