without human intervention, the concentration of co2 has climbed as high as 7,000 parts per million (ppm) in prior eras, whereas at present the concentration is just over 400 ppm.
without human intervention, the concentration of co2 has climbed as high as 7,000 parts per million (ppm) in prior eras, whereas at present the concentration is just over 400 ppm.
carbon dioxide:3
the current concentration is about 0.04% (410 ppm) by volume, having risen from pre-industrial levels of 280 ppm.