3 days ago
Major disaster from three years ago could impact Australia's winters for years
A major natural disaster that occurred two years ago could be impacting Australia's climate this winter, and may continue to do so for a number of years. Scientists say they are 'surprised' by the results in their study, which showed the effects may be felt around the world for up to a decade.
On January 15, 2022, an underwater volcano off the Pacific nation of Tonga exploded, releasing 1,000 times more energy than the Hiroshima bomb. It was one of the most powerful volcanic eruptions in recent history, and sent up to 150 million tonnes of water vapour into the stratosphere.
A study into the long-term impacts of that water vapour injection found it may temporarily alter local climates, including cooler winters in Australia, warmer winters and spring in North America, drier summers over northern Eurasia, and more rain over China's east coast.
Lead author and senior lecturer of the Climate Change Research Centre at UNSW, Martin Jucker, told Yahoo News it was "really unusual" for volcanoes to leave such a long-lasting impact.
"Volcanoes are generally known to impact the global climate, but that's usually a cooling due to all the smoke and for a few years. It's usually more like two to three years, not eight years."
He also said the research was complex, as a multitude of things can impact the weather and worsen or placate their findings.
'One very important thing about our study is that we look into the future, and there's no way to know how the global mean temperature or sea surface temperature, El Nino, El Nina, and all of these things, how they would look in the future. So we didn't include any of those effects. I only included the volcano and nothing else,' Jucker said.
In Australia, the study found anomalies in surface temperature that could see winters get up to 1°C cooler. Those in Western Australia may also see slightly lower temperatures in summer and autumn. Australia's surface temperature anomalies were described in the study as the 'most persistent, with significant cooling from year 1 to 8'.
The research also picked up slightly more rain than usual in WA, and wet anomalies over northern Australia.
Interestingly, the anomalies peak at years three and four after the eruption, which would be this year and next year. The three-year lag is because of the composition of the stratosphere, Jucker said.
'There are no weather systems, there's no clouds, no rain, or anything, and everything moves much more slowly. This water vapour was put into the stratosphere very locally, just above the volcano. So it needed time for this water to distribute itself across the entire globe and that takes a few years," he said.
The changes can be difficult to perceive, Jucker said, and may not even be noticeable until looked at as an average over the next four years or so.
'I still hope we do [see the changes] because I just find it exciting. I'm waiting to see if we can confirm it from a scientific point of view.
'We find this effect only if we average over a long time. So four years, from now to 2029, we average, and then we see this effect. Even after year three, we don't even see these effects if we just look down one individual year, for instance.'
While the study found weather anomalies around the world, the cooling in Australia and warming over North America don't have an overall impact on global temperature as they 'cancel out'.
"Now, what we did find is these regional impacts which would be starting about now, so three years after. And so they globally, they sum up to zero, but locally, there's a cooling," Jucker said.
"There's a cooling that we expect in winter over Australia over this time period, but there's a warming in North America in their winter, for instance. So all of these things cancel out, but regionally they're there."
He added that, like all scientific studies, it's important to remember that his findings are not definitive.
"So even when I say, we expect colder winters over Australia, it's really the probability of it being colder is higher. But it could be warmer, and that's fine. That would still be within our results. It's just that the probability of it being colder is higher," he said.
One prediction that has so far proven correct in Jucker's study is that the volcano's eruption would contribute to a hole in the ozone layer. The large hole appeared from August to December in 2023, which is what his simulations picked up almost two years in advance.
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