Professor Barry Brook holds the Sir Hubert Wilkins Chair of Climate Change and is Director, Research Institute for Climate Change and Sustainability at the University of Adelaide (see: http://www.adelaide.edu.au/directory/barry.brook and www.adelaide.edu.au/climatechange ) See also his superb, informative and authoritative “Brave New Climate”: Blog: www.bravenewclimate.com ).
Professor Barry Brook:: “If the planet is like an oven, it's still possible to turn down the temperature. The number is 300 and the methods will be extraordinary. In 2007, a climate awareness campaign was launched by well-known environmental author Bill McKibben. It was coined 350.org, with the slogan "350 is the most important number on the planet". The figure refers to a target concentration of carbon dioxide (CO2) in the Earth's atmosphere, in parts per million (ppm). This number was drawn from a recent study by a team of climate scientists, led by NASA's Dr James Hansen ... But there is another, more surprising, problem with 350. It's the wrong number. While 350 ppm should give us a reasonable shot at avoiding more than two degrees of warming, that's hardly a safe future to be aiming for. We need only to look at the impacts at less than one degree to know we're already committed to some tough adaptation problems … A target of 300 to 325 ppm CO2 - the levels of the 1950s - is necessary if we wish to cut additional warming and start to roll back the already damaging impacts. As such, 350 is not a target, it's a signpost to a goal. So we're aiming at 350 but the real goal is 300 and we're already at 385”. [1, 2].
[1]. Professor Barry Brook, “Six degrees of separation”, Sydney Morning Herald, 23 March 2009: http://www.smh.com.au/environment/earth-hour/six-degrees--of-separation-for-the-planet-20090324-984c.html .
[2]. Professor Barry Brook, “BraveNewClimate.com: http://bravenewclimate.com/ .