Back to 1988: 350 PPM co2

Back to 1988 (350 PPM) on CO2, Says NASA's Hansen. Andrew C. Revkin, NYTimes, March 19, 2008. "James E. Hansen, the NASA climate scientist who has long had a habit of pushing past where many colleagues [have dared] go in describing the risks posed by global warming, has done it again. He and eight co-authors have drafted a fresh paper arguing that [20 years ago] the world... shot past a safe... [level] of carbon dioxide, which they say would be around 350 parts per million... (The atmosphere currently holds about 385 ppm of the greenhouse gas.) Looking at evidence from past climate swings and greenhouse-gas concentrations, he concludes that a sustained concentration of CO2 at double the 280 ppm that prevailed for hundreds of millenniums before the industrial revolution would -- after a host of slowly-responding feedbacks kicked in to amplify the temperature rise -- result in an enormous warming of some 11 degrees Fahrenheit (6 degrees Celsius). To avoid a centuries-long slide to conditions profoundly different than those that saw the rise and spread of modern civilization, the paper concludes, humans need to reverse course on emissions rapidly... This is [Hansen's] first detailed defense of the [350 parts per million] target. The paper's main conclusions are below. Some longtime champions of Dr. Hansen, including the Climate Progress blogger, Joe Romm, see some significant gaps in the paper (it is a draft still) and part ways with Dr. Hansen over whether such a goal is remotely feasible. The draft paper... 'Target CO2: Where Should Humanity Aim?' [PDF, 38 pp] was posted Monday at Dr. Hansen's Columbia University Web page." Remember This: 359 Parts Per Million. Commentary by Bill McKibben, WashPost, December 28,2007. "The number every person needs to know."