In his speech today at Georgetown, President Obama said that the Keystone XL pipeline would only be approved if it "does not significantly exacerbate the problem of carbon pollution."
That word "exacerbate" would appear to leave a lot of wiggle room. It means to aggravate, to sharpen, or to make a bad problem worse. The anti-Keystone crowd naturally thinks that the pipeline, or anything that aids in the transport of oil sands crude would exacerbate carbon emissions. But that's not what the State Department found. In March, in its draft environmental impact review, State determined that Keystone XL would have a small impact on greenhouse gas emissions, simply because in the absence of Keystone the oil sands would get to market some other way — by one of the many other pipelines that already move oil sands south into the U.S. or west to the Pacific, or by train. (WaPo's Brad Plumer had this deft analysis at the time.)