Cassandra has moved. Ugo Bardi publishes now on a new site called "The Seneca Effect."

Thursday, September 15, 2011

Cassandra's curse: how "The Limits to Growth" was demonized

As part of a mini-series on "The Limits to Growth" (earlier posts here, here, and here), I am reprinting (with some minor modifications) a post that I published on "The Oil Drum" in March 2008. Above: image from the 1972 Report. 

In 1972, "The Limits to Growth" study arrived in a world that had known more than two decades of unabated growth after the end of the Second World War. It was a time of optimism and faith in technological progress that, perhaps, had never been so strong in the history of humankind. With nuclear power on the rise, with no hint of scarcity of mineral resources, with population growing fast, it seemed that the limits to growth, if such a thing existed, were so far away in the future that there was no reason to worry. And, even if these limits were closer than generally believed, didn't we have technology to save us? If we could reach the Moon, as we did, in 1969, what was the problem with such trifles as resource depletion and pollution? The future could only be shiny for ever and ever.

Against that general feeling, the results of "The Limits to Growth" showed that the future was not to be shiny at all. The authors had developed a model that could keep track of a large number of variables and of their interactions as the system changed with time. They found that the world's economy tended to collapse at some time in the 21st century. The collapse was caused by a combination of resource depletion, overpopulation, and growing pollution (this last element we would see today as related to global warming). Only specific measures aimed a curbing growth and limit population could avoid collapse.

There is a legend lingering around the first "Limits" book that says that it was laughed off as an obvious quackery immediately after it was published. It is not true. The study was debated and criticized, as it is normal for a new theory or idea. But it raised enormous interest and millions of copies were sold. Evidently, despite the general optimism of the time, the study had given visibility to a feeling that wasn't often expressed but that was in everybody's minds. Can we really grow forever? And if we can't, for how long can growth last? The study provided an answer to these questions; not a pleasant one, but an answer nevertheless.

The Limits to Growth study had everything that was needed to become a major advance in science. It came from a prestigious institution, the MIT; it was sponsored by a group of brilliant and influential intellectuals, the Club of Rome; it used the most modern and advanced computation techniques and, finally, the events that were taking place a few years after publication, the great oil crisis of the 1970s, seemed to confirm the vision of the authors. Yet, the study failed to generate further research and, a couple of decades after the publication, the general opinion about it had completely changed. Far from being considered the scientific revolution of the century, in the 1990s The Limits to Growth had become everyone's laughing stock: little more than the rumination of a group of eccentric (and probably slightly feebleminded) professors who had really thought that the end of the world was near. In short, Chicken Little with a computer.

The reversal of fortunes of "The Limits to Growth" was gradual and involved a debate that lasted for decades. At first, critics reacted with little more than a series of statements of disbelief. Just a few early papers carried a more in-depth criticism, notably by William Nordhaus (1973) and by a group of researchers of the University of Sussex that went under the name of the "Sussex Group" (Cole 1973). Both studies raised a number of interesting points but failed in their attempt of demonstrating that the Limits study was flawed in its basic assumptions. In addition, already these early papers showed an acrimonious streak that became common in the debate from the side of the critics. Political criticism, personal attacks and insults, as well as breaks of the basic rules of the scientific debate. For instance, the editor of the journal that had published Nordhaus' 1973 paper refused to publish a rebuttal.

With time, the debate on the Limits book veered more and more on the political side. In 1997, the Italian economist Giorgio Nebbia noted that the reaction against the study had arrived from at least four different fronts. One was from those who saw the book as a threat to the growth of their businesses and industries. A second was that of professional economists, who saw it as a threat to their dominance in advising on economic matters. The Catholic Church provided further ammunition for the critics, being piqued at the suggestion that overpopulation was one of the major causes of the problems. Then, the political left in the Western World saw the study as a scam of the ruling class, designed to trick workers into believing that the proletarian paradise was not a practical goal. And this is a clearly incomplete list; forgetting the political right, the believers in infinite growth, politicians seeking for easy solutions to all problems, and many others. All together, these groups formed a formidable coalition that guaranteed a strong reaction against the Limits to Growth study. This reaction eventually succeeded in demolishing the study in the eyes of the majority of the public and of specialists at the same time.

