High-resolution downscaled CMIP6 drought projections for Australia

Abstract

Climate change is projected to lead to changes in rainfall patterns, which, when coupled with increasing evapotranspiration, have the potential to exacerbate future droughts. This study investigates the impacts of climate change on meteorological droughts in Australia using downscaled high-resolution CMIP6 climate models under three Shared Socioeconomic Pathway (SSP) scenarios. The Standardised Precipitation Index (SPI) and the Standardised Precipitation Evapotranspiration Index (SPEI) were used to assess changes to the frequency, duration, percent time, and spatial extent of droughts. There were consistent increases in droughts projected for southwest Western Australia, southern Victoria, southern South Australia, and western Tasmania using SPI and SPEI. There were significantly larger increases for SPEI-derived droughts, with consistent increases projected for most of the country. Increases in drought appear to have mostly come at the expense of "normal"climatic conditions, with similar or increased time spent under extreme wet conditions, indicating an overall shift towards more extreme climatic conditions. The largest increases occurred at the end of the century and under the high-emissions scenario (SSP370), demonstrating the influence of emissions on extreme droughts. For instance, if emissions reached high levels by the end of the century, the area subject to extreme drought in drought-prone Southern Australia would be 2.8 times greater than if they were kept to low levels using SPI and 4 times greater if assessed using SPEI. The insights generated from these results and supplementary tailored datasets for Australian local government areas and river basins are essential to better inform decision-making and future adaptation strategies at national, regional, and local scales.