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A practical philosophy of complex climate modelling


We give an overview of the practice of developing and using complex climate models, as seen from experiences in a major climate modelling center and through participation in the Coupled Model Intercomparison Project (CMIP). We discuss the construction and calibration of models; their evaluation, especially through use of out-of-sample tests; and their exploitation in multi-model ensembles to identify biases and make predictions. We stress that adequacy or utility of climate models is best assessed via their skill against more naïve predictions. The framework we use for making inferences about reality using simulations is naturally Bayesian (in an informal sense), and has many points of contact with more familiar examples of scientific epistemology. While the use of complex simulations in science is a development that changes much in how science is done in practice, we argue that the concepts being applied fit very much into traditional practices of the scientific method, albeit those more often associated with laboratory work.

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  1. 1.

    We use the term ’evaluated’ in this paper (for assessing the adequacy of the model for a certain task) over ’validated’ since the latter term has connotations of ’truth’, which is of limited relevance here.

  2. 2.

    Alternative framings are discussed in detail in Katzav (2014).

  3. 3.

    Katzav (2014) outlines 5 ’views’ of climate model assessement, and this approach is akin to a combination of his description of the adequacy-for-process and ’conservative’ views.


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This paper has benefited greatly from extensive discussions with Wendy Parker and Joel Katzav, two anonymous reviews and from conversations at a workshop on climate model philosophy in Eindhoven in November 2013.

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Schmidt, G.A., Sherwood, S. A practical philosophy of complex climate modelling. Euro Jnl Phil Sci 5, 149–169 (2015).

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  • Climate models
  • Complex simulation
  • Model skill