Have you heard the urban legend that keeps making the rounds—that exporting massive amounts of coal to Asia could actually be good for the climate?

Well, when I was a kid, I was convinced that eating Pop Rocks and Coke could kill you. Someone had told me that Mikey, the kid from the Life cereal ad, died that way. And while the story seemed preposterous, it seemed too wacky for someone to have just made it up…so I took it as gospel, and told all my friends about it, too.

As Chip and Dan Heath document in their book, Made to Stick, this is far from an isolated example. Their research shows that kooky, unexpected ideas stick in your head, helping turn a silly story (and, in Mikey’s case, a false one) into a full-blown urban legend.

This, I think, helps explain why the idea that coal exports could be good for the climate keeps making the rounds. For reporters looking for an interesting, quirky coal export story, the idea passes the Made to Stick test: it sounds so crazy that it must be true! And what helps give the story extra legs is the source: a respected research center at Stanford University.

Or is that part of the urban legend too?

There really is a research center at Stanford—The Program on Energy and Sustainable Development (PESD)—that has published some pieces looking at the global coal market. And if you skim through their work, you can find tidbits and soundbites that, when taken out of context, seem to support the idea that shipping coal to Asia might reduce global climate-warming emissions.

But if you read their recent work carefully, you’ll see a much more cautious and nuanced view of the environmental effects of coal exports.

  • Take, for instance, this recent paper by Mark Thurber, the associate director of the PESD. Thurber makes two main points about coal exports. First, he argues that facilitating US coal exports will tend to increase coal prices in the US while decreasing coal prices overseas. And second, he argues that the precise environmental effects of these price changes are hard to gauge, and may be subject to different dynamics over different time scales. According to Thurber:

    It is unlikely that removing the port constraint on PRB coal exports will substantially increase global emissions of greenhouse gases in the short term, but long-term effects are more uncertain and require a more sophisticated analysis. [Emphasis added.]

    In the short term, he argues, the impacts of increasing US coal exports are difficult to predict…

    [P]reliminary modeling work…suggests that, in the short term, removal of the coal port constraint in the U.S. Pacific Northwest may not appreciably increase global greenhouse gas emissions and could even reduce them under certain assumptions.

    …but he goes to great pains to characterize the modeled outcomes of global coal demand as contingent, and heavily dependent on assumptions:

    While this is a plausible short-term outcome, the predicted results depend significantly on model assumptions. [Emphasis added.]

    Those “model assumptions” are mostly about how coal consumers in different parts of the world will respond to changes in coal supplies and prices. In particular, if you assume that Asian industries and utilities will burn the same amount of coal no matter how much coal the US exports, then increasing US exports won’t have any effect on Asia’s emissions. Leaving aside that this is an example of what philosophers call “begging the question“—a kind of circular reasoning in which you assume what you’re trying to prove—there’s a fair amount of empirical evidence that this particular assumption is wrong, at least over the long term. In China, for example, demand for coal already appears to be fairly price sensitive and is getting more so. This 2009 paper suggests that for every 10 percent increase in coal prices, China’s demand for coal declined by 11.6 percent over the long run (though short-term elasticities are much lower). This 2013 study concluded that US coal exports would significantly increase China’s emissions over the long haul. And while this 2014 research from the Australian National University gives a lower estimate for the price-sensitivity of Chinese coal consumers, it suggests that the nation’s coal consumption is growing increasingly reactive to the cost of coal.

    Regardless, Thurber isn’t saying that increasing exports will necessarily reduce emissions. He’s saying that the effects of coal exports are uncertain and that the models used to forecast those effects are highly dependent on the assumptions—but nobody can be sure what the right assumptions really are.

    In addition, Thurber is careful to note that the long-term effects of US coal exports include a significant upside risk for global coal emissions, in part because a reliable coal supply could lock developing economies into long-term capital investments in coal-fired power:

    [T]he availability of 150 million tonnes a year of PRB coal (and perhaps much more) and the knowledge that the “Saudi Arabia of coal” is open for business might indeed play some role in reassuring project developers in Asian countries with limited domestic coal reserves that coal plants are a safe investment.

    In short, Thurber’s work provides little support for the urban legend that coal exports would be good for the climate. Thurber’s analysis is muted, careful, appropriately recognizes the inherent uncertainty in political and market forecasts, and describes different dynamics for short- and long-term effects of coal exports. As a serious researcher, Thurber fully and appropriately recognizes the inherent uncertainty in coal consumption forecasts.

    But when translating academic research into an urban legend, the uncertainty gets lost…and all that remains is a catchy but unsubstantiated factoid, based on sound bites taken out of context.

    So the next time you hear someone argue that it’s a scientific fact that US coal exports would reduce global warming, remember Pop Rocks and soda pop—and the actor who most certainly did not die from the combination.