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An open letter to Steve Levitt

Filed under: — raypierre @ 29 October 2009

Dear Mr. Levitt,

The problem of global warming is so big that solving it will require creative thinking from many disciplines. Economists have much to contribute to this effort, particularly with regard to the question of how various means of putting a price on carbon emissions may alter human behavior. Some of the lines of thinking in your first book, Freakonomics, could well have had a bearing on this issue, if brought to bear on the carbon emissions problem. I have very much enjoyed and benefited from the growing collaborations between Geosciences and the Economics department here at the University of Chicago, and had hoped someday to have the pleasure of making your acquaintance. It is more in disappointment than anger that I am writing to you now.

I am addressing this to you rather than your journalist-coauthor because one has become all too accustomed to tendentious screeds from media personalities (think Glenn Beck) with a reckless disregard for the truth. However, if it has come to pass that we can’t expect the William B. Ogden Distinguished Service Professor (and Clark Medalist to boot) at a top-rated department of a respected university to think clearly and honestly with numbers, we are indeed in a sad way.

By now there have been many detailed dissections of everything that is wrong with the treatment of climate in Superfreakonomics , but what has been lost amidst all that extensive discussion is how really simple it would have been to get this stuff right. The problem wasn’t necessarily that you talked to the wrong experts or talked to too few of them. The problem was that you failed to do the most elementary thinking needed to see if what they were saying (or what you thought they were saying) in fact made any sense. If you were stupid, it wouldn’t be so bad to have messed up such elementary reasoning, but I don’t by any means think you are stupid. That makes the failure to do the thinking all the more disappointing. I will take Nathan Myhrvold’s claim about solar cells, which you quoted prominently in your book, as an example.

As quoted by you, Mr. Myhrvold claimed, in effect, that it was pointless to try to solve global warming by building solar cells, because they are black and absorb all the solar energy that hits them, but convert only some 12% to electricity while radiating the rest as heat, warming the planet. Now, maybe you were dazzled by Mr Myhrvold’s brilliance, but don’t we try to teach our students to think for themselves? Let’s go through the arithmetic step by step and see how it comes out. It’s not hard.

Let’s do the thought experiment of building a solar array to generate the entire world’s present electricity consumption, and see what the extra absorption of sunlight by the array does to climate. First we need to find the electricity consumption. Just do a Google search on “World electricity consumption” and here you are:


Now, that’s the total electric energy consumed during the year, and you can turn that into the rate of energy consumption (measured in Watts, just like the world was one big light bulb) by dividing kilowatt hours by the number of hours in a year, and multiplying by 1000 to convert kilowatts into watts. The answer is two trillion Watts, in round numbers. How much area of solar cells do you need to generate this? On average, about 200 Watts falls on each square meter of Earth’s surface, but you might preferentially put your cells in sunnier, clearer places, so let’s call it 250 Watts per square meter. With a 15% efficiency, which is middling for present technology the area you need is

2 trillion Watts/(.15 X 250. Watts per square meter)

or 53,333 square kilometers. That’s a square 231 kilometers on a side, or about the size of a single cell of a typical general circulation model grid box. If we put it on the globe, it looks like this:


So already you should be beginning to suspect that this is a pretty trivial part of the Earth’s surface, and maybe unlikely to have much of an effect on the overall absorbed sunlight. In fact, it’s only 0.01% of the Earth’s surface. The numbers I used to do this calculation can all be found in Wikipedia, or even in a good paperbound World Almanac.

But we should go further, and look at the actual amount of extra solar energy absorbed. As many reviewers of Superfreakonomics have noted, solar cells aren’t actually black, but that’s not the main issue. For the sake of argument, let’s just assume they absorb all the sunlight that falls on them. In my business, we call that “zero albedo” (i.e. zero reflectivity). As many commentators also noted, the albedo of real solar cells is no lower than materials like roofs that they are often placed on, so that solar cells don’t necessarily increase absorbed solar energy at all. Let’s ignore that, though. After all, you might want to put your solar cells in the desert, and you might try to cool the planet by painting your roof white. The albedo of desert sand can also be found easily by doing a Google search on “Albedo Sahara Desert,” for example. Here’s what you get:


So, let’s say that sand has a 50% albedo. That means that each square meter of black solar cell absorbs an extra 125 Watts that otherwise would have been reflected by the sand (i.e. 50% of the 250 Watts per square meter of sunlight). Multiplying by the area of solar cell, we get 6.66 trillion Watts.

That 6.66 trillion Watts is the “waste heat” that is a byproduct of generating electricity by using solar cells. All means of generating electricity involve waste heat, and fossil fuels are not an exception. A typical coal-fired power plant only is around 33% efficient, so you would need to release 6 trillion Watts of heat to burn the coal to make our 2 trillion Watts of electricity. That makes the waste heat of solar cells vs. coal basically a wash, and we could stop right there, but let’s continue our exercise in thinking with numbers anyway.

