Stephen isn t it worth noting in the article that historically CO2 bottoms out at about the 400 ppm level If you look at the Tertiary period in that graph it clearly shows CO2 levels starting at about 1000 ppm then leveling out far before industrial production began They have no where to go but up at least it appears that way from past behavior of the planet This just seems like relevant information that people reading up on Global Warming would want to know