Update Oct 18 11:07am PST: My email exchange with Steven Levitt is here.
Update Oct 19: My (concluding?) thoughts here.
Joe Romm at climateprogress.org posts a PDF of the climate change chapter in the forthcoming book Superfreakonomics by economist Steven Levitt and journalist Stephen Dubner, and in my opinion the chapter is misleading and incredibly disappointing. Here are some details, and BTW since Steven Levitt doesn’t do any research on climate economics my hunch is that Dubner is responsible for the misleading perspective in the book.
FYI you’ll need to read the PDF of the Superfreakonomics chapter to get the page references that follow.
- p 165: It’s fair game to bring up media stories about “global cooling” from the 1970s, but it’s not appropriate to compare a couple of media stories from the 1970s with the scientific consensus of the past decade. Yes there are wacky scientists who believe all sorts of things—e.g., that HIV doesn’t cause AIDS—but the current scientific consensus on climate change is supported by almost everybody. That doesn’t mean it’s correct, but it does mean that this is an unfair comparison.
PS. For more on the current scientific consensus, consider IPCC 2001 (“[M]ost of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”), National Academy of Sciences 2001 (“The IPCC’s conclusion… accurately reflects the current thinking of the scientific community on this issue”), American Meteorological Society 2003, American Geophysical Union 2003, or the American Association for the Advancement of Science 2000, all cited in Oreskes 2004. The most recent IPCC report is IPCC 2007: “Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.”
PPS. For an anecdotal/personal perspective, consider this: I know lots of climate folks at the University of Washington, and I don’t know a single one who doubts that human activity has played an important role. Maybe there are some skeptics at UW, and there certainly are smart climate scientists elsewhere who are skeptics, like Richard Lindzen at MIT, but the agreement among climate scientists is pretty much universal. Again, that doesn’t mean they’re correct, but it does mean there’s near-universal agreement among climate scientistst. Superfreakonomics makes a big understatement in saying (on p166) that “[t]here is essentially a consensus among climate scientists that the earth’s temperature has been rising and, increasingly, agreement that human activity has played an important role.”
- p 167: “But every time a Prius owner drives to the grocery store, she may be canceling out its emission-reducing benefit, at least if she shops in the meat section… The world’s ruminants are responsible for about 50 percent more greenhouse gas than the entire transportation sector” The first sentence here is mostly nonsensical: I’m not a huge fan of the Prius (I proudly drive a Toyota Echo that costs much less and gets great gas mileage), but unless the book is arguing that driving a Prius causes people to shop in the meat section, the fact of the matter is that driving a Prius to buy meat generates less carbon than driving a Hummer to buy meat.
As for the second sentence, this IPCC figure breaking down emissions from agriculture and transport makes me doubt what the book says, but I don’t know enough about these matters to say for sure. (Also, there are complications, like the fact that CO2 from fossil fuels stays in the atmosphere longer than methane from cows; so are we talking about the contribution to warming over the next year or over the next 100 years?) I do, however, agree with one point the book is trying to make here, which is that transportation contributes less to the problem than most people seem to think.
- pp 170-171: “When Al Gore urges the citizenry to sacrifice… the agnostics grumble that human activity accounts for just 2 percent of global carbon-dioxide emissions, with the remainder generated by natural processes like plant decay.” This sentence makes a conspiracy theory out of nothing! Take a look at this figure from the Energy Information Administration: it shows that, yes, human generation of CO2 is dwarfed by natural processes like plant decay. But it also shows that natural processes balance each other out: plant decay generates massive amounts of CO2, and plant growth takes in massive amounts of CO2 via photosynthesis. What you’re left with is a completely plausible story in which human activity slowly increases atmospheric concentrations of CO2 from pre-industrial concentrations of about 285ppm (parts per million) to current concentrations of about 385ppm that are going up by about 2ppm per year. You can see up-to-date figures here from NOAA’s Mauna Loa observatory, and a longer-term view from this IPCC figure going back 2000 years.
Nobody doubts this. Why is Superfreakonomics grumbling about it?
- p 184: “Yet [climate researcher Ken Caldeira's] research tells him that carbon dioxide is not the right villain in this fight.” Look on Caldeira’s website and you’ll find this: “Carbon dioxide is the right villain,” says Caldeira, “insofar as inanimate objects can be villains.” On Romm’s website he quotes Caldeira saying this: “If you talk all day, and somebody picks a half dozen quotes without providing context because they want to make a provocative and controversial chapter, there is not much you can do.”
