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What do climate scientists think?

Filed under: — gavin @ 24 June 2010 - (Español)

by Gavin and Eric.

… and why does it matter?

There is a lot of discussion this week about a new paper in PNAS (Anderegg et al, 2010) that tries to assess the credibility of scientists who have made public declarations about policy directions. This come from a long tradition of papers (and drafts) where people have tried to assess the state of the ‘scientific consensus’ (Oreskes, Brown et al, Bray and von Storch, Doran and Zimmerman etc.). What has bedevilled all these attempts is that since it is very difficult to get scientists to respond to direct questions (response rates for surveys are pitiful), proxy data of some sort or another are often used that may or may not be useful for the specifics of the ‘consensus’ being tested (which itself is often not clearly defined). Is the test based on agreeing with every word in the IPCC report? Or just the basic science elements? Does it mean adhering to a specific policy option? Or merely stating that ‘something’ should be done about emissions? Related issues arise from mis-specified or ambiguous survey questions, and from the obvious fact that opinions about climate in general are quite varied and sometimes can’t easily be placed in neatly labelled boxes.

Given these methodological issues (and there are others), why do people bother?

The answer lies squarely in the nature of the public ‘debate’ on climate. For decades, one of the main tools in the arsenal of those seeking to prevent actions to reduce emissions has been to declare the that the science is too uncertain to justify anything. To that end, folks like Fred Singer, Art Robinson, the Cato Institute and the ‘Friends’ of Science have periodically organised letters and petitions to indicate (or imply) that ‘very important scientists’ disagree with Kyoto, or the Earth Summit or Copenhagen or the IPCC etc. These are clearly attempts at ‘arguments from authority’, and like most such attempts, are fallacious and, indeed, misleading.

They are misleading because as anyone with any familiarity with the field knows, the basic consensus is almost universally accepted. That is, the planet is warming, that human activities are contributing to the greenhouse gases in the atmosphere (chiefly, but not exclusively CO2), that these changes are playing a big role in the current warming, and thus, further increases in the levels of GHGs in the atmosphere are very likely to cause further warming which could have serious impacts. You can go to any standard meeting or workshop, browse the abstracts, look at any assessment, ask any of the National Academies etc. and receive the same answer. There are certainly disputes about more detailed or specific issues (as there is in any scientific field), and lots of research continues to improve our quantitative understanding of the system, but the basic issues (as outlined above) are very widely (though not universally) accepted.

It is in response to these attempts to portray the scientific community as fractured and in disagreement, that many people have tried to find quantitative ways to assess the degree of consensus among scientists on the science and, as with this new paper, the degree of credibility and expertise among the signers of various letters advocating policies.

It is completely legitimate to examine the credentials of people making public statements (on any side of any issue) – especially if they make a claim to scientific expertise. It does make a difference if medical advice is being given by a quack or the Surgeon General. The database that Jim Prall has assembled allows anyone to look this expertise up – and since any new source of information is useful, we think this can be generally supported. Prall’s database has a number of issues of course, most of them minor but some which might be considered more problematic: it relies on citation statistics, which have well-known problems (though mostly across fields rather than within them), it uses Google Scholar rather than the standard (ISI) citation index, and there are almost certainly some confusions between people with similar names. Different methodologies could be tried – ranking via h-index perhaps – but the as long as small differences are not blown out of proportion, the rankings he comes up with appear reasonable.

So it is now possible to estimate an expertise level associated with any of the various lists and letters that are out there. Note that it is worth distinguishing between letters that have been voluntarily signed and lists that have been gathered with nothing but political point scoring in mind (the Inhofe/Morano list was egregious in its cherry picking of quotes in order to build up its numbers and can’t be relied on as an accurate reflection of peoples opinions in any way, and similarly contributing to RealClimate is not a statement about policy preferences!). Additionally, it isn’t always clear that every signatory of each letter really believes every point in the statement. For instance, does Lindzen really believe that attribution is impossible unless current changes exceed all known natural variations (implying that nothing could be said unless we got colder than Snowball Earth or warmer than the Cretaceous or sea level rose more than 120 meters….)? We doubt it. But as tests of political preferences, these letters are probably valid indicators.

