Probabilistic Inference for Future Climate Using an Ensemble of Climate Model Evaluations

This paper describes an approach to computing probabilistic assessments of future climate, using a climate model. It clarifies the nature of probability in this context, and illustrates the kinds of judgements that must be made in order for such a prediction to be consistent with the probability calculus. The climate model is seen as a tool for making probabilistic statements about climate itself, necessarily involving an assessment of the model's imperfections. A climate event, such as a 2^C increase in global mean temperature, is identified with a region of 'climate-space', and the ensemble of model evaluations is used within a numerical integration designed to estimate the probability assigned to that region.