When the Hunga Tonga–Hunga Ha’apai volcano erupted in January 2022 in one of the most violent explosions in modern times, it did something unorthodox.
It partially cleaned up the mess, getting rid of the very pollution it created.
A new study says that this accidental self-cleaning act could hold the key to one of the most urgent challenges in climate science, which is removing methane from the atmosphere.
Using advanced satellite measurements, researchers tracked an enormous cloud of formaldehyde streaming from the eruption plume across the South Pacific.
Formaldehyde is a short-lived chemical that forms briefly when methane is destroyed in the atmosphere, making it a lingering fingerprint of methane breakdown in action.
“When we analysed the satellite images, we were surprised to see a cloud with a record-high concentration of formaldehyde. We were able to track the cloud for 10 days, all the way to South America. Because formaldehyde only exists for a few hours, this showed that the cloud must have been destroying methane continuously for more than a week,” said Dr Maarten van Herpen, first author of the study published in Nature Communications.
SALT, SUNLIGHT AND CHEMISTRY
The mechanism behind this self-cleaning is as elegant as it is unexpected.
The eruption hurled enormous amounts of salty seawater and volcanic ash high into the atmosphere. When sunlight struck this mixture, it produced highly reactive chlorine atoms, which then latched onto methane molecules and broke them apart.
Researchers had previously observed a similar process when Saharan dust blows over the Atlantic and mixes with sea salt.
“What is new — and completely surprising — is that the same mechanism appears to occur in a volcanic plume high up in the stratosphere, where the physical conditions are entirely different,” said Professor Matthew Johnson from the University of Copenhagen.
WHY DOES IT MATTER?
The significance of this finding can be boiled down to one word. Methane.
Methane is responsible for one-third of global warming and is roughly 80 times more potent than CO2 over a 20-year period.
Crucially, it breaks down in the atmosphere within about a decade, meaning that cutting or neutralising methane now could produce visible climate results within years, not generations.
The discovery raises the possibility of artificially replicating this volcanic chemistry and engineering conditions where sunlight and salt particles work together to destroy methane in the air.
But a key obstacle has always been proving that such methods actually work. The study offers a solution to that too.
“How do you prove that methane has been removed from the atmosphere? How do you know your method works? It’s very difficult. But here we address that problem by showing that methane breakdown can in fact be observed using satellites,” said Dr Jos de Laat, senior author of the study.
Although the discovery offers hope, scientists are clear that safety and effectiveness must be rigorously tested before any intervention is attempted at scale.
But the volcano, in its violence, may have handed humanity a rare and unexpected gift.
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