New research from a collaborative team, including Texas A&M University atmospheric scientist Dr. Andrew Dessler, is challenging existing assumptions about the climate impact of the 2022 Hunga Tonga volcano eruption. The study explores how this significant event, which injected vast amounts of volcanic aerosols and water vapor into the atmosphere, has affected the global climate, particularly the extreme warmth observed in 2023 and 2024.
The Hunga Tonga-Hunga Ha’apai eruption in mid-January 2022 was a remarkable two-day event that introduced unprecedented amounts of water vapor into the stratosphere. Unlike typical volcanic eruptions that primarily eject ash and sulfur dioxide, leading to cooling by blocking sunlight, the submarine nature of Hunga Tonga resulted in an approximately 10% increase in stratospheric water vapor, a potent greenhouse gas.
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Initially, there was speculation that this water vapor might contribute to the extreme global warmth experienced in 2023 and 2024. However, the team’s research, published on July 24 in the Journal of Geophysical Research: Atmospheres, suggests the opposite. The study, titled “Evolution of the Climate Forcing During the Two Years after the Hunga Tonga-Hunga Ha’apai Eruption,” reveals that the eruption actually contributed to cooling the Earth.
Dr. Dessler and his colleagues, including first author Dr. Mark Schoeberl, chief scientist at the Virginia-based Science and Technology Corporation, and multiple NASA scientists, analyzed data from NASA and the National Oceanic and Atmospheric Administration (NOAA). Their methodology involved examining satellite observations of aerosols and water vapor to estimate the Earth’s climate system’s energy balance.
The analysis showed that the eruption caused more energy to leave the climate system than to enter it, thereby inducing a slight cooling effect. This finding contradicts the initial hypothesis that the eruption was responsible for the extreme warmth in 2023 and 2024.
“Our paper pours cold water on the explanation that the eruption caused the extreme warmth of 2023 and 2024,” Dessler explained. “Instead, we need to focus primarily on greenhouse gases from human activities as the main cause of the warming, with a big assist from the ongoing El Niño.”
This research carries significant implications for both scientists and the general public. By dismissing the volcanic eruption as a major factor in recent warming, the study reinforces the view that human-induced greenhouse gas emissions are the primary driver of climate change. This focus is crucial in addressing the ongoing debate and misinformation about the causes of global warming.
Dr. Schoeberl emphasized the importance of continued investment in satellite-based stratospheric measurements. “Our understanding of the Hunga Tonga eruption is largely thanks to the investment in stratospheric satellite measurements by NOAA and NASA over the past two decades,” he noted. “However, we need to be cautious about a potential ‘stratospheric data desert,’ as some of the most critical instruments are not being replaced.”
While the study answers several important questions, it also raises new ones. 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 over Antarctica.
The persistence of water vapor in the stratosphere beyond what was predicted by models suggests there is still much to learn about stratospheric circulation processes. The 2023 ozone hole refers to a significant thinning of the ozone layer over Antarctica, which allows more harmful UV radiation to reach the Earth’s surface.
As scientists continue to investigate these phenomena, the team’s work underscores the critical need for precise data and ongoing research to address the complexities of climate change. “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,” Schoeberl added.
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