Scientists stunned as volcano cloud starts destroying methane

In January 2022, the Hunga Tonga-Hunga Ha'apai volcano erupted, producing one of the most powerful volcanic events in recent history. Scientists have now discovered an intriguing consequence of that eruption: the massive volcanic cloud may have assisted in destroying some of the methane gas released by the volcano itself. This finding could have significant implications beyond a single event, as methane is a major contributor to global warming and breaks down much faster than carbon dioxide.

Researchers made this discovery by analyzing satellite images of the eruption's enormous plume. They detected exceptionally high levels of formaldehyde, a chemical byproduct of methane destruction in the atmosphere. Formaldehyde is extremely short-lived, so its presence in such large quantities indicated that methane was being actively broken down. The cloud was tracked for ten days, persisting over South America, which suggested the volcanic plume was continuously destroying methane for over a week.

The study's lead author, Dr. Maarten van Herpen, explained that while volcanoes typically emit methane during eruptions, it was previously unknown that volcanic ash could also help clean up this pollution. The researchers estimated that the eruption released around 300 gigagrams of methane, equivalent to the annual emissions of two million cows. Simultaneously, the plume removed approximately 900 megagrams of methane daily, comparable to the emissions of two million cows.

The researchers believe that the destruction of methane is due to a unique combination of volcanic ash, seawater, and sunlight. A similar process was identified in 2023 when scientists found that Saharan dust mixed with sea salt released by breaking waves to form tiny airborne particles called iron salt aerosols. When exposed to sunlight, these aerosols release chlorine atoms, which can attack methane molecules and help break them apart.

However, this mechanism was previously unknown to occur in volcanic plumes high in the stratosphere, where the conditions are vastly different.

Professor Matthew Johnson, from the University of Copenhagen, noted that the unique conditions of the Hunga Tonga eruption created an ideal environment for this chemical process to occur. The combination of salty seawater blasted upward with volcanic ash and subsequent sunlight striking the mixture likely produced highly reactive chlorine atoms. These chlorine atoms then reacted with methane in the plume, helping to destroy some of the methane released during the eruption.

The researchers detected an extraordinary amount of formaldehyde from space, providing evidence that this process was indeed taking place. Methane currently accounts for about one-third of global warming, despite being far less abundant than carbon dioxide. Over a 20-year period, methane is approximately 80 times more potent than CO2.

Its relatively short atmospheric lifetime of about 10 years makes it an attractive target for rapid climate action. Reducing methane emissions could potentially provide a noticeable climate benefit within a decade, making it an "emergency brake" on climate change. However, reducing methane is not a substitute for reducing carbon dioxide emissions, which are essential for long-term temperature stabilization.

This discovery could inspire researchers and companies to explore deliberate methods of accelerating methane destruction, although proving the effectiveness of such technologies in the atmosphere remains a significant challenge.