The fall of the Limits to Growth was greatly helped by a factor that initially had bolstered its credibility: the world oil crisis of the 1970s. The crisis peaked in 1979 but, in the years that followed, new oil resources started flowing abundantly from the North Sea and from Saudi Arabia. With oil prices plummeting down, it seemed to many that the crisis had been nothing but a scam; the failed attempt of a group of fanatic sheikhs to dominate the world using oil as a weapon. Oil, it seemed, was, and had always been, plentiful and was destined to remain so forever. With the collapse of the Soviet Union in 1991 and the "New Economy" appearing, all worries for the future seemed to be over. History had ended and all we needed to do was to relax and enjoy the fruits that our science and our technology would provide for us.

At this point, a perverse effect started to act on people's minds. In the late 1980s, all that people could remember of the Limits to Growth book, published almost two decades before, was that it had predicted some kind of catastrophe at some moment in the future. If the world oil crisis had been that catastrophe, as it had seemed to many, the fact that it was over was the refutation of the same prediction. This factor had a major effect on people's perception.

The change in attitudes was gradual and spanned a number of years but we can probably locate a specific date for the actual turning point. It happened in 1989 when Ronald Bailey, science editor of the Forbes magazine, published a sneering attack against Jay Forrester, the father of system dynamics, the method behind the Limits study  (Bailey 1989). The attack was also directed against Limits book which Bailey said was, “as wrong-headed as it is possible to be”.

To prove his point Bailey revived an observation that had already been made in 1972 by a group of economists on the "New York Times" (Passel 1972). Bailey said that:
“Limits to Growth” predicted that at 1972 rates of growth the world would run out of gold by 1981, mercury by 1985, tin by 1987, zinc by 1990, petroleum by 1992, copper, lead and natural gas by 1993.
In 1993 Bailey reiterated his accusations in the book titled “Ecoscam.” This time, he could state that none of the predictions of the 1972 Limits study had turned out to be correct.

Of course, Bailey’s accusations are just plain wrong, being based on data taken out of context. In table 4 of the second chapter of the book, we can find a row of data (column 2) for the duration, expressed in years, of some mineral resources in the assumption of continuing exponential growth. Bailey had presented these data as the only "predictions" that the study had made and he had based his criticism on that, totally ignoring the rest of the book.

Reducing a book of more than a hundred pages to a few numbers is not the only fault of Bailey's criticism. The fact is that none of the numbers he had selected was a prediction and nowhere in the book it was stated that these numbers were supposed to be read as such. Table 4 was there only to illustrate the effect of a hypothesis, that of continued exponential growth of the exploitation of mineral resources. Even without bothering to read the whole book, the text of chapter 2 clearly stated that this continued exponential growth was not possible. The rest of the book, then, showed various scenarios of economic collapse that in no case took place before the first decades of 21st century.

It would have taken little effort to debunk Bailey's claims. But it seemed that, despite the millions of copies sold, all the "Limits to Growth" books had ended in the garbage bin. Bailey's criticism had success and it started behaving with all the characteristics of what we call today “urban legends."

We all know how persistent urban legends can be, no matter how silly they are. At the time of Bailey's article and book, the Internet as we know it didn't exist yet, but word of mouth and the press were sufficient to spread and multiply the story of the "wrong predictions." Just to give an example, let's see how Bailey's text even reached the serious scientific literature. In 1993, William Nordhaus published a paper titled “Lethal Models” which was meant as an answer to the second version of the "Limits", published in 1992 with the title "Beyond the Limits".

Nordhaus' paper was accompanied by a series of texts by various authors grouped under the title of “Comments and Discussion” and in this section we find a short text by Robert Stavins, an economist from Harvard University, where we can read that:
If we check today to see how the Limits I predictions have turned out, we learn that (according to their estimates) gold, silver, mercury, zinc, and lead should be thoroughly exhausted, with natural gas running out within the next eight years. Of course, this has not happened.
All this is, obviously, is taken straight from Bailey's paper in "Forbes". Apparently, Stavins had forgotten that it is the duty of a serious scientist to check the reliability of the sources that he or she cites.

