Nicholas Stern, world’s top climate economist, endorses 350 ppm as “a very sensible long-term target.”

The great environmental writer and founder of, Bill McKibben, is the guest blogger.

Nicholas Stern is the most important climate economist in the world. After a stint as chief economist at the World Bank, he was asked by the government in his native Britain to conduct the most thorough review of the economics of global warming yet undertaken.

Released in October of 2006, the Stern Review drew praise from many of his brethren in the field — and it also drew gasps of shock and horror from anyone who bothered to read it. It laid out, quite clearly, the cost of doing too little or moving too late on climate change: economic damage that would be greater than WWI, WWII, and the Great Depression combined. In April, he published a powerful popular account of his work, Blueprint for a Safer Planet, and he’s been one of the leading forces preparing for the Copenhagen meeting.

So that’s the background. Today in Berlin, a reporter from one of the city’s papers, Daniel Boese, asked him about the 350 target — which goes well beyond the numbers he was using in his book even in April.It’s a sign of how quickly the tide is shifting, and also of Stern’s intellectual integrity, that he said: “I think it’s a very sensible long-term target.” He went on to explain: “People have to be aware that is a truly long-term target. We have already passed 350ppm, we are at 390 ppm of Co2 and at 435 ppm of Co2-equivalents right now. It is most important to stop the increase of flows of emissions short term and then start the decline of flows of annual emissions and get them down to levels which will move concentrations of CO2 back down towards 350ppm.”


Stern is right, of course — even if we do everything right at Copenhagen, we won’t be back at 350 soon. But unless we do everything right we’ll be back at 350 never ever. His call will help stiffen the push for real measures at the conference.

And in case you’re keeping score, here’s where we are at the moment. The world’s foremost climatologist, James Hansen, first calculated this number with his NASA team. The world’s foremost climate politician, Al Gore, endorsed it nine months ago. The UN’s chief climate scientist, and with Gore the only other man to win a Nobel for work on climate, India’s Rajendra Pachauri, endorsed it late last month. And today the world’s foremost climate economist.

But here’s the thing: none of this would have happened if you hadn’t endorsed it — if you hadn’t worked to build the largest movement about climate change ever. Onward!

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JR: For the science behind 350, see “Stabilize at 350 ppm or risk ice-free planet, warn NASA, Yale, Sheffield, Versailles, Boston et al.” Since the science is preliminary and it is not not yet politically possible to get to 450 ppm, let alone 350, my basic view, as expressed in that post, is Let’s start working now toward stabilizing below 450 ppm, while climate scientists figure out if in fact we need to ultimately get below 350. Either way, this is what needs to be done technology-wise: “How the world can (and will) stabilize at 350 to 450 ppm: The full global warming solution (updated).” The difference between the two targets is that for 450 ppm, you need to do the 12–14 wedges in four decades. For 350 ppm, you (roughly) need 8 wedges in about two decades plus another 10 wedges over the next three decades (and then have the world go carbon negative as soon as possible after that), which requires a global WWII-style and WWII-scale strategy (see “An open letter to James Hansen on the real truth about stabilizing at 350 ppm”).