Volcano plume from Hunga Tonga tracked methane cleanup over 10 days
Scientists found that the January 2022 Hunga Tonga–Hunga Ha'apai volcano eruption sent a plume across the South Pacific that carried record-high formaldehyde and kept changing as it moved toward South America. Maarten van Herpen, a researcher at Acacia Impact Innovation BV, said satellites showed the cloud was destroying methane for more than a week.
Hunga Tonga plume over South America
Van Herpen said: “When we analyzed the satellite images, we were surprised to see a cloud with a record-high concentration of formaldehyde. We were able to track the cloud for 10 days, all the way to South America. Because formaldehyde only exists for a few hours, this showed that the cloud must have been destroying methane continuously for more than a week.” The plume was tracked for 10 days, giving researchers a rare view of chemistry inside a moving volcanic cloud.
The same eruption that drove the plume into the stratosphere also hurled enormous amounts of salty seawater into the air with volcanic ash. Researchers think sunlight hitting that mixture formed highly reactive chlorine that helped break down methane released during the eruption. Formaldehyde forms as a short-lived intermediate when methane is destroyed in the atmosphere, so the satellite signal pointed to an ongoing cleanup process inside the cloud rather than a one-time reaction.
Matthew Johnson and the earlier 2023 finding
Matthew Johnson, a professor in the Department of Chemistry at the University of Copenhagen and one of the researchers behind both discoveries, said: “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,” The finding builds on a related process first discovered in 2023, when Sahara dust mixed with sea salt from sea spray over the Atlantic Ocean to form iron salt aerosols that produced chlorine atoms after sunlight hit them.
Van Herpen also said: “It is known that volcanoes emit methane during eruptions, but until now it was not known that volcanic ash is also capable of partially cleaning up this pollution.” The study was published in Nature Communications. Researchers say methane is responsible for one third of global warming, about 80 times as potent as CO2 over a 20-year period, and it typically breaks down within about 10 years.
Nature Communications findings
The January 2022 eruption of Hunga Tonga–Hunga Ha'apai in the South Pacific was described as one of the most violent volcanic eruptions in modern times, but the new result focuses on a less obvious outcome: the plume did not just carry pollution into the atmosphere, it also appeared to destroy some of the methane inside it. Researchers say methane reduction can act as an emergency brake on climate change, while reducing CO2 emissions remains essential to stabilize temperatures in the long term.
For readers, the practical takeaway is narrow but important: the plume gave scientists a real-world test of how ash, seawater, and sunlight can alter methane in the stratosphere, and the published findings now point to a possible route for further study. The next step is not a policy switch or a rapid fix, but more work on whether this same chemistry can be measured elsewhere and whether it can help explain how atmospheric methane breaks down after unusual eruptions.
