# The Limits to Growth

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The Limits to Growth (LTG) is a 1972 report[1] on the exponential economic and population growth with a finite supply of resources, studied by computer simulation.[2] Commissioned by the Club of Rome, the findings of the study were first presented at international gatherings in Moscow and Rio de Janeiro in the summer of 1971.[1]:186 The report's authors are Donella H. Meadows, Dennis L. Meadows, Jørgen Randers, and William W. Behrens III, representing a team of 17 researchers.[1]:8

Since its publication, some 30 million copies of the book in 30 languages have been purchased.[3] It continues to generate debate and has been the subject of several subsequent publications.[4]

The Limits to Growth: The 30-Year Update was published in 2004,[5] and in 2012, a 40-year forecast from Jørgen Randers, one of the book's original authors, was published as 2052: A Global Forecast for the Next Forty Years.[6]

World Model Standard Run as shown in The Limits to Growth

## Purpose

In commissioning the MIT team to undertake the project that resulted in LTG, the Club of Rome had three objectives:[1]:185

1. Gain insights into the limits of our world system and the constraints it puts on human numbers and activity.
2. Identify and study the dominant elements, and their interactions, that influence the long-term behavior of world systems.
3. To warn of the likely outcome of contemporary economic and industrial policies, with a view to influencing changes to a sustainable life-style.

## Methodology

The study used the World3 computer model to simulate the consequence of interactions between the earth and human systems.[7][8] The model was based on the work of Jay Forrester of MIT,[1]:21 as described in his book World Dynamics.[9]

The model was based on five variables: "population, food production, industrialization, pollution, and consumption of nonrenewable natural resources".[1]:25 At the time of the study, all these variables were increasing and were assumed to continue to grow exponentially, while the ability of technology to increase resources grew only linearly.[1] The authors intended to explore the possibility of a sustainable feedback pattern that would be achieved by altering growth trends among the five variables under three scenarios. They noted that their projections for the values of the variables in each scenario were predictions "only in the most limited sense of the word", and were only indications of the system's behavioral tendencies.[10] Two of the scenarios saw "overshoot and collapse" of the global system by the mid- to latter-part of the 21st century, while a third scenario resulted in a "stabilized world".[11]:11

### Exponential reserve index

A key idea in The Limits to Growth is the notion that if the rate of resource use is increasing, the amount of reserves cannot be calculated by simply taking the current known reserves and dividing by the current yearly usage, as is typically done to obtain a static index. For example, in 1972, the amount of chromium reserves was 775 million metric tons, of which 1.85 million metric tons were mined annually. The static index is 775/1.85=418 years, but the rate of chromium consumption was growing at 2.6 percent annually, or exponentially.[1]:54–71 If instead of assuming a constant rate of usage, the assumption of a constant rate of growth of 2.6 percent annually is made, the resource will instead last

${\displaystyle {\frac {\ln(1+0.026\times 418)}{0.026}}\approx {\text{95 years}}}$

In general, the formula for calculating the amount of time left for a resource with constant consumption growth is:[12]

${\displaystyle y={\frac {\ln((rs)+1)}{r}}}$

where:

y = years left;
r = 0.026, the continuous compounding growth rate (2.6%).
s = R/C or static reserve.
R = reserve;
C = (annual) consumption.

#### Commodity reserve extrapolation

The chapter contains a large table that spans for 5 pages in total, based on actual geological reserves data for total 19 non-renewable resources and analyzes their reserves at 1972 modeling time of their exhaustion under three scenarios: static (constant growth), exponential and exponential with reserves multiplied by 5 to account for possible discoveries. A short excerpt from the table is presented below:

Years
Resource Consumption, projected average annual growth rate Static index Exponential index 5× reserves exponential index
Chromium 2.6% 420 95 154
Gold 4.1% 11 9 29
Iron 1.8% 240 93 173
Petroleum 3.9% 31 20 50

The chapter also contains a detailed computer model of chromium availability with current (as of 1972) and double the known reserves as well as numerous statements on the current increasing price trends for discussed metals:

Given present resources consumption rates and the projected increase in the rates, the great majority of the currently important nonrenewable resources will be extremely costly 100 years from now. (...) The prices of those resources with the shortest static reserve indices have already begun to increase. The price of mercury, for example, has gone up 500 percent in the last 20 years; the price of lead has increased 300 percent in the last 30 years.