Wherever it comes from, waste heat is not usually taken into account in global climate calculations for the simple reason that it is utterly trivial in comparison to the heat trapped by the carbon dioxide that is released when you burn fossil fuels to supply energy. For example, that 6 trillion Watts of waste heat from coal burning would amount to only 0.012 Watts per square meter of the Earth’s surface. Without even thinking very hard, you can realize that this is a tiny number compared to the heat-trapping effect of CO2. As a general point of reference, the extra heat trapped by CO2 at the point where you’ve burned enough coal to double the atmospheric CO2 concentration is about 4 Watts per square meter of the Earth’s surface — over 300 times the effect of the waste heat.

The “4 Watts per square meter” statistic gives us an easy point of reference because it is available from any number of easily accessible sources, such as the IPCC Technical Summary or David Archer’s basic textbook that came out of our “Global Warming for Poets” core course. Another simple way to grasp the insignificance of the waste heat effect is to turn it into a temperature change using the standard climate sensitivity of 1 degree C of warming for each 2 Watts per square meter of heat added to the energy budget of the planet (this sensitivity factor also being readily available from sources like the ones I just pointed out). That gives us a warming of 0.006 degrees C for the waste heat from coal burning, and much less for the incremental heat from switching to solar cells. It doesn’t take a lot of thinking to realize that this is a trivial number compared to the magnitude of warming expected from a doubling of CO2.

With just a little more calculation, it’s possible to do a more precise and informative comparison. For coal-fired generation,each kilowatt-hour produced results in emissions of about a quarter kilogram of carbon into the atmosphere in the form of carbon dioxide. For our 16.83 trillion kilowatt-hours of electricity produced each year, we then would emit 4.2 trillion kilograms of carbon, i.e. 4.2 gigatonnes each year. Unlike energy, carbon dioxide accumulates in the atmosphere, and builds up year after year. It is only slowly removed by absorption into the ocean, over hundreds to thousands of years. After a hundred years, 420 gigatonnes will have been emitted, and if half that remains in the atmosphere (remember, rough estimates suffice to make the point here) the atmospheric stock of CO2 carbon will increase by 210 gigatonnes, or 30% of the pre-industrial atmospheric stock of about 700 gigatonnes of carbon. To get the heat trapped by CO2 from that amount of increase, we need to reach all the way back into middle-school math and use the awesome tool of logarithms; the number is

(4 Watts per square meter) X log2(1.3)

or 1.5 Watts per square meter. In other words, by the time a hundred years have passed, the heat trapped each year from the CO2 emitted by using coal instead of solar energy to produce electricity is 125 times the effect of the fossil fuel waste heat. And remember that the incremental waste heat from switching to solar cells is even smaller than the fossil fuel waste heat. What’s more, because each passing year sees more CO2 accumulate in the atmosphere, the heat trapping by CO2 continues to go up, while the effect of the waste heat from the fossil fuels or solar cells needed to produce a given amount of electricity stays fixed. Another way of putting it is that the climate effect from the waste heat produced by any kind of power plant is a one-off thing that you incur when you build the plant, whereas the warming effect of the CO2 produced by fossil fuel plants continues to accumulate year after year. The warming effect of the CO2 is a legacy that will continue for many centuries after the coal has run out and the ruins of the power plant are moldering away.

Note that you don’t actually have to wait a hundred years to see the benefit of switching to solar cells. The same arithmetic shows that even at the end of the very first year of operation, the CO2 emissions prevented by the solar array would have trapped 0.017 Watts per square meter if released into the atmosphere. So, at the end of the first year you already come out ahead even if you neglect the waste heat that would have been emitted by burning fossil fuels instead.

So, the bottom line here is that the heat-trapping effect of CO2 is the 800-pound gorilla in climate change. In comparison, waste heat is a trivial contribution to global warming whether the waste heat comes from solar cells or from fossil fuels. Moreover, the incremental waste heat from switching from coal to solar is an even more trivial number, even if you allow for some improvement in the efficiency of coal-fired power plants and ignore any possible improvements in the efficiency of solar cells. So: trivial,trivial trivial. Simple, isn’t it?

By the way, the issue of whether waste heat is an important factor in global warming is one of the questions most commonly asked by students who are first learning about energy budgets and climate change. So, there are no shortage of places where you can learn about this sort of thing. For example, a simple Google search on the words “Global Warming Waste Heat” turns up several pages of accurate references explaining the issue in elementary terms for beginners. Including this article from Wikipedia:


A more substantive (though in the end almost equally trivial) issue is the carbon emitted in the course of manufacturing solar cells, but that is not the matter at hand here. The point here is that really simple arithmetic, which you could not be bothered to do, would have been enough to tell you that the claim that the blackness of solar cells makes solar energy pointless is complete and utter nonsense. I don’t think you would have accepted such laziness and sloppiness in a term paper from one of your students, so why do you accept it from yourself? What does the failure to do such basic thinking with numbers say about the extent to which anything you write can be trusted? How do you think it reflects on the profession of economics when a member of that profession — somebody who that profession seems to esteem highly — publicly and noisily shows that he cannot be bothered to do simple arithmetic and elementary background reading? Not even for a subject of such paramount importance as global warming.

