Hunga Tonga-Hunga Haʻapai Eruption Cools Southern Hemisphere, Surprising Scientists

The recent findings on the Hunga Tonga-Hunga Haʻapai eruption have shaken long-held assumptions about the atmospheric effects of volcanic activity. A study led by UCLA scientists reveals that, contrary to expectations that the massive eruption in January 2022 would increase global temperatures by introducing large amounts of water vapor into the stratosphere, the eruption actually resulted in a cooling of approximately 0.1°C in the Southern Hemisphere. This unexpected outcome appears to be due to the formation of smaller sulphate aerosols, which effectively reflected sunlight back into space, thus cooling the atmosphere despite the initial influx of water vapor, a known greenhouse gas. Historically, previous volcanic eruptions like Mount Pinatubo have shown a cooling effect on climate due to similar atmospheric interactions. However, this study indicates a more complex dynamic with the interactions among sulphate aerosols, water vapor, and ozone that were not fully considered in previous research. The researchers utilized satellite data to track the atmospheric constituents over time, offering insights into how volcanic eruptions can indeed cool the planet under certain conditions. Ashok Gupta, the study's first author, emphasized the importance of understanding these interactions to inform future geoengineering strategies and the risks they pose. Moreover, the eruption reinforced how ground-level geological events can influence atmospheric phenomena as high as the upper atmosphere, impacting satellite operations and weather predictions worldwide. The discovery of secondary gravity waves as key drivers of atmospheric change during the eruption signifies a crucial linkage between Earth's surface activity and space, which may have implications for satellite safety and climate monitoring. The implications of these findings are profound, especially as they relate to climate change mitigation strategies. The study cautions against geoengineering initiatives that could inadvertently exacerbate climatic issues. Research suggests that our understanding of atmospheric chemistry and dynamics during extreme geological events must be further developed before making large-scale geoengineering decisions that could alter the delicate balance of Earth's climate.