Have you seen the newly released study on global temperatures? The previously available data only went back around 2000 years, but this goes back 11,000+ years. If we needed more incentive to begin acting dramatically right now, this is it. Andrew Sullivan calls it the “climate game-changer” and says:

To be perfectly frank, this graph shows our civilization to be unsustainable unless we dramatically alter its source of energy. Maybe we can adapt – in ways our ancestors did. But they were able to do so over much, much longer periods of time, and were not actually creating the situation.

Additional commentary here and here and here.