In January 2022, one of the most powerful eruptions in modern history occurred at the South Pacific submarine volcano Hunga Tonga Hunga Ha’apai. But now scientists have discovered that the eruption triggered an unexpected atmospheric reaction that partially removed methane, a powerful greenhouse gas, from the air. Researchers say this discovery could ultimately help scientists develop new strategies to slow global warming.
Scientists used satellite observations to detect unusually high levels of formaldehyde inside the huge plume produced by the eruption. This discovery immediately caught their attention because formaldehyde is produced when methane decomposes in the atmosphere.
“When we analyzed the satellite images, we were surprised to see a cloud containing record concentrations of formaldehyde. We were able to track the cloud all the way to South America for 10 days. Since formaldehyde is only present for a few hours, we found that this cloud must have been continuously destroying methane for more than a week,” explains the study’s lead author, Dr. Maarten van Herpen from Acacia Impact Innovation BV. nature communications.
“While it is known that volcanoes release methane during eruptions, it was not previously known that volcanic ash has the ability to partially clean up this pollution,” he added.
Chemical reactions caused by volcanic ash, sea salt, and sunlight
Researchers believe the eruption activated a rare chemical process previously identified in a completely different environment.
In a previous study published in 2023, scientists found that dust flying from the Sahara Desert across the Atlantic Ocean can combine with salt from sea spray to create tiny particles called iron salt aerosols. When sunlight hits these particles, chlorine atoms are released. These chlorine atoms react with methane and help break it down in the atmosphere. This discovery revolutionized scientists’ understanding of the atmospheric chemistry of the troposphere.
“What’s new and quite surprising is that the same mechanism seems to be occurring in plumes high up in the stratosphere, where the physical conditions are completely different,” says Professor Matthew Johnson of the Department of Chemistry at the University of Copenhagen, one of the researchers on both discoveries.
The Tonga eruption spewed large amounts of salty seawater into the stratosphere along with volcanic ash. Researchers believe that sunlight interacted with this mixture to produce highly reactive chlorine, which helped destroy the methane released during the eruption. The unusually high formaldehyde levels detected by the satellite served as evidence that methane breakdown was occurring.
Scientists say global methane estimates may need revision
The discovery also suggests that scientists may need to reconsider the global methane budget, which estimates how much methane enters and leaves Earth’s atmosphere.
“We now know that dust in the atmosphere, such as from volcanic eruptions, affects the methane budget – how much methane is added to the atmosphere and how much is removed,” says Matthew Johnson.
Why methane is important to climate change
Methane is responsible for about one-third of current global warming. Over 20 years, methane traps about 80 times more heat than CO2. But unlike carbon dioxide, methane does not persist in the atmosphere for centuries. Generally, they break down after about 10 years.
Because methane has a short lifetime in the atmosphere, reducing methane pollution can have relatively quick climate benefits. Scientists sometimes describe methane reduction as an “emergency brake” on climate change. Reducing methane concentrations could slow warming and reduce the risk of climate tipping points within the next decade. However, researchers stress that reducing CO2 emissions remains important for long-term climate stability.
Discovery could provide inspiration for future climate change technologies
The researchers say the discovery could help advance efforts to artificially accelerate the removal of methane from the atmosphere. Scientists around the world are currently investigating several possible approaches, but accurately measuring methane removal remains a major challenge.
“How do you prove that methane has been removed from the atmosphere? How do you know your method works? That’s very difficult. But here we address that problem by showing that the breakdown of methane can actually be observed using satellites,” says the study’s lead author, Dr. Jos de Raat of the Royal Netherlands Meteorological Institute.
The study utilized the TROPOMI instrument aboard the European Space Agency’s Sentinel-5P satellite, which tracks greenhouse gases and air pollution around the world on a daily basis.
“Recovering formaldehyde from TROPOMI in stratospheric volcanic plumes is a significant departure from the instrument’s standard operating conditions. We had to carefully correct for the satellite’s sensitivity to the unusual altitude of the signal and take into account interference from high concentrations of sulfur dioxide. Getting these corrections right was essential to ensure that what we were seeing was real,” said Dr. Isabelle de Smet of the Royal Institute for Aeronautics and Astronautics in Belgium.
Researchers believe this discovery could ultimately lead to practical engineering solutions aimed at reducing methane pollution.
“It makes sense that industry would seek to replicate this natural phenomenon, but only if it can be proven to be safe and effective. Our satellite approach could help us understand how humans can slow global warming,” concluded Matthew Johnson.
About research
- Researchers estimate that the Tonga eruption released approximately 300 gigagrams (Gg) of methane, equivalent to the methane emitted by more than 2 million cows in a year. At the same time, the plume removed approximately 900 megagrams (Mg) of methane per day. This is equivalent to the amount produced by approximately 2 million cows in a day.
- The study was published in the journal Nature Communications.
- The research team included Maarten van Herpen (Acacia Impact Innovation BV, Netherlands); Isabel de Smet (Royal Belgian Institute of Astronautics, Belgium); Daphne Meydan and Alfonso Sais-Lopez (CSIC, Spain). Matthew Johnson (University of Copenhagen, Denmark); Thomas Lockman (University of Utrecht, Netherlands); Jos de Laat (Royal Meteorological Institute of the Netherlands).
- This work was supported by Spark Climate Solutions.
