2025 News & Events

The Hunga Volcanic Eruption Atmospheric Impacts Report, a landmark international scientific assessment, has been released today under the Atmospheric Processes and their Role in Climate (APARC) project of the World Climate Research Programme (WCRP).

The report provides a comprehensive analysis of the atmospheric effects of the 15 January 2022 eruption of the Hunga volcano, the most explosive event of the satellite era. Combining unprecedented satellite, balloon, and ground-based observations with global modeling studies, the report documents the eruption's far-reaching effects on the stratosphere, climate, and ozone.

An Unprecedented Scientific Collaboration

Launched in late 2022, the Hunga assessment report brought together 159 scientists from 21 countries, coordinated by co-chairs Dr. Yunqian Zhu (University of Colorado, Cooperative Institute for Research in Environmental Sciences (CIRES) at the NOAA Chemical Science Laboratory (CSL)), Dr. William Randel (National Center for Atmospheric Research (NCAR)), Dr. Graham Mann (University of Leeds), and Dr. Paul A. Newman (University of Maryland, Baltimore County).

NOAA CSL's Chelsea Thompson provided graphic and layout coordination. CU CIRES researchers at NOAA CSL Alexandre Baron, Ewa M. Bednarz, and Yunqian Zhu served as chapter co-authors and contributing authors, and Eric Jensen contributed as a reviewer.

The report's seven chapters synthesize findings from observations, data analyses, and climate model simulations, including contributions from the Hunga Tonga-Hunga Haʻapai Impact Model Observation Comparison (HTHH-MOC) project – an international modeling effort involving more than ten global climate models. The chapters include basic eruption information, the Hunga cloud evolution on both short (less than 1-month) and multi-year time scales, impacts on atmospheric chemistry and dynamics, the stratospheric ozone layer, upper altitude effects, and surface radiative and temperature effects.

Key Scientific Findings

The 2022 Hunga eruption, a high-magnitude (volcanic explosivity index of 6) submarine explosion, was unique in injecting vast quantities of water vapor into the stratosphere – increasing global stratospheric water by about 10%, much of which remains in the atmosphere through 2025. Unlike past eruptions that caused stratospheric warming, Hunga's water vapor led to 0.5-1 K cooling of the mid-to-upper stratosphere and over 1 K in the mesosphere.

While the eruption perturbed stratospheric ozone in the Southern Hemisphere in the months following the eruption, its overall effects on the Antarctic ozone hole and surface climate were minor. The report emphasizes that record-high global temperatures in 2023-2024 were not caused by the eruption. Model simulations indicate that Hunga's surface cooling influence – about 0.05 K – was indistinguishable from natural climate variability.

A Legacy of Observation and Global Cooperation

The report underscores how decades of international investment in atmospheric observation networks enabled the rapid and detailed tracking of Hunga's plume. Instruments on NASA, NOAA, ESA, CNES, and JAXA satellites, as well as balloon campaigns and ground networks, captured the evolution of volcanic aerosols, water vapor, and trace gases from minutes after the eruption through subsequent years to the present. The report warns, however, that future observational gaps – from potential satellite mission cancellations or aging networks – could severely limit the world's ability to monitor and understand similar major events.

Towards Future Assessments

The Hunga Volcanic Eruption Atmospheric Impacts Report was developed as a three-year APARC activity (2023-2025), designed to precede the UNEP/WMO Scientific Assessment of Ozone Depletion: 2026. The findings provide a crucial reference for understanding volcanic impacts on the atmosphere and climate system in a warming world, and for judging our ability to model these effects.

"The Hunga eruption was unlike anything observed before," said Dr. 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."

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

The supporting datasets, including the HTHH-MOC simulations, will be publicly available through the Centre for Environmental Data Analysis (CEDA). The full report is available from APARC.