Tonga Meteorological Services
The eruption in 2022 triggered a rare chemical reaction of highly reactive chlorine radicals that destroyed methane in the atmosphere.
Scientists studying the massive 2022 eruption of the Hunga Tonga-Hunga Ha’apai volcano have discovered a atmospheric phenomenon never before observedwhich can help researchers better understand how greenhouse gases naturally break down in the atmosphere.
The underwater volcanic eruption in the South Pacific was one of the most powerful recorded in recent decades, releasing huge clouds of ash, seawater vapor and gases into the atmosphere. Although the eruption caused widespread disruption, researchers now believe it also triggered a rare chemical reaction capable of destroying methane — one of the most potent greenhouse gases in the world.
One, published in the journal Nature Communications, detected unusually high levels of formaldehyde in the volcanic plume using satellite observations. Formaldehyde is a byproduct formed when methane breaks down through chemical oxidation, providing what scientists describe as direct evidence that methane was being rapidly destroyed within the plume, says the .
“It is known that volcanoes emit methane during eruptionsbut until now it was not known that volcanic ash is also capable of partially cleaning up this pollution,” said atmospheric scientist Maarten van Herpen from Acacia Impact Innovation BV in the Netherlands, lead author of the study.
Methane exists naturally in the Earth’s atmosphere and plays an important role in regulating the planet’s temperature. However, excessive methane emissions from human activity, including agriculture and fossil fuel extraction, contribute significantly to global warmingbecause the gas retains heat much more effectively than carbon dioxide over shorter periods of time.
Researchers believe that the eruption of the Hunga Tonga volcano created ideal conditions for the destruction of methane. The volcano erupted beneath the Pacific Ocean, spewing seawater, salt particles, mineral aerosols and methane into the upper atmosphere. When sunlight interacted with this mixture, scientists believe it likely generated highly reactive chlorine radicals.
These chlorine compounds can trigger a chain reaction that breaks down methane molecules, ultimately producing compounds like formaldehyde.
Satellite data showed the formaldehyde-rich cloud drifting in the atmosphere for more than 10 daysfinally reaching South America. As formaldehyde survives only a few hours in the atmosphere, researchers concluded that the destruction of methane must have occurred continuously within the volcanic plume during this period.
Although the reaction has destroyed about 900 metric tons of methane per dayresearchers note that the volcano itself emitted much larger amounts of the gas — about 330 kilotons in total — meaning the eruption didn’t come close to offsetting its own emissions.
Still, scientists say the findings are important because they provide evidence that removing methane through chlorine oxidation can occur naturally and be measured directly in the atmosphere.
