Climate change in Superfreakonomics

Update Oct 18 11:07am PST: My email exchange with Steven Levitt is here.

Update Oct 19: My (concluding?) thoughts here.

Joe Romm at 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.

27 responses to “Climate change in Superfreakonomics

  1. The 70% increase in plant growth paper was looking at what happened if you held temperature constant with geoengineering. This means you reduce insolation by 2% to compensate for doubling CO2. That reduces plant growth, so what is the net effect? Not that you could have figured that out from L&D’s distorted description.

    See my post.

  2. Nice overview. L&N’s sulphate idea does nothing to lower atmospheric CO2 levels and would actually allow them to increase (by reducing the need to reduce CO2 emissions). And the sulphate injection itself will directly create a permanent increase in the acidity of precipitation. This double whammy would destroy ocean ecology and freshwater ecology at a magnitude not seen since the Permian. Nice work.

  3. “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.”

    Since when is increasing the number of growing days harmful to agriculture? Are we to suppose that if we had colder temperatures then we would be able to grow more food? If you actually have evidence to the contrary i think the world would love to hear it as it completely turns our understanding of agriculture on its head.

  4. Joshua, if you know plants, you know that the number of growing days (ie. temperature) is critical to all plants and trees. This is why peas and green will not grow in the deep U.S. South and why green peppers and melons will not grow well in Maine. Tree species’ range are greatly dependent on temperature. White birch, balsam fir and black spruce will not grow south of northern New England. Shagbark hickory, tulip trees, black walnut and many other trees will not grow north of Massachusetts. More important, cold winter temperatures are critical to keeping many tree and plant pests from migrating northward, such as pine beetles, which are now decimating the conifer forests of the Rocky Mountains because winter temperatures are no longer cold enough to kill the beetles and prevent their expansion northward. This is all very academic if you do some basic research on the ‘net.

  5. “This is all very academic if you do some basic research on the ‘net.”

    Isn’t that an oxymoron?

  6. “the current scientific consensus on climate change is supported by almost everybody. ”
    This is nonsense. For example, 31,000 scientists went to the trouble to mail in signatures on a petition in opposition:
    and I can tell you from personal experience, the petitions organizers made some effort to verify the credentials of the signatories, since after mailing in my signed card, I got a phone call from them months later for verification.

    No scientist I’m aware of whose funding isn’t dependent on kowtowing to the “consensus”, and who has looked into the technical basis for the claims, believes the global warming alarmism in the slightest. Walk into any physics or chemistry department, and find someone whose actually looked at the arguments, and ask them what they think. And, IMO, no reasonable scientist could possibly accept the baloney they are spouting. Global warmism is well on the disproven side of unproven.

  7. Thanks for the level-headed critique. I hope Mankiw’s link earns it a lot of eyeballs.

    Some of the tone and omissions of these passages are defensible as a part of the polemic public debate we are in. For example: Gore in his film emphasized single years like 1998 and NASA does a “hottest years” list on its web-site. In that context, it’s fair to point out that temperatures have fallen since 1998, even though the really “right” perspective is to concentrate on long-term trends, not individiual years. Similiarly, the book never asserts that the global cooling theory represented a “consensus” among scientists comparable to the current global warming “consensus”. (I worked as a scientist for 20 years and never heard the term “scientific consensus” until the AGW debate. I believe it has more political than scientific meaning.) It merely asserts that it had its turn as the media scare story, as global warming does today.

    The Caldeira flap is probably he biggest problem form a PR standpoint, but it’s ultimately the least substansive. What does “C02 is the villian” actually mean? How would you test such a statment emperically? Ultimately, I think the fault for the flap lies with Caldeira. Probably lured by a significant consulting fee, he associated himself with a commercial venture pushing a view he doesn’t acutually believe. That worked out as long as he could keep silent at strategic moments, but the book is making that impossible.

  8. BTW, I’m a PhD physicist who went to the trouble of reading many of the technical papers on the subject, including most of the last IPCC report. You are an economist, you probably appreciate that you need more data points than parameters for a theory/ computer model to be worth paying attention to. Well, guess what, the IPCC report admits on p596 that they don’t know if they have more free parameters than data points. Check the reference. That’s only one minor point among many– I figure its one you might appreciate. Their models have been falsified the subsequent cooling/ flat temps since 2001 at 95% or higher level. The theory says CO2 warming is a logarithmic effect, meaning we’ve already seen almost all the warming you’d ever expect. The models predict a signature of CO2 warming that has the tropical troposphere warming by far the most, double the surface– but the tropical troposphere hasn’t warmed an iota in the history of the time series. I could go on. The cosmic ray/solar explanation, which they routinely try to dismiss by pointing at strawmen like direct solar impact, is supported by impressive evidence. And on and on. No reasonable scientist with an open mind who makes a serious attempt to understand the subject could conclude global warmism is well based.

