In the wake of devastating Debbie: Australia's grim cyclone future

By KIMBERLY BONILLA

Scientists have expressed new fears that climate change is making extreme weather events worse, in the aftermath of the widespread destruction Cyclone Debbie brought to Queensland last week. 

Warmer sea surface temperatures, rising sea levels and a weakening arctic jet stream, have increased the destructive capacity of cyclones, scientists say, as well as other extreme weather events like heatwaves and floods.

For decades, scientists, politicians and policymakers have been hesitant to link climate change to specific weather events. 

But the latest climate attribution research, released early last week, showed how certain weather events were made more likely by climate change. 

"We came as close as one can to demonstrating a direct link between climate change and a large family of extreme recent weather events," said Prof Michael Mann,  director of the  Earth System Science Centre at Penn State.

Cyclone Debbie tore through the Queensland coast last week taking six lives while leaving more than 230,000 homes without power and more than 664 dwellings uninhabitable.

The unprecedented flooding that followed the cyclone was responsible for the lives lost, smashing communities between southeast Queensland and northern New South Wales. The Gold Coast alone received a month's worth of rain.

The damage bill of Queensland’s worst cyclone in six years was expected to be in the billions. 

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Debbie brought widespread flooding to Queensland and NSW.

Climate change and cyclones

Climate change has had an impact on tropical cyclones that cross into Australia according to scientists, including Monash University tropical weather expert Dr Hamish Ramsay.

“Climate change will and can exacerbate the condition of tropical cyclones,” Dr Ramsay said.

“One thing we know about climate change is that warmer air can hold more water vapour ... it can lead to heavier precipitation, rainfall and potential for floods,” he said.

On average, 11 cyclones have occurred in Australian waters in the annual cyclone season from November to April, between 1969 and 2016.

Studies found the number of cyclones could reduce by 30 per cent while their intensity could increase. There was a 100 per cent increase in category four and five cyclones globally.

Former chief of CSIRO Atmospheric Research and researcher at Monash University Dr Graeme Permian said this was because higher sea surface temperatures, from climate change, have created a high-energy fuel for cyclones.

“The oceans around Australia have warmed, we know that for certain. And increase in the intensity of cyclones is consistent with the fact that that warming is taking place,” Dr Graeme Pearman said.

Prof Walsh said since the 1980s, cyclones had reached their maximum intensities further away from the equator.

“This may well have an effect on the typical location of tropical cyclone formations,” he said.

A 2014 study reported in the prestigious Nature magazine revealed the point at which cyclones were most intense was moving away from the tropics at a rate of 62km per decade in the Southern Hemisphere. The reason for the observed trend was thought to be complex but was consistent with the growth of the tropics.

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Damage caused by huge waves at Collaroy Beach in Sydney.

Where do rising sea levels come in?

Cyclones could become a more dangerous threat to coastal areas due to rising sea levels, another consequence of climate change, said Professor of Earth Sciences at Melbourne University Kevin Walsh.

“Storm-surge incidents are bound to increase in the coastal region compared to the current instances due to sea level rise, ” Prof Walsh said.

A storm surge is created when the winds of a cyclone push water from the sea towards the coast, causing it to flood inland. Higher sea levels make previously unreachable places vulnerable to flooding and erosion.

This could mean more events like the storms in Sydney last year that produced huge waves, eroding 50m of Collaroy and Narrabeen beaches and damaging beachfront houses. In 2012, Darwin was hit by a powerful storm surge that caused low-lying cliffs to collapse.

Future action

Visible air pollution catalysed action on environmental regulation in the 1970s as there was a clear cause and effect.

As the connection between extreme weather events and climate change becomes clearer through science, so might extreme weather events catalyse action on climate change.