Bottom line: It is bad bad bad when a scientist you quote saying X in a book says Not X on the front page of their own website.
Update 10:30am: Dubner writes that Caldeira admits that he failed to read the chapter carefully and that’s where the bad quote comes from: “The only significant error,” he wrote to Romm, “is the line: ‘carbon dioxide is not the right villain in this fight.’ That is just wrong and I never would have said it. On the other hand, I f&@?ed up. They sent me the draft and I approved it without reading it carefully and I just missed it. … I think everyone operated in good faith, and this was just a mistake that got by my inadequate editing.” Shame on Caldeira, but there is still a question about how that line got into the book if Caldeira says he didn’t say it. And there’s the larger issue of the misleading perspective of the chapter as a whole. So my bottom line is still the same: It is bad bad bad when a scientist you quote saying X in a book says Not X on the front page of their own website.
- p 185: “Caldeira’s study showed that doubling that amount of carbon dioxide while holding steady all other inputs–water, nutrients, and so forth–yields a 70 percent increase in plant growth, an obvious boon to agricultural productivity.” I’m not 100% sure of this, but my understanding is that these types of studies also hold steady the input of temperature, and that the effect of temperature is mostly negative. Given the impacts that climate change will have on temperature and water availability, it’s misleading to focus only on CO2 (which, as I understand it, does indeed increase plant growth, at least for a while). It’s also worth noting that the increase in plant growth may not be in the seed or other edible part of the plant; see also UW professor David Battisti‘s work on this.
- p 186: “[T]he most authoritative literature on the subject suggests a rise [in sea level] of about one and a half feet by 2100.” This is wrong if it refers to the 2007 IPCC estimates because those estimates present a range “excluding future rapid dynamical changes in ice flow” (IPCC WG1 Summary, Table SPM3, p. 13). Elaboration comes from IPCC FAQ 10.2: “Recent satellite and in situ observations of ice streams behind disintegrating ice shelves highlight some rapid reactions of ice sheet systems. This raises new concern about the overall stability of the West Antarctic Ice Sheet, the collapse of which would trigger another five to six metres of sea level rise. While these streams appear buttressed by the shelves in front of them, it is currently unknown whether a reduction or failure of this buttressing of relatively limited areas of the ice sheet could actually trigger a widespread discharge of many ice streams and hence a destabilisation of the entire West Antarctic Ice Sheet. Ice sheet models are only beginning to capture such small-scale dynamical processes that involve complicated interactions with the glacier bed and the ocean at the perimeter of the ice sheet. Therefore, no quantitative information is available from the current generation of ice sheet models as to the likelihood or timing of such an event.”
- p 186: “Then there’s this little-discussed fact about global warming: while the drumbeat of doom has grown louder over the past several years, the average global temperature during that time has in fact decreased.” It’s not clear that this is little-discussed—see, e.g., this NY Times article—but in any case look at all the year-to-year variability in this NASA graph and then look at the decadal trend. Saying that temperatures over the last decade have decreased is misleading in the same way that it’s misleading to say that the Middle East has gotten more peaceful since 1948.
- pp 188-203: The book devotes this entire section to the idea of geo-engineering the planet by pumping SO2 into the atmosphere to cool the planet. I do not know enough about geo-engineering to comment much beyond saying that it’s speculative, but I do think it’s worth pointing out that cooling the planet doesn’t address other risks like ocean acidification, and since Superfreakonomics goes to the trouble of mentioning ocean acidification when introducing Ken Caldeira (pp 183-184) it would seem worth mentioning again in the section on geo-engineering.
PS. Does anybody other than conspiracy theorists really believe that (p 198) “[p]erhaps the single best objection to the [SO2 idea] is that it’s too simple and too cheap”?
PS. Romm’s follow-up attempt to blame Bill Gates, Warren Buffett, and the Gates Foundation strikes me as almost entirely lacking in evidence. As my girlfriend put it, just because Gates and Buffett et al. focus on global health doesn’t mean they’re climate skeptics. Usually I think Romm’s posts are pretty good, but the one linked at the beginning of this paragraph seems like it comes from left field.