Queensland could face devastating floods rivalling those seen in 2010-11 in just a year鈥檚 time, as the effects of climate change and an impending La Ni帽a weather event combine.
La Ni帽a brings warm water to the ocean around Queensland, and with it comes rain. Fresh research now shows that the effects of climate change made the flood-causing rains three times more likely that year.
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In 2010-11, Queensland suffered some of its worst flooding in a century. Some 35 people were killed, and so much water fell on Australia rather than in the sea that the world鈥檚 oceans dropped by about 7 millimetres. The events also caused A$2.5 billion (US$1.8 billion) of property damage, with A$30 billion wiped off the country鈥檚 GDP.
of Woods Hole Oceanographic Institution in Massachusetts and her colleagues wanted to know how much of the blame laid with that year鈥檚 La Ni帽a 鈥� and how much was caused by longer-term ocean warming.
The team used a suite of climate models that reliably simulate the extreme rainfall in 2010-11 and ran experiments to see what would have happened if there was no long-term warming or no La Ni帽a.
鈥淲e found that 2010-11 would have been a wet year no matter what because of La Ni帽a,鈥� says Ummenhofer. 鈥淗owever, the long-term ocean warming made this [flooding] event three times as likely as it would have been without the warming.鈥�
She says some of that warming could have been the result of a natural cycle known by two names 鈥� the Interdecadal Pacific Oscillation and the Pacific Decadal Oscillation.
But the period of time over which the team analysed the long-term trend in warming was the past 50 years, in which this oscillation hasn鈥檛 changed significantly 鈥� so almost all the warming looks to have been the result of anthropogenic climate change.
Doubling up
The finding is particularly troubling in the light of other research by of the Commonwealth Scientific and Industrial Research Organisation in Canberra, Australia, which predicts that extreme La Ni帽a events themselves will double in frequency this century because of climate change.
Ummenhofer says a 鈥渨orrying implication鈥� of the two studies together is that floods similar to those in 2011 may now be even more likely than her findings suggest, because extreme La Ni帽as will be both more common and bring more rainfall.
She says more research would be needed to confirm that. 鈥淏ut we know these things often have combined consequences,鈥� she adds.
Queensland might not have to wait to get a taste of this future. The world is in the grip of one of the strongest El Ni帽os on record. And extreme El Ni帽os usually flip within a year to become their opposites, La Ni帽as 鈥� which are then often extreme themselves.
鈥淚 would predict an extreme La Ni帽a developing by next year this time,鈥� says Cai. 鈥淚t is highly likely that January 2017 could see floods similar to those in 2011.鈥�
Ummenhofer says that predicting La Ni帽a is difficult, but agrees it鈥檚 a worrying possibility that one might happen next year and bring a repeat of the devastating floods.
Journal reference: Geophysical Research Letters, DOI:
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Read more: 鈥�Climate known: There will be more floods and droughts鈥�
