Climate change will make it more likely that floods in Queensland are a part of the weather system.

The severe floods that swept southeast Queensland this week forced hundreds of residents to flee Gympie. They also closed major roads after heavy rains had ravaged the state for several days. The rain is expected continue today, and it will travel south into New South Wales.

We research a weather system called “atmospheric rivers”, which is causing this inundation. Indeed, atmospheric rivers triggered many of the world’s floods in 2021, including the devastating floods across eastern Australia MarchTwo people were killed and 24,000 people were evacuated.

Our most recent publication ResearchThe first to quantify the effects these weather systems had on Australia’s economy was Another studyWe published in November a detailed look at the March floods last year.

We found that although atmospheric rivers can bring much-needed rain to the Murray Darling Basin, they are more likely to cause catastrophic floods in a warmer climate.

What are atmospheric rivers?

Atmospheric river are like highways of water vapor between the poles & tropics. They are found in the first one-three kilometres of the atmosphere. They are responsible Around 90%You can see the water vapour moving north to south across the globe, even though it only covers 10% of the globe.

This water can cause severe damage if it crashes into mountain ranges or interacts with cold fronts. Mountains and fronts lift water vapour higher in the atmosphere, where it cools and condenses to form giant, liquid-forming clouds. Atmospheric rivers can also be the site of intense thunderstorms.

Three atmospheric rivers were particularly destructive last year.

California was hit by an atmospheric river in January. Record-breaking rainfall and blizzards. It also triggered an Landslide on California’s iconic Highway 1.

Canada was battered in November, British Columbia record breaking rainfallVancouver was then isolated from the rest.

The March drenching caused widespread flooding in Eastern Australia. A$652 Millionworth the damage. All continental states and territories, except WA, were subject to simultaneous weather warnings.

What we found

Our Recent researchThis is the first quantitative summary of Australian atmospheric rivers. It’s not all bad news – most of the time, atmospheric rivers bring beneficial rainfall to Australia. About 30% of southeast Australia’s rainfall comes from atmospheric rivers, including in the Murray-Darling Basin.

This region needs rain. The Murray-Darling Basin supports more than 500 speciesThere are approximately 30,000 wetlands, as well as birds, reptiles, and fish. The Murray-Darling Basin is home to agriculture. A$24 BillionTo the Australian economy.

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We also discovered that atmospheric rivers were responsible for 30-40% of the heavy rainfall days in the Northern Murray Darling Basin, where towns like Orange, Tamworth, and Dubbo are located.

A heavy downpour in Australia’s bread basket might lead to happier farmers during a dry period, but following a wet summer – such as from La Niña – these days are less welcome.

La Niña saturates soil

La Niña can play a big role in flooding, as it exacerbates damage wrought by atmospheric rivers.

A La Niña was declared in spring in 2020 and fizzled out by March in 2021. A second La NiñaArrived in the summer of 2021 or 2022.

During a La Niña, winds that blow from east to west near the equator strengthen. This causes deep, cold ocean water to rise up to the surface of the East Pacific, near South America. It also allows for warm ocean waters to form near Australia.

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Warm sea surface temperatures promote rainfall, which is why La Niña is associated with Rainier weatherMore than half of Australia

The soil is like a sponge in the kitchen. It absorbs water, but once it has become saturated it cannot absorb more. This is what happened to eastern Australia in the months before the March floods – and when the record-breaking rain fell, the ground flooded.

Our Recent researchThe atmosphere was flooded with high levels of water vapour from two sources: an atmospheric river that originated off the Indian Ocean and a high pressure system that originated off the Tasman Sea.

On March 23, over 800kg of water vapour passed over Sydney every second – that’s 9.6 Sydney Harbours of water in one day.

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The soil moisture in south-east Queensland was also affected. above averageSince October last year. Last November was Australia’s wettestNovember is the wettest November ever with south-east Queensland receiving much-above-average rainfall.

This meant that the ground was already swollen. Queensland was inundated by the heavy rains this week.

What’s the role of climate change?

We also used the algorithm to calculate the likelihood of future atmospheric river as large as the one that flowed over Sydney in March 2021. latest generationClimate models

Earth is currently on track 2.7℃ warmingBy the end the century. In this scenario, the likelihood of a similar weather phenomenon to the March floods is 80% higher. This means that we are likely to see more flooding and extreme rainfall in Sydney.

We also know that climate changes will increase the number of atmospheric rivers on the planet. However, we need to do more research to determine how often these dangerous events will occur in southeast Queensland.

But this is not the end. There is still time to change the outcome if we urgently reduce emissions to stop global warming beyond 1.5℃ this century. Every little bit that we can do to reduce carbon emissions could mean one less flood and one fewer person who needs to rebuild.

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