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

A violent underwater volcanic eruption in the South Pacific last year may have inadvertently provided a novel mechanism for reducing atmospheric methane, a potent greenhouse gas, according to new research published in *Nature Communications*. The eruption of the Hunga Tonga-Hunga Ha’apai volcano in January 2022 was one of the most explosive events of the modern era, unleashing a plume of ash, steam, and gas nearly 40 miles above Earth’s surface. The eruption, hundreds of times more powerful than the Hiroshima nuclear explosion, generated a tsunami and a global sonic boom that circled the planet twice. Yet amid the devastation, scientists have identified an unexpected side effect: a self-cleaning process that appears to break down methane emissions.

Researchers analysing satellite data discovered an unusually large cloud of formaldehyde in the stratosphere, a byproduct typically formed when methane is oxidised in the atmosphere. The study authors suggest that the eruption’s massive injection of water vapour and volcanic ash—enough to fill 58,000 Olympic-sized swimming pools—triggered a chemical reaction similar to one observed over the Atlantic Ocean. In that earlier case, sunlight interacting with iron-rich particles from Saharan dust and sea salt produced chlorine atoms, which then reacted with methane, accelerating its breakdown. The Tonga eruption seems to have replicated this process at an unprecedented altitude.

Maarten van Herpen, a physicist and co-author from Acacia Impact Innovation, noted that the volcano emitted methane while simultaneously destroying it through reactions in the plume. “It has emitted methane and then destroyed these emissions through the particles in the plume,” he explained. Tracking the formaldehyde cloud for 10 days revealed continuous methane destruction, with an estimated 900 tons of methane neutralised daily. The eruption released roughly 330,000 tons of methane in total, though only a fraction was broken down in the stratosphere. Matthew Johnson, a chemistry professor at the University of Copenhagen and another study author, called the finding “new—and completely surprising,” highlighting its potential implications for climate mitigation.

Methane, which is about 80 times more effective at trapping heat than carbon dioxide over a 20-year period, accounts for roughly one-third of current global warming. Its atmospheric concentrations have doubled in the past two centuries, making the discovery of natural methane-removal mechanisms particularly significant. While the Tonga eruption’s impact was temporary, the findings suggest a previously unrecognised pathway for atmospheric methane reduction. Scientists caution that this is not a solution to climate change but could inform future research into enhancing natural methane sinks. Further study is needed to determine whether such processes can be replicated or scaled in ways that meaningfully contribute to reducing greenhouse gas levels.