Unfortunately, with this paper by Nordhaus the legend of the “wrong predictions” was even enshrined in a serious academic journal. With the 1990s, and in particular with the development of the Internet, the dam gave way and a true flood of criticism swamped the book and its authors. One after the other, scientists, journalists, and whoever felt entitled to discuss the subject, started repeating the same line over and over: the "Limits to Growth" study had predicted a catastrophe that failed to occur and therefore the whole idea was wrong.

After a while, the concept of “wrong predictions” became so widespread that it wasn’t any more necessary to state in detail what these wrong predictions were and why they had been so wrong. The criticism could also become weird, such as when the authors were accused of being part of a conspiracy designed to create "a kind of fanatic military dictatorship" (Gloub and Townsend, 1977) or aggressive, such as when someone declared that the authors of the book should be killed, cut to pieces, and their organs sent to organ banks. Today, we can find Bailey's legend repeated on the Internet literally thousands of times in various forms. Sometimes it is exactly the same text, cut and pasted as it is; in others, it is just slightly modified.

At this point, we may ask ourselves if this wave of slander had arisen by itself, as the result of the normal mechanism of urban legends, or if it had been masterminded by someone. Can we think of a conspiracy organized against the authors of the Limits book or against their sponsors, the Club of Rome? On this point we can find an analogy with an earlier case; that of Rachel Carson, well known for her book “Silent Spring” of 1962 in which she criticized the overuse of DDT and other pesticides. Carson's book was also strongly criticized and demonized. Kimm Groshong reviewed the story and she tells us in her 2002 study that:
The minutes from a meeting of the Manufacturing Chemists’ Association, Inc. on May 8, 1962, demonstrate this curious stance. Discussing the matter of what was printed in Carson’s serialization in the New Yorker, the official notes read: "The Association has the matter under serious consideration, and a meeting of the Public Relations Committee has been scheduled on August 10 to discuss measures which should be taken to bring the matter back to proper perspective in the eyes of the public."
Whether we can call that a "conspiracy" is open to discussion, but clearly there was an organized effort on the part of the chemical industry against Rachel Carson's ideas. By analogy, we could think that, in some smoke-filled room, representatives of the world's industry had gathered in the early 1970s to decide what measures to take against the Limits to Growth in order to “bring the matter back to proper perspective in the eyes of the public.” The recent story of the campaign against climate science, as told for instance by Hoggan and Littlemore (2010) and by Oreskes and Conway (2010), tells us that this kind of things have occurred and still occur.

We have no data indicating that something like that took place against "The Limits to Growth" and we'll probably never know. It is clear, anyway, that propaganda techniques are effective because they play on natural tendencies of the human mind. The 1989 article by Ronald Bailey and other attacks were no more than catalysts that unleashed our tendency to believe what we want to believe and to disbelieve what we don’t want to believe. We don't like inconvenient truths.

Now, in the early years of the 21st century, the general attitude towards the concepts of the "Limits" book seems to be changing again. The war, after all, is won by those who win the last battle. One of the first cases of reappraisal of the Limits study has been that of Matthew Simmons (2000), an expert on crude oil resources. It seems that the "peak oil movement" has been instrumental in bringing back to attention the Limits study and, indeed, oil depletion can be seen as a subset of the world model used in the study (Bardi 2008). Climate studies have also brought back the limits of resources to attention; in this case, intended as the limited capability of the atmosphere to absorb the products of human activities.

But it is not at all obvious that a certain view of the world, one that takes into account the finite amount of resources, is going to become prevalent, or even just respectable. The success of the smear campaign of the 1980s shows the power of propaganda and of urban legends in shaping the public perception of the world, exploiting our innate tendency of rejecting bad news.

Because of our tendency of disbelieving bad news, we chose to ignore the warning of impending collapse that came from the Limits study. In so doing, we have lost more than 30 years. Today, we are ignoring the warnings that come from climate science and we may be making an even worse mistake. There are signs that we may be starting to heed the warnings, but we are still doing too little, too late. Cassandra's curse is still upon us.

To know more on this subject, you can see my book "The Limits to Growth Revisited



Bailey, Ronald 1989, “Dr. Doom” Forbes, Oct 16, p. 45

Bardi, U. 2008, "Peak oil and the Limits to Growth: two parallel stories", The Oil Drum.

