What causes southeast Australia's worst droughts?

TLDR

Since 1995, Australia has experienced its most severe drought, the “Big Dry,” causing widespread water shortages, agricultural losses, river desiccation, and ecosystem damage, yet its origins remain unclear. The study aims to demonstrate that Southeast Australia's major droughts, including the Big Dry, are driven by Indian Ocean variability rather than Pacific conditions. This is due to a lack of Indian Ocean temperature patterns that normally enhance tropical moisture transport, reducing southeastern Australia’s rainfall. The Big Dry’s unprecedented intensity is further linked to recent higher temperatures.

Abstract

Since 1995, a large region of Australia has been gripped by the most severe drought in living memory, the so‐called “Big Dry”. The ramifications for affected regions are dire, with acute water shortages for rural and metropolitan areas, record agricultural losses, the drying‐out of two of Australia's major river systems and far‐reaching ecosystem damage. Yet the drought's origins have remained elusive. For Southeast Australia, we show here that the “Big Dry” and other iconic 20th Century droughts, including the Federation Drought (1895–1902) and World War II drought (1937–1945), are driven by Indian Ocean variability, not Pacific Ocean conditions as traditionally assumed. Specifically, a conspicuous absence of Indian Ocean temperature conditions conducive to enhanced tropical moisture transport has deprived southeastern Australia of its normal rainfall quota. In the case of the “Big Dry”, its unprecedented intensity is also related to recent higher temperatures.