In fact, this should be a no-brainer for the president, for all the reasons I stated earlier, and one more: the strategy of activists like McKibben, Brune and Hansen, who have made the Keystone pipeline their line in the sand, is utterly boneheaded.

Brune and McKibben have been very clear about what they hope to accomplish. Oil companies have invested upward of $100 billion to extract the unconventional oil in the sands. A pipeline is the only way to export it. The Keystone pipeline is Canada’s Plan A. Plan B is a pipeline to British Columbia, which would get the oil to China. If the president blocks Keystone, and the First Nation tribes continue their staunch opposition to the western pipeline, then Canada will have the second largest oil reserves in the world — and no place to sell it. The assumption of the activists is that by choking off the supply of new oil sources like the tar sands, the U.S. — and maybe the world — will be forced to transition more quickly to green energy.

Can you see how backward this logic is? As Adam Brandt, an energy expert at Stanford University, pointed out to me recently, so long as the demand is there, energy producers are going to search for new supplies of fossil fuel — many of them using unconventional means like tar sands extraction. “With growing global demand, the economic pressure to develop unconventional resources is enormous and not going away,” he said. “Can environmental groups expect to win a series of fights for decades to come, when the economic forces are aligned very strongly against them in each round?” The answer is obvious: no. The emphasis should be on demand, not supply. If the U.S. stopped consuming so much of the world’s oil, the economic need for the tar sands would evaporate.

On Monday, I finally spoke to Hansen. His knowledge and sincerity are easy to admire, even if his tactics are not. He told me he would like to see oil companies pay a fee, which would rise annually, based on carbon emissions. He said that such a tax could reduce emissions by 30 percent within 10 years. Well, maybe. But it would also likely make the expensive tar sands oil more viable. If you really want to eliminate expensive new fossil fuel sources, the best way is to lower the price of oil, which would render them uneconomical. But, of course, that wouldn’t exactly lower demand either.