There are a couple of watersheds in human evolution. Most people are comfortable thinking about tool use and language use as watersheds. But the ability to play non-zero-sum games was another watershed.
Global warming is one of those things, not like an earthquake where there's a big bang and you say, 'Oh, my God, this is really, has hit us. ' It creeps up on you. Half a degree temperature difference from one year to the next, a little bit of rise of the ocean, a little bit of melting of the glaciers, and then all of a sudden it is too late to do something about it.