Researchers say about 13 per cent fewer cyclones are forming each year than before human emissions began warming tropical oceans.

The findings are based on the careful reconstruction of a global, long-term record of tropical cyclone frequency stretching back to the mid-1800s.

"For most tropical cyclone basins, including Australia, this decline has accelerated since the 1950s when the warming has become unprecedented," says the study's lead author Savin Chand from Federation University Australia.

The warming climate is believed to have affected atmospheric circulation, making it harder for cyclones to form.

Dr Chand says the work is a big step forward in understanding long-term trends, with previous studies based on short term observational data from the satellite era that only goes back about 50 years.

"A number of studies came up in the past, using this short period of data which came up with different conclusions - conflicting conclusions - around what's happening to the trends," he said.

"This long-term dataset now give us better ways to quantify how human induced climate change has affected cyclone numbers."

Dr Chand noted while fewer cyclones might be good news, frequency is only one aspect of risk associated with tropical cyclones.

"Geographical distributions of cyclones are shifting, and tropical cyclones have been getting more intense in recent decades," he said.

"In some parts of the world, they are also moving closer to coastal areas where populations and developments are growing."

Coupled with increased rain related to cyclones and slower decay in hurricanes that make landfall, Dr Chand said these changes could be contributing to "accumulated" cyclone damage in tropical regions throughout the world.

But those other factors were not part of the study and so no direct conclusions about overall changes in risk can be made.

The study involved a team of Australian and international scientists and has been published in the journal Nature Climate Change.

Australian Associated Press