— Chapter 2, page 66

Due to the detailed nature and use of actual reserves of actual resources and their real-world price trends, the indexes have been interpreted as a prediction of the number of years until the world would "run out" of them, both by environmentalist groups calling for greater conservation and restrictions on use, and by skeptics criticizing the predictions accuracy.[13][14][15][16] This interpretation has been widely propagated by media and environmental organizations, and authors who, apart from a note about the possibility of the future flows being "more complicated", did not clearly constraint or deny this interpretation.[17] While environmental organizations used it to support their arguments, a number of economists used it to criticize LtG as a whole shortly after publication in 70's (Peter Passel, Marc Roberts, and Leonard Ross), with similar criticism reoccurring from Ronald Baily, George Goodman and others in 90's.[18] In 2011 Ugo Bardi in "The Limits to Growth Revisited" argued that "nowhere in the book was it stated that the numbers were supposed to be read as predictions", nonetheless as they were the only tangible numbers referring to actual resources, they were promptly picked as such by both supporters as well as opponents.[18]

While Chapter 2 serves as an introduction to the concept of exponential growth modeling, the actual World3 model uses an abstract "non-renewable resources" component based on static coefficients rather than actual physical commodities described above.

## Conclusions

After reviewing their computer simulations, the research team came to the following conclusions:[1]:23–24

1. If the present growth trends in world population, industrialization, pollution, food production, and resource depletion continue unchanged, the limits to growth on this planet will be reached sometime within the next one hundred years.[a] The most probable result will be a rather sudden and uncontrollable decline in both population and industrial capacity.
2. It is possible to alter these growth trends and to establish a condition of ecological and economic stability that is sustainable far into the future. The state of global equilibrium could be designed so that the basic material needs of each person on earth are satisfied and each person has an equal opportunity to realize his individual human potential.
3. If the world's people decide to strive for this second outcome rather than the first, the sooner they begin working to attain it, the greater will be their chances of success.
— Limits to Growth, Introduction

The introduction goes on to say:

These conclusions are so far-reaching and raise so many questions for further study that we are quite frankly overwhelmed by the enormity of the job that must be done. We hope that this book will serve to interest other people, in many fields of study and in many countries of the world, to raise the space and time horizons of their concerns and to join us in understanding and preparing for a period of great transition-the transition from growth to global equilibrium.

## Criticism

LTG provoked a wide range of responses, including immediate criticism.

Peter Passell and two co-authors published a 2 April 1972 article in the New York Times describing LTG as "an empty and misleading work ... best summarized ... as a rediscovery of the oldest maxim of computer science: Garbage In, Garbage Out". Passell found the study's simulation to be simplistic, while assigning little value to the role of technological progress in solving the problems of resource depletion, pollution, and food production. They charged that all LTG simulations ended in collapse, predicted the imminent end of irreplaceable resources. Passell also charged that the entire endeavour was motivated by a hidden agenda: to halt growth in its tracks.[19]

In 1973, a group of researchers at the Science Policy Research Unit at the University of Sussex, published Thinking about the Future; A Critique of The Limits to Growth, published in the United States as Models of Doom. The Sussex group examined the structure and assumptions of the MIT models. They concluded that the simulations were very sensitive to a few key assumptions and suggest that the MIT assumptions were unduly pessimistic. The Sussex scientists expressed their opinion that the MIT methodology, data, and projections were faulty and do not accurately reflect reality.[20] Some of the criticism was however recognized as valid and improving overall understanding of dynamic models, for example actual issue of "backcasting" the World3 model, which retrospectively "predicted" a huge drop in industrial production in 1880, which obviously did not happen. In the Acknowledgements section, the Sussex Group thanked their sponsors, which included BP, Imperial Chemical Industries and the UKAEA.

