Evrim Yazgin
Cosmos science journalist
Hurricanes John and Helene have made international headlines this week for the destruction wrought on Mexico and the southeastern US.
Climate experts and meteorologists warn that such extreme weather events are going to be more frequent due to global climate change. Storms are getting stronger, lasting longer and causing more damage to infrastructure and lives.
Milton Speer, a meteorologist at the University of Technology Sydney, explains why.
“It’s not surprising that we’re getting these severe storms – Category 3 and above,” Speer tells Cosmos. “As the climate warms, sea surface temperatures get higher. There’s more energy when there are the right conditions for storms to form.”
“The tropics have expanded and the dry zone that’s in the mid-latitudes has expanded. Everything has moved polewards. That means you’re getting longer periods of moisture being drawn out from the oceans. But that’s in the northern hemisphere.”
Speer says that global climate changes are also influencing weather systems around the Australian continent.
“We’re getting unusually short, sharp, heavy rainfall amounts,” he says. “The tropics have shifted further south. We’re still in a drought through southern Victoria and parts of southern South Australia and southwest Western Australia. We’re just getting rain at different times as well.”
The rain is coming from moisture drawn from the Indian Ocean, Speer says. And while more rainfall might be welcome news in some ways, sudden shifts such as these can negatively impact ecosystems and social infrastructure.
“It’s a recipe for floods on flat-lying land and can cut off roads.”
Such a deluge hit the Northern Rivers region of northern New South Wales in 2022. Thousands of homes were destroyed and 5 people died during the floods.
Australia has avoided storms as severe as those which have hit North and Central America’s densely populated areas. The death toll from Hurricane Helene has risen to 128 today, with hundreds more still missing.
“I think Australia’s probably been fairly fortunate in the past that we haven’t had a Category 5 [over] Broome, Darwin, Cairns, Townsville or Rockhampton,” says Andrew Gissing, CEO of Natural Hazards Research Australia.
Having said that, Gissing notes the havoc caused by storms in Australia’s history, including the 2022 floods, Cyclone Tracy which killed 66 people in Darwin in 1974, and the 1954 Coolangatta cyclone which killed up to 30 people.
“You have to remember, too, that the majority of people that die in cyclones internationally are impacted by the flooding itself,” Gissing says. “That’s what you’re really seeing in the US. Yes, you’ve had the storm surge. Yes, you’ve had significant wind damage. But you’ve had massive floods that have come out of it.”
Gissing stresses that a major part of efforts to protect people from storms is planning land use around flooding.
“I saw some pictures of a hospital that was in the middle of a flood plain in the US that was getting evacuated. It’s the worst place to be building these sorts of assets,” Gissing says. “Whilst ever we continue to build in high-risk, flood prone areas, we continue to exacerbate the disasters of the future.”
“We know with climate change that we’re experiencing fewer tropical cyclones,” Gissing notes. “But those that occur are likely to be more intense. We’re seeing evidence of tropical cyclones slowing as well, which means there’s more time to drop heavy rain.”
Gissing says building codes have been forced to change, but that intensifying tropical storms will mean regulations will need to spread to areas not currently associated with flooding.
He adds that policy is currently often based on “probability” rather than “risk”.
“We’ve got this fixation with the with the 1-in-100-year flood in Australia,” Gissing says. “It’s a probability-based land use planning system. It’s not a risk-based land use planning system.
He says that risk-based land use planning can prevent hospitals, nursing homes and other developments which involve vulnerable people, from being placed on flood plains.
“Agriculture, parkland – these are good uses for flood-prone areas. We want to keep vulnerable people out of high-risk flood plains.”
Speer agrees, saying that building planning has to take into account flood risk.
“There’s very good preparation, seeing that we’ve had some pretty devastating floods,” Speer says. “Local councils in those areas, like along the east coast, are quite prepared. But they’re prepared for rescues and that sort of thing. It’s very hard to mitigate the effects when buildings have been traditionally built on flood plains. Some councils are assessing their floodplain management plans and where buildings can be built.
“That’s one thing that can be improved. But often these councils, especially inland, just don’t have enough money.”