And it’s not as if the “black solar cell” gaffe was the only bit of academic malpractice in your book: among other things, the presentation of aerosol geoengineering as a harmless and cheap quick fix for global warming ignored a great deal of accessible and readily available material on the severe risks involved, as Gavin noted in his recent post. The fault here is not that you dared to advocate geoengineering as a solution. There is a broad spectrum of opinion among scientists about the amount of aerosol geoengineering research that is justified, but very few scientists think of it as anything but a desperate last-ditch attempt, or at best a strategy to be used in extreme moderation as part of a basket of strategies dominated by emissions reductions. You owed it to your readers to present a fair picture of the consequences of geoengineering, but chose not to do so.

May I suggest that if you should happen to need some friendly help next time you take on the topic of climate change, or would like to have a chat about why aerosol geoengineering might not be a cure-all, or just need a critical but informed opponent to bounce ideas off of, you don’t have to go very far. For example…


But given the way Superfreakonomics mangled Ken Caldeira’s rather nuanced views on geoengineering, let’s keep it off the record, eh?

Your colleague,

Raymond T. Pierrehumbert
Louis Block Professor in the Geophysical Sciences
The University of Chicago

807 Responses to “An open letter to Steve Levitt”

  1. 51
    B Buckner says:

    #32 Thomas Huld
    As indicated by your reference, the albedo of water approached 1.0 with a low sun angle, as is the case in the artic. Think of the beauty of the sunlight reflecting off of the water at sunset.

  2. 52
    Alexandre says:

    I loved Levitt´s first book. It´s mostly based on his own (et al.) respectable academic research.

    But I received this last one with sadness. It does sound like they did a poor fact-checking.

  3. 53
    Steve Missal says:

    Re: #29 Foobear: classic emotional trigger word post: “collective panties et al”; “Al Gore” (two varieties) twice; “hippie changes”; “horrible hypocrite” (alliteration to boot); “permanent economic depression” ; “belching tons of…” etc. A lot squeezed into a modest-sized post.
    The old canard about economic interests trumping actually doing something about global warming has finally given me, (speaking of permanent), everlasting mental heartburn. Dr. Levitt’s ‘solutions’ aren’t, as the post so clearly shows. I might pay more attention to Foobear’s thoughts if he (she?) didn’t slather on the endless ad hominem junk, with insinuations that all climate change advocates are marginal personalities, anti-business, etc. After all this, Foobear then manages to avoid addressing the actual facts stated in the post. An endless methodology of denialist argumentation.
    Is there some way we can get the rebuttal letter online in such a manner that it would receive the several hundred thousand hits too? It can’t be that impossible. Someone here has the expertise. Help.

  4. 54
    Knut Witberg says:

    Professor Pierrehumbert is glossing over the fact that that extra heat that is absorbed is not the problem, the problem is the forcing – the positive feedback – caused by the warming of the air. And that forcing is the controversial point in the global warming theory. Some even believe that the feedback is negative, so that a doubling of the CO2 in the atmosphere would cause much less than 1 C warmer earth. And observations since 1998 seemingly support that opinion. Time is the mother of truth…

  5. 55
    jr says:

    @47 Yes, evaporation of water over sea and cloud cover over land at the equator is the main reason for lower irradiance at the surface there than you might expect. From the tropics the irradiance level then tends to decrease as you move further from the equator (either northwards, or south).

  6. 56
    Mike Roddy says:

    Thanks, Raypierre, I’ve loved your posts for a long time. Very cogent, and devastating. It leads me to this question:

    This error, and others, were pointed out to Levitt and Dubner two weeks before publication. All they had to do was perform a mea culpa and agree to make corrections for the next edition, or possibly include a separate insert with addenda when they shipped the book.

    Instead, they defended themselves on their blog and on talk shows, and called serious critics such as Joe Romm character assasins. What happened?

    Apparently, as in bad commercial movies, the book and this chapter in particular were road tested with a sample reading audience. The reviews came out very positive. The test audience was composed of more people than qualified scientists who previewed the chapter. Then, the chapter leaked, and the storm hit.

    By then, the authors were already counting the money from the book sales, and became alarmed at the messiness of having to make last minute corrections. We’re talking about millions of dollars here. They made a common calculation: money is more important than truth or personal integrity, and it is certainly more important than the kind of fate that awaits our grandchildren. Their attempts to parse the factual errors in their book became the stuff of comedy, if there were ever a late night show for scientists.