The LTG team, in a paper entitled "A Response to Sussex", described and analyzed five major areas of disagreement between themselves and the Sussex authors.[21] The team asserted that the Sussex critics applied "micro reasoning to macro problems", and suggested that their own arguments had been either misunderstood or wilfully misrepresented. They pointed out that the critics had failed to suggest any alternative model for the interaction of growth processes and resource availability, and "nor had they described in precise terms the sort of social change and technological advances that they believe would accommodate current growth processes."

The report has been criticized by academics, economists and businesspeople.[22][23] Critics claimed that history proved the projections to be incorrect, such as the predicted resource depletion and associated economic collapse by the end of the 20th century.[24]:23 The Limits to Growth faced ridicule as early as the 1970s.[25][26] The methodology, the computer, the conclusions, the rhetoric and the people behind the project were criticised.[27] Yale economist Henry C. Wallich agreed that growth could not continue indefinitely, but that a natural end to growth was preferable to intervention. Wallich stated that technology could solve all the problems the report was concerned about, but only if growth continued apace. By stopping growth too soon, Wallich warned, the world would be "consigning billions to permanent poverty".[27]

Julian Simon, a professor at the Universities of Illinois and, later, Maryland, argued that the fundamental underlying concepts of the LTG scenarios were faulty, because the very idea of what constitutes a "resource" varies over time. For instance, wood was the primary shipbuilding resource until the 1800s, and there were concerns about prospective wood shortages from the 1500s on. But then boats began to be made of iron, later steel, and the shortage issue disappeared. Simon argued in his book The Ultimate Resource that human ingenuity creates new resources as required from the raw materials of the universe. For instance, copper will never "run out". History demonstrates that as it becomes scarcer its price will rise and more will be found, more will be recycled, new techniques will use less of it, and at some point a better substitute will be found for it altogether.[28] His book was revised and reissued in 1996 as The Ultimate Resource 2.[29] Robert Solow from MIT argued that prediction in The Limits to Growth was based on a weak foundation of data. Allen V. Kneese and Ronald Riker of Resources for the Future (RFF) stated, "The authors load their case by letting some things grow exponentially and others not. Population, capital and pollution grow exponentially in all models, but technologies for expanding resources and controlling pollution are permitted to grow, if at all, only in discrete increments."[30]

In 1997, the Italian economist Giorgio Nebbia observed that the negative reaction to the LTG study came from at least four sources: those who saw the book as a threat to their business or industry; professional economists, who saw LTG as an uncredentialed encroachment on their professional perquisites; the Catholic church, which bridled at the suggestion that overpopulation was one of mankind's major problems; finally, the political left, which saw the LTG study as a scam by the elites designed to trick workers into believing that a proletarian paradise was a pipe dream.[31]

## Positive reviews

With few exceptions, economics as a discipline has been dominated by a perception of living in an unlimited world, where resource and pollution problems in one area were solved by moving resources or people to other parts. The very hint of any global limitation as suggested in the report The Limits to Growth was met with disbelief and rejection by businesses and most economists. However, this conclusion was mostly based on false premises.

In a 2008 blog post, Ugo Bardi commented that "Although, by the 1990s LTG had become everyone's laughing stock, among some the LTG ideas are becoming again popular".[31] Reading LTG for the first time in 2000, energy economist Matthew Simmons concluded his views on the report by saying, "In hindsight, The Club of Rome turned out to be right. We simply wasted 30 important years ignoring this work."[32] Research from the University of Melbourne has found the book's forecasts are accurate, 40 years on.

In 2008 Graham Turner of CSIRO found that the observed historical data from 1970 to 2000 closely match the simulated results of the "standard run" limits of growth model for almost all the outputs reported. "The comparison is well within uncertainty bounds of nearly all the data in terms of both magnitude and the trends over time." Turner also examined a number of reports, particularly by economists, which over the years have purported to discredit the limits-to-growth model. Turner says these reports are flawed, and reflect misunderstandings about the model.[11]:37

