Diplomats from around the world converged here this week with the plan to put details on last year’s Paris climate accord and move the globe closer to controlling the industrial emissions that are heating the planet. Instead, with the election of Donald J. Trump — and his threat to withdraw the United States from the accord — shellshocked negotiators confronted potentially deep fissures developing in the international consensus on climate change . On the sidelines of the negotiations, some diplomats turned from talking of rising seas and climbing temperatures toward how to punish the United States if Mr. Trump follows through, possibly with a carbon-pollution tax on imports of American-made goods.