Hunga Tonga volcano, photographed during its eruption on 14-15 January 2022. Credit: Tonga Geological Services / ZUMA Press / Zuma / REA (Courtesy of Dr Mark Schoeberl)
Believed to be responsible for the extreme heat observed on Earth over the past two years, researchers say the Hunga Tonga eruption has actually cooled the climate.
Research from Texas A&M University is studying the climate effects of the 2022 eruption of Hunga Tonga volcano, showing that it caused cooling rather than warming. These findings contradict previously held beliefs and highlight the need for continuous satellite data to understand climate dynamics, reinforcing the dominant role of human-caused emissions in climate change.
A collaborative research team, including Dr. Andrew Dessler, an atmospheric scientist at Texas A&M University, is studying the climate effects of the 2022 eruption of Hunga Tonga volcano, simultaneously challenging previously held assumptions about its impact.
This remarkable two-day event, which occurred in mid-January 2022, injected large amounts of volcanic aerosols and water vapor into the atmosphere. Historically, large volcanic eruptions such as Tambora in 1815 and Mount Pinatubo in 1991 have had significant cooling effects on the global climate by blocking sunlight with their aerosols. However, the Hunga Tonga eruption presented a unique scenario: as a submarine volcano, it introduced an unprecedented amount of water vapor into the stratosphere, increasing the total stratospheric water content by about 10%.
Because water vapor is a powerful greenhouse gas, Dessler says there was initially speculation that it could be responsible for the planet’s extreme heat in 2023 and 2024. Instead, the team’s research results, published July 24 in the Journal of Geophysical Research: Atmospheresreveal the opposite: the eruption actually contributed to cooling Earth, like other major volcanic events.
The GOES-17 satellite captured images of an umbrella cloud generated by the submarine eruption of the Hunga Tonga-Hunga Ha’apai volcano on January 15, 2022. Crescent-shaped shock waves and numerous lightning flashes are also visible. Credit: NASA Earth Observatory image by Joshua Stevens using GOES imagery courtesy of NOAA and NESDIS
The cooling effect of a volcanic eruption
The team’s paper, “Evolution of the Climate Forcing During the Two Years After the Hunga Tonga-Hunga Ha’apai Eruption,” includes insights and analysis from Dessler, a professor in the Department of Atmospheric Sciences at Texas A&M and director of the Texas Center for Climate Studies; first author Dr. Mark Schoeberl, chief scientist at the Science and Technology Corporation, based in Hamburg, Virginia; and several scientists from the National Aeronautics and Space Administration (NASA).
Their methodology consisted of analyzing NASA and National Oceanic and Atmospheric Administration (NOAA) satellite observations of aerosols and water vapor, among other variables, to estimate the energy budget of Earth’s climate system. Their analysis found that the eruption caused more energy to flow out of the climate system than it did into it, resulting in a slight cooling effect.
“Our paper casts a chill on the explanation that the eruption caused the extreme heat of 2023 and 2024,” Dessler says. “Instead, we should focus primarily on greenhouse gases from human activities as the main cause of the warming, with a significant boost from the ongoing El Niño.”
Implications and future research
Dessler says the research has important implications for scientists and the general public. By ruling out volcanic eruption as a major factor in recent global warming, the team’s study reinforces their view that human-caused greenhouse gas emissions are the primary driver of climate change. This approach is particularly relevant given the ongoing debate and misinformation about the causes of global warming.
Additionally, Schoeberl says the study underscores the importance of continued investment in satellite stratospheric measurements.
“Our understanding of the Hunga Tonga eruption is largely due to investment in stratospheric satellite measurements by NOAA “We have learned a lot about astronautics and NASA over the past two decades,” Schoeberl added. “However, we must be cautious about a potential ‘stratospheric data desert’ as some of the most critical instruments are not replaced.”
Unresolved issues and the way forward
While this paper answers several important questions, Dessler acknowledges that it simultaneously introduces new ones. For example, the researchers highlighted some unresolved issues related to the Hunga Tonga eruption, such as the surprisingly low levels of sulfur dioxide produced by such a violent eruption and the eruption’s minimal impact on the 2023 ozone hole. The 2023 ozone hole refers to a significant thinning of the ozone layer over Antarctica, allowing more harmful UV radiation to reach the Earth’s surface. Additionally, the persistence of water vapor in the stratosphere beyond what was predicted by models suggests that there is still much to learn about stratospheric circulation processes.
As scientists work to resolve ongoing questions and deepen our understanding of the stratosphere, Schoeberl says the team’s work underscores the critical need for continued research and accurate data to address the challenges of climate change.
Reference: “Evolution of the Climate Forcing During the Two Years After the Hunga Tonga-Hunga Ha’apai Eruption” by MR Schoeberl, Y. Wang, G. Taha, DJ Zawada, R. Ueyama and A. Dessler, July 24, 2024, Journal of Geophysical Research: Atmospheres.
DOI: 10.1029/2024JD041296
