Climate change will clearly disrupt El Niño and La Niña this decade, 40 years sooner than we thought

You’ve probably heard a lot about La Niña lately. This pattern of cool weather is the main driver of the heavy rains and floods that have devastated much of southeastern Australia in recent months.

You may also have heard of El Niño, which alternates with La Niña every few years. El Niño typically brings drier conditions to much of Australia.

Together, the two phases are known as the El Niño-Southern Oscillation, the strongest and most consequential factor driving Earth’s climate. And in recent years there has been a lot of scientific interest in how climate change will affect this global weather factor.

Our new research, published today, sheds some light on the matter. He found that climate change will clearly affect the El Niño-Southern Oscillation by 2030, just eight years from now. This has big implications for how Australians prepare for extreme weather events.

The study suggests Australians should prepare for the arrival of more extreme weather sooner than previously thought. Pictured: NSW Premier Dom Perrottet with officials during a flood crisis.
Bianca De Marchi/AAP

A complex weather puzzle

The El Niño-Southern Oscillation occurs across the tropical Pacific and involves complex interactions between the atmosphere and the ocean. It can be in one of three phases: El Niño, La Niña, or neutral.

During an El Niño phase, the central and eastern tropical Pacific Ocean warms significantly. This causes a major change in cloud formation and weather patterns across the Pacific, typically leading to drought conditions in eastern Australia.

During a phase of La Niña, which is happening now, the waters in the central and eastern tropical Pacific Ocean are cooler than average. Associated changes in weather patterns include above average rainfall over much of Australia.

When the swing is in the neutral phase, the weather fluctuates around the long-term average.

Previous research has suggested that El Niño and La Niña events can vary depending on where the warm or cold ocean temperatures are in the tropical Pacific.

But climate change is also affecting ocean temperatures. So how could this play into El Niño and La Niña events? And where could the resulting change in weather patterns be detected? These are the questions that our research has attempted to answer.

Read more: 3 things a climate scientist wants world leaders to know ahead of COP27

What did we find

We looked at 70 years of El Niño-Southern oscillation data since 1950 and combined it with 58 of the most advanced climate models available.

We have found that the influence of climate change on El Niño and La Niña events, in the form of ocean surface temperature changes in the eastern Pacific, will be detectable by 2030. This is four decades earlier than previously thought.

Scientists already knew that climate change was affecting the El Niño-Southern Oscillation. But because the swing itself is so complex and variable, it’s been difficult to identify where the strongest change occurs.

However, our study shows that the effect of climate change, which manifests itself as changes in ocean surface temperatures in the eastern tropical Pacific, will be evident and unambiguous within about eight years.

So what does all of this mean for Australia? Warming of the eastern Pacific Ocean, fueled by climate change, will cause stronger El Niño events. When this happens, rainbands are pushed away from the western Pacific, where Australia is located. This is likely to mean more drought and dry conditions in Australia.

It’s also likely to bring more rain to the eastern Pacific, which stretches along the Pacific coast of Central America from southern Mexico to northern Peru.

Strong El Niño events are often followed by strong and prolonged La Niñas. This will mean a cooling of the eastern Pacific Ocean, pulling the rain belt back towards Australia, potentially leading to heavier rainfall and flooding of the kind we’ve seen in recent months.

Read more: Losses and damages: Who is responsible when climate change harms the world’s poorest countries?

residents clean up after floods
Australia should prepare for more intense rains and floods.
AAP/Getty pool

And now?

The weather associated with El Niño and La Niña has huge implications. It can affect human health, food production, energy and water supplies, and economies around the world.

Our research suggests that Australians, in particular, need to prepare for more floods and droughts as climate change disrupts the natural weather patterns of the El Niño-Southern Oscillation.

Our findings should be incorporated into policies and strategies for adapting to climate change. And most importantly, they add to the weight of evidence that we urgently need to reduce greenhouse gas emissions to stabilize the earth’s climate.

Read more: Climate change effects such as floods significantly worsen existing disadvantages for indigenous communities

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