A third consecutive La Niña in the Australian spring of 2022 would be a concerning development for Australians, according to researchers at the ARC Centre of Excellence for Climate Extremes.
“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.
La Niña is an important cause of rainfall variability of Australia. La Niña promotes increased winter-spring rainfall in eastern Australia and increased late summer-autumn rainfall along the east coast, often resulting in widespread flooding.
Why is a “double-dip” or “triple-dip” La Niña concerning?
When a “double-dip” La Niña happens, the places affected are often still saturated from the first event – meaning consequences like floods can be even worse the second time around. Rarely, La Niña can happen a third time in a row.
“It’s concerning that some climate models are predicting that a third consecutive La Niña could form later this year” says Dr Gillett.
“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”
What does climate science tell us about La Niña events and how do we predict them?
Experts at the ARC Centre of Excellence for Climate Extremes and other scientific bodies around Australia and the world bring together a range of scientific disciplines to improve the predictions of events like La Niña. These experts study the history of previous events and produce complex climate models, using supercomputers, to project what might happen to the climate under different conditions.
However, the projections from climate models need to be interpreted with care – these projections inform how Governments, industries and communities prepare for the future, so it’s important that the science keeps developing and decision makers are informed as we learn more. The Centre produces regular briefing notes to keep decision makers up to date on the latest science.
What does the future look like?
“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.”