Multi-year El Nino, La Nina events could become more common: Australian study
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The study said multi-year events can exacerbate the risks of extreme droughts, fires, rains and floods.
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CANBERRA – Australia could see more multi-year El Nino and La Nina events due to human-caused changes to the atmospheric patterns above the Pacific Ocean, a study has found.
The study, published by Australian National University (ANU) and the Australian Research Council Centre of Excellence for Climate Extremes on Thursday, found that changes in the Pacific Walker Circulation (PWC) – a pattern of winds and updrafts over the Pacific Ocean – have an impact on El Nino and La Nina, and how they behave in the future.
Led by Dr Georgy Falster from the ANU Research School of Earth Sciences, researchers discovered that the length of time it takes for the circulation – a major influence on global weather – to switch between El Nino and La Nina phases has slowed.
The strength of the PWC is an important indicator of whether a La Nina or El Nino period has begun. During El Nino, the warmer surface waters disrupt the PWC, and weaken or even reverse the trade winds that blow from east to west and form the bottom of the circulation.
When the circulation is weak, warmer temperatures and increased risk of bushfires in Australia associated with El Nino can be expected. When the PWC is strong, cooler temperatures and increased rainfall typically associated with La Nina can be expected.
The team led by Dr Falster used global data from ice cores, trees, lakes, corals and caves to build a picture of how the PWC has changed over time. Dr Falster warned in the study that as a result of the slower circulation, El Nino and La Nina could last longer and become more common in Australia.
“After Australia saw severe flooding and rainfall from a rare three-year La Nina event, our research has found that one of the key drivers of these events is changing, with slower transitions between La Nina and El Nino events,” she said in a media release. “That means in future we could see more of these multi-year La Nina or El Nino events as the atmospheric flow above the Pacific Ocean switches more slowly between La Nina and El Nino phases.”
The study said multi-year events can exacerbate the risks of extreme droughts, fires, rains and floods.
A rare three-year La Nina between 2020 and 2022 brought record rainfall to parts of Australia’s east coast and has been linked to widespread major flooding in the region in 2022.
“Ultimately, we know the planet is warming and that warming is caused by human-induced greenhouse gases. To plan and adapt for the impacts of climate change, we need to improve our knowledge of climate systems across the board,” Dr Falster said.
“We need to know how the Pacific Walker Circulation is responding to global warming, so we can help communities prepare for potential periods of flood, drought, rain and fire.” XINHUA
