Bill McKibben can be counted on to explain critical truths in simple ways, and in this case he had some help from his editors at the Washington Post, and from James Hansen, who took advantage of last year’s meeting of the American Geophysical Union to argue that we’re already over a key Earth-system tipping point.
There’s a lot of analysis behind this (check our Hansen’s web page if you want to see how much) but McKibben, a seasoned journalist, get’s just the right quote: “The evidence indicates we’ve aimed too high — that the safe upper limit for atmospheric CO2 is no more than 350 ppm.” And, of course, the current level of 383 ppm is well past 350. Does this mean that we’re doomed McKibben’s answer is “not quite,” and it’s the right one. But there’s no more time to waste. Continue reading “Remember This: 350 Parts Per Million”