Why increasing CO2 is a significant problem — in six easy steps
NASA scientist Gavin Schmidt continues to do terrific blogging at RealClimate explaining climate science and the immateriality of the illegally hacked e-mails to our broad understanding of human-caused global warming. That, of course, is why the anti-scientific ideologues are going after him so hard (see “Competitive Enterprise Institute to sue RealClimate blogger over moderation policy“).
He was asked recently on RC, “what percentage of global warming is due to human causes vs. natural causes?” I’m posting his reply here because it’s a good answer and frankly much clearer than the one science advisor John Holdren gave at today’s House hearing to an almost identical question — though I thought Holdren and Lubchenco were both terrific, especially in their opening statements, and I hope to get those videos up as soon as they are available. Schmidt explained:
Over the last 40 or so years, natural drivers would have caused cooling, and so the warming there has been … is caused by a combination of human drivers and some degree of internal variability. I would judge the maximum amplitude of the internal variability to be roughly 0.1 deg C over that time period, and so given the warming of ~0.5 deg C, I’d say somewhere between 80 to 120% of the warming. Slightly larger range if you want a large range for the internal stuff.
Schmidt has a new post today on the emails, in which he urges people to read a 2007 post that provides “an easy-to-understand explanation for why increasing CO2 is a significant problem without relying on climate models,” which I am reposting below: Read more