A study published in Nature Communications has documented a novel chemical process in the January 2022 eruption of the Hunga Tonga-Hunga Ha'apai volcano that destroyed atmospheric methane at a significant rate. Researchers observed that while the eruption released approximately 300 gigagrams (Gg) of methane, a separate chemical mechanism removed roughly 900 megagrams (Mg) of methane per day from the volcanic plume.
Mechanism of Methane Breakdown
The study identifies a chemical process involving iron salt aerosols. According to the researchers, volcanic ash mixed with sea salt forms particles that, upon exposure to sunlight, produce chlorine atoms. These chlorine atoms then react with and break down methane molecules.
This mechanism was first observed over the Atlantic Ocean in 2023, involving Sahara dust and sea spray. The new research demonstrates that the same process occurs in the stratosphere under different conditions.
Satellite Observations
Using the TROPOMI instrument aboard the Sentinel-5P satellite, scientists tracked the volcanic plume for ten days. The satellite detected unusually high concentrations of formaldehyde within the plume. Because formaldehyde has a short atmospheric lifespan (approximately a few hours), its sustained presence indicated continuous methane destruction.
Key Statements from the Research Team
Dr. Maarten van Herpen (Acacia Impact Innovation BV, lead author):
"When we analyzed the satellite images, we were surprised to see a cloud with a record-high concentration of formaldehyde. Because formaldehyde only exists for a few hours, this showed that the cloud must have been destroying methane continuously for more than a week."
Professor Matthew Johnson (University of Copenhagen, co-author):
"What is new—and completely surprising—is that the same mechanism appears to occur in a volcanic plume high up in the stratosphere."
Dr. Jos de Laat (Royal Netherlands Meteorological Institute, senior author):
"How do you prove that methane has been removed from the atmosphere? ... Here we address that problem by showing that methane breakdown can in fact be observed using satellites."
Background on Methane's Climate Role
Methane is a potent greenhouse gas responsible for approximately one-third of current global warming. Over a 20-year period, methane traps roughly 80 times more heat than carbon dioxide, though it breaks down in the atmosphere in about 10 years.
Broader Implications
The findings may require revision of the global methane budget to account for methane destruction from natural sources such as dust from volcanic eruptions.
Researchers noted the discovery could inform methods to artificially accelerate methane breakdown, with satellite observation providing a means to verify the effectiveness of such interventions.
Scientists also stated that reducing methane emissions could have a noticeable climate impact within a decade.