Computerized models of the earth's climate are at the heart of the debate over how policy should respond to climate change. Global climate models (GCMs)--also called general circulation models -- attempt to predict future climatic conditions starting with a set of assumptions about how the climate works and guesses about what a future world might look like in terms of population, energy use, technological development, and so on.

Analysts have pointed out, however, that many of the assumptions used in modeling the climate are of dubious merit, with biases that tend to project catastrophic warming, and have argued that climate models have many limitations that make them unsuitable as the basis for developing public policy. This paper examines two major limitations that hinder the usefullness of climate models to those forming public policy.