Northern Australia has suffered its fair share of trials and tribulations these past few months, with floods burying huge swathes of Queensland under water only to be hit by one of the most powerful cyclones ever to hit the country.
Extreme rain events such as these may be a growing trend though, according to new research.
The study, which will be published in the journal Paleoceanography, authored by Janice Lough, climate scientist of the Australian Institute of Marine Science (AIMS) in Townsville, Queensland, uses the growth patterns in corals to create a centuries-long rainfall record for northern Australia.
“This reconstruction provides a new insight into rainfall in northeast Queensland,” says Lough. “These coral samples, which date from 1639 to 1981, suggest that the summer of 1973–1974 was the wettest in 300 years. This summer is now being compared with that record-setting one.”
Lough’s research suggests that northern Australia could be in for more weather extremes.
According to her research, from the mid-18th century to the mid-19th century, northern Australia had a period of relatively low precipitation and rainfall variability. But this is looking to change, according to Lough’s research, as average rainfall for the region has significantly increased and become more variable since the late 19th century, with more frequent wet and dry extremes.
Lough took cores from long-lived Porites coral found along Australia’s Great Barrier Reef. The Porites grows in such a way that it leaves tell-tale signs of its age and the amount of water which had been washed into the ocean from the land. In the same way that scientists can measure climate and age from a trees rings, so Lough was able to measure average rainfall from the Porites coral.
The data shows that the frequency of extreme events has changed over the centuries, and is currently at a peak.
During the earliest part of the reconstructed record, from about 1685 to 1784, wet years occurred on average every 12 years, and very dry years every nine. From 1785 to 1884, the frequency dropped: very wet years occurred about every 25 years, and very dry years every 14 years. However, between 1885 and 1981, the extremes increased dramatically in frequency, with very dry years taking place every 7.5 years on average, and very wet years about once every three years.
Research such as Lough’s is vitally important in placing the current climate variability in the tropics and southern hemisphere in a historical context. There is a significant dearth of data for the region, and the records derived from the corals help understand what is happening and what might happen in the future.
Source: American Geophysical Union
Image Source: Eric Matson, AIMS