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Geoengineering is No Free Lunch — A Comment on SuperFreakonomics

I’m not going to wade too deeply into the controversy over SuperFreakonomics, the sure-to-be-bestseller by Steve Levitt and Stephen J. Dubner, which is due to be released this week. This is partly because other folks have done a good job of discussing the issues and partly because I feel like I have various conflicts of interest. On the one hand, I’ve met Steve Levitt a couple of times and can vouch for the fact that he’s a relatively apolitical person (and also a kind and generous one). On the other hand, I’m working on my own book project, which while not particularly similar to Superfreakonomics in content or approach will undoubtedly will be competing for some of the same audience (the percentage of the U.S. population that buys “serious”, nonbiographical nonfiction is fairly small). Suffice it to say that I think it’s a good book — more engaging in some ways than the original and easily worth a purchase — but that the fifth chapter on climate science is by far the weakest material in either of the two Freakonomics books.

The fifth chapter comes down in favor of a geoengineering approach to combating the global warming problem, which Levitt and Dubner argue will be cheaper and more practical than a substantial reduction in carbon emissions. What is geoengineering? It is intentionally altering the Earth’s climate system, presumably with the goal of balancing out the effects of global warming. Arguably the two most promising geoengineering approaches are:

— Finding some mechanism to shoot sulfur into the atmosphere — this is the approach that Levitt and Dubner concentrate on in SuperFreakonomics. Sulfur has a cooling effect, as can be observed, for instance, when there is a large volcanic eruption — volcanoes emit lots of sulfur and when Mount Pinatubo erupted in 1991 it cooled the planet’s temperatures by approximately 0.9° F for several months.

— Creating artificial cloudcover. Or to be more precise, modifying clouds to be more reflective, which would modify the earth’s albedo and cause more sunlight to be bounced back into space. This is the approach pursued by Dr. John Latham, a seventysomething British scientist employed by the National Center for Atmospheric Research in Boulder, Colorado, whom I spoke with on the phone several weeks ago.

I’m not going to describe the entirety of my conversation with Latham — which is intended primarily for the book. But the three most essential points he raised are as follows.

Firstly, Latham thinks geoengineering approaches are woefully underfunded — the word he used to describe the current levels of funding was “derisory” — just a few million dollars toward an approach which could potentially combat the multitrillion dollar problem of climate change. “All I can hope for in my lifetime is to see some real funding of the examination of the viability of geoengineering schemes,” he told me.

Secondly, Latham was adamant that geoengineering programs are not looked at as a substitute to carbon reduction schemes but rather as a complement to them. He told me:

“The thing that has scared everyone I know working in geoengineering, and the thing that has caused a lot of very good scientists to say we shouldn’t have it is the worry that if it was announced that geoengineering was to be thoroughly examined, there would be a temptation on behalf of the oil companies to say, “Oh well, they’re going to solve the problem, we can keep burning fossil fuels”. Which is the last thing anyone wants. But then to not examine it would be irresponsible. If we reach that tipping point, we want to be in the position to be able to help out.”

Thirdly, the largest hurdles to geoengineering are arguably not scientific but political. Although geoengineering approaches would almost certainly succeed in reducing the earth’s average temperature, the effects would not be uniform across the globe, nor would they precisely counterbalance the warming effects of CO2.

“There will be a different distribution of temperatures, and rainfall and wind features,” Latham told me. “If our technique was applied and it reduced rainfall in areas where they are struggling for every drop, than in case we couldn’t remedy that, we would consider not using our scheme.”

Certain computer simulations that Latham and his team ran identified, for instance, a reduction in rainfall in South America as a result of one of his suggested implementation proposals. A different implementation scheme might avoid that particular problem, but could cause problems in other areas. Latham seemed reasonably optimistic that with further funding for computer modelling**, such problems could be reduced — but they could not be entirely eliminated. Some regions would have their climates impacted negatively (in terms of crop yields, habitability, etc.) by geoengineering, certainly relative to the status quo and in some cases relative to large-scale warming.

That doesn’t mean that geoengineering would be “bad”, relative to the scenario of runaway warming. It could potentially be a lot, lot better, on balance, for most of the planet. But “on balance” skirts over the regional discrepancies. How would Brazil feel, for instance, if the most optimal scheme happened to reduce its crop yields by 20 percent? How would Bangladesh feel if the approaches increased precipitation in the Himalayas, which in turn increased the flooding in its river deltas? What if we were trying pick between two approaches, one of which might increase the habitability of the Australian Outback, but others of which might make it even less hospitable to human settlement? And just who has the right to shoot a few volcano’s worth of sulfur up into the atmosphere, anyway?

Finally, it should be remembered that geoengineering is not a one-time fix — if we continue to pollute the atmopshere with carbon, we would have to continually release more sulfur into the atmosphere (or seed more clouds, etc.) to combat it.

What you’d have, in other words, is a massive global coordination problem — exactly the sort of problem that makes global warming hard to control in the first place. “I suppose the only hope is for some much more powerful global body to exist that could override the shrill requirements of the particularly selfish,” Latham told me. “But goodness knows how to do that and whether it’s feasible.”


It’s routine to describe geoengineering as a “last resort”. I don’t prefer that language, because it might be the case that geoengineering is the only resort, and it could conceivably also be the case — as Levitt and Dubner argue — that it is actually cheaper than reducing carbon. Almost certainly, these approaches require much more funding and much more serious study. But it would not be a free lunch — the political hurdles would be massive, arguably larger than the scientific ones. And the larger the scale of the warming problem, the more geoengineering will be required, and therefore the higher the political hurdles will be.

** One potential irony here is that, because geoengineering approaches do not lend themselves very well to large-scale, physical experimentation prior to their actual implementation, they would almost certainly require extensive computer modelling. So anyone who is skeptical of what computer models tell us about carbon should be at least as skeptical of any guarantees made by geoengineers.

p.s. I’ve received a couple of e-mails to the effect that while geoengineering approaches like releasing sulfur might “solve” the temperature problem, they would not address the issue of ocean acidification, which also results from CO2 emissions. This is certainly worth mentioning; one of the scientists who wrote me described it as a problem “with consequences so enormous and unforseeable as to make a few degrees C of warming pale in comparison”.

p.p.s. To be clear, I have read the book (I was sent an advance copy two weeks ago).

Nate Silver is the founder and editor in chief of FiveThirtyEight.