historic low of sub ppm co levels shouldn't it be mentioned somewhere that at ppm today we are at an historic low of co concentrations when we look back at past co levels the only other time co has dropped below ppm has been the late carbiniferous some million years ago but at all other times co has been above ppm the graph here shows co levels with a black line and temperature is the blue line in fact it's been as high as ppm during the cambrian period which was so favorable to life that it resulted in the famous cambrian explosion an explosion of biodiversity this seems to contradict the predictions that our ppm level will result in dire consequences for life it's a basic crime of omission by leaving these facts out