Turner reprised these observations in another opinion piece in The Guardian in 2014. Turner used data from the UN to claim that the graphs almost exactly matched the 'Standard Run' from 1972 (i.e. the worst-case scenario, assuming that a 'business as usual' attitude was adopted, and there were no modifications of human behaviour in response to the warnings in the report). Birth rates and death rates were both slightly lower than projected, but these two effects cancelled each other out, leaving the growth in world population almost exactly as forecast.[33]

In 2010, Nørgård, Peet and Ragnarsdóttir called the book a "pioneering report", and said that it "has withstood the test of time and, indeed, has only become more relevant."[3]

The journalist Christian Parenti, writing in 2012, sees parallels between the reception of LTG and the contemporary global warming controversy, and went on to comment, "That said, The Limits to Growth was a scientifically rigorous and credible warning that was actively rejected by the intellectual watchdogs of powerful economic interests. A similar story is playing out now around climate science.".[34]

In 2012, John Scales Avery, a member of Nobel Prize (1995) winning group associated with the Pugwash Conferences on Science and World Affairs, supported the basic thesis of LTG by stating, "Although the specific predictions of resource availability in "[The] Limits to Growth" lacked accuracy, its basic thesis - that unlimited economic growth on a finite planet is impossible - was indisputably correct."[35]

## Legacy

The Club of Rome has persisted after The Limits of Growth and has generally provided comprehensive updates to the book every five years.

An independent retrospective on the public debate over The Limits to Growth concluded in 1978 that optimistic attitudes had won out, causing a general loss of momentum in the environmental movement. While summarizing a large number of opposing arguments, the article concluded that "scientific arguments for and against each position ... have, it would seem, played only a small part in the general acceptance of alternative perspectives."[36]

In 1989, a symposium was held in Hanover, entitled "Beyond the Limits to Growth: Global Industrial Society, Vision or Nightmare?" In 1992, Beyond the Limits (BTL) was published as a 20-year update on the original material. It "concluded that two decades of history mainly supported the conclusions we had advanced 20 years earlier. But the 1992 book did offer one major new finding. We suggested in BTL that humanity had already overshot the limits of Earth’s support capacity."[37]

Limits to Growth: The 30-Year Update was published in 2004. The authors observed that "It is a sad fact that humanity has largely squandered the past 30 years in futile debates and well intentioned, but halfhearted, responses to the global ecological challenge. We do not have another 30 years to dither. Much will have to change if the ongoing overshoot is not to be followed by collapse during the twenty-first century."[37]

In 2008, Graham Turner at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia published a paper called "A Comparison of 'The Limits to Growth' with Thirty Years of Reality".[11] It compared the past thirty years of data with the scenarios laid out in the 1972 book and found that changes in industrial production, food production, and pollution are all congruent with one of the book's three scenarios—that of "business as usual". This scenario in Limits points to economic and societal collapse in the 21st century.[38] In 2010, Nørgård, Peet, and Ragnarsdóttir called the book a "pioneering report". They said that, "its approach remains useful and that its conclusions are still surprisingly valid ... unfortunately the report has been largely dismissed by critics as a doomsday prophecy that has not held up to scrutiny."[3]

Also in 2008, researcher Peter A. Victor wrote, that even though the Limits team probably underestimated price mechanism's role in adjusting outcomes, their critics have overestimated it. He states that Limits to Growth has had a significant impact on the conception of environmental issues and notes that the models in the book were meant to be taken as predictions "only in the most limited sense of the word".[10]

In a 2009 article published in American Scientist titled "Revisiting the Limits to Growth After Peak Oil", Hall and Day noted that "the values predicted by the limits-to-growth model and actual data for 2008 are very close."[39] These findings are consistent with the 2008 CSIRO study which concluded: "The analysis shows that 30 years of historical data compares favorably with key features ... [of the Limits to Growth] "standard run" scenario, which results in collapse of the global system midway through the 21st Century."[11]

Researchers from China and Indonesia with Dennis Meadows

In 2011, Ugo Bardi published a book-length academic study of The Limits to Growth, its methods and historical reception and concluded that "The warnings that we received in 1972 ... are becoming increasingly more worrisome as reality seems to be following closely the curves that the ... scenario had generated."[40]:3 A popular analysis of the accuracy of the report by science writer Richard Heinberg was also published.[41]

