Anthropogenic warming reduces the likelihood of drought-breaking extreme rainfall events in southeast Australia

Future climate change is projected to increase the frequency and severity of droughts in many drought-prone regions of the world. However, coarsely-resolved and sometimes opposing rainfall changes across global climate models, and a lack of understanding of the weather-scale processes that cause droughts to begin and end, create uncertainties around these future changes in many regions. Here, we reveal that the co-occurrence of a deep low-pressure system over southeast Australia with an adjacent high-pressure system in the Tasman Sea is a key dynamic mechanism responsible for extreme and drought-breaking rainfall in southeast Australia. Regional climate models project a decline in the frequency of these events by 9% for every degree of global warming, with an 11.6% per degree decline in associated rainfall, increasing the risk of the region entering and staying in drought in the late 21st century. This critical dynamical context brings confidence to the projected increase in drought frequency and duration in southeast Australia and provides an opportunity to robustly identify future drought changes in parts of the world where similar mechanisms may also play a role in extreme, drought -breaking rainfall.