Satellite data from the 2022 Hunga Tonga plume showed chlorine-driven chemistry destroyed about 900 tons of methane a day, giving researchers a rare real-world test of how methane removal might be measured from space.
Formaldehyde lingering in the plume for days pointed to ongoing methane breakdown, and the eruption's unusual setup — 150 meters below sea level, blasting more than 100 million metric tons of salty water aloft — likely supplied the chlorine.
That methane loss was modest against the eruption's estimated 300,000 tons of methane emissions, but the findings, published May 7 in Nature Communications, could help evaluate future methane-removal proposals.
Researchers not involved in the study warned chlorine is far more likely to attack ozone than methane in the stratosphere — about 380 times faster — making chlorine-based geoengineering a risky climate strategy.
Methane drives roughly one-third of current global warming and lasts only about a decade in the atmosphere, but scientists said the priority remains cutting methane and CO2 emissions rather than trying to inject chlorine.
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The Hunga Tonga Eruption’s Double Impact: Record Methane Removal and Ozone Depletion in Earth’s Stratosphere
Overview
The Hunga Tonga–Hunga Ha’apai volcanic eruption on January 15, 2022, created a unique natural experiment in the atmosphere. The eruption injected large amounts of water vapor, ash, and gases high into the stratosphere, which led to two surprising effects: significant destruction of methane and depletion of ozone. Scientists found that volcanic ash helped form highly reactive chlorine atoms, which broke down methane molecules. While the eruption released a large amount of methane, it also removed even more each day, highlighting the complex and unexpected ways volcanic activity can change our atmosphere.