Australian researchers studying corals off the coast of Queensland have found the frequency of extreme rainfall events has increased over the past 100 years.
The study, accepted for publication in the journal Paleoceanography, examined hundreds of years of rainfall figures using coral from the Great Barrier Reef.
Dr Janice Lough, a climate change scientist at Australian Institute of Marine Science, says the corals have bands, like tree rings, that record freshwater levels in the ocean.
"They're wonderful history books and they predate when we've been able to measure rainfall with rain gauges or river flows with gauges," says Lough. "They triple the length of the records that we have to look at."
The researchers examined the corals under ultraviolet light, which cause the rings to appear as luminescent lines.
Lough says the intensity of the luminescence reflects river flow and hence rainfall in the area.
"We've been able to reconstruct north-east Queensland's summer rainfall back to the 17th century."
Highly variable rainfall
Lough says the coral records show Queensland rainfall has always been highly variable, with the summer of 1973-1974 being the wettest over the past 300 years.
"Extreme wet and extreme dry events have always occurred. But now we have evidence that those events are occurring more frequently than in earlier centuries, often with devastating effects," she says.
Lough says research would contribute to the body of knowledge currently being taken into consideration by town planners, managers, developers, emergency services and policy makers.
"The fact that extreme wet and extreme dry weather will happen more often and can potentially impact on thousands of people and millions of dollars worth of property, is something that the community will have to consider," she says.