La Niña: we knew it was coming, and it’s not going away

The major La Niña climate event responsible for record flooding in Queensland — and the largest ever cyclone to hit Australia in Yasi — is not over yet according to a senior climatologist at Britain’s Met office.

Dr Rob Allan, an Australian climate scientist who is a scientific manager at the Met Office’s Hadley Centre in Exeter, said the La Niña event was similar in intensity to the 1974 La Niña which created widespread flooding in eastern Australia.

“One can see similarities; we are looking at a major event which will cause these huge sorts of flooding,” he told Crikey. “No two events are the exactly the same but when they get to these large La Niñas you are going to get a very big response certainly in the eastern third of Australia.”

(Data from the Queensland Government’s Long Paddock website)

Dr Allan says the potential for a strong La Niña climate system was detected about the middle of 2010 and the Australian Bureau of Meteorology was alerted: “Most of the models and the people who run these models were seeing evidence of a strong La Niña event in the early to mid part of last year.”

Dr Allan, whose early career included study of the 1974 La Niña event, said the possibility of severe weather specifically affecting Queensland was predicted when the Pacific Ocean’s Niño 4 region cooled significantly.

“One of the things that is not well known regarding the flooding or the drought situation in Queensland is that once you start to get the changes of the cool water of the La Niña out into the Niño 4 region in the central equatorial Pacific Ocean — this is the area that is most likely to really wind the whole thing up and means you are going to get a major event in Queensland,” he said.

Although ocean-atmosphere models are indicating the system is beginning to wane, Dr Allan warned the system could be the beginning of a double event.

“Most of the models focus on three, six, nine months out into the future with their projections. Most of the models are seeing a waning of the event — whether there will be resurgence and a double event is another question,” he said.

And a double event would mean a high risk of flooding and cyclone systems again next summer: “That would be the concern because if you look back at the 1974 situation, the double event there occurred in 1974 and 1976.”