Volcanic plume removed methane after Hunga Tonga eruption ^{CEFR B1}

In January 2022 the submarine volcano Hunga Tonga–Hunga Ha’apai erupted in the South Pacific. The eruption produced a large plume, and researchers later found that the plume helped remove some of the methane the volcano emitted. Scientists used advanced satellite measurements and detected unusually high concentrations of formaldehyde, which exists in the atmosphere for only a few hours. Tracking the cloud for 10 days as it moved to South America showed methane was being destroyed continuously in the plume, says Maarten van Herpen from Acacia Impact Innovation BV.

Researchers link this discovery to a 2023 finding that Sahara dust mixed with sea salt can form iron salt aerosols; sunlight on those aerosols produces chlorine atoms that react with methane. The new study suggests a similar chemical process occurred in the volcanic plume, even though the plume rose into the stratosphere, where conditions differ, says Professor Matthew Johnson of the University of Copenhagen.

During the eruption large amounts of salty seawater and ash were injected into the stratosphere, and sunlight acting on them may have produced reactive chlorine that helped destroy methane. Methane is responsible for one third of global warming and is about 80 times as potent as CO2 over 20 years, though it typically breaks down within about 10 years. The team used the TROPOMI instrument on ESA’s Sentinel-5P and applied careful corrections for altitude and high sulfur dioxide. The paper appears in Nature Communications and includes researchers from CSIC, Spain and Utrecht University, Netherlands.