Tropical cyclones are uncommon in my home city, 650km (404 miles) south of the Tropic of Capricorn, but they’re not unheard of.
Usually, when cyclones get this far down, the prevailing weather systems at these latitudes blow them out into the vast expanse of the Pacific. That was the expectation as I watched Alfred meander down the Queensland coastline. It would take a left, any day now.
But last Saturday, I was sent a message from a contact to check the weather models. Instead of going left, most were now showing that Alfred would run into an area of high pressure in the atmosphere that would kick it right, straight towards south-east Queensland, the home of Brisbane, the Gold Coast, the Sunshine Coast … and about 4 million people. Northern New South Wales was also in the line of fire.
Anything that could be turned into a projectile at our home either came indoors or got strapped down: furniture, wheelie bins, pot plants on our balcony. There were Covid lockdown vibes at the supermarket. Maybe people thought the toilet rolls might soak up the torrential rain?
A week of anxious waiting and watching later, the cyclone stalled close to the coast. Alfred was downgraded to a tropical low by the time it made landfall in southern Queensland on Saturday. It smashed the region’s world-famous beaches and brought torrential rain, flooding thousands of homes and, at one point, cutting off power to more than 400,000 homes and businesses.
How the climate crisis will impact cyclones is a tricky question. Generally, scientists expect it could bring fewer cyclones overall, but those that do occur could be more destructive.
The last time this region had to worry about cyclones was 1974, when two struck, one making landfall 250km north of Brisbane and the second crossing a few weeks later as an ex-cyclone on the Gold Coast, to Brisbane’s south.
But things have changed since. The Coral Sea off Australia’s north-east coast, where Alfred formed, is warming, and this summer just gone was its warmest on record (Australia’s summer runs from December to February). The warmer ocean temperatures off the coast mean that the warmer temperatures that can feed a cyclone are stretching farther south.
The warmer ocean can also help a cyclone to bring even more rainfall, and the route Alfred took to the Queensland coast in its final days had waters that were as much as 1C (34F) warmer than the long-term average for that time of year.
The rise in sea levels – caused by oceans expanding as they warm, and by land ice melting – makes storm surges and coastal inundation from cyclones worse. The warmer atmosphere increases the amount of moisture that can fall as rain.
One group of scientists at universities and government agencies have suggested that for every degree of global heating, town and city planners in Australia should allow for a 15% increase in rainfall.
The population of greater Brisbane population has risen from about 1 million in 1974, when it last experienced a cyclone, to an estimated 2.5 million now, and the Gold Coast’s from about 100,000 to an estimated 750,000. Together with the Sunshine Coast to the capital’s north, one urban historian has described this south-east Queensland region as one of the world’s longest continuous urban coastal strips, stretching for 200km.
Climate risk analysts say this region, together with northern New South Wales, contains some of the highest risk areas in Australia for cyclones. Though cyclones have been rare in this region in the past, because of the population increase and the huge amount of property and infrastructure that has been built as a result, the risk of major damage to people and property is high.
But Brisbane doesn’t need a cyclone to flood. Brisbane’s mean annual rainfall is about 1.1 metres, but in 2022, parts of the city got that much in less than a week. Many parts of Brisbane and the Gold Coast, and northern areas of New South Wales, are built on flood plains beside rivers that can quickly swell and burst after torrential rains. Yet, houses are still being built in these areas.
Cyclone Alfred could have been much worse. It could have had a more direct route to the coast, sustaining much higher winds, instead of stalling and wobbling as it did. Brisbane might have “dodged a bullet” this time, but I can’t shake the feeling that we are still loading the gun.
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