In 2012, the Smithsonian Institution held a symposium entitled "Perspectives on Limits to Growth".[42] Another symposium was held in Hanover, Germany entitled "Already Beyond?"[43]

Limits to Growth did not receive an official update in 2012, but one of its coauthors, Jørgen Randers, published a book, 2052: A Global Forecast for the Next Forty Years.[44][45]

In 2012, writing in American Scientist, Brian Hayes stated that the model is "more a polemical tool than a scientific instrument". He went on to say that the graphs generated by the computer program should not, as the authors note, be used as predictions.[46]

In 2012, it was the object of a symposium by the Volkswagen Foundation.[47]

In 2014, Graham Turner concluded that "preparing for a collapsing global system could be even more important than trying to avoid collapse."[48]

In 2016, a report published by the UK All-Party Parliamentary Group on Limits to Growth concluded that "there is unsettling evidence that society is still following the 'standard run' of the original study – in which overshoot leads to an eventual collapse of production and living standards".[49] The report also points out that some issues not fully addressed in the original 1972 report, such as climate change, present additional challenges for human development.

In 2020, analysis by Gaya Herrington (Sustainability and Dynamic System Analysis Lead at KPMG in the United States but in a personal capacity) found that current empirical data is broadly in line with the 1972 projections.[50][51]

## Related books

Books about humanity's uncertain future have appeared regularly over the years. A few of them, including the books mentioned above for reference, include:[52]

