Australia should prepare for an imminent El Niño, with the Bureau of Meteorology and other agencies forecasting that the weather phenomenon is likely to develop in the coming months.
“The models are really aligning now,” Felicity Gamble, a senior BoM climatologist, said. “We are expecting a transition to El Niño sometime during winter.”
The World Meteorological Organization said on Tuesday there was a 90% chance of an El Niño developing in the Pacific before November – a phenomenon that historically has increased the likelihood of hotter and drier conditions for Australia’s east.
El Niño is the warm phase of the El Niño-Southern Oscillation (Enso), one of the key drivers affecting global climate. During an El Niño, sea surface temperatures in a central region of the equatorial Pacific become warmer than average, resulting in a shift in atmospheric circulation.
As a result, there is less atmospheric moisture and heavy rainfall over the north of Australia, which shifts to the central and eastern parts of the Pacific.
“In order to really say that an [El Niño] event is established, we also need to see that response in the atmosphere as well,” Gamble said. “We are seeing signs of that, but we’re not quite there yet.”
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The BoM last week said that models indicated the forecast El Niño – the first since spring 2023 – would be “at least moderate in strength, with the possibility of a strong event”.
However, Gamble emphasised that the strength of an El Niño does not “necessarily correlate exactly with the strength of the impacts in Australia”, as there were other climate patterns that influenced weather locally, such as the Indian Ocean dipole and the southern annular mode.
In Australia, El Niño has has tended to result in warmer-than-average temperatures across most of the south of the country, and been linked with an increased risk of drought, heatwaves, bushfires and coral bleaching. For eastern Australia, nine of the 10 driest winter-spring periods on record have occurred during El Niño years.
“An El Niño doesn’t necessarily mean we switch overnight into drought conditions and that we suddenly see increased fire risk – it’s a more nuanced story,” Gamble said. “You’ve got to really take into account some of those recent conditions that we’ve had in recent months.”
The influence of the El Niño in Australia was strongest during winter and spring, and “does tend to back right off in summer” – different to La Niña, Gamble said.
Dr Andrew Watkins, a Climate Councillor and former head of climate prediction at the BoM, said: “Climate change and El Niño are a very dangerous double act.
“Climate change is already pushing us to more time in drought, more bushfire weather and extreme heat. Climate pollution is reinforcing some of these impacts from El Niño.”
He said the strength of the El Niño – assessed by how far above normal sea surface temperatures are in an area in the central tropical Pacific – did “not automatically mean impacts in Australia will follow suit. For some countries closer to the equator, yes, but for Australia it’s a mixed bag.
“But the reality is that each time we see an El Niño event, it has led to periods of hotter and drier conditions.”
Watkins said climate change was tending to “pump up” existing variability, so that periods of dry became exceptionally dry, and when conditions were good for rainfall this delivered downpours.
A summary of a range of climate models published by the Columbia Climate School showed a wide range of possibilities for temperatures in the Pacific, but there was almost unanimous agreement that an El Niño would form.
Globally, El Niño can result in extreme rainfall and floods in the southern US and Central America, and failed monsoons on the Indian subcontinent.