.We are in novel territory : Check out this link (Shared via http://ow.ly):

At present pace, the world could reach 450 ppm in a few short decades. The record notches up another 2 ppm per year at present pace. Human civilization developed and flourished in a geologic era that never saw CO2 concentrations above 300 ppm.We are in novel territory again and we show no signs of slowing to get our bearings, let alone stopping.

http://ht.ly/kTeil