THE NEW YORK TIMES reports that the Trump administration has divided over whether to remove the United States from the Paris climate agreement, a landmark international deal with vast diplomatic and environmental significance. Withdrawing — or asking the Senate to decide what to do, which is effectively the same thing — would be an enormous and possibly irreparable error. This is not a hard call: Staying in the agreement is costless, while leaving would rightly provoke sharp and sustained international outrage.

The Paris agreement does not formally obligate the United States to make any particular level of emissions cuts. All it does is ask countries to announce emissions plans of their choosing and report on their progress. It has no major implications for U.S. sovereignty and demands no particular policy balance between environmental and industrial concerns. If the Trump administration wants to move that balance toward fossil fuel interests, it does not have to leave the Paris agreement to do so.

President Trump could modify the U.S. Paris commitment, or simply leave President Barack Obama’s Paris pledge in place. Although Mr. Trump has promised to rip up major elements of Mr. Obama’s climate plan, other policies, such as congressionally mandated renewables subsidies and state-level efforts, would continue apace. Crushing the Environmental Protection Agency’s Clean Power Plan would ill-prepare the country for the significant emissions cuts that it will have to make in coming decades, but it would not keep the nation from reducing its emissions by more modest levels in the near term. If the country is going to be achieving emissions cuts anyway, why not take some international credit for them?

Given all that, leaving Paris would be nothing more than a gratuitous thumb in the eye of practically every important nation on the planet, a bizarre and irrational unforced error.

The Times reports that Ivanka Trump and others pushing to stay in the Paris agreement might be mollified if the president declared that deal is a treaty that requires Senate ratification, tossing its fate into lawmakers’ hands. This is just another way to kill it, a ruse that would trick no foreign government. During the Paris negotiations, international diplomats bent over backward to accommodate the U.S. political system, specifically designing an agreement that relies on purely voluntary, nonbinding emissions commitments from every major polluting nation. Many governments would have much preferred a treaty with legally mandatory emissions requirements. But they recognized that the Senate, where rural and energy interests are quite powerful, would certainly scuttle it.

Neither Ms. Trump nor anyone else in the White House should imagine that the global reaction would be any different if the president, in effect, asks the Senate to do his dirty work for him rather than simply withdrawing from the Paris agreement himself. Like it or not, climate change has become a central concern on the global stage that drives a great deal of modern diplomacy. And for good reason: The only workable response to the threat is an international one based on U.S. leadership and mutual trust. Pulling out of Paris would uselessly undermine both.