Greenhouse gases and depletion of the ozone layer are causing southern Australia to become drier, researchers reported on Sunday.
Scientists at the US National Oceanographic and Atmospheric Administration (NOAA) said that southern Australia suffered a decline in rainfall that began around 1970 and increased over the next four decades.
The trend is likely to continue over most parts of the vast region for decades to come, they reported in the journal Nature Geoscience.
"The drying is most pronounced over southwest Australia, with total reductions in austral autumn and winter precipitation of approximately 40 percent by the late 21st century."
The rainfall data were fed into a new high-resolution computer model that simulated natural and man-made impacts on the global climate system.
The fall correlated with a surge in carbon emissions that drive global warming, and with the thinning of the ozone layer by now-banned chlorofluorocarbon (CFC) chemicals.
Volcanic eruptions and changes in the Sun's energy levels were not strong enough to explain the drying observed in past decades.
Parts of Australia have been gripped by devastating drought and heatwaves in recent years.
In March, the World Meteorological Organisation said record high temperatures in 2013 would have been "virtually impossible" without human emissions of heat-trapping greenhouse gases.
The 2013-2014 summer saw sweltering temperatures in Perth, in the southwest, and Adelaide, in the south, while Sydney went through its driest summer in 27 years, an independent watchdog, the Climate Council, said.