A new study by the University of New South Wales has found that Australia’s major cities face a growing threat from larger and more destructive hailstones as the climate continues to warm. Several regions are projected to see substantial increases in both the size and frequency of hail events.
Melbourne is expected to experience the most significant change, with hailstones measuring 10 cm predicted to occur once every three years by 2080-2100 – up from once every 20 years currently, an ABC News report noted.
In Sydney and Canberra, where giant hail already occurs roughly once every three years, the risk is projected to rise to once every two years under future climate scenarios. Perth and Kalgoorlie are also expected to face greater risks, although the trends differ depending on hail size.
“In Melbourne, we saw that in the historical simulations, you might expect a 10cm hailstone – so that’s like a pretty big hailstone – to occur once every 20 years in those simulations,” said study author Dr. Tim Raupach. “But in the future scenario, that time reduces to every three years.”
The primary driver behind larger hailstones is atmospheric warming. With every degree the atmosphere warms, it can hold 7% more moisture, according to Raupach. This extra moisture acts as “fuel” for storms when the right weather system develops, creating the potential for more powerful thunderstorms and larger hail.
“The ingredients you need for a hailstorm [are] instability in the atmosphere and you need the wind to be changing with height, that’s called wind shear, and you need plenty of moisture,” Raupach said.
However, the warming effects vary by location due to different atmospheric conditions. While Melbourne shows increases in both instability and wind shear, Brisbane experiences increased instability but decreased wind shear, which may explain why hailstone size changes aren’t as pronounced there.
Hailstorms have been responsible for more than 20% of Australia’s insured losses from 1967 to 2023, a report from 9News noted. The 1999 Sydney hailstorm remains Australia’s most expensive natural disaster in insurance history, causing $1.7 billion in losses at the time.
The study assumes a warming of about 2.8°C above pre-industrial levels by 2080-2100, which researchers say aligns with current emissions projections.
Raupach emphasised the need for both emission reductions and improved building standards, noting that Australian building codes don’t currently include hail resistance requirements. The booming rooftop solar industry adds another vulnerability, as panels can be damaged by large hailstones.
What measures should these cities adopt to prepare for the growing threat of larger hailstones? Share your insights in the comments below.
