Climate projections for Australia: a first glance at CMIP5

Abstract

The current national climate projections for Australia are based primarily on CMIP3 data and were published in 2007. The CMIP5 database will form the basis of the updated national projections scheduled for release in mid-2014, and preliminary CMIP5 data are progressively being made available to the research community. This paper presents a basic analysis of those preliminary data in terms of the simulated present climate and projected future climate for Australia. Our results suggest that many of the deficiencies identified in CMIP3 simulations of the region, including those associated with rainfall seasonality across southern Australia and the intensity of the monsoon, still persist in the CMIP5 ensemble. The CMIP5 models also tend to underestimate observed Australia (and global) mean temperature trends over the twentieth century, which was not a feature of CMIP3. With respect to future simulations of annual and seasonal mean temperature and rainfall, the CMIP5 ensemble was found to be highly consistent with existing CMIP3 derived projections. This finding confirms previous CMIP3 results that indicate a projected rainfall decline in southwest Western Australia (and to a lesser extent southeastern Australia), but does not provide improved model agreement on future rainfall changes in the tropics, where the spread in climate model simulations remains large. A novel approach to mapping model agreement on future climate projections is also presented, which combines a number of recently published methods.