Scientists stunned as volcano cloud starts destroying methane
A January 2022 eruption of Hunga Tonga released huge amounts of methane, but satellite data revealed that the volcanic plume also helped destroy some of that gas. The process involves ash, sea salt, and sunlight producing reactive chlorine that breaks methane apart, a finding that could reshape met…
In January 2022, the Hunga Tonga‑Hunga Ha’apai volcano erupted beneath the South Pacific, sending a massive plume of ash, gases, and seawater vapor high into the atmosphere. While the event was already noted for its explosive power, recent satellite observations have uncovered a surprising side effect: the plume may have actively destroyed a portion of the methane it released.
What Happened in the Cloud?
Using data from the European Space Agency’s Sentinel‑5P satellite, researchers tracked unusually high levels of formaldehyde—a short‑lived by‑product of methane breakdown—within the volcanic cloud. Formaldehyde appears only briefly when methane molecules are attacked by reactive species, so its presence indicates that methane destruction was occurring continuously for more than a week as the plume drifted toward South America.
The scientists estimated that the eruption released roughly 300 gigagrams of methane, comparable to the annual emissions of over two million dairy cows. At the same time, the plume removed about 900 megagrams of methane each day—an amount equivalent to the daily emissions of the same number of cows—through the chlorine‑driven chemistry that the study proposes.
How Does Ash Turn Into a Methane Cleaner?
The key to the reaction lies in the combination of volcanic ash, seawater salt, and sunlight. When ash particles mix with sea salt released by breaking waves, they form iron‑salt aerosols. Sunlight striking these aerosols releases chlorine atoms, which are highly reactive and can attack methane molecules, breaking them into smaller, less potent compounds.
Earlier work in 2023 had shown a similar process in the Atlantic, where Saharan dust interacted with sea spray. The Hunga Tonga eruption created ideal conditions for this chemistry at much higher altitudes, in the stratosphere, where the ash and salt were carried upward by the explosive force of the eruption.
Why Is Methane Destruction Important?
Methane is a potent greenhouse gas, about 80 times more effective than carbon dioxide over a 20‑year period. It also has a relatively short atmospheric lifetime—around ten years—making it a prime target for rapid climate action. If natural processes can accelerate methane removal, they could serve as an “emergency brake” on warming while longer‑term solutions to reduce CO₂ are pursued.
However, scientists caution that methane reduction is not a substitute for cutting carbon dioxide. Long‑term climate stability still depends on major CO₂ cuts.
What Could This Mean for Future Climate Strategies?
The discovery suggests that atmospheric dust—especially from volcanic eruptions—has been under‑accounted for in global methane budgets. Incorporating this process could alter estimates of how much methane is removed each year and refine climate models.
Researchers are also exploring whether the natural chemistry observed after Hunga Tonga could be replicated deliberately. While the idea of engineering atmospheric chemistry is controversial and would require rigorous safety testing, the volcanic plume provides a real‑world example of large‑scale methane destruction that could guide future mitigation research.
How Was the Data Obtained?
The study relied on TROPOMI, an advanced instrument on Sentinel‑5P that scans Earth’s atmosphere daily. Detecting formaldehyde in a stratospheric volcanic plume pushed the instrument beyond its usual operating conditions, requiring careful calibration to account for high sulfur dioxide levels and the plume’s altitude. The corrections confirmed that the formaldehyde signal was genuine and could be used to track methane breakdown.
Lead author Dr. Maarten van Herpen and collaborators from institutions across Europe and the Americas published their findings in Nature Communications, with support from Spark Climate Solutions.
While the eruption’s direct impact on global methane levels is modest, the study opens new avenues for understanding how natural processes can influence greenhouse gas concentrations and highlights the need for comprehensive methane budgets that include dust‑driven chemistry.
Why it matters
The finding shows that volcanic ash can accelerate methane destruction, a gas that drives near‑term warming. This insight could refine climate models and inspire engineered solutions to reduce atmospheric methane faster.
Key points
- Hunga Tonga eruption released ~300 Gg methane, but plume also destroyed ~900 Mg/day
- Formaldehyde detected as a marker of methane breakdown
- Ash‑salt‑sunlight chemistry releases chlorine that attacks methane
- Dust‑driven methane removal may need inclusion in global budgets
- Potential for engineered atmospheric methane removal inspired by natural process
Frequently asked questions
What is formaldehyde and why is it significant?
Formaldehyde is a short‑lived by‑product of methane breakdown. High levels in the plume indicate active methane destruction.
Can we replicate this process to reduce methane?
Scientists are exploring the idea, but any engineered approach would require extensive safety and efficacy testing.
Does this mean volcanic eruptions help the climate?
While the process can remove methane, the overall climate impact of eruptions is complex and includes cooling from aerosols and warming from greenhouse gases.