So, do the climate scientists who have publicly declared that they are ‘convinced of the evidence’ that emission policies are required have more credentials and expertise than the signers of statements declaring the opposite? Yes. That doesn’t demonstrate who’s policy prescription is correct of course, and it remains a viable (if somewhat uncommon) position to acknowledge that despite most climate scientists agreeing that there is a problem, one still might not want to do anything about emissions. Does making a list of signers of public statements, or authors of the IPCC reports, constitute a ‘delegitimization’ of their views? Not in the slightest. If someone’s views are widely discounted, it is most likely because of what they have said, not who they sign letters with.

However, any attempt to use political opinions (as opposed to scientific merit) to affect funding, influence academic hiring, launch investigations, or personally harass scientists has no place in a free society – from whichever direction that comes. In this context, we note that once the categorization goes beyond a self-declared policy position, one is on very thin ice because the danger of ‘guilt by association’. For instance, one of us (Eric) feels more strongly that some of Prall’s classifications in his dataset cross a line (for more on Eric’s view, see his comments at Dotearth).

But will this paper add much to the ‘there [is/is not] a consensus’ argument? Doubtful. People are just too fond of it.

But there really is.

427 Responses to “What do climate scientists think?”

  1. 401
    Rod B says:

    FurryCatHerder, et al, I think you are assuming this but it should not be left unsaid in these discussions. The wholesale conversion of our transportation system is every bit as culture-shaking and probably much more costly than building jillions of renewable energy sources. Yet until transportation is turned on its head the need for oil will not diminish much no matter how much renewable energy is out there.

  2. 402
    ccpo says:

    ccpo, Careful about your Fact #1. For the past 50 years, our food supply has been critically dependent on petroleum. Human population would never have had its last doubling if we hadn’t effectively learned to “eat” petroleum by turning it into soy and corn.

    Food insecurity could well spell the end for civilization, whether it arises due to the end of oil, climate change, or (most likely) both. All the more reason why we should be trying to get off of oil, and other fossil fuels ASAP–they’re too valuable to burn.

    Comment by Ray Ladbury — 5 July 2010 @ 7:41 AM

    A valid point, but food by itself won’t end civilization, most likely, only as part of the milieu. After all, the proximal cause of the fall in production would be PO, so this point is subsumed under that.

    Also, it simply is not difficult to get people growing a significant portion of their own food: Victory Gardens in the US and UK grew 40% of veggies during WWII. Ramp up was rapid and extensive. Some things really are easy to accomplish. A 40% reduction in food supply from Big Ag is easily address by home gardens. See Cuba.

  3. 403
    ccpo says:

    ccpo @ 379:


    Comment by FurryCatHerder — 5 July 2010 @ 9:01 AM

    None of the above addressed my point.


  4. 404
    ccpo says:

    RodB and Gilles, your questions are not worth response. Get serious if you want to discuss.

    Et al.:

    1. I am not going to discuss PO here when there is an excellent place to do that:
    1b. Suffice to say, solving PO is not something that can be done quickly. Hirch: 10 years with large disruptions, any less, possibly massive disruptions. Erego…
    1c. It is likely something that can’t be done at all, particularly in terms of avoiding disruptions and/or maintaining the lifestyle OECD nations currently have.

    2. I am not saying one or the other is worse in the short and medium term in terms of effects, I am saying you can’t separate them, so the debate is both boring and pointless.

    3. When I say PO can’t end civilization, I mean the core of it, not the cars and planes, etc. But what makes current civilization what it is is some basic anthropogenic structures and systems. Whether we live in straw bale homes or McMansions is not culture… at least not meaningful culture. The American Southwest civilization actually ended. It disappeared. The Maya? Virtually. It re-formed into something very different. PO really will not cause that in and of itself because we don’t need oil to read the books we already have, to enjoy the music we already know, to grow food we already grow, etc. A reduction in complexity? Sure. But going back 200 years technologically would not constitute an end to civilization or culture.