    This attitude could be what results in our doom. No sense being too hard on Levitt and Dubner, they are just morally ordinary human beings. Unfortunately, the stakes here call for bringing out our best.

  7. 57
    Jim22 says:

    You talk about CO2 trapping the heat. Does not water vaper trap most of the heat. I thought freakeconomicts silly but I do have a question.
    Who builds the solar panels and wires them up. Minor detail I know but it seems to me someone needs to start to build them and find out how to pay for them. Whats the cost of repairs when rain storms damage them.
    I am glad money is such a minor detail.

  8. 58
    Thomas Huld says:

    Marcus @43: The numbers at our web site include the effects of clouds, which is why irradiation in tropical Africa is so much lower than Sahara (or the Kalahari desert).

    B Buckner @50: That’s true, but as the sun angle goes to zero so does the horizontal irradiance, plus a lot of that reflected light will be absorbed on its way out of the atmosphere again. The roughness of the sea (waves) will have an influence too. I also took only one radiation value for a single location. All this makes it a back-of-a-BIG-envelope calculation.

  9. 59
    Mark says:

    Jim22. Who builds the concrete walls of the steam generators and wires the generators up?

    Minor detail I know but it seems to me someone needs to build them and find out how to pay for them. What is the cost of repairs when road access floods and they need their fuel?

  10. 60
    Mark says:

    “Think of the beauty of the sunlight reflecting off of the water at sunset.”

    Ah, but then the light is being intercepted by your eyes, and they will heat up and cause global warming!

    SEE! It’s not CO2 after all! It’s those EYES. Those eyes, always watching me. Hiding in the shadows…


  11. 61
    Marcus says:

    Zeke: note that the “paint roofs white” solution actually is _both_ a stock and flow solution: there’s the direct albedo benefit, and there’s the indirect reduction in air conditioning use in the summer, and therefore CO2 emissions (both for the house in specific, and for the general urban area due to a reduction in heat island effect).

    (also, since this is a common objection: my understanding is that in winter white roofs do not significantly add to the cost of heating, because there’s a reduction in insolation so less reflection, there’s occasional snowfall where the color doesn’t matter, and the white roofs actually reduce emissivity at night which is much longer in the winter).

  12. 62
    Hank Roberts says:

    Digression into opinion leads to argument and more digression. Look it up.
    Please. If you don’t look it up your memory only works backward.

    New: color-changing roof tiles; white when it’s hot; black when it’s cold. Next to be developed, color-changing roof paint. Think ‘electronic ink’ in e-book readers.

    Albedo: actual water isn’t a plane surface at the important wavelengths. “The average albedo of ice-free water was 4 per cent (based on 55 observations) with a standard deviation of 2 per cent.”

    Test for yourself: use Polaroid glasses, look at glare reflected from water; Look (kids, don’t!) at the Sun through those glasses, and it will blind you.
    The difference?

  13. 63
    Jim Galasyn says:

    Re #9 and the lime fix for ocean acidification, there is one serious proposal that merits attention: Cquestrate.

    First, you heat limestone to a very high temperature, until it breaks down into lime and carbon dioxide. Then you put the lime into the sea, where it reacts with carbon dioxide dissolved in the seawater. The important point is that when you put lime into seawater it absorbs almost twice as much carbon dioxide as is produced by the breaking down of the limestone in the first place.

    The proposal is pretty well thought out, but we haven’t heard from these folks in awhile…

  14. 64
    Marcus says:

    #61, Jim Galasyn: This still doesn’t address the fact that you’d need to be crushing gigatons of limestone every year. Also, is the source of heat carbon free? If not, that reduces the “carbon reduction yield” per ton of limestone. If the source of heat _is_ carbon free – why not use it to reduce carbon emissions in the first place?

  15. 65
    Justin Ciderbottom says:

    @61 and the energy used to heat the limestone produces how much CO2?

  16. 66
    Jeffrey Davis says:

    I suspect that the author of “Corn-pone Opinions” would have a negative opinion about the usefulness of open letters like this.

  17. 67
    JP says:

    If the efficiency of a coal power plant is 33%, shouldn’t producing 2 units of power result in producing 4 units of heat, not 6? Or is this a different definition of efficiency?

    Your point stands even if you use more pessimistic figures (e.g., 200 W/m of sunlight, Earth albedo of 1, solar panel albedo of 0, solar panel efficiency of 10%).

    [Response: The heat that is successfully converted to electricity eventually is released as waste heat as well after it does its work. There are a few things you can do with electricity that don't ultimately release all the energy as heat, but not many. --raypierre]

  18. 68
    Chas says:

    It would be great if the Steves read this and replied but they’ve talk shows to visit. Thank you for an interesting analysis.

  19. 69
    Jeffrey Davis says:

    re: 10

    “Now perhaps we know how most American economists missed the greatest housing bubble/ derivatives superbubble ever unleashed on the American public.”

