What's the difference? Scientists still argue — though not as much as deniers would have you believe — about the extent to which climate change is the result of human activity. And they still argue — quite a lot, actually — about how quickly the climate shifts in response to new conditions. As I understand Ruddiman, we humans may have been screwing up the climate for far longer than anyone thought. But that's good — because if we could change things then, we should certainly be able to change them now.

http://www.wired.com/science/planetearth/magazine/16-04/st_essay