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, it 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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