In recent months, climate gurus like James Hansen and Bill McKibben have done some boat-rocking in the environmental world by proposing a new goal for stabilizing atmospheric carbon concentrations. They now say the mark should be 350 parts per million (as opposed to the IPCC-backed goal of 450 ppm)—a more than 10 percent reduction from the current level of 390 ppm. Keith Johnson of The Wall Street Journal's enviro blog is skeptical:

Bill McKibben—who describes himself as "scholar in residence in environmental studies at Middlebury College"—admitted it's a daunting task... The group [] suggests enthusiasts donate $350 of their tax rebates to the organization to spread the good word. The mission would be easier if the group settled on the IPCC's more-moderate target of 450 ppm. Come to think of it, the fundraising checks would be bigger too.

And there's something to all of this: 450 is a bigger number than 350, and Bill McKibben does describe himself as "scholar in resdidence in environmental studies at Middlebury College"... because that's what he is.

At any rate, 350 ppm is, I'd guess, an impossible goal. But that doesn't mean it shouldn't be the "goal." After all, 450 is all but an upper threshold for carbon concentrations, and since we're likely to overshoot whatever mark we set for ourselves, lower seems fine to me. Here's another idea: Instead of 80 percent emissions reductions over the next 40 years, why not aim for carbon-neutrality by mid-century? May be hard. May be impossible. But the closer we get to "zero" net emissions the better, and "carbon neutrality" is a much more resonant and colorful concept than is a such-and-so percent reduction of whathaveyou.

--Brian Beutler