Australia's changing hydroclimate extremes

Dorethea Mackellar famously wrote in her poem "My Country" that Australia is a land of droughts and flooding rains. But has that really always been the case and are these droughts and flooding rains set to increase due to a warmer world? Australia being a large continent, is no stranger to climactic contrasts, as it is made up of distinct geographic, biophysical and climate regions - defined as Natural Resource Management (NRM) cluster regions - for example the wet tropics in the north-east and the desert regions in the central Rangelands. We examine the changes to Australia's unique NRM regions via a state-of-the-art seamless hydroclimate dataset from the Bureau of Meteorology, to analyse Australia's past to present to projected regional hydroclimate fields to track changes. We do this to understand what the future holds for Australia if we continue along the current emission scenarios. We examine patterns of change in hydroclimate extremes by assessing climate anomalies from past to the present (1963--2022). We examine the frequency of co-occurring extremes or compound events from present day climate and assess the relationship between them and natural disasters (1993--2022). In addition, we examine the change in frequency of projected compound events, across multiple storylines: wet, dry and middle of the range (1976--2005 compared to 2036--2065). We find that compared to the past, presently, across the southern and some central NRM regions, there are drying trends in precipitation, runoff and soil moisture, along with an increase in temperature. We find that natural disasters in Australia are related to the frequency of compound events, where the assessment of single regional climate drivers in isolation do not fully correspond to severe events in that region. Our results indicate that many NRM regions are cycling through hazards, which takes additional tolls on an already worn down community, where the frequency of compound events appears to be on the rise. In the future, the frequency of 'hot and dry' plus 'wet and windy' compound events are shown to increase across all regions for at least one of the future scenarios or storylines. This could indicate that more large-scale