This is an Extract from an Article in The Guardian

See here: http://www.theguardian.com/environment/earth-insight/2014/mar/21/climate-change-scienceofclimatechange?INTCMP=ILCNETTXT3487

Number games

What about the HANDY model itself? Is it too simplistic? Kloor’s modelling expert turns out to be an obscure student in Mathematical Ecology specialising in the modelling of Plankton, who pooh-poohs the study as oversimplistic as it has only four equations. But this simply misses the point.

An academic conference paper on the HANDY model by a cross-disciplinary team of natural and social scientists led by Dr Rodrigo Castro of the Department of Environmental Systems Science at ETH Zurich, Switzerland, delivered earlier this month, explains in detail why the HANDY model is so useful:

“It is our predicament that we live in a finite world, and yet we behave as if it were infinite. Steady exponential material growth with no limits on resource consumption and population is the dominant conceptual model used by today’s decision makers. This is an approximation of reality that is no longer accurate and started to break down. The World3 model, originally developed in the 1970s [aka the ‘Limits to Growth’ project which despite Kloor’s dismissals has turned out quite accurate according to American Scientist], includes many rather detailed aspects of human society and its interaction with a resource limited planet. However, World3 is a rather complex model. Therefore it is valuable for pedagogical reasons to show how similar behavior can be also realized with models that are much simpler. This paper presents a series of world models, starting with very simple exponential growth and predator-prey systems, then investigates a minimal human-nature model, Handy, and ends with a brief account of the World3 model. For the first time, a simple human-nature interaction model is made available in Modelica that distinguishes between dynamics of Elite and Commoner social groups. It is shown that Handy can reproduce rather complex behavior with a very simple model structure, as compared to that of world models like World3.”

The HANDY model’s utility, in other words, is precisely its ability to reproduce complex behaviour despite a simple model structure. Its most unique feature is described as follows:

“An interesting feature of Handy is that it introduces the accumulation of economic wealth, and divides the human population into rich and poor according to their unequal access to available wealth…

Social inequality is not only explicitly considered but also plays a key role in the sustainability analyses of the model. This makes Handy the first model of its kind that studies the impacts of inequality on the fate of societies, a capability seldom found even in complex world models.

Handy establishes a useful general framework that allows carrying out ‘thought experiments’ about societal collapse scenarios and the changes that might avoid them.

The model is a very strong simplification of the human-nature system, which results in many limitations. Despite its simplicity, such a model is easy to understand and offers a more intuitive grasp of underlying dynamical phenomena compared to more complex and less aggregated models.”

It is precisely this unique feature which enabled the HANDY model to depart from the work of Tainter to explore the potential instabilities of the rampant inequality in today’s global economy.