Australia’s changing hydroclimate extremes

Dorothea Mackellar famously wrote that Australia is ‘a land of droughts and flooding rains’. But has this always been true, and will these extremes intensify in a warmer world? Australia’s vast continent spans diverse hydroclimate regions – from the wet tropics in the north-east to the arid central rangelands – a land of climatic contrasts. Our study examines changes in these regions from past to future by: 1, assessing hydroclimate anomalies from 1963–2022; 2, exploring compound events and their link to disasters (1993–2022); and 3, projecting compound events under wet, dry and mid-range storylines (1976–2005 v. 2036–2065). Currently, southern and some central regions show drying trends in precipitation, runoff and soil moisture, alongside rising temperatures. Natural disasters are increasingly tied to compound events, where hazards cycle through communities already under strain. Worryingly, these events appear to be on the rise. Future projections show more frequent ‘hot and dry’ and ‘wet and windy’ extremes across all regions under at least one storyline. This suggests larger-scale droughts, longer fire seasons and more extreme fire danger days, across most of Australia as well as heavier rainfall, storms and stronger winds in the northern and central regions under the wet storyline, signalling an increased risk of flooding through extreme runoff. Our findings indicate that Australia’s hydroclimate extremes are changing and compounding, with significant implications for communities and disaster preparedness.