‘Triple La Niña’: Australia could face another rainy summer, US expert warns | La Niña

Australia’s east coast could be hit by a rare “triple La Niña” that brings flooding rains and colder weather for a third straight summer, says a senior US government scientist.

Experts say the prospect of a triple La Niña is real, but there are differences between different computer models and Australia can still prevent the return of summer floods.

Scientists and meteorologists are watching temperatures in an area in the tropical Pacific Ocean that has been unusually cold in recent months – a sign that the current La Niña could stay in place until summer or disappear and then return.

Dr. Mike McPhaden, a senior researcher at the US government’s National Oceanic and Atmospheric Administration (NOAA), said that “often La Niñas come in pairs — one year followed by a second.”

“But in very rare situations, La Niñas persist into a third year and it looks like that could be happening this year,” McPhaden said.

“Triple diving La Niñas are rare. The last one was from 1998 to 2001 – more than 20 years ago. This has the potential to be a triple La Niña that could come in early 2023.”

McPhaden, based in Seattle, is in Australia meeting with other scientists and held a public seminar in Sydney this week on conditions in the Pacific and what they could mean for the coming months.

Ocean surface temperatures in an area of ​​the tropical Pacific known as Nino 3.4 – covering about 6m sq km – are used to help assess whether there might be an El Niño or La Niña.

El Niños align with above-average temperatures in the tropical Pacific and tend to mean warmer, drier conditions for eastern Australia. La Niñas are associated with a higher probability of rainfall and lower temperatures and are linked to below-average temperatures in that region of the ocean.

McPhaden said in April that the Nino 3.4 region of the Pacific was the coldest since 1950. In May, it was the coldest since 1988.

He said that while the world’s oceans were warming because of global warming, there was enough natural variability to overcome that warming for short periods or in specific regions.

The Bureau of Meteorology declared a La Niña in October 2020 that lasted until March 2021. La Nina conditions returned in November 2021 and have lasted until now.

An agency update on current La Niña, issued earlier this week, said it was “slowly weakening,” and while most models suggested the Pacific could return to more neutral conditions, two computer models found that La Niña could remain in place throughout Australia’s winter. .

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Agus Santoso, an expert on changes in El Niño and La Niña at the University of New South Wales, said there have been about 10 consecutive La Niñas since the 1950s, but only two periods that have had three summers in a row with La Niña conditions. – 1998 to 2000 and 1973 to 1975.

He said that if cold conditions in the Pacific remained, then a La Niña was likely later this year “but I would say that is uncertain at the moment”.

In addition to being linked to flooding in Australia, McPhaden said the current La Niñas are linked to severe drought that covers much of the western US.

This also increased the risk of wildfires and was causing water shortages for agriculture and power generation, he said. “There is a developing water crisis in the western half of the United States – 90% are in severe or extreme drought because of this La Niña.”

While scientists are still trying to understand how the climate crisis might be affecting the scale and frequency of El Niños and La Niñas, McPhaden said global warming still plays a role in the weather events that came from them.

“The warmer atmosphere can now hold more moisture and that can bring even more rain and amplify La Niña impacts,” he said.

Professor Matthew England of the University of New South Wales’s climate change research center said current La Niña conditions are lasting longer than usual.

He said that at this time of year, forecast models were known to be less reliable, but a third La Niña would not be welcome news for many Australians.

“I don’t think anyone wants that to happen,” he said.

“We have seen how damaging these flood events are. And it would likely be those same coastal towns along the coast of Queensland and New South Wales that will be hit by these events.”

Ben Domensino, a meteorologist at Weatherzone, said he believed the odds of a third consecutive La Niña summer for Australia were “about 50/50”, but regardless of whether a La Niña stays in place or disappears and then returns, the next few months would likely bring cooler, wetter-than-average conditions.

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