    4. AGW can make life, itself, untenable. PO can’t even get close to that. This is obvious and really should not need any further discussion. Some things really are that obvious.

    5. Rapid climate change is well-documented. Don’t be intentionally dense.

    6. That we are or near tipping points is on its way to be established. I have no doubt we are already there in some cases. I’ve yet to be wrong in my forward-looking statements. Let’s hope to heck I am this time, but the new research says otherwise.

    I hope this clarifies things.


  5. 405

    ccpo @ 404:

    Then I haven’t the slightest idea =what= your point is.

    My “point” is very simple, and I’ve been very clear about it —

    The need to stop using fossil fuels is =more= urgent due to Peak Oil than due to AGW. You said that Peak Oil doesn’t trump AGW, which I can only take to mean that you think that Peak Oil isn’t a reason to stop using fossil fuels, but that AGW is. Which, by implication, means you think Peak Oil is a less urgent reason. As in, =less= need to stop using fossil fuels.

    I wrote this before the mort-gage crisis —

    Fortunately, the something which must be done is precisely the same something we need to do to avert a catastrophic collapse of the global economy in the very near term — quit relying on fossil fuels. When I first started actively engaging the climate change folks on the subject, oil was half the price it is today. The global economy is heading in a direction where unless oil prices begin to decline, the global economy will stall and collapse. There is only one way to reduce the price of oil in a free market economy — reduce consumption. As we near Peak Oil, increasing production is not an option, no matter how much Pres. Bush pounds his fist on the table, demanding that oil production in the Arctic be permitted.

    We think of the Great Recession as being caused by the bizarre debt instruments, but something caused them to implode, and the spike in oil prices in 2008 was just the warm-up.

    So. You were saying that Peak Oil isn’t a more urgent reason than AGW to move from fossil fuels?

  6. 406

    Rod B @ 402:

    FurryCatHerder, et al, I think you are assuming this but it should not be left unsaid in these discussions. The wholesale conversion of our transportation system is every bit as culture-shaking and probably much more costly than building jillions of renewable energy sources. Yet until transportation is turned on its head the need for oil will not diminish much no matter how much renewable energy is out there.

    What wholesale conversion?

    The “wholesale conversion” can start =now= and not disrupt anyone, other than people who have some deep-seated, burning need to waste oil.

    Three or four years ago I spec’d a solar power system that would replace all the electricity I get from the grid, plus what I spend in motor fuels. The cost? It was about $65K then, and would be on the order of $39K now. The monthly savings (pretending I didn’t have solar already …) would be on the order of $400 at current electricity and gasoline prices. The monthly mort-gage expense for 10 years at 5% fixed is $408. Assuming a 5% rate of inflation, the cost reaches break-even in a few months (5% of $408 is about $20 ….), is paid for in 10 years with positive ROI after year 1, and free power from years 10 through 25.

    You aren’t willing to have your life disrupted so you can drive for free?!?

  7. 407
    Gilles says:

    FCH#407 : your computation of ROI holds for a “test particle”, but not for the whole society. Solar power is useful up to some amount, like wind power. If electricity could power the whole society, countries where hydropower is cheap and abundant would have already made their transition to 100 % renewable electricity , cheap, convenient (much more than sun), carbon free, and safe. They haven’t. There must be a good reason for that. It is unlikely that electricity can power more than 50 % of the energetic needs, and that, due to intermittency , solar and wind can power more than 20 % of the grid, leaving 10 % of the total energy needs – i don’t know any country where this threshold is overcome. Most likely, this threshold won’t be reached worldwide before the oil begins to severely deplete – and then even if it were reached , it won’t prevent the economy to crash since nothing else could replace it.

