Picture: Sun in the clouds. Credit: Bradley Hook.

The southeast of Australia, the most densely populated region of the country, is affected by various climate extremes that pose significant risks to communities and infrastructure. Previous research has shown that aspects of many of the relevant extremes (e.g. heatwaves, weather conducive to bushfires, drought, heavy rainfall, thunderstorms) could change in the future under climate change. However, much of this research has been done on extremes that may occur as frequently as every year, on average. It is usually rarer events that cause the most damage.

This paper used statistical techniques to investigate changes in extreme climate events that currently occur, on average, only once every 20 years. These techniques are applied to data related to heat, rainfall, drought and conditions conducive to bushfires and thunderstorms from detailed climate modelling commissioned by NSW and ACT Governments.

Overall, the results showed an increase in the frequency of extreme conditions across the majority of southeast Australia by the end of the 21st century. This was true for all of the different types of extremes considered but was especially conclusive for heat extremes and conditions conducive to thunderstorms. Results for the capital cities of southeast Australia showed increases in the frequency of multiple different types of climate extreme. Several cities were projected to experience some extremes more than six times more frequently at the end of the century than under current climate conditions.

The study is an exemplar of the use of detailed climate modelling to assess future changes in potentially damaging climate extremes. It reveals relevant limitations in climate modelling and analysis techniques. Although, it does not address the issue of coincident climate extremes, which are often responsible for the most damage to communities and infrastructure, it provides information relevant to planning for managing future climate risks.

  • Paper: Herold, N., S. M. Downes, M. H. Gross, F. Ji, N. Nishant, I. Macadam, N. N. Ridder, and K. Beyer. “Projected Changes in the Frequency of Climate Extremes over Southeast Australia.” Environmental Research Communications 3, no. 1 (January 2021): 011001. https://doi.org/10.1088/2515-7620/abe6b1.