Whatever led President Obama to believe that his personal intercession at the climate-change summit would achieve something major, his very presence in Copenhagen made "a significant breakthrough" a political imperative, no matter how flimsy. And that's exactly what a senior Administration official called a last-ditch deal—details to come—in a media leak as we went to press last evening and the conference headed into overtime.

Mr. Obama's inexplicable injunction yesterday that "the time for talk is...