Hunga Tonga volcano, photographed during its eruption on 14-15 January 2022 Credit: Tonga Geological Services / ZUMA Press / Zuma / RÉA (Courtesy of Dr Mark Schoeberl)
Widely believed to be responsible for Earth’s extreme heat over the past two years, researchers say the Hunga Tonga eruption actually cooled the climate.
Texas A&M University research examines the climate effects of the 2022 eruption of the Hunga Tonga volcano, finding that it caused cooling, not warming. This contradicts earlier beliefs and highlights the need for continuous satellite data to understand climate dynamics, reinforcing the dominant role of human-induced emissions in climate change.
A joint research team including Texas A&M University atmospheric scientist Dr. Andrew Dessler is investigating the climate effects of the 2022 eruption of the Hunga Tonga volcano, while challenging previous assumptions about its impact.
The remarkable two-day event, which occurred in mid-January 2022, injected massive 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 produced significant cooling effects on the global climate by blocking sunlight with their aerosols. However, the eruption of Hunga Tonga presented a unique scenario: as an underwater volcano, it injected 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 initial speculation that it might be the cause of extreme global warming in 2023 and 2024. Instead, the team’s findings, published July 24 in Journal of Geophysical Research: Atmospheresreveal the opposite: the eruption actually contributed to cooling Earth, like other large volcanic events.
The GOES-17 satellite captured images of an umbrella-type cloud generated by the underwater eruption of the Hunga Tonga-Hunga Ha’apai volcano on January 15, 2022. Crescent-shaped shock waves and numerous flashes of light 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 report, titled “Evolution of Climate Impacts in the Two Years After the Hunga Tonga-Hunga Ha’apai Eruption,” includes insights and analysis from Dessler, a professor in the Texas A&M Department of Atmospheric Sciences and director of the Texas Center for Climate Research ; first author Dr. Mark Schoeberl, chief scientist at the Virginia-based Science and Technology Corporation in Hamburg, Va.; and numerous scientists from the National Aeronautics and Space Administration (NASA).
Their methodology involved parsing NASA and National Oceanic and Atmospheric Administration (NOAA) satellite data for observations of aerosols and water vapor, among other variables, to assess the energy balance of Earth’s climate system. Their analysis revealed that the eruption resulted in more energy leaving the climate system than entering it, thus causing a slight cooling effect.
“Our paper throws cold water on the explanation that the eruption caused the extreme heat in 2023 and 2024,” explained Dessler. “Instead, we should focus primarily on human-caused greenhouse gases as the main cause of warming, with a big help from the ongoing El Niño.”
Implications and future research
According to Dessler, this research has important implications for both scientists and the general public. Ruling out volcanic eruption as the main driver of recent warming, the team’s study reinforces its contention that human-induced greenhouse gas emissions are the main driver of climate change. This focus is particularly relevant given the ongoing debate and misinformation about the causes of global warming.
In addition, Schoeberl says the study highlights the importance of continued investment in satellite measurements of the stratosphere.
“Our understanding of the Hunga Tonga eruption is largely due to investment in stratospheric satellite measurements by NOAA and NASA over the past two decades,” added Schoeberl. “However, we must be cautious about a potential ‘stratospheric data desert’ as some of the most critical instruments are not being replaced.”
Unresolved issues and the way forward
Although this paper answers several important questions, Dessler admits that it simultaneously 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 powerful eruption and the minimal impact of the eruption on the 2023 ozone hole. The 2023 ozone hole refers to significant thinning of the ozone layer over Antarctica, allowing more harmful ultraviolet rays to reach the Earth’s surface. Furthermore, the persistence of stratospheric water vapor beyond what is 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 climate forcing in the two years following the Hunga Tonga-Hunga Ha’apai eruption” by MR Schoeberl, Y. Wang, G. Taha, DJ Zawada, R. Ueyama and A. Dessler, 24 Jul 2024. Journal of Geophysical Research: Atmospheres.
DOI: 10.1029/2024JD041296