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## Notes

1. ^ from 1972, so 2072

## References

1. Meadows, Donella H; Meadows, Dennis L; Randers, Jørgen; Behrens III, William W (1972). The Limits to Growth; A Report for the Club of Rome's Project on the Predicament of Mankind. New York: Universe Books. ISBN 0876631650. Retrieved 26 November 2017.
2. ^ MacKenzie, Debora (4 January 2012). "Boom and doom: Revisiting prophecies of collapse". New Scientist. Retrieved 2017-11-28.
3. ^ a b c Nørgård, Jørgen Stig; Peet, John; Ragnarsdóttir, Kristín Vala (March 2010). "The History of The Limits to Growth". The Solutions Journal. 1 (2): 59–63. Retrieved 1 July 2014.
4. ^ Farley, Joshua C. "The Limits to growth debate". The University of Vermont. Retrieved 1 December 2017.
5. ^ Meadows, Donella H.; Randers, Jorgen; Meadows, Dennis L. (2004). The Limits to Growth: The 30-Year Update. White River Junction VT: Chelsea Green Publishing Co. ISBN 1931498512. Retrieved 27 November 2017.
6. ^ Randers, Jørgen (2012). 2052: A Global Forecast for the Next Forty Years. White River Junction VT: Chelsea Green Publishing Co. ISBN 978-1-60358-467-8. Retrieved 29 March 2019.
7. ^ The models were run on DYNAMO, a simulation programming language.
8. ^ Edwards, Paul N. (2010) A Vast Machine: Computer Models, Climate Data, and the Politics of Global Warming MIT Press ISBN 9780262290715 pp. 366–71
9. ^ Forrester, Jay Wright (1971). World Dynamics. Wright-Allen Press. ISBN 0262560186.
10. ^ a b Peter A. Victor (2008). Managing Without Growth, Edward Elgar Publishing, pp. 92–93, ISBN 978-1-84720-078-5
11. ^ a b c d Turner, Graham (2008). "A Comparison of 'The Limits to Growth' with Thirty Years of Reality". Socio-Economics and the Environment in Discussion (SEED). CSIRO Working Paper Series. Commonwealth Scientific and Industrial Research Organisation (CSIRO). 2008–09: 52. doi:10.1016/j.gloenvcha.2008.05.001. ISSN 1834-5638. Retrieved 25 July 2021.
12. ^ Limits To Growth, pg 60, Derivation: ${\displaystyle R=\int _{0}^{y}Ce^{\rho t}\ dt={\frac {C}{\rho }}\left(e^{\rho y}-1\right)}$ reverts to ${\displaystyle y={\frac {\ln \left(1+\rho {\frac {R}{C}}\right)}{\rho }}.}$
13. ^
14. ^
15. ^ "Treading lightly". The Economist. 19 September 2002. Archived from the original on 15 May 2019.
16. ^ Bailey, Ronald (4 February 2004). "Science and Public Policy". Reason. Retrieved 26 November 2017.
17. ^ Limits to Growth. 1972. p. 63. Of course, the actual nonrenewable resource availability in the next few decades will be determined by factors much more complicated that can be expressed by either the simple static reserve index or the exponential reserve index. We have studied this problem with a detailed model that takes into account the many interrelationships among such factors as varying grades of ores, production costs, new mining technology, the elasticity of consumer demand, and substitution with other resources
18. ^ a b Bardi, Ugo (2011). The Limits to Growth Revisited. ISBN 9781441994158.
19. ^ Passell, Peter; Roberts, Marc; Ross, Leonard (1972-04-02). "The Limits to Growth". The New York Times. Retrieved 2 December 2017.
20. ^ Cole, H. S. D.; Freeman, Christopher; Jahoda, Marie; Pavitt, K. L. R., eds. (1 April 1973). Models of Doom: A Critique of the Limits to Growth (1st, hardcover ed.). Universe Publishing. ISBN 0876631847.
21. ^ Meadows, Donella H; Meadows, Dennis L; Randers, Jørgen; Behrens III, William W (February 1973). "A response to Sussex". Futures. 5 (1): 135–152. doi:10.1016/0016-3287(73)90062-1.
22. ^ Meyer, N. I.; Nørgård, J.S. (2010). Policy Means for Sustainable Energy Scenarios (abstract) (PDF). Denmark: International Conference on Energy, Environment and Health – Optimisation of Future Energy Systems. pp. 133–137. Archived from the original (PDF) on 9 October 2016. Retrieved 27 November 2017.
23. ^ Cole, H S D (1973). Models of Doom: A Critique of The Limits to Growth. Universe Books. ISBN 0876639058. Retrieved 27 November 2017.
24. ^ van Vuuren, D. P.; Faber, A (2009). Growing within Limits – A Report to the Global Assembly 2009 of the Club of Rome (PDF). Bilthoven: Netherlands Environmental Assessment Agency. ISBN 9789069602349. Retrieved 27 November 2017.
25. ^ Kaysen, Carl (1972). "The Computer That Printed out W*O*L*F*". Foreign Affairs. 50 (4): 660–668. doi:10.2307/20037939. JSTOR 20037939.
26. ^ Solow, Robert M. (1973). "Is the End of the World at Hand?". Challenge. 16 (1): 39–50. doi:10.1080/05775132.1973.11469961. JSTOR 40719094.
27. ^ a b Alan Atkisson (2010). Believing Cassandra: How to be an Optimist in a Pessimist's World, Earthscan, p. 13.