Cole H.S.D., Freeman C., Jahoda M., Pavitt K.L.R., 1973, “Models of Doom” Universe Books, New York

Golub R., Townsend J., 1977, “Malthus, Multinationals and the Club of Rome” vol 7, p 201-222

Groshong, K. 2002, "The Noisy Response to Silent Spring: Placing Rachel Carson’s Work in Context!, Pomona College, Science, Technology, and Society Department Senior Thesis

Hoggan, James; Littlemore, Richard (2009). Climate Cover-Up: The Crusade to Deny Global Warming. Vancouver: Greystone Books. ISBN 978-1553654858.

Nebbia, G. 1997, Futuribili, New Series, Gorizia (Italy) 4(3) 149-82

Nordhaus W., 1973 “Word Dynamics: Measurements without Data“, The Economic Journal n. 332.

Nordhaus W. D., 1992, “Lethal Models” Brookings Papers on Economic Activity 2, 1 Passel, P., Roberts, M., Ross L., 1972, New York Times, April 2

Oreskes, Naomi and Conway, Erik, 2010, "Merchants of Doubt", Bloomsbury, US

Simmons, M., 2000, “Revisiting The Limits to Growth: Could The Club of Rome Have Been Correct, After All?”


  1. ""[I]n The Grundrisse... Marx argues that the circulation and accumulation of capital cannot abide limits. When it encounters limits it works assiduously to convert them into barriers that can be transcended or by-passed. This focuses our attention upon those points in the circulation of capital where potential limits, blockages and barriers might arise, since these can produce crises of one sort or another.""

    --David Harvey

  2. Small typo ?:
    "Cassandra's curse is still be upon us." -> "Cassandra's curse is still upon us."

  3. My comment to the prior post, is also on the ways our cultural fixations separate us from the realities around us, as you're discussing here. It's on how men become fixated on their social role of planting seed to multiply the planting of seed.

    I also collect hard evidence of the disconnect, like some of the fascinating evidence that the "greens" completely shrink from discussing (turn tail and run as fast as they can). The world economic history of growth and efficiency is just marvelously clear. As the world uses economic efficiency 2.5 new energy uses are produced for every 1.0 units of energy savings...!

    Another very curious, and I think informative, one is seen with using Google "ngrams" to track word usage over the past 200 years. It appears that the usage of the word "complex" in English books that Google has scanned grew roughly in pace with economic growth since 1840... but then leveled off **just as the complexity of growth started to become unmanageable** in 1960. It's as if to say, "well if it's getting too complex, let's just stop talking about it!" ;-)

  4. Great article. As I'm an admirer of Jay Forrester, and the Limits to Growth team, I appreciate your comments on the work.

    Two small corrections. The first Apollo landing was July, 1969, not 68. The link to the Simmons paper no longer works. It would be nice if you could post it on your site. I have the pdf, if you don't. cline_frasier [!]

  5. Thanks for the corrections, I'll fix the post asap. One of the problems with keeping a blog is that typos and small mistakes are unavoidable. Of course they can be corrected; the problem is that posts are reproduced over and over on the Web and it is the "wrong" version that is diffused all along. There doesn't seem to be a way to avoid that. Well......

  6. Thanks for the comment, pfh. I must confess that I didn't know about Google's "ngrams". Hugely interesting. So many things to learn!

  7. As always, Ugo, a fascinating and insightful read. For those of us who keep up with John Michael Greer, what you've described here fits nicely in with his notion of cultural myths. Greer has said:

    "The mismatch between our rationalist assumptions and the myths and symbols that still shape our behavior defines a faultline running through the middle of the modern mind... We think with myths as inevitably as we see with eyes and eat with mouths."

    I think the response to - i.e.. the demonization of - the LTG study that you have described is a manifestation of one of these faultlines. The myth of human progress, of humans as separate from nature, of techno-magic, etc - all of these myths were challenged by LTG, and thus *had* to be demonized. Our unwitting adherence to myth demanded it.

    There is rarely anything rational about rationalization, after all. :)

    Regarding a 'new consensus' about LTG that may or may not be presently forming, I think it's largely academic at this stage in the sense of effectuating change on the level needed. IMO, David Korowicz from FEASTA probably has it right, and is in agreement with your discussion of the Seneca effect:

    "We are at the cusp of rapid and severely disruptive changes. From now on the risk of entering a collapse must be considered significant and rising. The challenge is not about how we introduce energy infrastructure to maintain the viability of the systems we depend upon, rather it is how we deal with the consequences of not having the energy and other resources to maintain those same systems. Appeals towards localism, transition initiatives, organic food and renewable energy production, however laudable and necessary, are totally out of scale to what is approaching."

