Richard Alley quotes:

The more the climate is forced to change, the more likely it is to hit some unforeseen threshold that can trigger quite fast, surprising and perhaps unpleasant changes.

The ice sheets seem to be shrinking 100 years ahead of schedule.

If humans weren't here and we didn't care about anything that lives here, if this were a video game, I'd push the button and see what happens, because it'd be really exciting; but it's not a video game.