The Australian Actuaries Climate Index results for the summer of 2023/24 show that both low and high temperatures were warmer than usual.

Additionally, high levels of extreme rainfall and wind were observed in the northeast. 

The Index, which measures the frequency of extreme weather conditions and how they vary over time, showed elevated temperatures across the northeast between last December and February. The East Coast (South) and Wet Tropics cluster regions of NSW and Queensland recorded the third and fourth highest high temperature index values to date. Eastern parts of Queensland, NSW, and Victoria also recorded the highest low (minimum) temperature index value to date. A sometimes overlooked consequence of global warming involves higher minimum temperatures, which can raise the risk of pests and diseases spreading across parts of Australia and affect agricultural production. 

Meanwhile, the extreme rainfall index was high for northeastern parts of Queensland, which was struck by Cyclone Jasper and Cyclone Kirrily during the summer. As a result, the Index recorded its 34th consecutive positive value, indicating that the frequency of extreme weather was above the average for the Index’s base period of 1981-2010. 

Rade Musulin, lead compiler of the Australian Actuaries Climate Index, said the results indicate that we need to maintain our focus on future-proofing building codes and land use policies, while also paying attention to how warmer-than-usual temperatures can impact ecosystems. 

“Insects and pathogens may change their geographic scope, particularly if higher minimum temperatures persist into winter, because they will not be killed off as early as they normally would,” he said. 

“Those warmer temperatures can also impact agricultural production and people’s health, particularly because it is harder to sleep if it does not cool down after a sweltering day.” 

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Last summer was the third warmest on record, according to the Bureau of Meteorology, which has forecast an increased likelihood of unusually high temperatures between May and July. 

“We need to be on guard if these warmer temperatures from summer continue into autumn and winter,” said Musulin. 

Musulin noted that although we have been in an El Niño cycle usually associated with hot, dry conditions, the significant rain events in Queensland during the summer were likely affected by elevated sea surface temperatures pushing more moisture into the air. 

“When you have warmer temperatures and high sea surface temperatures, you get more precipitation. This can contribute to bigger fuel loads in the bush, which combined with factors such as insect damage to trees, can raise the risk of bushfires next summer,” he said. 

“For example, warmer temperatures have significantly influenced the range and impact of pine beetle infestations in Canada, and this has been linked to recent extreme wildfires there.”