Keystone XL: Game over?

The impending Obama administration decision on the Keystone XL Pipeline, which would tap into the Athabasca Oil Sands production of Canada, has given rise to a vigorous grassroots opposition movement, leading to the arrests so far of over a thousand activists. At the very least, the protests have increased awareness of the implications of developing the oil sands deposits. Statements about the pipeline abound.

Jim Hansen has said that if the Athabasca Oil Sands are tapped, it’s “essentially game over” for any hope of achieving a stable climate. The same news article quotes Bill McKibben as saying that the pipeline represents “the fuse to biggest carbon bomb on the planet.” Others say the pipeline is no big deal, and that the brouhaha is sidetracking us from thinking about bigger climate issues. David Keith, energy and climate pundit at Calgary University, expresses that sentiment Andy Revkin says “it’s a distraction from core issues and opportunities on energy and largely insignificant if your concern is averting a disruptive buildup of carbon dioxide in the atmosphere”. There’s something to be said in favor of each point of view, but on the whole, I think Bill McKibben has the better of the argument, with some important qualifications. Let’s do the arithmetic.

There is no shortage of environmental threats associated with the Keystone XL pipeline. Notably, the route goes through the environmentally sensitive Sandhills region of Nebraska, a decision opposed even by some supporters of the pipeline. One could also keep in mind the vast areas of Alberta that are churned up by the oil sands mining process itself. But here I will take up only the climate impact of the pipeline and associated oil sands exploitation. For that, it is important to first get a feel for what constitutes an “important” amount of carbon.

That part is relatively easy. The kind of climate we wind up with is largely determined by the total amount of carbon we emit into the atmosphere as CO2 in the time before we finally kick the fossil fuel habit (by choice or by virtue of simply running out). The link between cumulative carbon and climate was discussed at RealClimate here when the papers on the subject first came out in Nature. A good introduction to the work can be found in this National Research Council report on Climate Stabilization targets, of which I was a co-author. Here’s all you ever really need to know about CO2 emissions and climate:

  • The peak warming is linearly proportional to the cumulative carbon emitted
  • It doesn’t matter much how rapidly the carbon is emitted
  • The warming you get when you stop emitting carbon is what you are stuck with for the next thousand years
  • The climate recovers only slightly over the next ten thousand years
  • At the mid-range of IPCC climate sensitivity, a trillion tonnes cumulative carbon gives you about 2C global mean warming above the pre-industrial temperature.

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