Hmmmm.... Yes, this is from modelling as there is no measurement precedent.What did we find out?
Thelarge ozone holefrom August to December 2023 was at least in part due to Hunga Tonga. Our simulations predicted that ozone hole almost two years in advance.
Notably, this was the only year we would expect any influence of the volcanic eruption on the ozone hole. By then, the water vapour had just enough time to reach the polar stratosphere over Antarctica, and during any later years there will not be enough water vapour left to enlarge the ozone hole.
As the ozone hole lasted until late December, with it came a positive phase of theSouthern Annular Modeduring the summer of 2024. For Australia this meant a higher chance of a wet summer, which was exactly opposite what most people expected with the declared El Niño. Again, our model predicted this two years ahead.
In terms of global mean temperatures, which are a measure of how much climate change we are experiencing, the impact of Hunga Tonga is very small, only about 0.015 degrees Celsius. (This was independently confirmed by another study.) This means that the incredibly high temperatures we have measured for about a year now cannot be attributed to the Hunga Tonga eruption.
Disruption for the rest of the decade
But there are some surprising, lasting impacts in some regions of the planet.
For the northern half of Australia, our model predicts colder and wetter than usual winters up to about 2029. For North America, it predicts warmer than usual winters, while for Scandinavia, it again predicts colder than usual winters.
The volcano seems to change the way some waves travel through the atmosphere. Andatmospheric wavesare responsible for highs and lows, which directly influence our weather.
It is important here to clarify that this is only one study, and one particular way of investigating what impact the Hunga Tonga eruption might have on our weather and climate. Like any other climate model, ours is not perfect.
We also didn’t include any other effects, such as the El Niño–La Niña cycle. But we hope that our study will stir scientific interest to try and understand what such a large amount of water vapour in the stratosphere might mean for our climate.
Whether it is to confirm or contradict our findings, that remains to be seen – we welcome either outcome.