    But actually there is no “need” of anything – just like there was no need to develop as we did. There may be a desire to keep our civilization, but if you accept getting back to preindustrial ages, there is no real issue. There is no question that “we must go out of oil”. We’ll do anyway. The only point is what we’ll be able to do without it. I don’t know, you don’t know, and actually nobody knows. The present crisis offers an interesting view of what the future world can look like. No brutal disappearance of cars, no demographic crash, no starvation – just a series of recession that will make people poorer and poorer : may be in a somewhat warmer world, but the will most likely don’t care, with regards to the inconvenience of the FF depletion. If I had to bet on the future of the world, I would bet on that.

  8. 408
    Rod B says:

    FurryCatHerder (407), it seems you might have overlooked the wholesale replacement of every car, truck, most buses and trains and all but evidently your and a few other’s motorcycles. I trust you don’t believe this is just a couple of weekend’s worth of chores.

  9. 409
    Jene says:

    Global warming has become perhaps the most complicated issue facing world leaders. On the one hand, warnings from the scientific community are becoming louder, as an increasing body of science points to rising dangers from the ongoing buildup of human-related greenhouse gases — produced mainly by the burning of fossil fuels and forests. On the other, the technological, economic and political issues that have to be resolved before a concerted worldwide effort to reduce emissions can begin have gotten no simpler, particularly in the face of a global economic slowdown.

  10. 410

    Rod B @ 409:

    Yes, the replacement of every vehicle on the road. The same as every vehicle on the road is already replaced on a regular basis.

  11. 411
    flxible says:

    re 411: The [i]average[/i] age of registered private vehicles in the US is about 8 years, commercial vehicles [busses, freight trucks, etc] can last much longer – we can expect newer ones to last still longer …. I’ve never owned a vehicle newer than about 20 myears old, currently driving a 1958 pickup – you’re maybe thinking every vehicle in current use, and the new ICE ones being sold daily, will be replaced under BAU norms by ….. when? 2050? 2100? By what, pray tell? What are the alternatives for the freight vehicles that daily deliver your goods? I’m rebuilding a 1947 bus for a ‘retirement home’ – maybe you have a practical way to power it electrically that even a profit making capitalist enterprise could afford?

  12. 412
    Hank Roberts says:

    tracked, e.g.

    “Vehicles are also being scrapped at higher rates than in past years. A total of 5.6% of all cars and trucks were scrapped in 2008 as compared to 5.2% in ’07…”

    Larger vehicles are often diesels — older ones emitting problematic pollution, which is why the new ones are much cleaner (well, in Europe) and those operating in air pollution districts are regulated. Biodiesel burns cleaner in refitted old ones.

    > retirement home
    Diesels can go 100k or more between rebuilds, again likely longer on biodiesel; the refit for biodiesel seems like a no-brainer alternative to electric-everything.

  13. 413
    Hank Roberts says:

    Two new teaching videos:

    From their home page:

    “… computer simulations that help people visualize the long-term climate impacts of decisions being undertaken today …. that can help stabilize the climate system.

    We are modelers and scientists developing climate simulations ….

    Learn about our simulator for climate negotiator analysts and other leaders, tune in as we track the progress of the UNFCCC negotiations, explore our freeware online climate change simulation …..

  14. 414
    flxible says:

    > retirement home
    Diesels can go 100k or more between rebuilds, again likely longer on biodiesel; the refit for biodiesel seems like a no-brainer alternative to electric-everything.

    a good diesel can go way more than 100K between rebuilds, especially the old polluting Detroits, but in what’s remaining of my life I’d be suprised if I put 50K on getting no place in no hurry, any decent $1000 ICE will outlast me.

    As much as I’d like to run on biofuel, I can’t stand the noise and stink of diesels, even the newest big ones aren’t great in that respect, and new diesels sell for 10,000$ up, and require properly made biodiesel [like NOT waste veg oil, but stuff from crops that should be providing food], as well as needing expensive professional shop services regular, and very spendy parts, even routine maint parts – and that doesn’t include the trans that would be needed that could double the cost – a good GM 454 with a common OD truck trans will do the job and I can maintain it myself. I’m spending the money I have on alternatives for when I’m stationary, like PV panels and quality 12V appliances.

