Climatologist Andrew Weaver asks me to direct folks to this website and this video, ”in case the tar sands piece that Neil [Swart] and I published yesterday gets spun as a ‘tars sands is good’ story”:

I do think Weaver’s study — “The Alberta oil sands and climate” in Nature Climate Change (subs. req’d) – is a tad confusing. For instance, it doesn’t even include the extra emissions from tar sands extraction in its calculations!! So people who don’t actually read it carefully are likely to misreport its findings.

According to Time magazine, “Pipeline Politics: Are the Oil Sands ‘Game Over’ for the Climate? One Study Says No”:

The good news from the Nature Climate Change paper is that, should environmentalists lose their battle, the consequences might not be quite as bad as they’ve made it out to be.

Except that isn’t what the study finds. Indeed, the final paragraph states

If North American and international policymakers wish to limit global warming to less than 2 °C they will clearly need to put in place measures that ensure a rapid transition of global energy systems to non-greenhouse-gas-emitting sources, while avoiding commitments to new infrastructure supporting dependence on fossil fuels.

In short, if you care about the 2C (3.6F) target, building something like the tar sands pipeline is a really bad idea.

By the way, if you care about a 3C (5.4F) target, building something like the tar sands pipeline is also a really bad idea — see IEA’s Bombshell Warning: We’re Headed Toward 11°F Global Warming and “Delaying Action Is a False Economy.” Risking 3C, roughly 550 ppm [assuming there aren't major carbon-cycle feedbacks], is not a good idea at all, as many studies make clear (see, for instance, New study of Greenland under “more realistic forcings” concludes “collapse of the ice-sheet was found to occur between 400 and 560 ppm” of CO2).

If 7+°F global warming — 10+°F warming over most of U.S. — by century’s end is fine with you, then the tar sands is not worth bothering about. Of course that is “incompatible with organized global community, is likely to be beyond ‘adaptation’, is devastating to the majority of ecosystems & has a high probability of not being stable (i.e. 4°C [7F] would be an interim temperature on the way to a much higher equilibrium level),” according to Professor Kevin Anderson, director of the Tyndall Centre for Climate Change in Britain (see here).

NASA’s James Hansen himself says of the new paper:

“The argument that the currently known amount of carbon in the tar sands pit is small compared to the total fossil fuels burned in two centuries is fallacious and misleading — every single source, even Saudi Arabia, is small compared to the total. If we once get hooked on tar sands and set up infrastructure, the numbers will grow as mining capabilities increase. Tar sands are particularly egregious, because you get relatively less energy per unit carbon emitted and there is associated environmental damage in the mining.”

Indeed, the point of the new study is pretty much the same as the forthcoming paper from Hansen (see figure below). I’d put it this way:

There are big pools of carbon that the world must not burn. Since the United States is responsible for more cumulative CO2 emissions than any other country and has to cut emissions by more than 80% in four decades to do our fair share to avert catastrophe, it’s quite safe to say that from America’s perspective, the huge pool of unconventional oil vastly dirtier than conventional oil up north is definitely on the no-burn list.

The study makes that point in a fairly straightforward way:

To have a 66% chance of limiting warming to less than the 2 °C limit put forth in the 2009 Copenhagen Accord, one carbon– climate modelling study estimated that total future global carbon emissions should be limited to less than 5.9×1017 g C (ref. 9). If this amount were to be distributed equally among the current global population, the resulting allowable per capita cumulative carbon footprint would be 85 tonnes of carbon. The eventual construction of the Keystone XL pipeline would signify a North American commitment to using the Alberta oil-sand reserve, which carries with it a corresponding carbon footprint. For comparison, by fully using only the proven reserves of the Alberta oil sands, the current populations of the United States and Canada would achieve a per capita cumulative carbon footprint of 64 tonnes of carbon.

Let me clear up one serious confusion about the study right now. The study does not actually include the extra emissions from tar sands extraction in its core calculations, as it states clearly:

Additional emissions resulting from natural gas, diesel and electricity use during bitumen extraction, upgrading and refining have not been included here, but could increase these numbers (see Supplementary Information).

The authors separately do a calculation on their website that indicate those extra emissions would add some 17% to the emissions they calculate.

