Ever since Bill McKibben and his organization 350.org chose the Keystone XL pipeline as a rallying point for their anti-climate change movement, a few persistent critics, led by New York's Jonathan Chait, have questioned McKibben's political acumen. Given the undeniable fact that EPA regulations on coal-fired power plants will have a far greater effect on overall carbon emissions than Keystone XL, aren't McKibben and company wasting their time on a side issue?

A key piece of support for this argument was a State Department estimate that the pipeline would have a negligible effect on total carbon emissions, because the oil would simply be shipped by rail. This gave credence to the Chait view, since it implied that McKibben hadn't just picked a less-than-ideal issue as a stand-in for climate change as a whole, but was spending a whole lot of time and energy on an initiative that would literally have almost no impact on climate change.

However, a new study has re-examined the issue and come to a sharply different conclusion. Finding that the State Department analysis didn't consider the effect the pipeline might have on the world oil market, it quadruples state's high-end estimate of what effect Keystone XL might have on carbon emissions, from 27 million tons of additional carbon dioxide per year to 110 million tons.

The study probably isn't the last word on the issue. But the fact that the state analysis didn't consider the global market is a pretty glaring omission. Furthermore, it has always seemed implausible that the pipeline would have no effect whatsoever on total oil consumption; supporters of Keystone have overestimated Canada's ability to transport the oil without the pipeline, which would require some significant construction on Canada's part.

Now, you could argue that 110 million tons is still not very much compared with world emissions of nearly 40 billion tons annually. But as I've argued at length, the Keystone XL fight is about the logic of political organizing, not the arid and bloodless logic of policy design. What American politics desperately needs is a mass movement to add organizational heft and energy to the formal but inch-deep commitment the center-left has shown to climate policy. Bill McKibben knows all about and supports EPA regulations, but the plain fact is that Keystone XL is a far, far better issue for mass mobilization. Without that, the long-term chance of serious climate policy is low.

As Steve Randy Waldman once wrote, "policy is a third-order pile of BS" compared with the creation and maintenance of the moral norms that underpin society.

Still, we have yet more evidence that stopping Keystone XL would, in fact, be a substantively decent move. The question now is whether Chait will acknowledge that this new study punches a big hole in his anti-McKibben case. Back when the State Department analysis came out, he jumped on it with palpable glee. So far he has not mentioned this new one, which adds some weight to my ongoing suspicion that the whole goofy controversy was nothing more than a bunch of pointless contrarianism.