    For the freighters littering N American highways, biodiesel [that takes food off the tables of many] MIGHT help reduce CO2 output slightly in order to keep food on the tables of those that could afford it, but it’s not a lot of help. . . . And the increased scrappage recently is a result of govt incentives, at least here in Canada – not to mention the high price scrap metal has been bringing because the Chinese have been gobbling it up.

    “What goes around comes around” they say, the only solution for drastic decreases in emissions is massive decreases in global consumption, which won’t happen as long as the unsustainable population size isn’t addressed.

  15. 415
    Rod B says:

    Hank, doesn’t biofuel require a lot of long term sequestering in the plants stalks (?) and roots to have a significant net efffect on CO2 emissions, and isn’t that prospect a little uncertain?

    If there is decent net savings (Does the added N2O emissions — doubled, maybe — that some have indicated mitigate it much?) I would agree that it seems like biodiesel conversion is a much shorter row to hoe than all electric conversion. btw, diesels routinely go 250,000-350,000 miles and more before rebuilds; can’t bio conversions be done without rebuilding?

  16. 416
    flxible says:

    Rod – “Biodiesel” [currently mostly from rapeseed and soy] can be used directly in all existing [old and new] diesel engines, where conversion is required is in the use of straight vegetable oil [or waste oil], and new diesels can have problems with it, only the older ones work well, depending on the injection system and quality of the oil, and it’s frequently mixed with petrodiesel. Helpful to a limited extent, as the energy returned is good for energy invested, BUT the developed world is driving up the price of cooking oil for the poorer countries by using food crops for biofuel and by folks putting palm plantations in places that could be growing food.

    “According to the EPA’s Renewable Fuel Standards Program Regulatory Impact Analysis, released in February 2010, biodiesel from soy oil results, on average, in a 57% reduction in greenhouse gases compared to fossil diesel, and biodiesel produced from waste grease results in an 86% reduction”

  17. 417
    Brian Dodge says:

    “biodiesel [that takes food off the tables of many]… ” flxible — 10 July 2010 @ 4:19 PM
    It’s not necessarily as bad as one might think:

    soybeans are 40% protein, 35% carbohydrate, and 20% oil. Conversion of the oil to biodiesel doesn’t remove the protein and carbohydrate from the food supply, and in fact almost all soybeans are processed into oil and soy protein concentrate. According to wikipedia “Soybeans can produce at least twice as much protein per acre than any other major vegetable or grain crop, 5 to 10 times more protein per acre than land set aside for grazing animals to make milk, and up to 15 times more protein per acre than land set aside for meat production.” If we replaced 10% of our meat intake with soy protein, and converted the freed up land to soy instead of meat, the total food protein production could increase by 140%.
    “When you make ethanol out of corn, about one-third is ethanol, one-third is carbon dioxide and one-third is dried distillers grain with solubles (DDGS), says Mindy Schweitzer, marketing manager at POET Nutrition.”
    “For beef cattle, on a dry-matter basis, DDGS have 5% more net energy than No. 2 yellow corn, Gibson says of his company’s Dakota Gold. For dairy cattle, it’s 10% more net energy.”
    “Newer research at land-grant universities shows much higher nutritional values for ethanol coproducts than what has been published historically, according to [POET livestock nutritionist Matt] Gibson.”
    “Upon conversion from corn to DDGS, on an average, protein was concentrated 3.59 times; oil, 3.40 times; ash, 3.32 times; and total non-starch CHO, 2.89 times.”

    Between 1997 and 2007 US farmland declined by ~33 million acres[1]: if that land were put back into corn production, it could produce 14 billion gallons of biofuel ethanol[2] plus the additional food value of the DDGS. If the concentrated CO2 emissions were captured and sequestered, it would be carbon negative.

