Sydney faces almost one-third more hailstorm days, Brisbane is at a rising risk of a direct hit from a category-three cyclone, and south-eastern Australia will have to endure three times as many high-risk bushfire days over the century because of climate change, one of the world's biggest re-insurers says.

The costs to Australia from natural catastrophes has almost quadrupled from 1980 to reach $6.3 billion year, a figure which soar to $23 billion by 2050, according to Munich Re's latest Expect the Unexpected report.

A massive shelf cloud off the coast of Sydney. Credit:Nick Moir

Most of the threats, ranging from droughts to heatwaves and sea-level rise, will be worsened by a warming planet caused by rising greenhouse gas levels, Eberhard Faust, head of climate risk research for Munich Re, told Fairfax Media.

"All these perils could be affected negatively by climate change," Dr Faust said. "We think the risk will increase over the decades to come."