How much are volcanic events contributing to climate change around the planet? One expert has explained how different eruptions can cause different and significant impacts on the planet's temperature.
Recent eruptions in Indonesia have thrust the issue back into the spotlight.
Holger Vömel from the US National Center for Atmospheric Research in Boulder, Colorado told Breakfast this morning: "These eruptions, they inject a lot of material into the atmosphere.
"The eruption of Ruang last week was a fairly sizeable eruption for the local scale – but, on the global climate, it was not terribly large."
To understand the issue, it's important to understand the atmosphere has two layers, he explained.
The lower layer, the troposphere, is where the earth's weather occurs. It extends about 15km above the world's surface.
"This eruption injected some material actually above that," Vömel said. "This is why scientists are interested.
"In the stratosphere – this is the layer above the troposphere – we have the ozone layer but not much more, it's relatively boring.
"There is no rain, there is no strong winds, no storms, and stuff that gets injected up there just stays up there.
"It can stay up there for a really long time – so then the only question is, how much stuff did actually make it into the stratosphere?"
Vömel said last week's volcanic activity was on the smaller side in terms of climate effect.
The best comparison was Mount Pinatubo's 1991 eruption in the Philippines, he explained.
"That injected vast amounts of material well over 30-40km into the atmosphere, so much bigger than that one.
"This material stayed in the atmosphere for several years, so it can actually stay up there for a very long time.
"An eruption, if you think about it – you see all the ash, the smoke, the stones, the rocks... That stuff comes down fairly quickly, within days or so," he added. "But there are also a lot of gasses."
Sulphur dioxide was "the big one in this game". It formed small particles that acted like mirrors and reflected sunlight back into space.
"That will cool the atmosphere a little bit," Vömel said. "Because they're so small, they can stay up there for a very, very long time."
Sulphur dioxide vs water vapour
The 2022 Hunga-Tonga Hunga-Ha'apai volcanic eruption in the Pacific was a bit different, he explained.
Because the Tonga volcano was underwater, the event blasted massive amounts of ocean water vapour into the atmosphere.
"Think of 60,000 Olympic-sized swimming pools evaporated all in the stratosphere – which is normally really bone, bone dry," he said.
"So now we have all this extra water vapour in the stratosphere and this water vapour has the potential to trap heat – so potentially it might warm the climate a little bit, unlike the volcanoes that inject a lot of sulphur dioxide, that reflect sunlight."
And water vapour stayed up there for "much longer" than sulphur dioxide, up to eight or 10 years.
Scientists are still working on understanding the degree to which the two effects cancel each other out, he said.
"The story isn't finished yet. For scientists in my field — a very, very fascinating topic."
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