The Tonga plume appears to have run the same chemistry, but high in the stratosphere, not near the ocean surface. Because the volcano erupted underwater, it blasted salty seawater upward with the ash. Sunlight striking that salty, dusty mix generated highly reactive chlorine, which then chewed through methane.

"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 of the University of Copenhagen's Department of Chemistry.

The satellite also saw plenty of sulfur dioxide in the plume. That forced the team to recalibrate TROPOMI's sensitivity to formaldehyde at unusual altitudes.

"Retrieving formaldehyde from TROPOMI in a stratospheric volcanic plume is far outside the instrument's standard operating conditions," said Dr. Isabelle De Smedt of the Royal Belgian Institute for Space Aeronomy. "Getting these corrections right was essential to confirm that what we were seeing was real."

Why does destroying methane matter for climate?

Methane drives roughly one-third of today's warming. Though far less abundant than carbon dioxide, methane traps heat about 80 times more efficiently over 20 years. It also disappears faster — usually within about 10 years, while CO₂ lingers far longer.

That short lifetime makes methane an attractive target for quick climate action. Cut methane emissions now and the climate may begin responding within a decade. Researchers sometimes call methane cuts an "emergency brake" on near-term warming, though they warn it cannot replace deep cuts in CO₂.

Could scientists copy the volcano's trick?

The Tonga plume offers a natural proof of concept for atmospheric methane removal — a field that explores whether humans can speed up methane breakdown.

"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."

A major hurdle lies in measurement. Atmospheric methane spreads across the entire globe, so small changes are hard to verify.

"How do you prove that methane has been removed from the atmosphere? How do you know your method works? It's very difficult," said Dr. Jos de Laat of the Royal Netherlands Meteorological Institute, the study's senior author. "But here we address that problem by showing that methane breakdown can in fact be observed using satellites."

How will this change climate accounting?

The methane budget is the ledger scientists use to track methane sources and sinks. Previous estimates have not accounted for the gas-destroying power of mineral dust.

"We now know that atmospheric dust — for example from a volcanic eruption — impacts the methane budget, meaning the budget of how much methane is added to the atmosphere and how much is removed," Johnson said. "Because dust has not previously been taken into account, it is important that we correct the data on which these estimates are based."

The research team included van Herpen, De Smedt, Daphne Meidan, Alfonso Saiz-Lopez, Johnson, Thomas Röckmann, and de Laat. Spark Climate Solutions funded the work.