The Times Australia
The Times World News

.

Greenhouse gases are changing air flow over the Pacific Ocean – raising Australia's risks of extreme weather

  • Written by Georgina Falster, Postdoctoral Fellow, Australian National University
Greenhouse gases are changing air flow over the Pacific Ocean – raising Australia's risks of extreme weather

After a rare three-year La Niña event[1] brought heavy rain and flooding to eastern Australia in 2020-22, we’re now bracing for the heat and drought of El Niño at the opposite end of the spectrum.

But while the World Meteorological Organisation has declared[2] an El Niño event is underway, Australia’s Bureau of Meteorology is yet to make a similar declaration[3]. Instead, the Bureau remains on “El Niño alert”.

The reason for this discrepancy is what’s called the Pacific Walker Circulation[4]. The pattern and strength of air flows over the Pacific Ocean, combined with sea surface temperatures, determines whether Australia experiences El Niño or La Niña events.

In our new research, published today in the journal Nature[5], we asked whether the buildup of greenhouse gases in the atmosphere had affected the Walker Circulation. We found the overall strength hasn’t changed yet, but instead, the year-to-year behaviour is different.

Switching between El Niño and La Niña conditions has slowed over the industrial era. That means in the future we could see more of these multi-year La Niña or El Niño type events. So we need to prepare for greater risks of floods, drought and fire.

What is the Pacific Walker Circulation? An explainer.

Read more: La Niña is finishing an extremely unusual three-year cycle – here's how it affected weather around the world[6]

An ocean-atmosphere climate system

La Niña and its counterpart El Niño are the two extremes of the El Niño Southern Oscillation — a coupled ocean-atmosphere system that plays a major role in global climate variability.

The Walker Circulation is the atmospheric part. Air rises over the Indo-Pacific Warm Pool[7] (a region of the ocean that stays warm year-round) and flows eastward high in the atmosphere. Then it sinks back to the surface over the eastern equatorial Pacific and flows back to the west along the surface, forming the Pacific trade winds. In short, it loops in an east-west direction across the equatorial Pacific Ocean.

Read more: Curious Kids: where does wind actually come from?[8]

But the Walker Circulation doesn’t always flow with the same intensity — sometimes it is stronger, and sometimes it is weaker.

Periods of stronger or weaker Walker Circulation have major impacts on Australian climate[9]. A stronger Walker Circulation means stronger-than-average trade winds, and generally La Niña-like ocean conditions. This often brings wetter weather to eastern Australia.

On the flip side, a weaker Walker Circulation brings weaker-than-average trade winds, and El Niño-like ocean conditions. A weak Walker Circulation is often associated with drier weather across northern and eastern Australia.

So far, the Walker Circulation is what’s missing from the current El Niño event developing in the Pacific Ocean: it has not weakened enough for the Bureau to declare an El Niño event.

Animated GIF illustrating the Pacific Walker Circulation
In the Pacific Walker Circulation, warm air rises above the western Pacific Ocean, cools down and sinks over the east of the Pacific Ocean, circling back and continuing an important atmospheric cycle for the entire planet. The ARC Centre of Excellence for Climate Extremes via Canva.com[10]

What’s happening to the Walker Circulation?

The Walker Circulation is a major influence[11] on weather and climate in many places around the world, not just Australia.

A stronger-than-usual Walker Circulation even contributed to the “global warming slowdown[12]” of the early 2000s. This is because a stronger Walker Circulation is often associated with slightly cooler global temperature.

So we need to know how it is going to behave in the future. To do that, we first need to know if — and if so, how — the Walker Circulation’s behaviour has changed due to human activities. And to do that, we need information about how the Walker Circulation behaved before humans started affecting the climate system.

A group of Australian researchers drilling at the million-year-old ice summit in Antarctica
Data from ice cores helped build a picture of how the Pacific Walker Circulation has changed over time. ROB DICKSON/AAP[13]

We reconstructed Walker Circulation variability over the past millennium. We used global data from ice cores, trees, lakes, corals and caves to build a picture of how the Walker Circulation changed over time.

We found that on average, there has not yet been any industrial-era change in the strength of the Walker Circulation. This was surprising, because computer simulations of Earth’s climate[14] generally suggest global warming will ultimately cause a weaker[15], or more El Niño-like, Walker Circulation.

There are a few possible reasons for this. One is that a buildup of fine particles in the air[16], such as smoke or industrial pollution, may be driving a stronger Walker Circulation, hence “cancelling out” the weakening effect of global warming.

Another is there may have been some weakening, but so far it is too small to be detectable among the Walker Circulation’s large year-to-year variability.

Read more: Smoke from the Black Summer fires could have made the triple La Niña more likely[17]

Our research also does not rule out the possibility that with future increases in global temperature, the Walker Circulation will indeed weaken, in a trend to more El Niño-like conditions. In that scenario, Australians might expect decreased rainfall in the north and east[18], as well as warmer temperatures across the continent, and less snow in the Australian Alps[19].

Even though the average strength of the Walker Circulation has not changed in the industrial era, there has been a subtle change in the length of time taken for the Walker Circulation to switch from one state to the next.

The Walker Circulation now switches more slowly between weak and strong phases, and we suspect this is influenced by climate change. This has potentially important implications for climate extremes, as El Niño and La Niña conditions could hang around for longer.

Our research also found that major explosive volcanic eruptions — at least as big as the 1982 eruption of El Chichón — can trigger an El Niño-like weakening of the Walker Circulation one to three years after the eruption. Unfortunately, volcanic eruptions remain extremely difficult[20] to predict, so this doesn’t help our long-term climate predictions.

