June 28, 2022 | Published by |

A third consecutive La Niña would be a concerning development for Australians, according to researchers at the ARC Centre of Excellence for Climate Extremes.

ARC Centre of Excellence for Climate Extremes Research Fellow Dr Zoe Gillett

“La Niña has been on the mind of many Australians for two years in a row” says Dr Zoe Gillett, Centre Research Fellow.

“La Niña is an ocean temperature and wind pattern across the Pacific Ocean. It has global impacts and promotes increased rainfall over much of Australia. Eastern Australia has experienced extreme rainfall and flooding associated with La Niña for two consecutive summers. These events have affected entire communities across large parts of the country and impacted our agriculture and supply chains. La Niña in two consecutive summers – what we call a double-dip La Niña – is not uncommon and happens in about 50% of events. This persistence can increase climate risks due to increased rain falling on already saturated catchments” says Dr Gillett.

“It’s concerning that some climate models are predicting that a third consecutive La Niña could form later this year. Triple-dip La Niña events are rare and have only happened twice since 1950. However, it is currently too early to tell if a third La Niña will eventuate. As of June, four out of seven forecasting models are predicting La Niña will return in late spring. The possibility of more rain falling on already saturated catchments would be a concerning development for communities still recovering”

The ENSO index from NOAA is based on the sea surface temperature variations in the Niño 3.4 region (170°W-120°W, 5°S-5°N). The blue line shows the La Niña phase of ENSO, and the red line shows the El Niño phase (note reversed y-axis for easier visualisation of La Niña). The dashed blue line indicates the threshold used to define La Niña events (shaded blue). NOAA uses a threshold of -0.5°C. Note: other agencies use different thresholds and ENSO index definitions. Double-dip and triple-dip La Niña events are labelled.

The Centre has released a briefing note (PDF version here) for decision makers to understand the implications of La Niña for Australia now and into the future.

“Multi-year La Niña events might be predictable more than a year in advance based on the strength of the preceding El Niño event. El Niño is the opposite to La Niña and usually leads to reduced rainfall over eastern Australia. However, the current La Niña event is puzzling because it developed without a previous strong El Niño. Scientists will be working to understand its causes over the coming years” says Dr Gillett.   

“Most climate models show that in an increased greenhouse warming world we should expect almost double the number of extreme La Niña events compared to last century. We’re likely to swing more often from the extremes of El Niño to the extremes of La Niña. This means swapping from droughts to flooding rains more often, but we do have to interpret these climate models with care. The models are getting better, but to help governments, industries and communities prepare for a future with more extremes, we need to keep developing the modelling and the science.”

A full briefing on multi-year La Niña events from the Centre is available here. (PDF version here)

Media contact: Jonathan Brown, jb.brown@unsw.edu.au 0491 008 719 (Forwarding number, cannot receive SMS)

Editor’s note:

New paper: A paper has also been published today by Nature Climate Change featuring contributions from Centre Associate Investigator Dr Agus Santoso:

Future extreme La Niña and El Niño events could also make our world even hotter. The more extreme La Niña and El Niño events that are predicted in the future could themselves make our world hotter with Australian scientists showing that they would reduce the ability of the Southern Ocean to take up heat, meaning more heat is retained in the atmosphere. The swings in the climate pattern known as the El Niño–Southern Oscillation are projected to get bigger under climate change – with more extreme La Niña and El Niño. But the authors say alongside the increase in the frequency of extreme weather events here in Australia, these bigger swings will also help to amplify global warming as they make the Southern Ocean less able to absorb heat.

https://www.nature.com/articles/s41558-022-01398-2

Dr Santoso can be contacted directly at a.santoso@unsw.edu.au

About the Centre:

The ARC Centre of Excellence for Climate Extremes reduces Australia’s economic, social and environmental vulnerability to climate extremes. Funded by the Australian Research Council (ARC), it brings together five Australian universities and a suite of outstanding national and international Partner Organisations.

The participating universities are the University of New South Wales, Monash University, the Australian National University, the University of Melbourne, and the University of Tasmania.