    Most people who eyeball the $13 trillion loss that lack of government oversight and regulation produced would scuttle the notion of Efficient Markets and Rational Actors. In comparison, Tulip Mania was a headache while the over-leveraged derivatives market losses was a ward full of stroke victims. An entire year’s GDP. Gone.

    Don’t expect an apology from UC economists.

  20. 70
    Mark says:

    “and the lime fix for ocean acidification”

    We put the lime in the coconut?

  21. 71
    Christopher Hogan says:

    I’m an economist, and I was embarrassed on behalf of my profession when I read this, having had to work through the “waste heat” argument for a friend just a few weeks back. As you said, it’s not as if it’s hard to do.

    You’ve already noted elsewhere that other prominent economists such as Paul Krugman have mentioned the deficiencies in the Freakonomics analysis.

    But there is definitely a strain of thinking within my profession that says, in effect, I don’t need to understand the technology in order to pontificate about the economics. I call it the “one size fits all” model of economics. Back when I taught industrial organization, I made sure my students understood at least the rudiments of the underlying technologies in the industries studied. As far as I could tell, no one else did. Cars, farms, electricity, trains — pretty much all of a piece beyond the abstraction of a production function.

    For what it’s worth, economists at the U.S. Congressional Budget Office have said that an 80% reduction in GHG emissions in the US by 2050, for the fixed, large-scale industrial sources accounting for perhaps 75% of US GHG output, would knock perhaps 2 percent off US GDP in that year. (That’s the target of both the current Senate Kerry-Boxer bill and the House Waxman-Markey bill.) With some uncertainty around that estimate. The CBO is as close to a truth-telling organization as you can find in the US these days, and I would accept their estimate as being plausible. Right now, we spend about 5% of GDP on energy, so that estimate says, roughly, that we’d double the real cost of the energy for the sources covered. That seems quite conservative (high) as an estimate of eventual cost of this transition. But certainly more plausible than a prediction of “permanent depression”, which would of course be unprecedented in US economic history.

    My point is that only some economists are idiots. This is a profession where we have no conservation laws but we use sophisticated math. (Figure that one out if you can. Most economists don’t even know what a conservation law is or why it matters that economic quantities don’t obey them.) So, you tend to get kind of a sloppy attitude toward the numbers. Which, when you are talking about will-o-the-wisp quantities such as stock market values, might be justified. But which is jarringly out of place when applied to actual physical quantities for which basic conservation laws hold.

  22. 72
    Christopher Hogan says:

    Ah, speaking of inattention to numbers, try 50% increase instead of doubling of cost.

  23. 73
    Steve Fish says:

    Jim22 (#55, 30 October 2009 @ 10:43 AM):

    My silicon PV panels are very robust in rain, wind, and hail. Their expected life is 50 years. Amorphous panels are being made into roofing.


  24. 74
    P. McCann says:

    Bravo Professor Pierrehumbert! Now if only your letter could get as much exposure as Freak-o-garbage, we’d be much safer.

  25. 75
    Martin Vermeer says:

    Jim22 #55: read this.

  26. 76
    John N-G says:

    Hank Roberts #60: The difference is that the sunlight reflected off the water is polarized. What was your point?

  27. 77
    ccpo says:

    Once again, glad to see some teeth coming into the renunciation of skepticism/cornucopian B.S.

    ‘Bout time.


  28. 78
    EL says:


    “I just finished the book yesterday, and was expecting Real Climate to get its collective panties in a bunch over Super Freakonomics. The most important point in the book – that 1) it is difficult-to-impossible to actually implement the kinds of hippie changes people like Al Gore advocate (nearly every zero-carbon advocate is a horrible hypocrite on the matter) and 2) There can be approaches that will solve the problem without plunging the world into a permanent economic depression, which is more unethical than emitting CO2 into the atmosphere.

    Also, his points on the anti-scientific claims that a lot of Al Gore clones make (”CO2 is a poison!” “Our lifestyle is unsustainable!”) are all perfectly valid.

    Hell, if we really want to stop global warming, all we really have to do is get our coal plants to start belching tons of particulate matter into the air again. Of course, acid rain will start making a comeback, but you can’t have it all, right? ”

    CO2 in large concentrations is a poison, and our lifestyle is unsustainable. Anyone who believes that exponential growth is sustainable is mathematically ignorant. And our current lifestyle depends upon exponential growth.

  29. 79

    On the white roof tile thing–and specifically the “lost solar heating” in winter–maybe someone should also point out that even when it is snowless, applying heat to the *outside* of your insulation is not going to be the most effective way to go.

    Great post!

  30. 80
    Matthias Jakob says:

    Good letter. To the point. Trouble is that a whole lot more people will read (and believe) Levitt, then your open letter. Perhaps we (as in us professionals concerned with climate change) should write very successful books for the masses. Can we?

  31. 81
    CM says:

    Literary digression: Like a memory of the future, that image above has been nagging me all day — an area of darkness covering an appreciable fraction of the planet, like a hole punched through the clouds; where have I seen this before? … Oh yes, what year is it next year?

