Abstract
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.
Highlights
Global warming is a major international concern and requires a global effort to reduce anthropogenic greenhouse gas concentrations
We propose a methodology for making these choices, and provide an example of using this methodology within the New South Wales (NSW)/Australian Capital Territory (ACT) Regional Climate Modelling (NARCliM) project. This methodology aims to sample the uncertainty in both global climate models (GCMs) and regional climate models (RCMs), as well as spanning the range of future climate projections present in the full GCM ensemble
Similar to choosing RCMs, the choice of GCMs in this experiment is made in order to sample the range of uncertainty in the ensemble of GCMs that simulate the climate of the target region well
Summary
Global warming is a major international concern and requires a global effort to reduce anthropogenic greenhouse gas concentrations. GCMs have generally been chosen based on the ease of access to the data required to create RCM boundary conditions, or due to members of a particular GCM’s organisation being involved in the project, and RCMs have been chosen if project members have past experience using them. While such choices were quite pragmatic, advances in computing infrastructure, data sharing and international cooperation through projects such as the 5th Coupled Model Intercomparison Project (CMIP5) and CORDEX, allow more objective choices to be made (McSweeney et al, 2012; Overland et al, 2011). This methodology aims to sample the uncertainty in both GCMs and RCMs, as well as spanning the range of future climate projections present in the full GCM ensemble
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