    Biofuels are by no means a panacaea, and effectively producing biofuels and food requires some forethought about the demands on water, land, and the remaining natural environment(e.g., conversion of tropical forest to palm oil plantations), plus modeling of the pathways of energy & mass flows through a system with people/cows/goats/pigs/chickens/tilapia, corn/soybeans/alfalfa/duckweed/truck crops, poop/sewage flows, fertile/marginal soil areas, macronutrients/micronutrients and annual weather and climate. Questions such as ” does the overall productivity increase if fewer ruminants and more other animals are grown because the higher metnane biogas -> ammonia fertilizer -> increased corn yield + higher pig/chicken FCR offset the ability of cows/goats to digest cellulose?” can be approximated with modeling without the losses inherent in an experimental free market approach. Some farmers might choose to grow more cows and forego some profit just because they like cows. Corporations operating under only their fiduciary responsibility might choose to produce more fuel and “take food off the tables of many” whose starvation won’t affect their profit.

    I think that rational civilized government policies ought to give incentives, coercion, and even mandates to maximize the life, liberty, and pursuit of happiness of individuals, as well as promote the common welfare.
    Carbon taxes, sequestration rebates, and mandatory food/fuel ag production ratios are potential tools to achieve these ends.

    [2] “158.6 bushels of corn per acre. 2.77 gallons of ethanol per bushel of corn. 439 gallons of ethanol per acre”

  18. 418
    Rod B says:

    Brian Dodge, just for comparison and context, converting all gasoline using vehicles to 100% corn-based ethanol would require almost 7x the current acreage in corn, and 30% more than the current total cropland of the US.

  19. 419
    Didactylos says:

    Corn ethanol is not a good choice. Besides being a waste of money and a puny impractical half-measure, it has also done extreme damage to the reputation of biofuels, especially in the US.

    So, America: if you are serious, then stop subsidising corn, remove tariffs on biofuel imports, and find out which biofuels are economical and effective on a truly level playing field.

  20. 420
    John E. Pearson says:

    419: Rod said that you could power all the US cars with corn if you used 130% more land than the US currently uses for crops.

    I don’t believe you. From what I’ve been able to understand, the EROI on corn is so low that it is still uncertain as to whether it is positive. The land required to produce enough fuel to even make a difference with corn might well be way more than 130 % of our current croplands.

  21. 421
    Patrick 027 says:

    Re 418 Brian Dodge –
    Between 1997 and 2007 US farmland declined by ~33 million acres[1]
    ~ 51,563 mi^2
    ~133,546 km^2
    ~ 1.7 to 1.8 % of US excluding Alaska
    ~ 1.07 TWe for 10 % efficient conversion of 200 W/m2 to electricity with 1 m2 of panel per 2.5 m2 of land (*roughly* the ‘fuel equivalent’ of all U.S. energy use, though there are some uses of fuel that would require more electricity to replace than that proportionality)

    (PS how much of that decline was from urban sprawl? I’ve read that’s a real problem, because some of the best farmland is being lost (of course, people would settle where the land is good, wouldn’t they)).

  22. 422
    Rod B says:

    Didactylos (420), I agree that corn ethanol is not very attractive. But I didn’t follow your suggestion. First, corn ethanol is a biofuel is it not? In any case my concern still stands: we would still have to import a jillion tons a day or still devote a jillion more acres that we don’t readily have to raising whatever ethanol alternative(s) we choose.

    John E. Pearson, I’m not 100% sure what EROI is, but if you are questioning the marginal corn productivity on the 400 million acres or so we would have to add, you are correct. Most of that land won’t come close to the bushel/acre yield that current corn land does. We’ll just have to give the Rocky Mtns and the Sonoran Desert a shot! Maybe we could invade and absorb Mexico which does have some corn productive soil — hell, and maybe solve the illegal immigration problem at the same time!

  23. 423
    Brian Dodge says:

    “Corn ethanol is not a good choice.” Compared to what? Burning up 10 milllion BTU per acre of fossil fuels to grow corn, shipping it to a feed lot and converting it to beef at a 7:1 FCR, and dumping the CO2 and methane emitted in this process into the atmosphere for someone else to deal with?

