Design of a regional climate modelling projection ensemble experiment – NARCliM

Abstract

Including the impacts of climate change in decision making and planning processes is a challenge facing many regional governments including the New South Wales (NSW) and Australian Capital Territory (ACT) governments in Australia. NARCliM (NSW/ACT Regional Climate Modelling project) is a regional climate modelling project that aims to provide a comprehensive and consistent set of climate projections that can be used by all relevant government departments when considering climate change. To maximise end user engagement and ensure outputs are relevant to the planning process, a series of stakeholder workshops were run to define key aspects of the model experiment including spatial resolution, time slices, and output variables. As with all such experiments, practical considerations limit the number of ensemble members that can be simulated such that choices must be made concerning which global climate models (GCMs) to downscale from, and which regional climate models (RCMs) to downscale with. Here a methodology for making these choices is proposed that aims to sample the uncertainty in both GCM and RCM ensembles, as well as spanning the range of future climate projections present in the GCM ensemble. The RCM selection process uses performance evaluation metrics to eliminate poor performing models from consideration, followed by explicit consideration of model independence in order to retain as much information as possible in a small model subset. In addition to these two steps the GCM selection process also considers the future change in temperature and precipitation projected by each GCM. The final GCM selection is based on a subjective consideration of the GCM independence and future change. The created ensemble provides a more robust view of future regional climate changes. Future research is required to determine objective criteria that could replace the subjective aspects of the selection process.Published by Copernicus Publications on behalf of the European Geosciences Union.

Comparison of various climate change projections of eastern Australian rainfall

“…GCMs used are Run 4 of CCCMA-CGCM3.1 (T47) and Run 1 of MIROC3.2(medres) that simulate an increase in mean annual rainfall over NSW, and Run 1 of ECHAM5/MPI-OM and Run 1 of CSIRO-Mk3.0 that project a decrease. Full details of the NARCliM modelling methods are outlined in Evans et al (2014).…”

Procedure for selecting GCM datasets for climate risk assessment

“…Suppiah et al (2007) calculated the root mean square error (RMSE) and correlation coefficient between observations and model projections for the 1961 -1990 period for temperature, rainfall, and sea level pressure. They also applied the demerit point system (DPS) as the basis for GCM selection (Whetton et al 2005;Suppiah et al 2007;Collier et al 2011;Evans et al 2014). In their study of the Xindian River Basin, Dahan River Basin, and Touchien River Basin in Taiwan, Lien et al (2013) applied the DPS and weighted average ranking method (WAR) (Bentley and Wakefield 1998).…”

A Bayesian posterior predictive framework for weighting ensemble regional climate models

“…Here we consider the same data as Olson et al (2016a) temperature output from NARCliM (New South Wales/ACT Regional Climate Modeling Project, Evans et al, 2014). This project is the most comprehensive regional modelling project for south-eastern Australia, and the first to systematically explore climate model structural uncertainties.…”

“…Regional climate models (RCMs) are powerful tools to produce regional climate projections (Giorgi and Bates, 1989;Christensen et al, 2007;van der Linden and Mitchell, 2009;Evans et al, 2013Evans et al, , 2014Mearns et al, 2013;Solman et al, 2013;Olson et al, 2016b). These models take climate states produced by global climate models (GCMs) as boundary conditions, and solve equations of motion for the atmosphere on a regional grid to produce regional climate projections.…”