  32. 82
    WAG says:

    I dug up some Calvin & Hobbes cartoons that I think say it all – Levitt and Dubner talking about geoengineering is about as reasonable as having a six-year-old fix your sink instead of a plumber: 2009/ 10/ what-do-superfreaks-and-calvin-hobbes.html

  33. 83
    Ike Solem says:

    Great article!

    Quote: “A more substantive (though in the end almost equally trivial) issue is the carbon emitted in the course of manufacturing solar cells, but that is not the matter at hand here.”

    True, but the concept of solar breeders was proposed in the late 1970s and has been updated today. A solar breeder is a silicon ore-processing and solar panel manufacturing facility powered entirely by wind and solar.

    The main issue with such a facility is that hours of operation coincide with maximum sunlight, which is not so much of a problem, really.

    The original reference (as far as I know) on the solar breeder concept is J. Lindmeyer, 1978:

    It was pointed out that a photovoltaic panel manufacturing plant can be made energy-independent by using energy derived from its own roof using its own panels. Such a plant becomes not only energy self-sufficient but a major supplier of new energy, hence the name solar breeder. The reported investigation establishes certain mathematical relationships for the solar breeder which clearly indicate that a vast amount of net energy is available from such a plant for the indefinite future. It is pointed out that if solar electric plants would be built according to the solar breeder principle, their operation as a net energy source would be automatically assured.

    Such projects were shut down in the early 1980s as the Reagan-era DOE slashed all funding and support – and were never restarted. The initial upfront cost of such a facility is large, and thus requires large-scale financing via Wall Street and the major banks, who refuse to back such projects. They do back fossil fuel projects on an immense scale, but over the past few decades most mega-projects are undertaken with government support, credit guarantees, and IMF/World Bank financing – that’s true for Canadian tar sands, the Nabucco gas pipeline, the Chad-Cameroon Exxon/World Bank oil pipeline, etc., etc., – but large scale government support and bank financing for renewable energy megaprojects remains non-existent in the U.S.

    I’d like to see Levitt conduct a side-by-side economic analysis of current externally-financed fossil fuel and renewable energy projects in Africa, for example – or take a look at the level of government subsidies in the U.S. for fossil fuel projects vs. renewable energy projects – but I’m not holding my breath.

    P.S. Please forward this RealClimate article to Jon Stewart at the Daily Show – his interview with Levitt was mind-bogglingly uninformed, and he pretty much swallowed everything Levitt had to say. He and his staff might benefit from reading this article – at the very least, a dissenting opinion should also be allowed.

  34. 84
    Antonio San says:

    The dear Professor Pierrehumbert will then care to explain how a global warming world is supposed to offer more extreme weather?

    [Response: I don't think I ever said that, but there are are several kinds of extremes that have fairly robust physical underpinnings. First, by the Clausius Clapeyron relation, a warmer world will have more water in it, certainly at low altitudes where most of the vapor storage is. That means that the strongest possible rain events increase (roughly exponentially) with temperature. Second, the additional water vapor and higher sea surface temperature can energize more severe hurricanes (that's Emanuel's work). Third, when land dries out, the typical summer temperature can be hotter than the hottest summer on record in many places, and lead to severe crop failures. See Battisti and Naylor's article on this recently in Science magazine. That should to for starters. The one point that some people loosely make about severe weather, which is not justified, is to say that "storms" will get more severe. That depends on what kind of storms you are talking about. Conventional midlatitude synoptic weather systems live off the temperature gradient between pole and equator, and insofar as that gradient tends to go down in a warmer world, the winds (though not the rain) in the storms is expected to get somewhat weaker. The actual behavior in models and theory is a subject of intense investigation right now. --raypierre]

  35. 85
    Hank Roberts says:
    Another red herring misdirecting attention from the topic. Tag team at work?

  36. 86
    James Staples says:

    Cool! I like that you put your ‘example square’ right where I’ve been bugging certain people (I sort of helped some one to NOT get themselves, well, killed; so they humor me, by listening – sometimes) to put them; the ‘Empty Quarter’.
    I tell them Allah will Bless the first Arabian Nation to CAP IT’S WELL’S, by taking up the responsibility of fixing the damage they’ve done in making all of those Gazillions of Dollars.
    To Dr. Levits defense; he DID indicate, when appearing on The Daily Show, that he was NO SCIENTIST and that he didn’t understand – nor did he pretend to understand – Global Warming; stressing, instead, that he was ‘just an Econimist’, blah, blah, blah.
    Now, I’ll have to add his book to the dozens of others on my ‘Future Reads List’ (Darn You! I wasn’t planning for that one – but you make me feel the need for ‘loyalty’ and ‘solidarity’!)

  37. 87
    David B. Benson says:

    Well skewered!

