Satellite quantification of enhanced methane oxidation applied to the stratospheric plume following Hunga Tonga-Hunga Ha’apai eruption

A giant underwater blast with climate clues

In early 2022, the Hunga Tonga–Hunga Ha’apai volcano sent a colossal plume high above the clouds, grabbing headlines for its sheer power. This study shows that the eruption also created a rare natural experiment in the sky, revealing how methane—a major greenhouse gas—is destroyed and how future attempts to clean methane from the air might be tracked from space. By following a short‑lived gas called formaldehyde high in the atmosphere, the authors uncovered an unexpectedly strong burst of methane breakdown and a surprising chemical engine driving it.

Why methane in the air matters

Methane traps far more heat than carbon dioxide over a few decades and is responsible for about half a degree of global warming today. The good news is that methane does not last long in the air—roughly ten years—so cutting emissions or speeding up its natural destruction could cool the planet within a decade. The challenge is that not all methane sources can be eliminated, and natural emissions from wetlands and warming landscapes are rising. That has led scientists to explore whether it might be possible to deliberately boost methane removal in the open air, for example by adding chemicals that speed up its breakdown. Any such effort, however, would need reliable methods to prove how much extra methane is actually being destroyed.

Using a volcanic plume as a natural testbed

The Hunga Tonga–Hunga Ha’apai eruption blasted material up to about 55 kilometers high, far into the stratosphere—much higher than typical volcanic plumes. Satellites quickly spotted huge amounts of water vapor, sulfur gases, and fine particles spreading around the globe. The authors focused on a different signal: an unusually large buildup of formaldehyde at around 30 kilometers altitude, far above the layer where this gas is normally found. Using data from the TROPOMI instrument and other satellites, they showed that this formaldehyde was tightly linked to the volcanic aerosol cloud and persisted for at least ten days, even though sunlight should have destroyed any one parcel of formaldehyde within a few hours. The only way to sustain such high levels was for new formaldehyde to be continuously produced inside the plume.

Tracing the fingerprints of methane breakdown

Formaldehyde is a short‑lived stepping stone in the chain of reactions that turn methane into carbon dioxide and water. In remote regions without strong local pollution or fires, almost all formaldehyde comes from methane. By carefully quantifying the extra formaldehyde and how quickly sunlight removes it, the team could back‑calculate how fast methane must have been destroyed in the plume. Their analysis points to about 900 metric tons of methane oxidized per day, with peak local losses of up to 60 parts per billion per day—huge compared with normal stratospheric conditions. That much destruction implies that the eruption injected a large dose of methane high into the atmosphere and that an unusually powerful chemical trigger was at work to attack it.

A hidden chlorine engine in volcanic ash

To explain the rapid methane loss, the researchers looked at other satellite measurements inside the plume, including chlorine‑bearing gases and ozone. They concluded that the methane destruction was driven largely by highly reactive chlorine atoms, rather than by the more familiar hydroxyl radicals alone. Known chlorine‑recycling pathways, and cycles involving bromine, could not generate enough chlorine to match the observations, especially over many days. Instead, the authors propose that fine volcanic ash particles coated with sulfate and sea salt, and containing iron, acted like microscopic chemical reactors. When exposed to sunlight, iron and chloride on these particles can generate bursts of reactive chlorine. Calculations using realistic amounts of iron and particle surface area suggest that this “iron–chloride photochemistry” could plausibly sustain the required chlorine production even high in the stratosphere.

A new way to watch methane removal from space

Beyond explaining an unusual volcanic plume, this work demonstrates a new tool for monitoring how fast methane is being removed from the atmosphere. Because the method tracks formaldehyde using ultraviolet light, it works well over oceans, where many proposed methane‑removal schemes would operate but where direct methane measurements from space are difficult. The authors show that their satellite‑based formaldehyde approach was sensitive enough to detect the Hunga Tonga–driven methane loss, even though it was far smaller than some future engineered interventions being discussed. In plain terms, the study reveals a hidden chemical engine in a spectacular eruption and offers a practical way to verify whether future efforts to scrub methane from the air are actually working.

Citation: van Herpen, M.M., De Smedt, I., Meidan, D. et al. Satellite quantification of enhanced methane oxidation applied to the stratospheric plume following Hunga Tonga-Hunga Ha’apai eruption. Nat Commun 17, 3746 (2026). https://doi.org/10.1038/s41467-026-72191-4

Keywords: methane, volcanic eruption, satellite observations, atmospheric chemistry, climate mitigation