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CSIRO [Australia’s national science agency] research commissioned by the federal government suggests climate change could dramatically reduce the number of tropical cyclones in the Australian region and decrease wave heights on the nation’s east coast.

The surprise findings, which appear to contradict some common predictions about the impact of climate change, are contained in scientific papers on “Projecting Future Climate and its Extremes”, obtained under Freedom of Information laws by The Australian Online.

One paper, by CSIRO researcher Debbie Abbs, found rising temperatures could halve the frequency of tropical cyclones.

“Climate change projections using this modelling system show a strong tendency for a decrease in TC numbers in the Australian region, especially in the region of current preferred occurrence,” Dr Abbs said.

“On average for the period 2051-2090 relative to 1971-2000, the simulations show an approximately 50 per cent decrease in occurrence for the Australian region, a small decrease (0.3 days) in the duration of a given TC and a southward movement of 100km in the genesis and decay regions.”

Another paper, by Mark Hemer, Kathleen McInnes and Rosh Ranasinghe, predicted small but significant falls in likely wave heights as temperatures rose.

Their June 2010 research said wave heights could fall by a “relatively robust” 5mm-10mm along the NSW coast by the end of the century.

“Projected changes are larger and significant on the northern coast,” it said.

“While projected changes are typically small, in some circumstances we project a large reduction in storm wave energy along the NSW coast of up to 50 per cent decrease.

“The potential impacts of such decreases in storm wave energy on the coastal environment are unknown.”

A third paper suggests an increase in frequency of intense rainfall events in most Australian regions by 2055.

The paper, by Tony Rafter and Ms Abbs, says the “magnitude of change varies widely”.

It says central Queensland could experience a 110 per cent rise in the frequency of one in 20 year rain events, while Victoria could experience between 21 per cent fewer and 25 per cent more one in 20 year events.

The findings highlight scientific indecision about some of the likely impacts of global warming.

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