    It is crucial to learn the right lessons in order to recraft a more sustainable human society in a post-collapse environment, and LTG offers that opportunity. That's where I personally see the value in this.

    - Oz

  8. Interesting to see your posts about LTG.

    I don't know if any demonization conspiracy was necessary. I first saw a documentary on LTG at college, in 1979. Our tutor was like a modern Cassandra, almost in tears of despair at the disinterest and ridicule expressed by students.

    To be fair, the date when TSHTF was more than our lifetimes away then and surely "they" would sort it out by then. We watched Star Trek and believed that by 2000 we'd all have personal space cars or teleporters and that robots would do all the work. Fusion research was just taking off and once we had that cracked, we were off to the stars!

    Now, what was that stuff about limits again...?

  9. The Simmons article is available at

  10. Umberto
    I appreciate the post. Especially since the post happens to fall on this final day of Al Gore's 24 hours of "Climate Reality".

    It is apparent in the current political discourse on climate in the US that the opponents to action on climate, e.g. conservative free-market think tanks, are the same organizations that are also opponents of the theories and research behind LTG.

    This paper by Jacques, et al in Environmental Politics, 2008**, identifies the role of conservative think tanks in promoting a viewpoint that denies the seriousness of environmental problems. Jacques reports that 92% of the published literature between 1972 and 2005 that claims to be objective in the evaluation of science behind environmental issues were published by conservative free-market and mostly-US based think tanks.

    Jacques reports that there became an increased number of such books immediately in the aftermath of the 1992 Earth Summit in Rio where it appeared that international cooperation on environmental issues would be increasing.

    - Jeff

    ** "The organisation of denial: Conservative think tanks and environmental scepticism"
    Peter J. Jacques*, Riley E. Dunlap and Mark Freeman, Environmental Politics, Vol. 17, No. 3, June 2008, 349–385

  11. About the use of the word complex: I don't see a leveling off in 1960s. It continues to rise, but at a slowing pace, until year 2000. When I extend the range of dates to 2011, I see a dramatic decline in this, the 21st, century. I wonder if this decline is real. I don't understand in detail how Google gathers and processes the data. It might be something to do with how the data is handled. Anyway, my impression of current literature is that complexity is something of a buzz word now. It doesn't have a useage that correllates with the system dynamics thinking that went into the Limits to Growth, IMHO. i.e, I search in vain for quantitative measures of complexity. I hope someone can prove me mistaken in this opinion.

  12. One miscalculation made by the LTG people was to not understand that "ever-lasting-growth" (ELG) is a non-negotiable tenant of the capitalist religion and to also not understand that capitalism (C) is an ingrained religion of Western Civilization.

    We cover up our real religion (the worship of money) by paying pretense homage to other religions. But the truth is that in our daily lives we have only one god before us, the almighty Dollar (or Euro or less might Lira, Pound, etc. for you people on the other side of the pond).

    The publication of LTG was the ultimate blasphemy and had to be quashed at all cost.

    Even in more recent times, Al Gore's publication of his movie, "An Inconvenient Truth" is seen as a subset of LTG (it says there is a limit to how much our atmosphere can soak up as a communal garbage pit) and it too has met with a full frontal counter attack by the high priests of the "ever-lasting-growth" ELG-C religion.

    In past civilizations, people have killed each other over religion. This time, it's no different. We are the same delusion-driven monkeys we've always been.

  13. Ugo,

    excellent analysis, as usual. I think the explanation of this persistent "urban legend" is quite simple.

    "Debunking" of Limits to Growth is all what we (all) want to hear. Nobody wants to know that his/her behaviour has bad (future) impacts on environment and that there are limits to such a behaviour.

    That is why why "anti-AGW" campaign was/is so successful.


  14. Well, yes, it is true that our mind is fixed towards growth and that we don't want to hear anything different. But it may be specific of our times and it may fade out rapidly. I am planning to write something on this point.

