Former NSW fire and rescue commissioner Greg Mullins told a Climate Council forum on Friday that Australia faces more "compound events" as heatwaves lead to flash droughts, which lead to massive fires.
"It's just knock after knock after knock," Mr Mullins, founder of Emergency Leaders for Climate Action (ELCA), said.
"It makes it very difficult for insurance companies, for governments, who have to foot the bill."
Since October 2020, there have been six declared Insurance Catastrophes with 212,000 claims totalling over $2.7 billion, the Insurance Council of Australia told AAP.
Australian insurers write 43 million business and household policies each year.
They have paid out more than $8.9 billion in natural disaster claims over the last three years, with more than $6.1 billion paid out since the 2019-20 bushfires.
Climate Council research chief Simon Bradshaw said serious challenges are already locked through to mid-century, even if the world succeeds in halving emissions this decade.
"But we would see significantly less impact than if we just continued to let things rip," Dr Bradshaw said.
"The magnitude of the risks we face beyond about 2040 - so well within the lifetime of a lot of people today - is going to be strongly influenced by what we do through this next decade to cut emissions."
The incoming La Nina weather pattern, on top of almost two years of COVID-19 and a mouse plague on the east coast, is adding to losses.
Andrew Gissing, a catastrophe loss and climate risk modeller at Risk Frontiers, said La Nina is often associated with the most damaging summers.
He said hundreds of thousands of people are at risk of direct impact from multiple floods and cyclones in coming months, along with significant economic losses as transport systems get disrupted by damage to roads and bridges.
"Underinsurance, which is a problem among these communities, certainly adds to the challenge," Mr Gissing said.
Mr Mullins said parts of Australia are already seeing more floods and hail damage from La Nina.
"We will be hit by more and more disasters because the extreme weather is more frequent than it used to be and its intensity is ramping up," he said.
Nor would city dwellers dodge the intensity, as more areas are subject to higher risks, including areas of Melbourne and regional centres in Victoria that are increasingly facing significant flash flooding, he said.
Dr Bradshaw warned of the uneven impacts from disasters.
"It's often older people, younger people, primary producers, people in lower socio-economic areas who bear a disproportionate brunt of various risks," he said.
"This further drives home the imperative of taking stronger action on climate change. We can create not only a safer but a fairer Australia."
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