Could a volcanic eruption be making Scandi winters colder?

Scientists have predicted the far-reaching impact of a 2022 volcanic eruption in the South Pacific.

Scandinavian winters could be about to get a lot colder – and it all links back to a volcanic eruption that happened on the other side of the world in early 2022.
In the coming years, it could bring ice cover back to the Baltic Sea at levels not seen in decades.
When the Hunga Tonga-Hunga Ha’apai submarine volcano erupted in the South Pacific on 15 January 2022, a record 100-150 million tonnes of ocean water evaporated high into the stratosphere. This is the equivalent of 60,000 Olympic-sized swimming pools.
Since then, it has been linked to the unusually large hole in the ozone layer seen in 2023 and Australia’s wetter-than-expected summer of 2024, according to researchers at the University of New South Wales (UNSW) in Sydney.
Setting out on the “impossible” task of measuring the vapour’s future impacts, they turned to climate models to predict what’s to come.
As we head into winter, could temperatures in Europe be affected by the distant eruption? It could soon become clear if the forecasts – released in a study published in the Journal of Climate earlier this year – are accurate.
The only way scientists can measure water vapour across the entire stratosphere is via satellites – technology that has only existed since 1979.
Since the Tonga volcano eruption is the only one of its kind to take place since then, the UNSW researchers had to rely on climate simulations to predict its impacts. 
The model accurately forecast the worsened hole in the ozone layer and Australia’s wet summer almost two years in advance.
Now, the scientists are keenly watching whether their winter predictions will also prove accurate.
Their models forecast colder and wetter than usual winters in northern Australia up until 2029, along with colder winters in Scandinavia and warmer winters in North America.
This is because the volcanic eruption may have altered the way ‘atmospheric waves’ of air – which influence global weather – travel through the atmosphere.
Almost three years after the eruption, the vapour is starting to collect at the bottom of the stratosphere, where its influence on the weather could strengthen, lead researcher Martin Jucker explained to Swedish magazine Science Illustrated.
In Scandinavia, temperatures could drop by 1 to 1.5C, potentially harking back to the 1980s when Baltic Sea ice coverage hit 96 per cent.
But, Jucker warned, since the troposphere – where these scenarios will play out – is “much more chaotic and complex than the stratosphere”, only time will tell if their predictions are accurate.
Competing weather influences will likely play a part in the accuracy of the models. 
Meteorologists predict that this winter will be cooler than last year’s in Europe due to La Niña – a natural climate pattern which occurs when sea surface temperatures in the central and eastern Pacific Ocean drop below average – the opposite of the warm El Niño phase.
Experts at the World Meteorological Organization have predicted a 60 per cent chance of La Niña conditions emerging between October and February.  
The weather pattern generally brings colder than normal temperatures across western Europe with forecasters expecting temperatures will drop as we head towards November and December.
It could also lead to more frequent and heavier snowfall in the Alps.
In the case of Australia’s wet summer, though, predictions relating to El Niño – the warming phase of the cycle that preceded La Niña – were turned on their head, proving the difficulty of knowing how these weather influences will interact.