  15. Regarding things we do and don't want to hear...

    Consider that the vast majority (about 96%) of Americans are non-vegetarians, and the meat that they eat comes from the industrial (factory) system. It is the simplest of tasks to demonstrate that these systems routinely - as part of the model - torture animals in unbelievably cruel ways. It's not even hidden - the available evidence is abundant (and this is leaving aside the environmental impact of feedlot operations, which is not inconsiderable). This harm is being done now - not 10 or 20 or 50 years from now.

    Now, most people like animals as a rule, or at least do not wish them to be tortured or to be caused to suffer, yet even after being exposed to the evidence, people will typically continue to make whatever excuses need to be made to allow them to continue to eat that meat (even though you can find, in most urban centers these days, 'cruelty-free' meat which is not much more expensive - and is certainly healthier, lacking the hormones, antibiotics, etc).

    Now these are folks who would quite probably vote for a law which outlawed the current treatment of animals in the meat industry (and in fact who have voted in localities nationwide for animal cruelty laws as applied to pets and such). Yet, they remain adamant in their eating habits, despite having been shown this is detrimental to their health, to the planet's health and to the well being of the animals involved.

    What does this tell us?

    Perhaps there is no connection, but it seems to me that there is.

    I think that America as a society has become so disconnected from the concept of our choices and behaviors (especially the choice of where to spend our dollars) on the one hand, and the consequences of those choices and behaviors on the other, that we'll continue to make the choices we have been making, and that we are used to making, until we no longer have those choices to make. As William Rees noted in a recent paper:

    Psychologist Robert Povine argues from the available evidence that the
    starting assumption in behavioral psychology should be “that consciousness doesn’t play a role in human behaviour. This is the conservative position that makes the fewest assumptions.”

    In other words, if we were rational beings who made decisions based on conscious cogitation, we'd not still be pumping CO2 and other GHGs into the atmosphere, regardless of what a bunch of conservative think tanks said. Those think tanks are not the root problem - they are merely facilitating the lousy decisions made by countless individuals who are operating out of (largely unacknowledged) unconscious motivations.

    This big question, as Professor Bardi has noted here is: is this culturally conditioned, or rooted more deeply in evolution?

    What makes me optimistic is that, when we look at past cultures, we do in fact find evidence that such matters are at least to some degree culturally determined. I'm thinking in particular of potlatch-based societies.

    - Oz

  16. Hello,

    I just wanted to inform you that I translated this article in french and I put it online at this adress :

    Vincent Pavard

  17. Merci, Vincent. C'etait un plaisir de voir mon article traduit en francais

  18. Ugo, I found this short article about the weakness of the LTG approach. Smil is a serious scientist, therefore his critique should be carefully considered. What do you think about it?

  19. Thanks for the link, Diego. I had missed this 2005 article by Smil in my review on the literature on LTG. Now I have added it to my collection.

    Unfortunately, Smil keeps disappointing me. It is true that he is a serious scientist and that he has given valuable contributions to environmental sciences, but - really - he seems to be more and more living in a world of his own, where he doesn't recognize anything but his own work as valid. Some of his recent statements on peak oil are an example of this attitude.

    About this specific paper, well, what to say? You can read it yourself and you'll find that it contains nothing but a series of declarations of disbelief and much beating of the bush in the form of irrelevant examples (say, the evolution of Apple and Microsoft).

    What does Smil say, in the end? Yes, the model is approximate, yes, many variables are highly aggregate, yes, it cannot predict revolutions such as the fall of the Berlin wall. Sure, all that is perfectly known - the model has limitations.

    As I said, I had missed this reference (there is a vast literature on LTG), so I didn't cite it in my book. If I had seen it, however, it would have gone in the section where I discuss the general validity of models. How do you decide if a model is good or not? Well, it depends on what you are trying to do. All models are approximate and, therefore, all can be defined as "wrong". But most (not all) models can be useful if you understand their limitations.

    So, I think it is a very poor attitude the one shown by Smil (and many others) who simply look at the model and say "Oh, it is approximate, so it is no good). Too easy. As I discuss in my book, a model can be proven as wrong by finding internal inconsistencies in it, or it may be shown that there are better models. Smil doesn't do anything like that. So, I can conclude applying to him the same statement that he uses to conclude his paper "nihil novum sub sole."

