Reactions to President Donald Trump’s withdrawal from the Paris accord on climate change are -- forgive me -- overheated. The ACLU is calling it an “assault on communities of color,” for some reason, and environmental activist Tom Steyer says it’s a “traitorous act of war against the American people.” For his part, Trump says that staying in the agreement would have assured us a future of “lost jobs, lower wages, shuttered factories and vastly diminished economic production.”

Yet Trump and his critics alike know that very little in the accord is binding on the parties to it....