What this means is that if the U.S. and Canada use only the proven reserves of the Alberta oil sands – 170 billion barrels, which we could do this century if production is quadrupled — then in fact we’d hit 75 tonnes of carbon per capita cumulative carbon footprint. The point is, even this modest exploitation of the tar sands — a small fraction of the total “oil in place” — would blow out any chance of the U.S. and Canada contributing our share to the 2C target. Or a 3C target.

That is the point Hansen and McKibben and I and many others have been making over and over again:

CO2 emissions by fossil fuels [1 ppm CO2 ~ 2.12 GtC, where ppm is parts per million of CO2 in air and GtC is gigatons of carbon] via Hansen. Significantly exceeding 450 ppm risks several severe and irreversible warming impacts. Hitting 800 to 1,000+ ppm — which is our current emissions path and the inevitable outcome of aggressively exploiting unconventional fuels like the tar sands as Nocera advocates — represents the near-certain destruction of modern civilization as we know it as the recent scientific literature makes chillingly clear. [Estimated reserves and potentially recoverable resources are from EIA (2011) and GAC (2011).]

This is also pretty clear from Weaver’s paper. But it is presented in a way that the global warming hand-wavers — those who never tell you what their temperature or concentration target is — can, well, wave away with their hands:

As you see, by including all of the coal and gas, it looks like the tar sands make such a tiny contribution as to be insignificant. But the tar sands contributions is only insignificant in a world with a climate that is ruined, one that simply will not support 9 billion or more people. In short, if we destroy civilization with coal, tar sands isn’t a big deal. Woo-hoo!

As Bill McKibben puts it:

Today’s study is akin to saying: “True, smoking six packs a day is going to kill you. But if you want to make certain you die, smoke a hundred packs a day. And if you really want to make sure you die tomorrow, lie down in front of a train.”

Time magazine reports

Andrew Weaver and Neil Swart of the University of Victoria in Canada first modelled the warming impact of burning the 170 or so billion barrels of crude believed to be technically recoverable from the Albertan oil sands. They found that burning all of that carbon would produce just 0.02 to 0.05 C of warming. As David Biello of Scientific American points out, global warming to date is 15 times greater than that.

Should energy companies figure out a way to mine and burn all 1.8 trillion barrels of oil believed to be in the oil sands, the warming would obviously be greater—but not that much greater. Weaver and Swart estimate all that oil would lead to an additional 0.36 C of warming. Given that many scientists believe we need to prevent 2 C of warming above pre-industrial levels to avoid catastrophic effects—and that we’re already a little less than halfway there—the oil sands seem to represent an important but not decisive front in the climate battle.

The 170 billion isn’t the technically recoverable oil. It’s the “economically viable proven reserve,” which will rise over time as oil prices rise (and extraction technology improves).

And burning it, including all related emissions from extraction and the like, is probably at least 0.04 C of warming, which is about 10% of the total additional warming we can risk if we are sane.

So just the “economically viable proven reserve” we could well burn this century are a big, big deal. The oil-in-place is an unmitigated disaster.

Now you can certainly argue that we aren’t going to stabilize at 2C, but that is a political conclusion and has no bearing on whether climate scientists and climate hawks are right that going beyond 2C is dangerous and immoral.

Certainly if we do going beyond 2C it’d be nuts not to try as hard as humanly possible to stabilize at, say, 2.5C (4.5°F), which again means we need to stop wasting staggering amounts of money to expand dirty fossil fuel resources like the tar sands.

David Biello of Scientific American writes on the study with this sub-hed, “The Keystone XL pipeline wouldn’t be a major environmental calamity, but oil addiction is.” He concludes:

Nevertheless, building the pipeline keeps us in the carbon habit, through which the U.S. burns roughly 20 million barrels of oil a day along with copious quantities of coal and natural gas. Ending our fossil fuel addiction is the only way to truly combat climate change.

So Keystone is no big deal, yet we need to end our fossil fuel addiction. But if we are planning to end our fossil fuel addiction in a timely enough fashion to avert catastrophic warming, then, as the study says, we ought to be “avoiding commitments to new infrastructure supporting dependence on fossil fuels” which would certainly include Keystone.

Bottom Line: In the world we must strive to achieve, however difficult or implausible it may seem today, expanded extraction of the tar sands has no place.