  9. Relying on the IPCC for scientific facts is like asking the Pope for an explanation of the Star of Bethlehem. IPCC has moved beyond science. It is a faith based religion.

    Their Mass is time slicing the historical record. For every warming period “due to man” you can find a cooling period, or warming period of longer and shorter duration where man could not have possibly been the driving factor.

    IPCC climate charts are projections based on skimpy and faulty models or selective stats.

  10. One other point: the 2001 IPCC report you cite, proudly featured (in the summary!) the hockey stick graph. It was the main piece of evidence. If the hockey stick graph were correct, there would be grounds for alarmism. But its baloney– which the National Academy of Sciences report (much too politely) observed. So pointing at 2001 comments is misleading at best. And since 2001, the earth has gotten cooler and the “near term projections” of the 2001 report were falsified at the 95% level if you do a statistical analysis.

  11. Here’s a summary of some of the environmental threats to our oceans. The way things are going, there could be no fish left in the oceans in as little as 40 years.

  12. I was pretty disappointed in this attack. Essentially the book is being attacked for being politically incorrect.

    Most starkly, there is no consensus on an issue if any one person disagrees. It doesn’t take much of a web search to turn up prominent scientists objecting to the alarmist view, even before you look into people who aren’t formally scientists but have as much insight as the specialists. Notable examples are Anthony Watts, Roy Spencer, and Steve McIntyre. Additionally, be sure to look up the case of Christopher Landsea. He’s pretty serious, too, and he withdrew from the IPCC claiming it is too politicized. Not even the IPCC membership, stacked as it is through a political process, can maintain a consensus with its members.

    Consensus aside, try understanding the argument of the alarmist view. Science, after all, is not supposed to be something we have to take on authority. The argument rests on CO2 growth causing no direct problem, but that there is are positive feedbacks that will take over past a certain point. There’s a huge weakness in this argument, however: why hasn’t it happened in the past? CO2 and temparature have both varied extremely through Earth’s history, yet the ecosystem hasn’t collapsed yet.

    Finally, warmer weather and higher CO2 are very likely to improve agriculture on the whole. It’s stretching to say otherwise. Yes, crops would have to move to different areas, but we are talking about transition on the order of decades.

    So, again, it’s disappointing. I don’t like watching so very many scientists turn to politics. They do technically impressive work but then draw conclusions exactly in line with political advantage. Where are the people who actually try to figure out what’s happening in the physical world?

  13. Eric… you sound legit, can we get more on your background, credentials, etc…?

  14. I think the bottomline is that the IPCC 2001 hockey stick is a jump the shark moment. I am open to evidence but it is not there in a compelling form. There is plenty of evidence that if the US dramatically ramps the cost of energy jobs go overseas in greater numbers to Countries that have less emission controls than we do.

  15. 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 is like saying murder accounts for a tiny proportion of deaths, so it doesn’t really matter if the murder rate skyrockets.

  16. Only polymaths truly understand the mythomania that is *climate change*.

  17. “the fact of the matter is that driving a Prius to buy meat generates less carbon than driving a Hummer to buy meat”

    I don’t think he’s making a value judgement of meat eating Prius drivers there, but rather a statement on the not-so-obvious emissions of red meat production. My bias would say not too many Prius drivers are red meat eaters to begin with, but if you’re simply concerned about emissions, it might be cheaper to stop eating red meat rather than to buy a Prius. And if you can afford it, and believe in catastrophic AGW, do both!

  18. Hi,

    With regard to the state of scientific opinion on Global Cooling in the ’70s, the following link, which contains a transcript of a Letter sent to President Nixon from the Chair of a conference upon the subject may be illuminating,

    I’m old enough to recall that the cooling effect was reported upon widely, and was supported by a significant scientific minority – nothing like the present consensus upon AGW, of course – but it wasn’t just a few articles in the press as set out above.

  19. Eric –

    I think you should state your credentials on your claims (not links to fringe web sites), including your academic affiliation. If you are legitimate, no need to stay anonymous, you’re a PhD physicist after all. There was once a petition showing 10,000 scientists named Steven (or Stephanie) to agree that global warming is a problem, so petitions don’t really do it for most of us.

    What is always interesting to me is the stridency of the denial of global warming by some, which I obviously find unconvincing. Let’s just say we do the steps that global warming worriers suggest: reduce use of fossil fuels, emphasize the use of renewable and non-CO2-creating energy sources, above all use energy efficiency wherever practical. Where’s the harm? We certainly are going to run out of oil at some point, so why not switch earlier rather than later — the costs are the same either way? And, why take the chance that the global warming models that show significant harm might be right? It leaves me completely baffled that some are so passionately opposed. I can only conclude that it is political and ideological, not scientific.

