Andrew Weaver of the University of Victoria is one of Canada’s more outspoken scientists, and in the past two weeks he’s done even more speaking out than usual. First, it was the federal government’s alleged muzzling of scientists. Then on Sunday Weaver, along with PhD candidate Neil Swart, published a commentary in Nature Climate Change which showed that the potential global warming from Alberta’s oil sands is actually quite small compared to that from other fossil fuel sources, such as coal and natural gas. That may sound surprising, but it shouldn’t. The numbers weren’t exactly new; it’s the way Weaver and Swart presented them that made all the difference. And despite what some may argue, this study in no way provides a green light for oil sands development. Weaver is obviously a busy guy, but I did manage to talk to Neil Swart earlier this week. Here’s the story behind the latest paper.

It all started last fall, when the debate over the Keystone XL pipeline was in full swing. Things got a little heated, and at some point someone (many sources credit NASA’s James Hansen) called Alberta’s oil sands “the fuse to the biggest carbon bomb on the planet.” Weaver and Swart are no fans of the oil sands, but the phrase struck them as a bit hyperbolic. They got to wondering just how much the world would heat up if all the oil in Alberta was burned. “We looked around and couldn’t find the numbers, and that’s when we decided to calculate them,” says Swart.

This wasn’t as hard as it might seem. Figures for the total reserves in the oil sands were readily available from Alberta’s Energy Resources Conservation Board. Other fossil fuel reserves were found by digging through BP’s latest statistical review of world energy, and a report from the International Institute for Applied Systems Analysis (IIASA). The next step was to put each form of fuel on an equal basis by converting the amount of fuel into an amount of carbon: a tonne of coal contains more C atoms than a tonne of oil, so the only fair way to compare them is on a carbon basis. (While it’s true that extraction takes energy, that energy often comes from fossil fuels as well, so rather than double-count it, Swart and Weaver chose to leave extraction out of their main analysis.)

The final step was to determine how much warming all that carbon would lead to. This too was fairly straightforward. In 2009 a key paper in Nature written largely by Canadian researchers demonstrated that over the medium-term (100 to 1000 years) the total warming due to anthropogenic CO2 emissions depends only on the total amount emitted, not the rate. This is important so it bears repeating: if you were to release a given amount of carbon over 1 year or 100 years, the total medium-term warming would be about the same. The authors go on to say that for every trillion tonnes of C put in the atmosphere, we’ll get approximately 1.0 to 2.1 degrees C of warming, no matter how fast or slow it’s emitted.

This enabled Swart and Weaver to calculate that if we burned every last drop of oil sands oil tomorrow, the global temperature change would be only about 0.36 degrees C of warming. But of course, not all that oil is considered recoverable. Restricting their analysis to proven recoverable reserves showed only 0.03 degrees C of warming. This compares to 0.53 degrees C of warming calculated for burning the total world oil supply, 2.86 degrees C for the total world natural gas supply, and 14.79 degrees C for the total world coal supply.

It’s important to bear in mind that at its most basic level, all the paper is saying is that there are more carbon atoms sequestered in the form of coal and natural gas than there are in the form of oil. This much we knew, and some sources have been saying as much for a long time. So what’s new about this paper? I’ll let Neil Swart express himself in his own words:

This is not a research article. There’s no new scientific techniques, or anything sophisticated about it. But it was peer-reviewed, using a level of quality control that allows it to be submitted into the scientific discourse. It’s an opinion piece, but one based very much on a set of facts. Yes, the data is publicly available, but that data is typically expressed in terms of barrels of oil, or tonnes of coal. What I can really get my head around is a temperature number, so that’s why we went down this path. We wanted to illustrate these points in the simplest and clearest manner. Our goal was to establish a good set of reliable facts on which to base our discussion, rather than emotional rhetoric.

What could be better than scientists using their skills to bring clarity to a complex issue? Than communicating data in a way the general public can understand? Then wanting to base a discussion on facts rather than rhetoric? To me, the biggest wonder is not the fact that coal poses a bigger potential danger than the oil sands. It’s that it took so long for someone to express this well-known fact in a way that will (hopefully) stick in people’s heads.

But lest you get the wrong impression, this study absolutely does not give the oil sands a clean bill of health. As Andrew Weaver himself points out, there is still plenty to worry about when it comes to oil sands development: release of environmental toxins, destruction of boreal forest, water management issues, impact on First Nations communities, etc. His key point is that the oil sands, symbolic as they may be, are merely a symptom of a larger problem, which is our addiction to fossil fuels writ large. The only way out is to reduce our consumption and support our scientists and engineers as they look for cleaner, greener, and more renewable sources of energy.