Analyzing the Climate Sensitivity of the HadSM3 Climate Model Using Ensembles from Different but Related Experiments

JC Rougier, DMH Sexton, JM Murphy, D Stainforth

Research output: Contribution to journalArticle (Academic Journal)peer-review

118 Citations (Scopus)

Abstract

Global climate models (GCMs) contain imprecisely defined parameters that account, approximately, for subgrid-scale physical processes. The response of a GCM to perturbations in its parameters, which is crucial for quantifying uncertainties in simulations of climate change, can—in principle—be assessed by simulating the GCM many times. In practice, however, such “perturbed physics” ensembles are small because GCMs are so expensive to simulate. Statistical tools can help in two ways. First, they can be used to combine ensembles from different but related experiments, increasing the effective number of simulations. Second, they can be used to describe the GCM’s response in ways that cannot be extracted directly from the ensemble(s). The authors combine two experiments to learn about the response of the Hadley Centre Slab Climate Model version 3 (HadSM3) climate sensitivity to 31 model parameters. A Bayesian statistical framework is used in which expert judgments are required to quantify the relationship between the two experiments; these judgments are validated by detailed diagnostics. The authors identify the entrainment rate coefficient of the convection scheme as the most important single parameter and find that this interacts strongly with three of the large-scale-cloud parameters.
Translated title of the contributionAnalyzing the Climate Sensitivity of the HadSM3 Climate Model Using Ensembles from Different but Related Experiments
Original languageEnglish
Pages (from-to)3540 - 3557
Number of pages18
JournalJournal of Climate
Volume22, issue 13
DOIs
Publication statusPublished - Jul 2009

Bibliographical note

Publisher: American Meteorological Society

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