Pay no attention to the model behind the curtain

Abstract

Many widely used models amount to an elaborate means of making up numbers-but once a number has been produced, it tends to be taken seriously and its source (the model) is rarely examined carefully. Many widely used models have little connection to the real-world phenomena they purport to explain. Common steps in modelling to support policy decisions, such as putting disparate things on the same scale, may conflict with reality. Not all costs and benefits can be put on the same scale; not all uncertainties can be expressed as probabilities; and not all model parameters measure what they purport to measure. These ideas are illustrated with examples from seismology, wind turbine bird deaths, and climate policy.