Abstract

50 years after the publication of the seminal report to the Club of Rome “The Limits to Growth” (1972) it is possible to reassess the role of models as tools to examine the future and, within some limits, predict it. It has been said that “all models are wrong, but some are useful.” It is true, but what does it mean in practice, especially facing an incredible proliferation of models in all fields of science? To understand this subject, I am discussing some of the best known, and most common, models, starting from “world modeling” (the subject of the “Limits to Growth” study, to move to climate models, ecosystem models, and other kind of model. The complexity of the subject is nothing less than bewildering, but it is possible to discern some trends, and produce some recommendations. Often, simpler models turn out to have a better record as predicting tools than complex ones. The case of “The Limits to Growth” is an illustration of this point: although it was a very simple model compared to the current standards, its basic scenario turned out to be able to describe the trajectory of the world system up to now.