It has long been stated that 450 parts per million (ppm) represents a dangerous threshold for atmospheric carbon dioxide concentrations in regard to climate change. Noted climate activist Bill McKibben traces the arbitrary manner in which this was arrived [ark]. He further reports that leading climate scientist Jim Hansen [search], on the basis of more intensive observation of global warming as it unfolds, now proposes that the threshold for dangerous climate change is in fact 350 (ppm)!?

So what you may ask? Humanity has already pushed carbon concentrations from 275 ppm to 383 ppm. Thus the world’s leading climate scientist has concluded we have already surpassed the point where global heating is dangerous, and is on the verge of becoming abrupt and run-away.