    “I don’t believe you. From what I’ve been able to understand, the EROI on corn is so low that it is still uncertain as to whether it is positive.”
    Pimental and Patzek, using 1979 production data, found a net negative EROEI of -15kbtu/gallon. The USDA, using 2001 production data, found a net positive EROEI of 31Kbtu/gallon.
    “THE NET ENERGY BALANCE OF CORN ETHANOL” Roger Conway Office of Energy Policy and New Uses/USDA

    “..converting all gasoline using vehicles to 100% corn-based ethanol would require almost 7x the current acreage in corn, and 30% more than the current total cropland of the US.”
    “pasture and range land, 587 million acres (25.9 percent); cropland, 442 million acres ”
    442 million acres of cropland would yield 177 billion gallons of ethanol(at 400 gallons of EtOH/acre), compared to the current consumption of gasoline of ~140 billion gallons. Converting 60 percent of the pasture/rangeland would provide 140 billion gallons per year of EtOH, and ~500 million tons of DDGS for animal feed. At a crappy 10:1 FCR, that would yield 50 million tons of beef, compared to US 2008 consumption of of 27.3 billion pounds. (~30 times more beef “on the table”, for those who have trouble doing the math).

    I am aware that 150 bushels corn/400 gal EtOH per acre is very optimistic for 60 percent of the current range/grassland – a lot is too dry, and this is likely to get worse – and i don’t recommend corn/beef monocultures, or hoping for some other sort of magic bullet . Duckweed can produces ~25 times the starch per acre as corn(In NC climate, grown on hog farm effluent), but midwest cold weather reduces this potential. Oil Palm produces ~500 gallons/acre of biodiesel, and it’s a perennial – less fuel for plowing & planting, and squeezing the oil out is less energy intensive than distilling ethanol. It won’t grow in the US(except Hawaii, maybe south Florida), but the places where it does grow(indonesia, Maylasia) have low labor costs, so buying it from there is a good choice economically. Because creating the plantations often means burning the tropical forest and draining the underlying peat soils, there’s an initial large release of stored carbon. The growth of the trees will sequester some of the CO2; capture/sequestration of fermentation CO2 would be a continuous process. A tax on CO2 emissions, and credits for CO2 sequestration might make ethanol more economic, and certainly carbon negative.

  24. 424
    Brian Dodge says:

    ~3.6 times more beef… aaargh

  25. 425
    Rod B says:

    Brian Dodge, I have some quibbles with your numbers, though your analysis is pretty good, IMO. Of the current 440-some million acres of cropland, about 320-some million acres are harvested, and 80-some million acres is in corn. The roughly 175 billion gal. of gasoline burned by vehicles would require about 235 billion gal. of ethanol for full replacement. Using your 400 gal. per acre takes about 580 million acres of corn — a little more than your figure but probably within the range. The big question is the 400 gal of ethanol per acre. At the high yield end it’s probably more like 470 gal (we’re still close) for the 80 million current corn acres. But it’s grossly optimistic for rangeland, and even optimistic for much of the other cropland. If the overall average is 200-250 gal/acre about 1 billion acres all exclusively in corn is now required, which is more than all of the current US farmland (crop, range, pasture).

    The added benefit of DDGS feed is misleading since it would merely replace part of the 55% of corn that is used for feed directly today and it is not an acceptable complete cattle diet. And since we’ve taken all of the other grains and pasture cattle feed, instead of going up cattle production drops precipitously, as would pigs, chickens, turkeys not to mention wheat, soybeans, cotton, vegetables, etc, etc ad infinitum.

  26. 426
    Brian Dodge says:

    “The added benefit of DDGS feed is misleading since it would merely replace part of the 55% of corn that is used for feed directly today and it is not an acceptable complete cattle diet.”
    If the analysis starts by ascribing all the energy inputs(fuel to run the tractors, produce the fertiliser, transport the products, and distill the ethanol) to the production of ethanol, the energy contained in the ethanol is still more than used in production. The energy cost of production of the DDGS, containing the protein, fiber, and various other nutrients, is therefore zero. Replacing some corn/soybeans/hay going into the food supply for cows with this product saves the fossil fuel that would be used to grow those products. According to ‘Fossil Energy Use in the Manufacture of Corn Ethanol’ , August 2002, Dr. Michael S. Graboski
    “72% of the land supplying corn to wet and dry mills would need to be planted in the absence of ethanol production for ruminant feeding and corn oil replacement. Thus, while the apparent yield of ethanol per harvested acre is currently 372 gallons, the actual yield when replacement is taken into account is approximately 1,300 gallons per acre.”

