Judy Curry has posted a very informative article on her weblog Climate Etc titled
I recommend reading the entire article. I posted a comment at her weblog on her excellent, much needed contribution which reads
“Judy – this is an excellent much needed summary of climate modeling issues!
To add to the discussion on this thread, I wrote this post
What Are Climate Models? What Do They Do? [https://pielkeclimatesci.wordpress.com/2005/07/15/what-are-climate-models-what-do-they-do/]
where I recommended three categories of modeling –
“Process studies: The application of climate models to improve our understanding of how the system works is a valuable application of these tools……the term sensitivity study [can be used] to characterize a process study. In a sensitivity study, a subset of the forcings and/or feedback of the climate system may be perturbed to examine its response. The model of the climate system might be incomplete and not include each of the important feedbacks and forcings.
Diagnosis: The application of climate models, in which observed data is assimilated into the model, to produce an observational analysis that is consistent with our best understanding of the climate system as represented by the manner in which the fundamental concepts and parameterizations are represented. Although not yet applied to climate models, this procedure is used for weather reanalyses (see the NCEP/NCAR 40-Year Reanalysis Project).
Forecasting: The application of climate models to predict the future state of the climate system. Forecasts can be made from a single realization, or from an ensemble of forecasts which are produced by slightly perturbing the initial conditions and/or other aspects of the model…..”
I concluded in that post that
“… the IPCC and US National Assessments appropriately should be communicated as process studies in the context that they are sensitivity studies. It is a very convoluted argument to state that a projection is not a prediction. The specification to periods of time in the future (e.g., 2050-2059) and the communication in this format is very misleading to the users of this information. This is a very important distinction which has been missed by impact scientists who study climate impacts using the output from these models and by policymakers.”
See also our related papers; e.g.
Pielke Sr., R.A., 2002: Overlooked issues in the U.S. National Climate and IPCC assessments. Climatic Change, 52, 1-11 https://pielkeclimatesci.files.wordpress.com/2009/10/r-225.pdf
Rial, J., R.A. Pielke Sr., M. Beniston, M. Claussen, J. Canadell, P. Cox, H. Held, N. de Noblet-Ducoudre, R. Prinn, J. Reynolds, and J.D. Salas, 2004: Nonlinearities, feedbacks and critical thresholds within the Earth’s climate system. Climatic Change, 65, 11-38. https://pielkeclimatesci.files.wordpress.com/2009/10/r-260.pdf
I look forwward to further comments on this thread, and urge you also to publish your post in BAMS or other similar venue.”