Two-year consecutive concurrences of positive Indian Ocean Dipole and Central Pacific El Niño preconditioned the 2019/2020 Australian “black summer” bushfires

• Published in: Geoscience letters Vol. 7; no. 1; pp. 1 - 9
• Main Authors: Wang, Guojian, Cai, Wenju
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 10.11.2020; Springer Nature B.V; SpringerOpen
• Subjects: 2019/20 Australian bushfires; Anomalies; Atmospheric Sciences; Biogeosciences; Burning; Central Pacific El Niño; Climate; Climate change; Climate models; Climate variability; Consecutive events; Dipoles; Drought; Drying; Earth and Environmental Science; Earth Sciences; El Nino; El Nino phenomena; Geophysics/Geodesy; Greenhouse effect; Oceanography; Planetology; Positive Indian Ocean Dipole; Rain; Rainfall; Research Letter; Summer; Trends; Tropical climate; Wildfires; Indian Ocean; Australia; Climate change; Positive Indian Ocean Dipole; 2019/20 Australian bushfires; Central Pacific El Niño
• ISSN: 2196-4092; 2196-4092
• DOI: 10.1186/s40562-020-00168-2

The 2019/20 Australian black summer bushfires were particularly severe in many respects, including its early commencement, large spatial coverage, and large number of burning days, preceded by record dry and hot anomalies. Determining whether greenhouse warming has played a role is an important issue. Here, we examine known modes of tropical climate variability that contribute to droughts in Australia to provide a gauge. We find that a two-year consecutive concurrence of the 2018 and 2019 positive Indian Ocean Dipole and the 2018 and 2019 Central Pacific El Niño, with the former affecting Southeast Australia, and the latter influencing eastern and northeastern Australia, may explain many characteristics of the fires. Such consecutive events occurred only once in the observations since 1911. Using two generations of state-of-the-art climate models under historical and a business-as-usual emission scenario, we show that the frequency of such consecutive concurrences increases slightly, but rainfall anomalies during such events are stronger in the future climate, and there are drying trends across Australia. The impact of the stronger rainfall anomalies during such events under drying trends is likely to be exacerbated by greenhouse warming-induced rise in temperatures, making such events in the future even more extreme.