Republican lawmakers are scratching their heads over President-elect Trump’s ambitions to take over Greenland and the Panama Canal, grand plans the incoming commander in chief put back on the table over the Christmas and New Year’s recess.

Global warming is making both places more important to global shipping and trade. To imagine the kind of future a hotter, dryer climate may bring, and the geopolitical challenges it will create, look no farther than two parts of the world that Donald Trump wants America to control: Greenland and the Panama Canal.