Believe it or not, intelligent, informed people who are passionate about preserving a livable climate disagree about whether or not the Keystone XL pipeline is a target worthy of environmental ire.

Keystone XL has been called "game over for the climate" by none other than NASA climate scientist James Hansen, and Bill McKibben (full disclosure: he sits on Grist's board) has gotten himself arrested in order to stop its construction. Protests against Keystone XL have been popping up all over.

But an important piece by Lloyd Alter in (of all places) Treehugger points out that tar sands oil is already getting to market, but in a far more dangerous way — by rail. In other words, as scary as a giant pipeline might be, it's probably safer than the way we're shipping that same oil now. (Separate from Keystone's impact on the climate, there's a healthy debate about the magnitude of the inevitable spills that will accompany its operation.)

Meanwhile, Canadian energy economist Andrew Leach points out that the argument over whether or not the Keystone XL pipeline will further America's addiction to oil neglects the fact that, on balance, the pipeline will probably have no net effect on gasoline prices.

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If anything, the immediate effects of Keystone XL will be to increase gas prices in some parts of the country, because it eliminates the supply bottleneck in the Midwest that is artificially depressing prices there. (That's the same bottleneck that shipping by rail already addresses, but shipping by rail is more expensive than using a pipeline.)

This runs contrary to the logic of retired U.S. Army brigadier general Steven M. Anderson, who argued in The Hill that Keystone XL will simply perpetuate our dependence on oil, and thereby endanger our national security.

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In the abstract, it seems true enough that anything that makes oil easier to get or gives us access to new supplies of it will only further our addiction. The problem with that logic is that it ignores the fact that oil is a global market, and its price is for the most part not set by the U.S. Keystone XL is not a unique enabler of the extraction of tar sands oil — there are plenty of customers for that oil already, and global markets have for the most part already figured out how to get it to them.

As Leach and Alter note, there's plenty of empirical evidence that trying to address oil addiction by constraining the supply side of the equation is doomed to failure. If we want to get off oil, we have to address the demand side. That means efficiency, and in a perfect world, taxes on fossil fuels that reflect their external costs. For example, a tax that reflected the extra carbon that tar sands oil represents would probably do far more to curb its use than the presence or absence of the Keystone XL pipeline.