  20. Deniers keep claiming that the weather has cooled since 1998. The British Met Office refutes that thus:

    “… trends over the past 10 years show only a 0.07 °C increase in global average temperature. Although this is only a small increase, it indicates that there has been no global cooling over this period. In fact, over the past decade, most years have remained much closer to the record global average temperature reached in 1998 than to temperatures before the 1970s. All the years from 2000 to 2008 have been in the top 14 warmest years on record.”

  21. What’s amusing is that two of those major errors are failures to think marginally which, some might say, is the only thing economists like Levitt are actually supposed to be good at.

    The Prius smear: “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 2 percent line: “human activity accounts for just 2 percent of global carbon-dioxide emissions, with the remainder generated by natural processes like plant decay.”

    Someone needs to ask Levitt what he believes the effect on price would be when demand is completely inelastic and you have a 2% decrease in supply.

  22. Not that one should attach too much weight to the Associated Press doing “science”, but this recent story seems to support the idea that those who think there is a “global cooling” trend are at best being selective with their datasets and at worst working backward from their conclusions.

  23. Regarding agriculture, degree days, temperature, CO2 concentrations, etc.: Just because you don’t know much about crops don’t think it is as simple as you suppose. There is a big difference between degree-days, a way to talk about the length of the growing season, and peak temperatures. High temperatures at the wrong time, especially around flowering, can ruin the yields of many crops. Also, I don’t think CO2 availability is the limiting factor for many crops (need to check on that). But I know that maximum temperatures and water availability are limiting factors for the yields of many. On the other hand at higher temperatures, when transpiration increases, higher CO2 levels could compensate in part for higher water needs. Stomata close to avoid water loss, but must open to admit CO2. Higher [CO2] might mean enough could be absorbed with less water loss. And we could switch to more C4 crops. It will be complicated.

  24. Regarding Eric’s comments:

    Just because the specific numerical predictions of the 2001 IPCC report are imperfect does not mean that the main point — anthropogenic warming — is incorrect. As any scientist should know, almost every model describing a complex system has shortcomings, but as long as the essential behaviors of the model are correct then the model is useful. So scientists (even physicists) keep the model anyway — no need to throw out the baby with the bathwater.

    I have not read the 2001 report, but I think figures TS.2 and TS.5 of the 2007 report ( are pretty convincing, even in the absence of a predictive model as clean as Newtonian physics.

  25. Check out the open letter to Steven Leavitt from a professor of geophysics at the University of Chicago. It shows basic aritmetic errors or absence of calculatons in the critque on using solar power. Evidently, Leavitt was mislead into thinking that waste heat is an important factor in climate change. This is a simple question often asked by first time bloggers.

    The letter is posted at

    The chapters on climate change in the new book are a complete and unmitigated embarrassment

  26. Climate Change made the typhoons in the south pacific very destructive. Typhoon Ketsana made a lot of mess in Philippines and Vietnam *

  27. Thanks for writing this. This the best criticism of their chapter I have come across because it is reasoned and ballanced and careful not to overextend the criticisms . I read the book yesterday and was incredibly suspicous. As a non-expert I couldn’t directly question most of the science (actually my physics background allows me to see a few things as highly iffy) but the tone really sets alarm bells off, for example the irrelevant attacking of al gore a non-scientist who became a big figure very late in the enviromentalist movement and accusing climate scientists (not just bloggers and activists) of treating climate change like a religion “Cruzen’s embrace of geoengineering was considered such a heresy within the climate-science community that some peers tried to stop the publication of his essay.” Also the overreliance on supposed whiz kid technologists most who lack real expertise. I have very similar qualifications to nathan myhrvold btw (exept i am slightly closer to experiment and still currently do academic research), but ask for detail on climate change and you’ll get back gibberish, at least you would if i was ever foolish or arrogant enough to answer.

    What really broke my heart though is that when I decided to google this to see if the stuff they wrote had been debunked I found blogs which did not just provide clear technical arguments demostrating where dubner and levitt errored, they were also angry rants and contained some misrepresentations of the dubner and levitt’s position too along with rather paranoid assumptions about their motives (one can speculate a luttle hear but it should be in a careful reasoned manner) and jumping on scraps of info to support this paranoia with weak arguments. It’s especially upsetting because it removes one of the ways lay people can differentiate between the experts and the quacks. I guess scientists bloggers don’t use the same care when wrioting blogs as they do when writing papers, but i really wish they would.

    Anyway thanks for being different.

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