    And thanks again for the link

  20. Ugo, I agree on Smil's general attitude, which I don't like, although I appreciate his works, especially his constant search for the best available numerical estimates. I think as well that he has been unfair in his rebuttal of the LTG approach. What I maintain from his critique, though, is that there is a difference between "approximate" and "arbitrary". He makes only one specific example, the death rate from pollution, which in the model, as I understood, is linearly dependent on the total pollution fluxes. Now, if there IS such a linear dependence, the model may be approximate but correct. But if this dependence is arbitrary, the model might be fundamentally wrong, no matter how precise the numerical imputs are. I confess I don't have such detailed understanding of the LTG model, so I cannot really say if, in this case, Smil has a good point. Thank you anyway for your interesting comments. I discovered only recently your blog, and I find it both insightful and entertaing to read.

  21. It is fine Diego, these points can and should be discussed. So, if you look a the issue, the difference between "arbitrary" and "approximate" is an issue that is not at all simple. How would you define, exactly, the difference?

    To make an example, in climate science the dependence between CO2 concentration and temperature is usually taken as logarithmic - which means it can be linearized. This is the result of known physical factors, but when we try to use it to model climate, we know that there is a host of negative and positive feedbacks that can affect this dependence. So, the models take into account some of these feedbacks, but there is a lot of uncertainty and some feedbacks are not considered. For instance, hydrate release could sharply increase the warming effect of CO2. So you could say that the models are based on "arbitrary" assumptions.

    The point is that models have to be USEFUL, and if they are to be useful, first of all they have to exist. It means that if you try to make the perfect model, you'll end up with no model at all. Which is OK for some people when they don't like the results of a specific model; but it is not the scientific attitude. Climate models are valid within the assumptions made and what they tell to us is useful in the sense that they tell us that warming is to be expected. Then, you must be aware that warming could be much more rapid than the models say.

    In the end, models are useful when they provide a warning. That is what both climate models and the LTG model are doing. Then, we go back to the point I was making before: if you go into the details of a complex model, you can always find points that you can criticize as approximations. Of course. Models can always be improved.

    But that's not the point. The point is that all models are formalization of one's assumptions. They are useful, if nothing else, in verifying the validity of one's assumption. So, if you think that pollution should be treated in a mode detailed way than it is done in the LTG model, well, make a better model or at least ask modelers to make one. Don't just go on harping "Oh, you see, the model is approximate here, therefore it must be wrong." It is, in the end a self-defeating attitude.

  22. Good point Ugo, I totally agree and that's why I find Smil's critique unfair. The LTG model was the first attempt at modelling the general behavior of the "world", and if only for that it is a huge step forward from the simple statement that "of course infinite growth isn't possible". However, I still have some doubts. If you stretch your definitions far enough, then nothing is really "wrong" or "right". Is there a degree of approximation or arbitrariness beyond which a model becomes simply wrong? And how can a "wrong" model be useful? If a model is wrong, it is going to give you the wrong warnings. Then you might say that it is useful because it forces you to state your assumptions, but in this case why bothering at all with models, simply state directly your assumptions and let's discuss them.
    But I'm becoming too philosophical... Maybe that's a good topic for a future post!

  23. The book "Limits to Growth" -for better or for worse as it may be - (or as it may be deemed to be, or to have been, by assorted audiences or readers over time) has been one of the most influential books on my own general thinking about the future of our world and in orienting my professional life. (spent mostly in the development assistance field) I was 26 years old when the book first came out in 1972 and I had graduated from MIT as an engineer just five years earlier. So I also was reasonably familiar with the general intellectual context and the systems thinking that gave rise to the book.

    And I have since read both of its Updates as well as Ugo Bardi's more recent "Revisiting Limits to Growth" as well as many other "related" books including also Paul Gilding's "The Great Disruption" and Jorgen Randers' "The World in 2052". (which I just finished reading yesterday) So I consider myself reasonably familiar with the entire topic. And during my professional life (I recently retired) I also worked on environmental business management, corporate social responsibility, “the triple bottom line”, cleaner production, national and enterprise productivity and competitiveness and many other related topics at both the policy and the project levels)

    I thought Ugo Bardi did an exceptionally good job (and also a very much needed job) of documenting and explaining reasonably precisely the various "ups and downs" which the book enjoyed or suffered (and why and due to whose general or specific actions or influences) during its 40 year history of existence since initial publication. i.e. the retracing of its “acceptance-rejection trajectory” -as one could call it- from being initially generally accepted to being ever more rejected all the way until it was finally almost totally discredited and right up until its much more recent "resurgence" and partial public vindication.

