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Scientists identified, after the Tonga submarine eruption in January 2022, a rare atmospheric reaction capable of destroying part of the methane in the volcanic plume, a discovery that could revise climate calculations and guide new forms of satellite monitoring.
The submarine eruption of Hunga Tonga-Hunga Ha’apai in January 2022, in the South Pacific, triggered an unexpected atmospheric reaction capable of partially removing methane from the atmosphere. The discovery, published in Nature Communications, surprised scientists by revealing record levels of formaldehyde in the volcanic plume.
Formaldehyde drew attention because it appears when methane decomposes in the atmosphere. Satellite observations showed a cloud with an unusual concentration of the substance, tracked for 10 days to South America, despite formaldehyde existing for only a few hours.
Methane was destroyed by an unexpected reaction in the volcanic plume
The prolonged presence of formaldehyde indicated that the volcanic cloud was continuously destroying methane for more than a week. This finding was made after analyses of satellite images conducted by researchers involved in the study.
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The Tonga eruption was already considered one of the most powerful in modern history. Now, the episode is also being observed as a rare case of interaction between volcanic ash, saltwater, sunlight, and atmospheric gases.
Volcanoes are known to emit methane during eruptions. The novelty is the possibility that volcanic ash may also contribute to partially cleaning up this pollution, something that had not yet been identified in this type of environment.
Researchers link the phenomenon to a chemical process previously observed in another scenario. In 2023, scientists had identified a similar reaction involving Sahara Desert dust, sea salt, and sunlight over the Atlantic Ocean.
In this process, dust combines with sea salt to form iron salt aerosols. Under the action of sunlight, these particles release chlorine atoms, which react with methane and help decompose the gas in the atmosphere.
Ash, sea salt, and sunlight explain the phenomenon
The unexpected point was finding a similar mechanism in the high stratosphere, within a volcanic plume. The physical conditions of this environment are totally different from those observed in the troposphere over the Atlantic.
During the Tonga eruption, large quantities of saltwater were launched into the stratosphere along with volcanic ash. The interaction of this mixture with sunlight would have created highly reactive chlorine.
This chlorine helped destroy the methane released during the eruption itself. The elevated levels of formaldehyde detected by satellites served as a direct signal that methane decomposition was underway.
The discovery may also affect global estimates of the methane balance. This balance measures how much of the gas enters and leaves the Earth’s atmosphere, forming the basis of calculations used by scientists to track the presence of the pollutant.
Atmospheric dust, including that generated by volcanic eruptions, had not been considered in these calculations. Therefore, researchers advocate for corrections to the data used to estimate methane input and removal.
The topic has climate relevance because methane accounts for about one-third of current global warming. Over a 20-year period, it traps approximately 80 times more heat than carbon dioxide.
Unlike CO₂, methane does not remain in the atmosphere for centuries. Its decomposition usually occurs in about 10 years, making its reduction a possible climate response with faster effects.
Methane reduction can have a faster climate impact
Reducing methane pollution could produce climate benefits in a relatively short timeframe. Scientists describe this strategy as a kind of “emergency brake” for climate change.
Decreasing methane levels could help slow warming in the next decade. It could also reduce risks associated with climate tipping points, although researchers emphasize that cutting CO₂ emissions remains essential for long-term climate stability.
The team believes the discovery could stimulate efforts to artificially accelerate the removal of methane from the atmosphere. Various approaches are being explored by scientists, but proving the effective removal of the gas is still a challenge.
The study showed that methane decomposition can be observed by satellites. This monitoring capability is considered important for evaluating whether eventual removal methods actually work.
The research used data from the TROPOMI instrument, installed on the European Space Agency’s Sentinel-5P satellite. The equipment daily monitors greenhouse gases and air pollution on a global scale.
The detection of formaldehyde in a stratospheric volcanic plume required careful corrections. The satellite’s sensitivity needed to be adjusted to the unusual altitude of the signal, in addition to considering interference from high concentrations of sulfur dioxide.
These corrections were fundamental to confirm that the observed signal was real. The analysis allowed validating the presence of formaldehyde and relating it to the destruction of methane within the volcanic plume.
Study points to numbers from the Tonga eruption
Researchers estimate that the Tonga eruption released approximately 300 gigagrams of methane. This amount is comparable to the annual methane emissions produced by more than two million cows.
At the same time, the volcanic plume removed about 900 megagrams of methane per day. This volume is equivalent to the daily emissions of approximately two million cows, according to the estimates presented in the study.
The possibility of replicating this natural phenomenon sparks interest for future engineering solutions. Scientists emphasize, however, that any attempt would depend on proof of safety and effectiveness.
The research was published in the journal Nature Communications. The team included Maarten van Herpen, Isabelle De Smedt, Daphne Meidan, Alfonso Saiz-Lopez, Matthew Johnson, Thomas Röckmann, and Jos de Laat.
The authors are affiliated with institutions in the Netherlands, Belgium, Spain, Denmark, and other European centers. The work was supported by Spark Climate Solutions and reinforces the role of satellite monitoring in the study of methane.
Materials provided by the University of Copenhagen.
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