Projected Changes in Mean Climate and Extremes from Downscaled High-Resolution Cmip6 Simulations in Australia

Abstract

High-resolution climate change projections are required to understand local and regional climate change impacts. We used CCAM (Conformal Cubic Atmospheric Model) to dynamically downscale CMIP6 GCMs (Global Climate Models) over Australia under three emissions scenarios, producing a set of 60 simulations at a 10 km resolution. Previous work has evaluated the performance of the downscaled models in the historical period. Here, we evaluate the impact of end-of-century climate change in the downscaled CMIP6-CCAM models for mean and extreme climate under three Shared Socioeconomic Pathways (SSP126, 245 and 370). We find the changes in mean climate are similar in the host CMIP6 and downscaled models. For extreme temperature, we find that extreme maximum temperatures (TXx) warm more than extreme minimum temperatures (TNn). Extreme precipitation generally increases in summer and decreases in winter; however, there is a large amount of model spread on the location and magnitude of change. Consecutive dry days also decrease in most areas in summer and increase in winter. Heatwaves become more frequent and hotter by the end of the century. These results suggest a hotter, wetter summer, with longer, more frequent and more intense heatwaves, and a hotter and drier winter in most areas. This dataset provides useful new high-resolution information on how climate change is likely to impact Australia, which will be a valuable resource to underpin local adaptation responses to future impacts.

Keywords: Australian climate, CMIP6, Conformal Cubic Atmospheric Model, dynamical downscaling, high-resolution projections, climate extremes, heatwaves