A methodology for probabilistic predictions of regional climate change from perturbed physics ensembles
- 14 June 2007
- journal article
- Published by The Royal Society in Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
- Vol. 365 (1857), 1993-2028
- https://doi.org/10.1098/rsta.2007.2077
Abstract
A methodology is described for probabilistic predictions of future climate. This is based on a set of ensemble simulations of equilibrium and time-dependent changes, carried out by perturbing poorly constrained parameters controlling key physical and biogeochemical processes in the HadCM3 coupled ocean–atmosphere global climate model. These (ongoing) experiments allow quantification of the effects of earth system modelling uncertainties and internal climate variability on feedbacks likely to exert a significant influence on twenty-first century climate at large regional scales. A further ensemble of regional climate simulations at 25 km resolution is being produced for Europe, allowing the specification of probabilistic predictions at spatial scales required for studies of climate impacts. The ensemble simulations are processed using a set of statistical procedures, the centrepiece of which is a Bayesian statistical framework designed for use with complex but imperfect models. This supports the generation of probabilities constrained by a wide range of observational metrics, and also by expert-specified prior distributions defining the model parameter space. The Bayesian framework also accounts for additional uncertainty introduced by structural modelling errors, which are estimated using our ensembles to predict the results of alternative climate models containing different structural assumptions. This facilitates the generation of probabilistic predictions combining information from perturbed physics and multi-model ensemble simulations. The methodology makes extensive use of emulation and scaling techniques trained on climate model results. These are used to sample the equilibrium response to doubled carbon dioxide at any required point in the parameter space of surface and atmospheric processes, to sample time-dependent changes by combining this information with ensembles sampling uncertainties in the transient response of a wider set of earth system processes, and to sample changes at local scales.Keywords
This publication has 120 references indexed in Scilit:
- A Demonstration of the Uncertainty in Projections of UK Climate Change Resulting from Regional Model FormulationClimatic Change, 2006
- Constraints on climate change from a multi‐thousand member ensemble of simulationsGeophysical Research Letters, 2005
- Marine boundary layer clouds at the heart of tropical cloud feedback uncertainties in climate modelsGeophysical Research Letters, 2005
- New estimates of future changes in extreme rainfall across the UK using regional climate model integrations. 1. Assessment of control climateJournal of Hydrology, 2004
- Amazonian forest dieback under climate-carbon cycle projections for the 21st centuryTheoretical and Applied Climatology, 2004
- Thawing sub‐arctic permafrost: Effects on vegetation and methane emissionsGeophysical Research Letters, 2004
- Probability of regional climate change based on the Reliability Ensemble Averaging (REA) methodGeophysical Research Letters, 2003
- Strong carbon cycle feedbacks in a climate model with interactive CO2 and sulphate aerosolsGeophysical Research Letters, 2003
- Comparative responses of EPIC and CERES crop models to high and low spatial resolution climate change scenariosJournal of Geophysical Research: Atmospheres, 1999
- Hydrologic and atmospheric models: The (continuing) problem of discordant scalesClimatic Change, 1994