A paper just out in Nature Climate Change finds that the climate cost of exploiting the Alberta tar sands is very slight: +0.03°C.
Neil Swart and Andrew Weaver added up the carbon in the oil sands -- total (1.8 trillion barrels), the economically viable "proven reserves" (170 Bb), and the amount currently under active development (26 Bb).
They then simply applied a carbon-climate response of 1.5°C per trillion metric tonnes of carbon burned. The result is the chart shown to the right. (The response function is, they write, observationally constrained to be between 1.0 - 2.1°C.)
That's less than I calculated last month, but then, I was being somewhat loose with my numbers, and the carbon-climate response I assumed was equivalent to 2°C/TtC.
It's difficult to argue that an extra 0.03°C of warming will be catastrophic, whatever future warming is. It won't even be noticeable. They didn't add any tar sands premium -- extra greenhouse gases from the tar sand-based oil itself, and the extra energy needed to extra the tar sands, compared to conventional oil, which is something like 20% -- that would make the temperature change +0.04°C instead. Meanwhile those proven reserves are worth about $17 trillion at today's prices -- one-fourth of world GDP; ten times Canadian GDP. I don't know how much of this money Canada will actually retain -- a CBC program I watched recently suggested it may be as low as $1/barrel. Still, $170 B is nothing to scoff at. And, of course, the world still runs on oil, and that's simply not going to change anytime soon.
Climate, of course, isn't the only consideration regarding the Keystone XL pipeline, and maybe not even the prime consideration. But it has been a used as an argument to stop building the pipeline. That simply isn't credible. (Though Bill McKibben recently told Joe Nocera, "Keystone, by itself, won't make or break the environment.")
Of course, that's the problem with all such considerations as this -- individually any additional carbon emitted looks very small, if not infinitesimal -- but collectively it all adds up, over decades, to an enormous impact. Humans have never been good at dealing with these kind of issues, either in our personal lives (it's only one doughnut) or collectively.
So I would say: Joe Nocera beats Joe Romm.
PS: Who's betting Romm ignores this paper?