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“Um, now we have an ocean down here.”
It was a wild weekend, with train services thrown into chaos, cars abandoned and people running for shelter as five states were hit by storms and flash floods.
Dr Kimberley Reid is a postdoctoral researcher at the University of Melbourne.
It says rain storms hit New South Wales, Queensland, Victoria, Tasmania, South Australia and the Australian Capital Territory.
“Eastern Australia has been hit by what we call an atmospheric river, which is like a river of water vapor in the sky stretching from Cairns to the southern coast of Victoria. And we have a low pressure system in greater Australia that helps drawing warm, moist tropical air to the south. Additionally, in the tropics we have what scientists call an active Madden-Julian oscillation, but in simple terms, it’s basically a pulse of stormy activity traveling from the Indian Ocean. to the Pacific Ocean, and that may help trigger these weather events.”
Queensland was hit hardest by the wild weather, with parts of the Gold Coast inundated with more than 200mm of rain in just 24 hours.
Sydney recorded more than 25 millimeters in an hour, while Canberra and Hobart each recorded around 10 millimeters in just an hour.
More than 900 calls have been received into the SES since the start of the week, the majority of which involved fallen trees, leaky roofs and requests for sandbags.
Angus Hines, Australian Bureau of Meteorology, says there are particular phenomena driving these current wild weather systems.
“Generally, the connection is that on hot days like we’re getting, as you say, several hot days, very hot across southern and eastern Australia right now, when we have these hot temperatures, what ago is actually promotes evaporation from the ocean.So we get more evaporation from the oceans around Australia and that puts a lot more moisture into the atmosphere in the form of water.So when it’s very hot for a prolonged period of time, you tend also to get much wetter conditions are developing at least close to the coasts of Australia, close to the oceans on both sides of the country And that means we have fuel available when it starts raining, really heavy rain.
For Dr. Reid, although this scenario seems scary, heavy rains are not uncommon, especially in summer.
“What’s particularly notable is that the oceans around Australia are quite warm. So, for example, in the northwest of Australia, the ocean is quite warm and that’s what we call the negative ocean dipole Indian. I don’t think it’s been officially declared, but it’s close to being declared. And this is basically like La Nina in the Indian Ocean. And this warm ocean water can help push moist tropical air from the tropical area southward towards Sydney and Melbourne is probably going to have a pretty wet December.”
He says it’s difficult to predict extreme rainfall events.
“Unlike temperature, extreme precipitation is much more variable. It changes from very dry to very wet. This means it is much more difficult to derive trends from the data, but what we know is that precipitation is caused by two key ingredients: that which we call thermodynamics, so in other words, the air is warm and it’s moist? And dynamics, so it’s things like low pressure systems and cold front And you need this combination of moisture in the air plus a weather system , as a low pressure system, for trigger severe flooding. And so scientists are pretty confident that the thermodynamic aspect, so the warm, moist atmosphere, will probably increase, but what we’re less sure about is the dynamics, so where exactly the weather systems might go.
However, while Dr Reid says while wet weather is not uncommon in Australia, it remains important to prepare.
“Although we have seen heavy, heavy rainfall in recent years, we know that Australia can also be very dry. And so we need to make sure we prepare for both ends of the spectrum, for very dry and very dry periods. This is especially true for eastern Australia. For western Australia, we’re seeing increased drought and so they would probably want to emphasize preparing for more drought and further bushfires.”
Climate change is a major factor in all of this.
“That’s a major concern about the climate, because the way it is right now in this warmer climate, it means there’s a lot of humidity around. So when we have heavy rain events, when we have extreme weather events, they” will be even heavier in a warmer climate. The extremes will become even more extreme. This is the trend for the last few centuries. I think Australia has warmed about a degree and a half since about 1900. That warming is certainly contributing to this effect of heavier rainfall as well.”
That’s why this kind of wild weather isn’t exclusive to Australia.
Notable storms have also occurred in Spain, Chile, Brazil, Dubai and other countries this year alone – and at a time when many countries are dissatisfied with the resolutions of the United Nations Climate Change Conference in November.
But as St Lucia Parliamentary Undersecretary Pauline Antoine-Prospere has highlighted, the climate emergency is worsening and requires urgent solutions.
“The implications for our economies, our people and our ecosystems are grave. Our development outcomes are compromised, as national infrastructure, built with massive multilateral loans, is destroyed before the debt is repaid and we must rebuild from zero. The cost of these disasters is growing exponentially with each increase in global warming.”