What is the message for Australians?

In terms of predicting how the Walker Circulation will change in the future, we can now focus attention on the particular climate models whose outputs most closely match[21] what we discovered from our reconstruction.

That is, models that show no industrial-era weakening trend. This approach might help us get more accurate predictions of future Walker Circulation change.

The other thing we can do is to be prepared for more consecutive-year El Niño and La Niña events, and the sustained wet or dry spells they could bring to Australia.

And if there is a major volcanic eruption? Be prepared for a couple of years of weak Walker Circulation, and the warm, dry weather that can bring.

Read more: New study helps solve a 30-year-old puzzle: how is climate change affecting El Niño and La Niña?[22]

References

  1. ^ rare three-year La Niña event (theconversation.com)
  2. ^ has declared (public.wmo.int)
  3. ^ yet to make a similar declaration (www.bom.gov.au)
  4. ^ Pacific Walker Circulation (climateextremes.org.au)
  5. ^ Nature (doi.org)
  6. ^ La Niña is finishing an extremely unusual three-year cycle – here's how it affected weather around the world (theconversation.com)
  7. ^ the Indo-Pacific Warm Pool (geoscienceletters.springeropen.com)
  8. ^ Curious Kids: where does wind actually come from? (theconversation.com)
  9. ^ major impacts on Australian climate (climateextremes.org.au)
  10. ^ The ARC Centre of Excellence for Climate Extremes via Canva.com (climateextremes.org.au)
  11. ^ major influence (agupubs.onlinelibrary.wiley.com)
  12. ^ global warming slowdown (www.nature.com)
  13. ^ ROB DICKSON/AAP (photos.aap.com.au)
  14. ^ computer simulations of Earth’s climate (climateextremes.org.au)
  15. ^ ultimately cause a weaker (www.nature.com)
  16. ^ a buildup of fine particles in the air (www.nature.com)
  17. ^ Smoke from the Black Summer fires could have made the triple La Niña more likely (theconversation.com)
  18. ^ decreased rainfall in the north and east (climateextremes.org.au)
  19. ^ less snow in the Australian Alps (www.bom.gov.au)
  20. ^ extremely difficult (agupubs.onlinelibrary.wiley.com)
  21. ^ most closely match (agupubs.onlinelibrary.wiley.com)
  22. ^ New study helps solve a 30-year-old puzzle: how is climate change affecting El Niño and La Niña? (theconversation.com)

Read more https://theconversation.com/greenhouse-gases-are-changing-air-flow-over-the-pacific-ocean-raising-australias-risks-of-extreme-weather-211029

Times Magazine

Headless CMS in Digital Twins and 3D Product Experiences

Image by freepik As the metaverse becomes more advanced and accessible, it's clear that multiple sectors will use digital twins and 3D product experiences to visualize, connect, and streamline efforts better. A digital twin is a virtual replica of ...

The Decline of Hyper-Casual: How Mid-Core Mobile Games Took Over in 2025

In recent years, the mobile gaming landscape has undergone a significant transformation, with mid-core mobile games emerging as the dominant force in app stores by 2025. This shift is underpinned by changing user habits and evolving monetization tr...

Understanding ITIL 4 and PRINCE2 Project Management Synergy

Key Highlights ITIL 4 focuses on IT service management, emphasising continual improvement and value creation through modern digital transformation approaches. PRINCE2 project management supports systematic planning and execution of projects wit...

What AI Adoption Means for the Future of Workplace Risk Management

Image by freepik As industrial operations become more complex and fast-paced, the risks faced by workers and employers alike continue to grow. Traditional safety models—reliant on manual oversight, reactive investigations, and standardised checklist...

From Beach Bops to Alpine Anthems: Your Sonos Survival Guide for a Long Weekend Escape

Alright, fellow adventurers and relaxation enthusiasts! So, you've packed your bags, charged your devices, and mentally prepared for that glorious King's Birthday long weekend. But hold on, are you really ready? Because a true long weekend warrior kn...

Effective Commercial Pest Control Solutions for a Safer Workplace

Keeping a workplace clean, safe, and free from pests is essential for maintaining productivity, protecting employee health, and upholding a company's reputation. Pests pose health risks, can cause structural damage, and can lead to serious legal an...

The Times Features

Duke of Dural to Get Rooftop Bar as New Owners Invest in Venue Upgrade

The Duke of Dural, in Sydney’s north-west, is set for a major uplift under new ownership, following its acquisition by hospitality group Good Beer Company this week. Led by resp...

Prefab’s Second Life: Why Australia’s Backyard Boom Needs a Circular Makeover

The humble granny flat is being reimagined not just as a fix for housing shortages, but as a cornerstone of circular, factory-built architecture. But are our systems ready to s...

Melbourne’s Burglary Boom: Break-Ins Surge Nearly 25%

Victorian homeowners are being warned to act now, as rising break-ins and falling arrest rates paint a worrying picture for suburban safety. Melbourne residents are facing an ...

Exploring the Curriculum at a Modern Junior School in Melbourne

Key Highlights The curriculum at junior schools emphasises whole-person development, catering to children’s physical, emotional, and intellectual needs. It ensures early year...

Distressed by all the bad news? Here’s how to stay informed but still look after yourself

If you’re feeling like the news is particularly bad at the moment, you’re not alone. But many of us can’t look away – and don’t want to. Engaging with news can help us make ...

The Role of Your GP in Creating a Chronic Disease Management Plan That Works

Living with a long-term condition, whether that is diabetes, asthma, arthritis or heart disease, means making hundreds of small decisions every day. You plan your diet against m...