Rainfall, averaged over the entire Australian continent, has increased over the past 50 years, according to new research. While many areas over Australia recently have experienced drought, the trend in other areas has been towards wetter conditions.

"Unfortunately, the wetter conditions have occurred in the more sparsely populated regions," says Dr Ian Smith, a climate scientist at CSIRO Atmospheric Research.

Dr Smith's analysis of rainfall data compiled by the Bureau of Meteorology shows that rainfall has increased over the summer half of the year in large parts of western, northern and central Australia over the period 1952 to 2002. The subsequent two summers since the analysis was completed have also been relatively wet in those parts of the continent.

"The trends are sufficiently large and widespread to be classified as unusual in a historical context," says Dr Smith. "Furthermore, the wetter conditions may be signs of a changing climate, as foreshadowed by climate experts almost 20 years ago."

The study into increasing rainfall will be published in the next issue of the Australian Meteorological Magazine. The trends towards wetter conditions contrast with the long-recognised trend towards drier regional conditions - such as the sudden decrease in rainfall in south-west Western Australia in the mid-1970s, a drying trend over south-east Australia since 1996, and a longer-term drying trend over southern Australia since the 1970s.

In a related paper published in Geophysical Research Letters early this year, Dr Richard Wardle of the University of Melbourne and Dr Smith looked at the relationship between increasing summer rainfall and Australia's rising temperature. "Using a climate model we found that forcing the land to absorb more energy causes a complex response whereby the monsoon region becomes wetter and cooler in summer but in the drier regions it becomes wetter and warmer," he says.

"This result is important because it indicates that a regional response to climate change can be very different to the large-scale response. This may be important when interpreting paleoclimate records and is likely to be important when estimating the effects of future climate change," Dr Smith says.

Dr Smith is presenting at the Australia New Zealand Climate and Water Forum in Lorne, Victoria, this week see www.bom.gov.au/events/anzcf2004 [external link, new window]. There is free day registration for media participants.