  38. 88

    Many many thanks for this thread. I was pleased to see the author appear among the posters, even though he apparently could not defend his book very well.

    The posts here, with the possible exception of Mark, who always seems to speak from a position of assumed moral and technological superiority, and is quick to label a new possibly innocent question as “trolling,” have also been very useful.

    I heard on NPR the other day that the percentage of Americans who think AGW is “real” has dropped precipitously in the past couple of years; once over 70%; now only slightly more than 50%.

    I have also noted some here to say “educating the public is not my job.”

    If not the job of those who know what’s really going on, who is going to do it? We get stuck with George will and jokes about fat Al Gore. I hear a lot of this.

    This site is not the solution. A year ago I suggested to three of my colleagues, one a geophysicist, another a professor of statistics and a third recently retired from a top engineering job at GM. All three have since expressed to me their rejection of the site BASED ON THE COMMENTS. Too much nastiness and put-downs. I kept on telling them to just read the articles; that anyone could post about anything in the discussions. But I was too late — these three are now firmly in the opposing-IPCC camp. If they are typical, and of course I will not claim that on a sample of three, this site might be, because of the discussions, turning more people against the IPCC reports than gaining adherents.

    At the very leeast, Gavin, you might put up a disclaimer at the beginning of the discussion section, as well as every 50 posts, that anyone at all can post here and that some posts are not necessarily to be taken seriously.

    Including this one, of course.

  39. 89
    Jeffrey Davis says:

    Levitt responded in free verse. Does anyone else find that odd?

  40. 90
    caerbannog says:

    Change the topic from climate-science to history here, and you could have a scene out of “Fast Times at Ridgemont High” (Mr. Arnold Hand vs. Jeff Spicoli).

    This is certainly not an entirely fair comparision, though: I’m certain that Dr. Pierrehumbert is nicer than Mr. Hand, and that Dr. Levitt is more sober than Jeff Spicoli.

  41. 91
    tharanga says:

    The issue of carbon emissions during the manufacture of solar cells was, in the not-too-distant-past, a serious objection:

    Levitt wasted a couple sentences on the waste heat, when he could have instead given some numbers behind the current life cycle analysis of solar cells. This would have been rather more educational. Given the current life cycle analysis, solar is still fine, but it would have highlighted the need for doing the life cycle analysis.

  42. 92
    David Horton says:

    Excellent analysis, but it could go even further. The small black square in the middle of the desert is a vivid illustration of the small scale of the problem. But in the real world of course this small square is fragmented into millions of pieces, mostly spread over surfaces already quite dark, and certainly variable. I have panels on a green roof, my daughter has them on a grassy hill. I suppose I could spread a piece of white material on the ground of the same area as our panels, but I don’t need to – in building her house my daughter has created a drive way of light colored material many times larger than the panels. And just up the road, extensive road works are scraping away vegetation on the sides of the roads and spreading white material. This kind of variation goes on all the time, and to imagine that the resulting impact of dark surfaced panels is great is foolish. Even in the case where all the panels of the world were placed in one spot, on an otherwise light surface like a desert or, say, Greenland, Ray’s analysis shows that even that effect is trivial. In addition of course few people would suggest that all energy can or should be derived from solar panels. If you add wind, geothermal and tidal sources this further reduces the dark panel impact. Or do the freaky authors think that because wind turbines are usually painted white we should instead only use them?

    A moment’s reflection (hah!) would have shown Dr Levitt that the proposition was nonsense. The fact that he proceeded to make it suggests (a) contrarianism gone mad and (b) a search for media stardom.

  43. 93
    Russell Seitz says:

    Steve, it’s a fair cop- you should change your mind to fit the facts.

    On the other hand, why has Freakonomics been lambasted so, while Malcolm Gladwell gets a pass for similar geoengineering coverage ?

    [Response: Reference? Be happy to take a look. - gavin]

  44. 94


    Most of the numbers I’ve seen on white roofs (e.g. focus a lot more on the albedo forcing than the energy reduction from cooling.

    Based on his numbers it would take 39 years of cooling reduced by 30% to match the albedo forcing for a sample white roof. This is based on a quick model:

    roof_size = 2700.0 / 10.764 #assumed roof square footage divided by square meters per square foot
    kg_per_meter = 100.0 #via Akbari, 1 ton CO2-eq per 10 square meters
    annual_cooling_use = 1831.56 #kwh US average based on 2005 RECS
    white_roof_savings = 0.3 #30 percent
    electric_ef = 0.5 #kg carbon per kwh, rough US average

    white_roof_albedo = roof_size * kg_per_meter
    white_roof_cooling = annual_cooling_use * (1 – white_roof_savings) * electric_ef

    years_needed = white_roof_albedo / white_roof_cooling

    So people touting white roof programs as a carbon reduction strategy are indeed relying on the modeled CO2-eq reductions from albedo as a big chunk of it. Some folks are even considering selling carbon offsets from painting roof white, which has some fun implications in terms of trading “flow” albedo for “stock” GHG forcings :-p

