13 September 2022
Jacinta Bowler
Jacinta Bowler is a science journalist at Cosmos.
They were published in the Best Australian Science Writing 2022.
With many places around the country still reeling from recent floods, the Bureau of Meteorology has confirmed that we’re in for another wet one.
The BoM says we are in the third La Niña in row — a relatively rare atmospheric event — with the outcomes made much worse by climate change. This is the third time three consecutive La Nina’s have happened since 1900.
La Niña, (Little girl in Spanish) and its counterpart El Niño (Little boy in Spanish) are large-scale weather events that happen in the Pacific Ocean.
El Niño was originally named by Peruvian fishermen when they noticed the warmer currents around their coast.
“During La Niña events, waters in the eastern tropical Pacific Ocean are cooler than normal, and waters in the western tropical Pacific Ocean warmer than normal. This causes changes in wind, cloud and pressure patterns over the Pacific,” says Bureau of Meteorology head of long-range forecasts, Dr Andrew Watkin.
“When this change in the atmosphere combines with changes in ocean temperature, it can influence global weather patterns and climate, including increasing rainfall over large parts of Australia”.
On the East coast, there’s likely to be more rain and windy conditions over summer, and an increased risk of floods.
More tropical cyclones than usual are also likely in north-eastern Australia.
“It does also mean we get cooler temperatures for Australia, particularly in parts of eastern Australia in the south, overall,” Watkin said last year. “But we can still get heat waves. Even if they’re not as extreme they do they tend to be longer and more humid.”
The one silver lining is that because there will probably be more rain, there’s likely to be fewer bushfires than a typical summer.
However, many dams and catchments are already full, so more rain could be a disaster for those still recovering. Since 1990, Australia has experienced 20 La Nina events, with 12 of those having coincided with flooding.
There have been two other occasions since 1900 when three La Nina events occurred in a row: 1973 and 1998. The BOM also includes 1954 to 1957, though the final La Nina was more neutral.
“The problem with a triple La Niña is that the ground is very wet already, our rivers are quite high, our creeks are full and our dams are quite full,” Dr Margaret Cook, environmental historian and lecturer at the University of the Sunshine Coast and researcher at Griffith University told the ABC.
“So we have less capacity to absorb this enormous amount of rain.”
QUT expert in risk management, Adjunct Professor Mark Gibbs suggests that this is a good time to start preparing.
“It is an early and timely reminder for all to get storm-prepared, pull out your flood emergency plan, and think about how to respond if the waters begin to encroach,” he said.
“Major floods often occur later in the storm season (after Christmas), and this can lead to a false sense of security if flooding has not occurred before Christmas.”