    DDGS isn’t a complete diet, but straight corn isn’t economic either. For ruminants, the starch in corn can be used for ethanol production, and replaced by cellulose from lower quality sources – corn stover from the fields, hay, verge grass, the wood shavings & straw from chicken litter(and the cows can capture undigested food and the urea/ammonia nitrogen contained in the feces), or even shredded waste paper.

    There’s also the issue of who goes first. Manufacturers won’t make & the public won’t buy cars that can run on flexfuel if there’s none at the gas station. So they wait. The oil companies can’t supply gasahol unless there are distilleries providing them with ethanol, and can’t sell it if there aren’t flex fuel vehicles. So they wait. No venture capitalist is going to build a cellulosic ethanol plant without a market for the ethanol, and a supply of wood chips, switchgrass, waste paper, corn stover…. So they wait. Farmers won’t produce more cellulose than their ruminants need unless there is a cellulose to ethanol plant buying. So they wait.

    Every day we wait, the US uses ~14.4 million barrels of oil, and only 0.85 million barrels of EtOH.
    We could be using ~15 mbpd of oil, and zero ethanol, and more money would be going overseas and less to US farming; or we could be using 13 mbpd oil and 2mbpd ethanol, sending less money abroad, increasing farm income, and using some of that cash flow to develop fossil fuel replacements that we are eventually going to need anyway.
    Every day we wait, the cost of that change increases (lost opportunity cost).
    Every day we wait, our range of choices narrows.
    The money we are “saving” by having cheap beef, pork, and chicken isn’t being set aside to pay for the future cost of curing our oil addiction.[1]

    But a farmer can grow more corn, or less cattle, and send corn to an ethanol plant, and still make money, especially if there’s a subsidy. And a venture capitalist will build an ethanol plant with readily available corn, and a federal gasahol mandate. And if he’s smart (most are), he’ll spend a little extra to make sure it can be converted to cellulosic ethanol if the time comes. The oil companies have to make gasahol if its mandated, but they can still make money selling it, and the corn-to-ethanol distilleries will supply it. Some of the profits will have to go toward upgrading their supply chain to handle ethanol, but that’s tax deductible. And the car companies will make flexfuel hybrids, ’cause the mileage mandates are there, and the gasahol production and distribution system is there.
    And in fact, government policies over the last decade have started this process.

    And if we are smart and lucky, the cash flow from corn ethanol will provide the money and incentives to convert most of the production stream to cellulosic/duckweed/algal source materials in a decade or so. and the DDGS from those sources will provide some of the additional food we need for the additional population we’ll have. In years where we have a bumper crop of corn, and produce more than we need for feed, the market to distilleries will provide built in price supports; the DDGS from the other ethanol feedstocks will provide some cushion to food production in years when the corn crop is bad.

    [1] The beef industry is hurting right now, but it’s not just from the increased cost of corn. Pork and chicken have higher FCR, and lower costs, even though non-ruminants require higher quality feeds. The recession has cause a shift in consumer buying habits to cheaper meats. The one case of BSE in the US was likely the main reason for a 30% drop in beef exports in 2004, though trade protectionism played a part, with the BSE as an excuse(sorta like 9/11->Al Qaeda->Saddam Hussein->WMD->Iraq oil reserves, but I digress).

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    cormac says:

    Interesting post, well done. One point that doesn’t seem to get mentioned much in all the blogosphere comment; I have the the official PNAS Anderegg paper in front of me and it contains no list whatsoever, black or otherwise. So why the fuss?

    (Yes, there is a list is on a blog written by one of the authors – but that is a different thing)
    Regards, Cormac.