Editing World3 (section)

== Criticism of the model ==
There has been criticism of the World3 model. Some has come from the model creators themselves, some has come from economists and some has come from other places. 

In the book ''Groping in the Dark: The First Decade of Global Modelling'',<ref name="Meadows-1982">{{cite book|last1=Meadows|first1=Donella H.|title=Groping in the dark: the first decade of global modelling| date=1982| publisher=Wiley| location=New York|isbn=0471100277|url=https://books.google.com/books?id=QPaQAAAAIAAJ|access-date=28 November 2017}}</ref>{{RP|129}} [[Donella Meadows]] (a ''Limits'' author) writes: <blockquote>We have great confidence in the basic qualitative assumptions and conclusions about the instability of the current global socioeconomic system and the general kinds of changes that will and will not lead to stability. We have relatively great confidence in the feedback-loop structure of the model, with some exceptions which I list below.  We have a mixed degree of confidence in the numerical parameters of the model; some are well-known physical or biological constants that are unlikely to change, some are statistically derived social indices quite likely to change, and some are pure guesses that are perhaps only of the right order of magnitude. The structural assumptions in World3 that I consider most dubious and also sensitive enough to be of concern are:

*the constant capital-output ratio (which assumes no diminishing returns to capital)
*the residual nature of the investment function
*the generally ineffective labour contribution to output</blockquote>

A detailed criticism of the model is in the book ''Models of Doom: A Critique of the Limits to Growth''.<ref name="Cole-1973">{{cite book|last1=Cole|first1=H. S. D.|last2=Freeman|first2=Christopher|title=Models of Doom: A Critique of the Limits to Growth|date=1973|publisher=Vhps Rizzoli|isbn=0876639058}}</ref>{{RP|905-908}}

Czech-Canadian scientist and policy analyst [[Vaclav Smil]] disagreed with the combination of physically different processes into simplified equations:
{{quote|But those of us who knew the [[DYNAMO (programming language)|DYNAMO]] language in which the simulation was written and those who took the model apart line-by-line quickly realized that we had to deal with an exercise in misinformation and obfustication rather than with a model delivering valuable insights.  I was particularly astonished by the variables labelled ''[[World3 nonrenewable resource sector|Nonrenewable Resources]]'' and ''Pollution''. Lumping together (to cite just a few scores of possible examples) highly substitutable but relatively limited resources of liquid oil with unsubstitutable but immense deposits of sedimentary phosphate rocks, or short-lived atmospheric gases with long-lived radioactive wastes, struck me as extraordinarily meaningless.<ref name="Smil-2005">{{cite book|last1=Smil|first1=Vaclav|title=Energy at the Crossroads; Global Perspectives and Uncertainties|date=2005|publisher=MIT Press|location=Cambridge|isbn=9780262693240|url=https://mitpress.mit.edu/books/energy-crossroads|access-date=28 November 2017}}</ref>{{RP|168}} }}

He does however consider continuous growth in world [[GDP]] a problem:

{{quote|Only the widespread [[scientific illiteracy]] and [[innumeracy]]—all you need to know in this case is how to execute the equation <math>y = x * e^{rt}</math>—prevents most of the people from dismissing the idea of [[sustainable growth]] at healthy rates as an oxymoronic stupidity whose pursuit is, unfortunately, infinitely more tragic than comic. After all, even cancerous cells stop growing once they have destroyed the invaded tissues.<ref name="Smil-2005"/>{{RP|338-339}} }}

Others have put forth criticisms, such as Henshaw, King, and Zarnikau who in a 2011 paper, ''Systems Energy Assessment''<ref>Henshaw, King, Zarnikau, 2011 ''Systems Energy Assessment''. ''Sustainability'', 3(10), 1908-1943; doi:10.3390/su3101908</ref> point out that the methodology of such models may be valid empirically as a world model, but might not then also be useful for decision making. The impact data being used is generally collected according to where the impacts are recorded as occurring, following standard I/O material processes accounting methods. It is not reorganized according to who pays for or profits from the impacts, so who is actually responsible for economic impacts is never determined. In their view

*The economic motives causing the impacts, that might also control them, would then not be reflected in the model.
*As a seeming technicality, it could bring into question the use of many kinds of economic models for sustainability decision-making.

The authors of the book ''Surviving 1,000 Centuries'' consider some of the predictions too pessimistic, but some of the overall message correct.<ref name="Bonnet-2008">{{cite book|last1=Bonnet|first1=Roger-Maurice|last2=Woltjer|first2=Lodewijk|title=Surviving 1,000 Centuries; Can we do it?|date=2008|publisher=Springer|location=Berlin|isbn=9780387746333|url=https://books.google.com/books?id=83zhYT7kvgkC&q=Surviving+1,000+Centuries&pg=PA314|access-date=28 November 2017}}</ref>{{RP|4-5}}
{{blockquote|text=...[We] come to the well-known study, ''Limits to Growth'', published under the sponsorship of the 'Club de Rome' - an influential body of private individuals.  A first attempt was made to make a complete systems analysis of the rapidly growing human-biological-resource-pollution system.  In this  analysis the manifold interactions between the different parts were explicitly taken into account.  The conclusion was that disaster was waiting around the corner in a few decades because of resource exhaustion, pollution and other factors.  Now, 35 years later, our world still exists, ... So the 'growth lobby' has laughed and proclaimed that ''Limits to Growth'' and, by extension, the environmental movements may be forgotten.  This entirely misses the point.  Certainly the timescale of the problems was underestimated in ''Limits to Growth'', giving us a little more time than we thought.  Moreover, during the last three decades a variety of national or collaborative international measures have been taken that have forced reductions in pollution, as we shall discuss.  A shining example of this is the [[Montreal Protocol]] (1987) that limited the industrial production of [[fluorocarbons]] that damage the [[ozone layer]] and generated the 'ozone hole' over Antarctica. The publication of ''Limits to Growth'' has greatly contributed towards creating the general willingness of governments to consider such issues.  Technological developments have also lead to improvements in the efficiency of the use of energy and other resources, but, most importantly, the warnings from Malthus onward have finally had their effect as may be seen from the population-limiting policies followed by China and, more hesitantly, by India.  Without such policies all other efforts would be in vain.  However, the basic message of ''Limits to Growth'', that exponential growth of our world civilization cannot continue very long and that a very careful management of the planet is needed, remain as valid as ever.}}

At least one study disagrees with the criticism. Writing in the journal ''Global Environmental Change'', Turner notes that "30 years of historical data compare favorably with key features of the 'business-as-usual' scenario called the 'standard run' produced by the World3 model".<ref>{{Cite journal | doi = 10.1016/j.gloenvcha.2008.05.001 | title = A comparison of the Limits to Growth with 30 years of reality | year = 2008 | last1 = Turner | first1 = G. | journal = Global Environmental Change | volume = 18 | issue = 3 | pages = 397–411  | bibcode = 2008GEC....18..397T }}</ref>