    So I would like to add just one more point to the above discussion which may not have been made before in quite the same way:

    Let us hypothetically consider that the Club of Rome and the original MIT team authors also might have added two additional "scenarios" (which I will call the pessimistic book-reception scenario and the optimistic book- reception scenario) which they also might have considered as part of their work, or as an appendix to the main text.

    But these two additional scenarios would NOT have dealt with any of the future likely or unlikely World Model Scenarios being modeled by the book, (that work was already very well done and certainly thoroughly enough) but instead would deal with the likely acceptance or rejection of the book itself by society, and with its most likely trajectory and societal impact in terms of either spurring humanity towards assorted remedial or preventive actions (by either governments, civil society or various private sectors) or failing to do so, or maybe even (perversely) having an opposite effect.

    What additional variables would have had to be considered by the authors to try to come up with the above two scenarios and how would they interact with the other variables treated by the book?

    It may have seemed "natural" to the authors and to the Club of Rome which sponsored the book (though I have no way of knowing precisely what they thought or didn't think at the time around the book's first publication date) that the book might be slow to becoming fully accepted but that slowly it would be, and that eventually humanity would take its messages on board and begin to take various appropriate actions. (or at least do more than it might otherwise have done had the authors not done their research work and published the book).

    1. unfortunately impossible to add the remainder of my comment above

    2. unfortunately impossible to add the remainder of my comment above, the system is not accepting any of the two words to be recognized

  24. Let us hypothetically consider that the Club of Rome and the original MIT team authors also might have added two additional "scenarios" (which I will call the pessimistic book-reception scenario and the optimistic book-reception scenario) which they also might have considered as part of their work. (and perhaps included in some form as an Appendix)
    But these two additional scenarios would NOT have dealt with any of the future likely or unlikely World Model Scenarios being modeled by the book, (that work was already well done and certainly thoroughly enough) but instead would have dealt with the likely acceptance or rejection of the book itself by society, and of its most likely trajectory and societal impact in terms of either spurring humanity towards assorted remedial or preventive actions (by either governments, civil society or various private sector actors or by the international public sector or by some combination of these) or failing to do so, or maybe even (perversely) having an opposite effect.
    What additional variables would have had to be considered by the authors to try to come up with the above two scenarios and how would they interact with the other variables already treated by the book?
    And if the ultimate impact on society and its future trajectory was indeed the purpose of the book then perhaps it would have been better to consider not only the optimistic scenario of the book’s gradual acceptance followed by various positive actions, policies and etc. to alter humanity's collision course with various physical and natural limits, but also the pessimistic scenario that the book would either at best be misunderstood or at worst be either "naturally" or deliberately and purposefully maligned and discredited.
    Would this have been a legitimate question to ask back around 1972? And had it been asked and answered correctly might anything have been done differently?
    If one takes a quick look now at the more recent formulation by the Club of Rome of "A New Path to World Development" (which can be viewed at the following link: )
    …one readily sees that the Club now sees this path as consisting of five interactive components or “clusters of inter-connected issues” and namely:

    1. Environment and Resources: Climate Change, Energy Security, Ecosystems and Water
    2. Globalisation: Distribution of Wealth and Income, Employment, Economic Restructuring, Trade and Finance
    3. International Development: Demographic growth, Environmental Stress, Poverty, Food Production, Health and Employment
    4. Social Change: Values, Culture, Identity, and Behavior
    5. Peace and Security: Justice, Democracy, Governance, Solidarity, Security and Peace

  25. I think this article makes the mistake of thinking that people reacted too closely to the Limits to Growth book, when they were ALSO reacting to the (overblown & dramatic) apocalyptic narrative of the revolutionary left & popular eco-narrative (different, but similar). I enjoyed the book on the 70s by Frances Wheen for pointing out just how much paranoia and end thinking there was in that decade.



Ugo Bardi is a member of the Club of Rome, faculty member of the University of Florence, and the author of "Extracted" (Chelsea Green 2014), "The Seneca Effect" (Springer 2017), and Before the Collapse (Springer 2019)