16 January 2026
The international APARC report on the Hunga volcanic eruption in 2022 provides new insights into the extent to which individual extreme events can change the global atmosphere - and why such processes must be taken into account in climate assessments and political decisions.
Better understanding of atmospheric processes
The eruption of the Hunga Tonga-Hunga Haʽapai submarine volcano in January 2022 was an extraordinary natural event: an explosion with the highest eruption cloud ever observed from space hurled enormous amounts of water vapour into the stratosphere. The 11th report of the international research programme APARC - Atmospheric Processes And their Role in Climate - combines comprehensive satellite, balloon, and ground-based observations with global modelling studies. In these studies, computer models are used to simulate how gases and aerosols spread in the atmosphere and change the processes there. The analyses highlight the complexity of the interaction between chemistry, radiation, and dynamics in the atmosphere and the consequences of this eruption for the stratosphere, the climate, and the ozone layer. Such processes must be understood and correctly classified in order to distinguish natural fluctuations from long-term climate changes.
International cooperation - coordinated by Jülich
More than 150 scientists from over 20 countries were involved in the report, which underwent a rigorous peer review process. The project is part of the World Climate Research Programme (WCRP) and was coordinated by the APARC International Project Office based at Forschungszentrum Jülich. The APARC Office, which is coordinated by Jülich's Institute of Climate and Energy Systems - Stratosphere (ICE-4) and the Jülich Supercomputing Centre, accompanied the project's entire development process over several years.
Jülich was also involved in a scientific capacity: researchers from ICE-4 investigated the state of the stratospheric aerosol layer before the Hunga eruption, which was characterized by several moderate volcanic eruptions and large fires, and thus contributed to the results.
Key findings - and their context
Due to its underwater location, the Hunga eruption injected vast quantities of water vapour into the stratosphere, causing the global water vapour content there to rise by around 10 %. In the first few years after the eruption, this excess led to a cooling of the middle and upper stratosphere and later also of the mesosphere. This is because water vapour at high altitudes increases the radiation of heat into space. This effect was not observed in previous major volcanic eruptions. In the months following the eruption, there were also temporary changes in stratospheric ozone in the southern hemisphere, but overall the effects on the Antarctic ozone hole and the surface climate were minor. And despite the enormous energy released by the eruption, Hunga had no measurable impact on the record-high global temperatures in 2023 and 2024.
Significance for future climate assessments
The findings of the APARC report form an important scientific basis for future international assessments, such as the 2026 Scientific Assessment of Ozone Depletion by the World Meteorological Organization (WMO). Such assessments will inform future political decisions on the protection of the stratospheric ozone layer and the climate, and help to correctly classify extreme natural events in the context of climate change.
The report shows how crucial long-term and reliable atmospheric observations are for achieving this understanding. Decades of international investment have made it possible to track the effects of the Hunga eruption so quickly and in such detail. Measuring instruments on satellites owned by major space and weather organizations, as well as balloon campaigns and ground networks, delivered key data from the first minute of the eruption to the present day.
At the same time, the report makes it clear that the observation infrastructure in atmospheric research is under pressure - on the one hand from possible cuts in funding for satellite missions, and on the other from ageing measuring instruments and networks. Without continuous measurements, fundamental changes in the atmosphere could go unnoticed in the future and similar major events could no longer be adequately monitored. This would also mean the loss of an important scientific basis for climate assessments and political decisions.
Original Publication
APARC, 2025: The Hunga Volcanic Eruption Atmospheric Impacts Report. Yunqian Zhu, Graham Mann, Paul A. Newman, and William Randel (Eds.), APARC Report No. 11, WCRP-10/2025, doi: 10.34734/FZJ-2025-05237, available at www.aparc-climate.org/publications/
