It is undoubtedly clear that continuing to burn or export fossil fuels will increase climate change and the risk of extreme weather.
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| As NSW faces flooding again, Victorian towns enter stage 2 water restrictions. A woman and her dogs pictured paddling past an SES flooding sign on Friday. Photograph: Renee Moore/AAP |
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Author Dr Kimberley Reid is a postdoctoral research fellow in atmospheric sciences at the University of Melbourne
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As New South Wales once again faces heavy rainfall and flooding, the Victorian towns of Euroa and Violet Town will enter stage 2 water restrictions next Wednesday.
The weather pattern bringing heavy rainfall to NSW is a common wet-weather scenario for the coast. A high-pressure system in the Tasman Sea has stalled, and the anticlockwise airflow around the high is pushing moist air from the ocean over land. At the same time, about three kilometres above the surface, a low-pressure system is lifting the moist ocean air up. As moist air rises, it forms clouds, storms, and finally rain.
While this weather pattern itself isn’t unusual, the duration of the pattern is. Typically, high pressure in the Tasman may hang around for one to two days. But the current high has been there for the past four days, bringing unrelenting rainfall to NSW. The rain is falling on already sodden ground, increasing the likelihood of flooding.
This is reminiscent of what we saw during the March 2021 floods. Unfortunately, the forecast for the next few days is also reminiscent of March 2021. After the rain from the east finally moves away, another strong band of rain is forecast to cross NSW from the west on Monday.
Scientists are actively researching how climate change is shaping Australia’s weather systems. We are not sure if weather systems will stall more often or not, mostly because we don’t yet have the computing power to run high-definition climate models needed to study them.
However, climate modelling capability is growing every year. Just last week, Australian climate scientists took part in a global hackathon to analyse data produced by models with about 50 times higher resolution than a typical one.
Earlier studies using lower definition models suggest we may see a decrease in stalled high pressure in the Tasman Sea, and low-pressure systems may also occur less often but produce more intense rainfall when they do happen.
While future high- and low-pressure systems are uncertain, atmospheric moisture is likely to increase in a warmer world.
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"Australia’s climate targets are only as good as the action behind them. We need to aim higher Amanda McKenzie Read more |
The March 2021 floods prompted my colleagues and me to assess how often Sydney may experience persistently high amounts of atmospheric moisture over the region.
High atmospheric moisture is a key ingredient in heavy rainfall. When it lingers, persistent rainfall and flooding become more likely.
We found that by 2080–2100, the chance of these high moisture events may increase by about 80% under both moderate and high emissions scenarios. With more moisture in the atmosphere, low-pressure systems could trigger more intense rain due to global heating.
As NSW sandbags, Adelaide is ramping up its desalination plant to secure the city’s water supply. Parts of South Australia, Victoria, Tasmania, and Western Australia have received very much below average rainfall over summer and autumn.
One to five days of heavy rainfall per year can determine whether drought occurs in Australia, where drought is largely driven by a lack of these events.
Climate patterns in the Indian and Pacific Oceans — which influence year-to-year rainfall variability — have been in neutral or dry phases. Neither El Niño nor La Niña has appeared since autumn 2024. La Niña tried to emerge over summer but didn’t develop.
The visually spectacular northwest cloudband — capable of delivering rain from Broome to Hobart — has been absent this year. Instead, slow-moving high-pressure systems have brought persistently dry conditions to southern Australia.
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Like flooding, drought frequency in a warming climate remains a leading area of research. Because droughts are rare, identifying trends is more difficult than for more regular indicators like maximum temperature.
The “tinderbox drought” of 2017–2019 was the first in Australia where the severity would not have been possible without global heating.
In addition, southwest Australia has experienced a robust rainfall decline since the 1970s — a trend projected to continue.
Droughts and floods have long marked Australia’s psyche. But increasingly, the fingerprints of a warming planet are showing in more intense rainfall and more severe drought.
Continuing to burn or export fossil fuels will only intensify the risk of extreme weather devastating Australia.
Links
- Climate change is supercharging rainfall and floods in Australia – Climate Council
- State of the Climate 2022 – CSIRO & Bureau of Meteorology
- Australia’s black summer of fire was not normal – and we can prove it – The Conversation
- Droughts in Australia will become more severe with climate change, scientists say – ABC News
- Human influence on the 2019–2020 “Black Summer” extreme fire weather in eastern Australia – Geophysical Research Letters
- Explainer: Climate change and extreme weather in Australia – Climate Council
- Australia's climate targets are only as good as the action behind them – we need to aim higher
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