    [Response: An interesting set of numbers. Just to make things even more interesting, I'm going to follow Polya's dictum in How to Solve It, which says that one way to solve a new problem is to reformulate it so that it looks like one you already solved. Doing that here, we can think of the white roof as a kind of solar cell that generates "negawatts" by reducing the cooling demand. For the ten square meter roof, using the stated typical cooling and averaging over a year, the power saved is (.3 X 1831 kw-hr * 1000. W/kw)/(24*365 hours).
    That works out to an average of 62.7 Watts. Using a 250 Watt per square meter incident solar flux, the 10 square meters receives energy at a rate of 2500 Watts. That means the white roof is like a solar cell with an efficiency of 2.5% . That low efficiency increases your payback time, but depending on the details of what you assume about the albedo of the white roof and the original roof, the "waste heat" part of the calculation is similar to my solar cell example, at least the version where I neglect the waste heat due to coal burning. Taking into account the low effective efficiency of the white roof, I can maybe get the payback time up to around 10 or 12 years, but 39 is a stretch. If you take into account the waste heat of the fossil fuel that would be burned to make the 30% of electricity the white roof saves you, the payback time goes down somewhat. So, I think there must be something amiss in the calculation you refer to, and I'll leave it to the readers to have the fun of sorting through it and trying to identify the assumptions that yield such a long payback time. --raypierre]

  45. 95
    Marcus says:

    Two important references for Steve Levitt:
    1) Classic children’s songs:

    2) Futurama:×01.php “Thus solving the problem once and for all!”

  46. 96
    gavin says:

    With respect to Steve Levitt’s comment above, it’s worth pointing out two things. First, that the issue is not whether he and his co-author are blasphemous, but whether they are competent. And secondly, that Mr. Levitt pointedly failed to respond on our earlier thread which directly tackled the issue of geo-engineering with the kind of commentary, he has claimed elsewhere, the book chapter was designed to encourage. Instead, his comment will mostly be understood as an attempt to play the Monty Python card instead of dealing with the issue. – gavin

  47. 97
    Chris Dudley says:

    Raymond in #67,

    It is an important point that nearly all fossil fuel use leads to heat entering the environment, the exception being radio waves from our FM stations and stray street lights escaping to space directly. There is really no distinction regarding waste heat. In the case of solar power, the albedo is not really going to be different from what is covered up, roof shingles, but applying the concept of waste heat is even more misplaced. There is no waste since PV is intercepting a flow. We would not consider wind that is not intercepted by a wind mill to be waste wind. The same is true of PV. In fact, if a solar panel is used to run a cell tower, it may well have a cooling effect should its albedo be the same as the background since the Sun’s light is sent directly back out to space as radio signals. The idea of waste heat has been misapplied by the freakers for both the fossil fuel plant and the solar panel.

    It is worth noting that Nanosolar’s cells have energy payback times measured in weeks and the glass in panels made with their cells is a larger cost component than the cells themselves. The bulk of solar power is going to have to have similar characteristics to be competitive with itself. Thus, the question of accumulating carbon debt is completely bogus for annual growth rates less that 600% or so.

    There are people who feel very threatened by renewable energy who inject this sort of spurious stuff into arguments. Thanks for knocking it down.

  48. 98
    David Allen says:

    #9 – How do you make the CO2 in the ocean react with the limestone from the White Cliffs of Dover, rather than the limestone in coral and mollusc shells?

    [Response: Actually you are making the CO3-- react with the H+ to make HCO3-. basically (ha!) you are making the ocean dissolve the added carbonate instead of the carbonate in corals and molluscs. - gavin]

  49. 99
    Mike Donald says:

    That small square on the globe reminded me of similar in the book “The Hot Topic” by Gabrielle Walker and Sir David King. Their reference was Nathan S. Lewis of the California Institute of Technology who has a neat 73 page pdf “Powering the Planet” on the web. It has similar calcs to raypierre so Zeke, don’t be shy – multiple confirmations are always welcome.

    But my favourite is “Sustainable Energy – without the hot air” by David JC MacKay. In electronic format on the web and plenty of darn good calcs in it.

  50. 100
    David Allen says:

    #50 Hang on. Green rooves are green beacause they reflect green light and absorb [infra]red thus increasing the building’s temperature and air-cconditioning demand.

    I expect I’m wrong but can you please tell me why?

    [Response: The albedo effect of green roofs is somewhat advantageous because vegetation typically has a higher albedo than the roofing they replace. Green vs. black, so they at least reflect something. The biggest effect of a green roof, according to John Frederick's studies here at U. of C., come from evaporative cooling, and that accords with my own back-of-the-envelope calculations. That does mean that green roofs are not so good in a dry place, since you'd have to irrigate them to keep them fully functional. --raypierre]

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