A violent volcanic eruption may have revealed a new weapon to tackle a potent planet-heating gas

A satellite image of the eruption, which sent a plume of ash, steam and gas nearly 65 kilometres (40 miles) into the stratosphere. (Japan Meteorology Agency via AP via CNN Newsource)

When an underwater volcano erupted in the South Pacific in January 2022, it sent a plume of ash, steam and gas nearly 65 kilometres (40 miles) above the Earth’s surface. It was one of the most violent volcanic eruptions of modern times. It may also have also revealed a new weapon in the fight against a potent planet-heating gas, according to new research.

The Hunga Tonga-Hunga Ha’apai volcano erupted with a power hundreds of times stronger than the Hiroshima nuclear explosion, setting off a tsunami and a sonic boom that went around the planet twice. It then did something “unexpected,” according to the authors of the new study published Thursday in the journal Nature Communications. It started cleaning up some of its own pollution.

The scientists’ discovery came from looking at advanced satellite data of the eruption. “We found a huge cloud of formaldehyde that should normally not be there,” said Maarten van Herpen, a study author, and a physicist and executive director at Acacia Impact Innovation, a Dutch consultancy. Formaldehyde often forms when methane, a potent planet-heating gas, is destroyed in the atmosphere.

The researchers believed they were observing a chemical process that had previously been identified over the Atlantic Ocean.

Scientists had found that when Saharan dust is blown over the Atlantic, it mixes with salt spray and forms small iron-based particles. As the sunlight hits them, it produces chlorine atoms, which react with methane in the atmosphere and help break it down.

Something similar appears to have happened with the Hunga Tonga-Hunga Ha’apai volcano, according to the study. Its eruption sent enough salty water vapor into the stratosphere to fill around 58,000 Olympic-size swimming pools along with volcanic ash. The study scientists believe that when the sunlight hit the mixture, chlorine formed and broke down some of the methane produced by the eruption.

“It has emitted methane and then destroyed these emissions through the particles in the plume,” van Herpen said.

They tracked the formaldehyde cloud for 10 days. “Because formaldehyde only exists for a few hours, this showed that the cloud must have been destroying methane continuously for more than a week,” van Herpen added.

The researchers estimate the eruption produced around 330,000 tons of methane, of which around 900 tons were broken down a day.

It’s “new — and completely surprising” that the same process observed in the Atlantic appears to have played out in a volcanic plume high up in the stratosphere, said Matthew Johnson a study author and chemistry professor at the University of Copenhagen, who was involved in the 2023 discovery.

The scientists say their findings could provide a valuable new tool to tackle climate change.

Methane is around 80 times more effective at trapping heat than carbon dioxide over a 20-year period. It currently accounts for around a third of global warming and concentrations in the atmosphere have doubled over the last two centuries.

Although reducing carbon pollution, which stays in the atmosphere for hundreds of years, is key to tackling the climate crisis, slashing methane has been seen as something of a low-hanging fruit. It’s relatively short-lived, and cutting levels could have an important impact on reducing global heating in the short-term.

Pete Edwards, an atmospheric chemist at the University of York who was not involved in the research, said the findings were interesting but “very difficult” to confirm. “The use of only formaldehyde observations to infer a mechanism, although novel, does not help address the known uncertainties within our current understanding of atmospheric chemistry,” he told CNN.

The findings could theoretically be used to destroy methane emissions at the source, van Herpen said. They could also inform geoengineering methods — attempts to artificially bring down global temperatures. Iron-based particles could be injected into the atmosphere over the ocean to mimic the chemical process observed in the wake of the eruption and remove methane.

But Edwards urges caution. The study is based on the stratosphere, while this methane removal strategy would happen in the troposphere, he said. The impacts would be difficult to predict, he added, “with potential unintended consequences on climate, air pollution and ecosystem health.”

Emily Dowd, a climate scientist at the University of Leeds, echoed this. “The proposed chemistry still needs to be thoroughly tested in atmospheric models,” she told CNN.

The study authors agree more research needs to be done. “It’s an obvious idea for industry to try to replicate this natural phenomenon ­— but only if it can be proven to be safe and effective,” Johnson said. “Our satellite method could offer a way to help figure out how humans might slow global warming.”

Laura Paddison, CNN