What happened to Obama’s famous nuance? His subtlety? His Burkean grace notes? His Niebuhrian distrust of glib certitudes? None were on display today in Copenhagen, where he gave a stirring call to arms to fight climate change — on the seas and oceans and on the beaches, and in the fields and in the streets, as it were. Obama wanted “bold and decisive” action, to fight a “grave and growing” danger. He was impatient with mere talk — he wanted action. He used the word “must” several times and in contrast to his warnings to our enemies, actually seemed to mean it. So where did all of Obama’s famous complexity go? He saves that mostly for things he’s ambivalent or doesn’t care much about (usually in the area of national security) or for occasions when he needs to obfuscate (the Philadelphia race speech). When it’s something that truly moves him — like massive new spending programs, or a sprawling, government-heavy revamp of health care, or new government intrusion into every aspect of the economy in the name of fighting climate change — then he’s positively Churchillian.