28. ^ Simon, Julian (August 1981). The Ultimate Resource (Hardcover ed.). Princeton: Princeton University Press. ISBN 069109389X.
29. ^ Simon, Julian L (1996). The Ultimate Resource 2 (Paperback ed.). Princeton: Princeton University Press. ISBN 0691042691. Retrieved 6 December 2017.
30. ^ United States Congress House Committee on Merchant Marine and Fisheries Subcommittee on Fisheries and Wildlife Conservation (1973). Growth and Its Implications for the Future: Hearing with Appendix, Ninety-third Congress, First[-second] Session ... U.S. Government Printing Office.
31. ^ a b Bardi, Ugo (9 March 2008). "Cassandra's Curse: How The Limits to Growth was demonized". The Oil Drum: Europe. Retrieved 1 December 2017.
32. ^ Simmons, Matthew R. (October 2000). "Revisiting The Limits to Growth: Could the Club of Rome Have Been Correct After All?" (PDF). Mud City Press. Retrieved 29 November 2017.
33. ^ Turner, Graham; Alexander, Cathy (2 September 2014). "Limits to Growth was right. New research shows we're nearing collapse". The Guardian. Retrieved 28 November 2017.
34. ^ Parenti, Christian (5 December 2012). "'The Limits to Growth': A Book That Launched a Movement". The Nation (24–31 December 2012 issue). Retrieved 30 November 2017.
35. ^ Avery, John Scales (2012). Information Theory and Evolution. Singapore: World Scientific. p. 233. ISBN 978-981-4401-22-7.
36. ^ Sandbach, Francis (1 November 1978). "The Rise and Fall of the Limits to Growth Debate". Social Studies of Science. 8 (4): 495–520. doi:10.1177/030631277800800404. PMID 11610433. S2CID 1564426.
37. ^ a b Meadows, Donella; Randers, Jurgen; Meadows, Dennis (2004). Limits to Growth: The 30-Year Update. Vermont, USA: Chelsea Green Publishing Co. p. xii.
38. ^ "Prophesy of economic collapse 'coming true'", by Jeff Hecht, New Scientist, 17 November 2008
39. ^ Hall, Charles A. S.; John W. Day (May–June 2009). "Revisiting the Limits to Growth After Peak Oil" (PDF). American Scientist. Sigma Xi, The Scientific Research Society/State University of New York College of Environmental Science and Forestry. 97 (3): 230–237. doi:10.1511/2009.78.230. Retrieved 1 July 2014.
40. ^ Bardi, Ugo (2011). The Limits to Growth Revisited. New York: Springer. ISBN 9781441994158. Retrieved 27 November 2017.
41. ^ Heinberg, Richard (2011). The End of Growth: Adapting to Our New Economic Reality (3rd printing ed.). Gabriola Island, BC: New Society Publishers. ISBN 978-0865716957.
42. ^ "Perspectives on Limits to Growth: Challenges to Building a Sustainable Planet" (PDF). Smithsonian Institution. Smithsonian Institution—Club of Rome. 2012-03-01. Retrieved 28 November 2017.
43. ^ "Documentation: "Already Beyond? - 40 Years Limits to Growth"". Volkswagen Stiftung. Retrieved 28 November 2017.
44. ^ Randers, Jorgen (June 2012). 2052. A Global Forecast for the Next Forty Years. White River Junction, VT: Chelsea Green Publishing Co. ISBN 978-1603584210.
45. ^ "2052. A Global Forecast for the Next 40 Years". 2052. A Global Forecast for the Next 40 Years. Retrieved 28 November 2017.
46. ^ Brian Hayes (May–June 2012). "Computation and the Human Predicament – The Limits to Growth and the Limits to Computer Modeling". American Scientist. doi:10.1511/2012.96.186.
47. ^ "Symposium: Already Beyond? - 40 Years Limits to Growth". Volkswagen Stiftung. 28 November 2012. Retrieved 2017-11-28.
48. ^ Turner, Graham (August 2014). Rickards, Lauren (ed.). Is Global Collapse Imminent? (PDF). sustainable.unimelb.edu.au (Research Paper No. 4). MSSI Research Papers. Melbourne, Australia: Melbourne Sustainable Society Institute, The University of Melbourne. p. 16. ISBN 978-0-7340-4940-7. Retrieved 2014-10-19. Regrettably, the alignment of data trends with the LTG dynamics indicates that the early stages of collapse could occur within a decade, or might even be underway. This suggests, from a rational risk-based perspective, that we have squandered the past decades, and that preparing for a collapsing global system could be even more important than trying to avoid collapse.
49. ^ Jackon, Tim; Webster, Robin (April 2016). Limits Revisited: A Review of the Limits to Growth Debate (PDF) (Report). London: All-Party Parliamentary Group on Limits to Growth. Retrieved October 23, 2016.
50. ^ Ahmed, Nafeez (14 July 2021). "MIT Predicted in 1972 That Society Will Collapse This Century. New Research Shows We're on Schedule". Vice.com.
51. ^ Herrington, Gaya (2020). "Update to limits to growth: Comparing the World3 model with empirical data". Journal of Industrial Ecology. Wiley. 25 (3): 614–626. doi:10.1111/jiec.13084.
52. ^ a b Alan Atkisson (2010)"Believing Cassandra: How to be an Optimist in a Pessimist's World", Earthscan, pp. 17–18.