An underwater volcanic eruption in the Pacific Ocean has reshaped scientific understanding of how volcanoes can influence Earth’s atmosphere and climate. A new international assessment has revealed that the 2022 eruption of Hunga Tonga–Hunga Haʻapai sent material to the very edge of space, triggering long-lasting changes in the upper atmosphere and causing cooling rather than warming.
Unlike typical volcanic eruptions that mainly affect land and oceans, this rare event altered atmospheric chemistry, temperature patterns, and air circulation at altitudes rarely reached by volcanoes.
The Hunga Tonga–Hunga Haʻapai volcano erupted in January 2022 from a shallow underwater location in the tropical Pacific. The interaction between magma and seawater caused an unusually violent explosion, propelling ash, gases, and water vapor far higher than most known eruptions.
Satellite observations showed that the volcanic plume reached layers close to space, making it the highest plume ever recorded from a submarine eruption. Scientists relied on satellite data, weather balloons, aircraft measurements, and ground-based monitoring to track how volcanic material spread through the atmosphere over time.
One of the most striking findings of the assessment was the enormous amount of water vapor released by the eruption. Researchers estimate that global stratospheric water vapor levels increased by around 10 percent after the blast, an unprecedented rise.
Much of this excess moisture remains in the upper atmosphere even in 2025, making the eruption’s impact unusually long-lasting. Scientists say no previous volcanic event in modern records has produced such a sustained increase in stratospheric water vapor.
Researchers explained that the water-rich nature of the eruption played a critical role in altering atmospheric behavior, highlighting the importance of global cooperation in monitoring rare climate-altering events.
Most large volcanic eruptions warm the upper atmosphere because dark particles absorb sunlight. However, the Hunga eruption produced the opposite effect. The large amount of water vapor released heat into space, leading to noticeable cooling in the stratosphere.
Measurements indicate temperature drops of about 0.5 to 1 degree Celsius across wide regions of the upper atmosphere, with cooling effects extending into higher layers months later. This behavior stands in sharp contrast to eruptions such as Mount Pinatubo in 1991, which caused temporary global surface cooling driven by sulfur aerosols.
Sulfur dioxide typically drives volcanic climate impacts by forming reflective sulfate particles that block sunlight. While the Hunga eruption released sulfur from magma, most of it was trapped by seawater before reaching the atmosphere.
Only a limited amount of sulfur entered the stratosphere, resulting in much lower sulfate levels than those produced by historic eruptions like Pinatubo. Scientists found that the abundant water vapor caused rapid particle growth, followed by slow settling into lower atmospheric layers.
Despite dramatic changes in the upper atmosphere, Earth’s surface temperatures remained largely unaffected. Scientists estimate that surface cooling reached only about 0.05 degrees Celsius, a change too small to separate from natural climate variability.
Researchers stressed that the eruption did not contribute to the record global warming observed in 2023 and 2024, helping rule out volcanic activity as a driver of recent temperature spikes.
The additional water vapor altered chemical reactions in the upper atmosphere and led to short-term ozone reductions, particularly in parts of the Southern Hemisphere. However, scientists noted that these changes were mainly caused by shifts in air circulation rather than chemical destruction.
Antarctic ozone depletion remained within normal ranges, and researchers said the findings support ongoing international efforts under the Montreal Protocol to protect ozone recovery.
Scientists say the Hunga Tonga eruption has changed how volcanic impacts on the atmosphere are understood, especially for underwater eruptions. Because the water vapor released remains in the stratosphere far longer than sulfur aerosols, the eruption’s effects will linger well beyond those of typical volcanic events.
The study underscores the importance of global collaboration, advanced climate modeling, and continuous atmospheric monitoring to understand rare events that can subtly but significantly influence Earth’s climate system.
The findings have been published in a peer-reviewed scientific journal and continue to guide climate researchers worldwide as they assess both natural and human-driven atmospheric changes.