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The Hunga Tonga volcano, photographed during its eruption on January 14-15, 2022. Credit: Tonga Geological Services / ZUMA Press / Zuma / RÉA (Courtesy of Dr. Mark Schoeberl)
Although the Hunga Tonga eruption is widely believed to be responsible for the Earth’s extreme heat over the past two years, researchers say it actually cooled the climate.
Research from Texas A&M University looks at the climate effects of the 2022 eruption of the Hunga Tonga volcano and finds that it caused cooling rather than warming. This contradicts previous beliefs and underscores the need for continued satellite data collection to understand climate dynamics, reinforcing the dominant role of human-induced emissions in climate change.
A collaborative research team, including atmospheric scientist Dr. Andrew Dessler of Texas A&M University, is investigating the climate effects of the 2022 Hunga Tonga volcano eruption, while challenging previously held assumptions about its impact.
The 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 led to 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 potent greenhouse gas, Dessler says there was initial speculation that it could explain extreme global warming in 2023 and 2024. Instead, the results of the team’s research, published July 24 in the journal Geophysical Research Journal: Atmospheresreveal the opposite: the eruption actually contributed to cooling Earth, similar to 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. Also visible are crescent-shaped shock waves and numerous lightning bolts. 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, titled “Evolution of climate forcing during the two years following the Hunga Tonga-Hunga Ha’apai eruption,” includes information 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 Virginia-based Science and Technology Corporation in Hamburg, Virginia; and several scientists at the National Aeronautics and Space Administration (NASA).
Their methodology involved analyzing POT and satellite observations of aerosols and water vapor, among other variables, from the National Oceanic and Atmospheric Administration (NOAA) to estimate the energy balance of Earth’s climate system. Their analysis revealed that the eruption caused more energy to leave the climate system than entered it, inducing the slight cooling effect.
“Our paper debunks the explanation that the eruption caused the extreme heat of 2023 and 2024,” Dessler said. “Instead, we should focus primarily on greenhouse gases from human activities as the main cause of warming, with a big help from the current El Niño phenomenon.”
Implications and future research
According to Dessler, this research has important implications for both scientists and the general public. By ruling out the volcanic eruption as a major factor in recent warming, the team’s study strengthens its argument that human-induced 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.
Schoeberl also says the study underscores the importance of continued investment in satellite-based stratospheric measurements.
“Our understanding of the Hunga Tonga eruption is largely due to the investment in stratospheric satellite measurements made by National Oceanic and Atmospheric Administration “Over the past two decades, we have used a lot of NASA data,” Schoeberl added. “However, we must be cautious about a potential ‘stratospheric data desert,’ as some of the most critical instruments are not being replaced.”
Unresolved questions and the way forward
While this paper answers several important questions, Dessler acknowledges that it also introduces new ones. For example, the researchers highlighted some unresolved issues related to the Hunga Tonga eruption, such as the unexpectedly low levels of sulfur dioxide produced by such a violent eruption and the minimal impact the eruption had on the 2023 ozone hole. The 2023 ozone hole refers to a significant thinning of the ozone layer over Antarctica, allowing more damaging ultraviolet radiation to reach Earth’s surface. In addition, the persistence of water vapor in the stratosphere beyond what models predict suggests 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 highlights the critical need for continued research and accurate data to address the challenges of climate change.
Reference: “Evolution of climate forcing during the two years following the Hunga Tonga-Hunga Ha’apai eruption” by M.R. Schoeberl, Y. Wang, G. Taha, D.J. Zawada, R. Ueyama, and A. Dessler, 24 July 2024, Geophysical Research Journal: Atmospheres.
Research document: 10.1029/2024JD041296
