The Hunga Volcanic Eruption Atmospheric Impacts Report, released under the Atmospheric Processes and their Role in Climate (APARC) project of the World Climate Research Programme (WCRP), which is co-sponsored by the World Meteorological Organization (WMO), combines satellite, balloon, and ground-based observations with global modeling to track the eruption plume from minutes after the explosion through multiple years. It concludes that the water-rich plume increased global stratospheric water vapor by about 10 percent, with much of this additional moisture still present in 2025.

"This assessment shows how Hunga's water-rich plume reshaped the stratosphere in ways not seen before. It underscores the importance of sustained observations and advanced modelling, and the value of international scientific collaboration through WCRP in delivering robust climate insights," said Tim Naish, Chair of the WCRP's Joint Scientific Committee.

The report notes that international satellite instruments, specialized balloon campaigns, and ground networks captured the evolution of volcanic aerosols, water vapor, and trace gases from the immediate aftermath of the eruption through the following years.

Key scientific findings summarized in the report include that the 15 January 2022 Hunga eruption produced the largest underwater explosion ever recorded by modern scientific instruments and injected large quantities of water vapor into the stratosphere, increasing global stratospheric water by about 10 percent, much of which remains in the atmosphere through 2025. While the eruption perturbed stratospheric ozone in the Southern Hemisphere in the months that followed, the overall effects on the Antarctic ozone hole and on surface climate were minor.

The authors emphasize that record-high global temperatures in 2023 and 2024 were not caused by the Hunga eruption, with model simulations indicating a surface cooling influence of about 0.05 K that is indistinguishable from natural climate variability. The report's seven chapters synthesize findings from observations, data analyses, and climate model simulations, including contributions from the Hunga Tonga-Hunga Haapai Impact Model Observation Comparison (HTHH-MOC) project, an international modeling effort using more than ten global climate models.

Chapter topics include basic eruption information, the evolution of the Hunga cloud on short (less than one month) and multi-year time scales, impacts on atmospheric chemistry and dynamics, changes in the stratospheric ozone layer, upper-atmospheric effects, and surface radiative and temperature responses.

Launched in late 2022, the assessment brought together 159 scientists from 21 countries and was coordinated by Co-Chairs Yunqian Zhu of the University of Colorado Cooperative Institute for Research in Environmental Sciences and NOAA Chemical Sciences Laboratory, William Randel of the National Center for Atmospheric Research, Graham Mann of the University of Leeds, and Paul A. Newman of the University of Maryland-Baltimore County.

"The Hunga eruption was unlike anything observed before," said Yungian Zhu. "It taught us how profoundly water-rich eruptions can affect the stratosphere and how essential global cooperation is in capturing and understanding such rare events".

The report underscores that decades of international investment in atmospheric observation networks enabled rapid and detailed tracking of the Hunga plume, with satellite instruments, balloon measurements, and ground-based networks following volcanic aerosols, water vapor, and trace gases from minutes after the eruption through subsequent years.

At the same time, the assessment warns that future observational gaps arising from potential satellite mission cancellations or aging observing systems could severely limit the world's ability to monitor and understand similar major events.

"This report reflects an extraordinary effort by the global scientific community," said Graham Mann. "It not only documents the impacts of Hunga but also highlights the importance of maintaining our ability to observe the planet's atmosphere".

Supporting datasets, including HTHH-MOC model simulations, will be made publicly available through the Centre for Environmental Data Analysis (CEDA) to support further research on volcanic impacts on atmospheric composition, dynamics, and climate.

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