Hailstorms could become more damaging in cities including Sydney, Canberra, Melbourne and Perth due to climate change, raising risks for insurance losses, new research shows.

The University of NSW study, supported by QBE, shows an increase in hail size over some capital cities and a likelihood of greater frequency in Sydney, Canberra and Brisbane.

Hailstorms were responsible for more than 20% of insured losses from 1967 to 2023, and damage was largely driven by the size of the hailstones.  

Lead author Tim Raupach, from UNSW Sydney’s Institute for Climate Risk and Response, says simulations of historical and future periods show hailstone size changes.

“We can see increases in hail size produced by the model around Sydney, Canberra, Melbourne and Perth,” he said. “For example, in past simulations, very large 10cm hailstones were expected once every 20 years around Melbourne, but in a warmer future, it’s once every three years.”

Hailstorms usually occur in spring and summer, when warm air and moisture are pushed higher into the atmosphere.

Dr Raupach says hail size is controlled by the strength of thunderstorm updrafts, while storm areas with more moisture and that are colder also have an impact.

Australia is particularly exposed to hailstorms along the east coast from just north of Brisbane to south of Sydney.

Report co-author Joanna Aldridge, from QBE, says Australian building standards do not include hail resilience, which leaves many properties vulnerable.

The Insurance Council of Australia database shows insured losses from the 1999 Sydney hailstorm would be $8.8 billion if normalised for today’s property numbers and values.  

UNSW says Australia’s largest recorded hailstone fell near Mackay in Queensland and was about 16cm across – more than double the diameter of a cricket ball.

Dr Raupach says the rising number of rooftop solar panels shapes as an emerging vulnerability, as seen during a storm in Brisbane in 2020 and others in the US.

Reducing greenhouse gas emissions remains a crucial objective and there is a need to consider how to strengthen cities to resist hail damage, he says.

Dr Raupach receives funding from QBE, Guy Carpenter and the Australian Research Council.