Australia on the brink of an unprecedented weather moment

History may be made in 2024 if long-range forecasts for Australia from international climate models prove correct.

Image of Australians standing in the rain.
Australia may be in for some heavy rainfall later this year. Source: Getty

The Bureau of Meteorology has officially declared the end of El Nino, with suggestions a La Niña may be coming our way in a few months. This would then be the first time in history that Australia has seen an El Niño or La Niña weather event declared five years in a row.

Let’s recap: What are ENSO, El Niño and La Niña?

El Niño Southern Oscillation (ENSO) is the oscillation between El Niño and La Niña conditions, according to the Bureau of Meteorology (BoM).

El Niño, which occurs on average every three to eight years, refers to the warming of the central and eastern tropical Pacific Ocean, leading to a major shift in weather patterns across the Pacific including drier conditions. La Niña is the opposite of El Niño and brings with it an increased likelihood of above average rainfall, particularly in eastern and northern Australia. When neither El Niño nor La Niña are active, ENSO is in what is called "neutral".

Read more: What are El Niño and La Niña, and how do they change the weather?

Why do experts think La Niña could be coming?

The BoM stated "International climate models suggest ENSO will likely continue to be neutral until at least July 2024" before a possible La Niña forming by spring.

Climate Professor Shayne McGregor from Monash University told Yahoo News Australia there are a "couple of things" that lead people to believe La Niña is coming.

The first reason is a history of El Niño events being more often than not followed by La Niña events. "This suggests there is an increased chance of a La Niña event occurring relative to a neutral/normal year," he said.

As well as this, McGregor explained there are "temperature signals in the subsurface ocean" that are consistent with the beginning of a La Niña event.

"However, it is important to note that the signs of an ending El Niño event look like the beginning of a La Niña, so there is some ambiguity here."

If La Niña were to be declared, it would mean an increased chance of wetter-than-"normal conditions" during July and November, when the "strongest impacts" of the weather events are felt. "There would also be a reduced chance of having particularly dry conditions during these months."

Map of Australia showing the mean winter–spring rainfall during La Niña years.
The map shows the mean winter–spring rainfall during La Niña years. Source: BoM

Australia has never had events declared five years in a row

Australia has experienced three La Niñas followed by an El Niño, and if La Niña does grace us by spring that would mean an event had been declared five years in a row — which is unprecedented.

Such a sequence has not been recorded previously, Cai Wenju, a former senior CSIRO researcher, told Guardian Australia.

But, McGregor tells Yahoo, this is not something he is concerned about at this stage. "We really have not observed these events over a long period, [so] the chance to see something we have not seen before has a relatively high chance," he said. "However, ENSO does appear to have been very active in recent years."

He does note, however, there is some "alignment with climate model projections" which indicates ENSO will fluctuate more and more due to climate change. "But we are a long way from being able to attribute this recent increase in ENSO activity to climate change."

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