The Last Time CO2 Was This High, Humans Didn’t Exist

NASA scientists react to 400 ppm carbon milestone “Passing the 400 mark reminds me that we are on an inexorable march to 450 ppm and much higher levels. These were the targets for ‘stabilization’ suggested not too long ago. The world is quickening the rate of accumulation of CO2, and has shown no signs of slowing this down. It should be a psychological tripwire for everyone.” – Dr. Michael Gunson