El Niño and La Niña events could last for up to two or three years in the future, according to new international research.
Key points:
- A team of scientists has found a link between changing weather patterns over the Pacific Ocean and the length of both El Niño and La Niña
- They say the findings could help communities around the world better prepare for disasters
- Dr Georgy Falster of ANU, a member of the team, says climate change has led to the shift
An international team of scientists has found that changes to the Pacific Walker Circulation (PWC) — shifts in atmospheric patterns above the Pacific Ocean — have implications for weather events.
El Niño periods are often marked by severe bushfires and drought in Australia, while La Niña typically brings with it wetter conditions, include flooding.
ANU College of Science postdoctoral fellow Georgy Falster, who became involved in the research at Washington University in St Louis before returning to Australia, said we could expect to see slower transitions between La Niña and El Niño.
She said it was clear that climate change was a factor in the shift.
“The circulation of the atmosphere over the Pacific Ocean has changed,” Dr Falster said.
“It’s also more likely we’ll see a longer gap separating El Niño and La Niña, meaning dry El Niño years are less likely to be followed straight away by wet La Niña years.”
The team, comprising of Dr Falster, Bronwen Konecky, Sloan Coats and Samantha Stevenson, used data from ice cores, trees, lakes, corals and caves around the world to find out how the weather and climate of the Pacific had changed during the past 800 years.
They then used that data to see how the PWC had changed from before and after the rise of greenhouse gases, and their results have now been published in the science journal Nature.
Link between climate change and PWC
The research focused on the impact of both natural and human-made forces on the PWC.
The team found that volcanic eruptions could cause the PWC to weaken, leading to “El Niño-like conditions” and that the PWC had an “outsized influence on weather and climate worldwide”.
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“Most climate models predict that the PWC will ultimately weaken in response to global warming,” the researchers wrote.
“Previous studies using observations and climate models identified a greenhouse-gas-driven PWC weakening through the twentieth and twenty-first centuries, following a thermodynamically driven decline in vertical mass flux over the tropical Pacific.”
They also found that while the PWC’s reaction to greenhouse gases was subtle, what was more pronounced was the relationship between volcanic eruptions and El Niño.
They said significant El Niño-like conditions typically occurred in the year following a volcanic eruption “probably associated with El Niño-like easterly surface wind anomalies over the equatorial Pacific”.
Dr Falster, who is also a research fellow at the ARC Centre of Excellence for Climate Extremes, said the huge Pacific Ocean had “wide-ranging impacts across the globe”.
“If atmospheric circulation over the Pacific Ocean changes, that has major impacts on the weather we experience across the planet,” she said.
The team hopes the information gathered will help communities better prepare for the impacts of climate change.
“Ultimately, we know planet Earth is warming and that warming is caused by human-induced greenhouse gases,” Dr Falster said.
“To plan and adapt for the impacts of climate change, we need to improve our knowledge of climate systems across the board.
“We need to know how the Pacific Walker Circulation is responding to global warming so we can help communities prepare for potential prolonged periods of flood, drought, rain and fire.”
