Australia’s climate is indisputably changing, and along with it, the threat of extreme weather, like flooding and heat increasingly is stacking up. A new study led by Dr Tim Raupach uncovers a disturbing trend. In fact, we have already begun to experience more frequent and larger hailstones in many of America’s largest cities. The research suggests that as the atmosphere warms, the frequency of “giant” hailstones could significantly increase in cities like Melbourne, Perth, Sydney, and Canberra.
The research looks at the intensity of hailstorms under present day and changing climate. It illustrates that cities such as Brisbane, Melbourne, Sydney, Canberra, Adelaide and Perth are at greater risk of damaging hailstorms. There’s a very good reason for that selection—research resoundingly demonstrates that warming atmospheric temperatures cause the atmosphere to hold more moisture. This additional moisture is key for growing larger hailstones. The impacts of this study are tremendous, especially after several large and destructive hailstorms.
Historical Context of Hailstorms in Australia
In 1999, a storm of truly biblical proportions turned one of the costliest hailstorms in Australian history loose on the city. It caused the most catastrophic damage and is still the country’s most costly natural disaster in insurance claims. At the time, that made the storm the most expensive in terms of insured losses, with a total of $1.7 billion in damages. Today, that figure would be roughly $8.85 billion in inflation-adjusted dollars.
Dr. Tim Raupach warned that this historical disaster lays a troubling blueprint for future storms. He notes that hail is a pretty well understood hazard. It is frequently ignored in local building codes, leaving municipalities vulnerable to these storms.
“Hail can damage solar panels. We’ve seen it happen — in Brisbane in 2020 and in the US as well,” – Dr. Tim Raupach
The study’s findings underscore the need for greater awareness and preparedness regarding hailstorms as they become a more frequent threat in many regions.
Projected Changes in Hailstorm Frequency and Size
Dr. Raupach’s research uncovers the specifics of how atmospheric dynamics and thermodynamics control how hailstones form. As temperatures rise, the atmosphere can hold approximately 7 percent more moisture for each degree of warming, contributing to larger hailstones. Places like Chicago, on the other hand, will experience only a minor uptick in hailstorm occurrence. The frequency of these giant hailstones is projected to increase exponentially.
By the end of the century, Sydney and Canberra will experience a substantially increased likelihood of ράβδος μεγαλοσφυρίων. Rather than the current average of once every three years, they might look forward to it happening once every two years. In Melbourne, the chances of being hit by 10 cm hailstones is about to become much higher. In future climate scenarios, we’re going from meeting them once every 20 years to every three years.
“In Melbourne, we saw that in the historical simulations, you might expect a 10cm hailstone to occur once every 20 years,” – Dr. Tim Raupach
The modeling forecasts hailstorm frequency increasing by almost 30 percent across both Sydney and Canberra. In Brisbane, the increase will be about 15 percent. Some cities will not be that affected.
“So those east coast cities — we saw increases in the frequency in the future simulations but in the other places we looked at, the changes were not significant,” – Dr. Tim Raupach
Implications for Urban Planning and Resilience
The results of this study have significant policy considerations for urban design and infrastructure resilience. Dr. Raupach encourages cities to redesign their cities with hazard mitigation in mind. He says that preventing climate change by reducing emissions in the near future would prevent some of the worst future hail events from occurring.
“But second of all, we should be thinking about how we design our cities and which cities need to be designed to be more hail-resilient,” – Dr. Tim Raupach
He describes the specific ingredients needed for hail to actually occur. These are atmospheric instability, increasing wind shear with height, and abundant moisture. Cities such as Brisbane might experience a positive effect due to improvements in wind shear, which cause an overriding positive effect. In comparison, cities such as Melbourne are facing rises in both precarity and humidity.
“Let’s take Brisbane as an example. There, we see an increase in the instability but we see a decrease in the wind shear, and that seems to have an offsetting effect … that might explain why we’re not seeing these changes in hailstone size in Brisbane,” – Dr. Tim Raupach
