A report released today by the World Climate Research Programme provides a comprehensive analysis of the atmospheric effects of the January 15, 2022 eruption of the Hunga volcano, the most explosive volcanic 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 Earth’s stratosphere, climate system, and ozone layer. The report’s 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, according to the authors.

Work on the Hunga Volcanic Eruption Atmospheric Impacts Report began in late 2022 and brings together scientists from 21 countries. CIRES researcher Yunqian Zhu led the report with colleagues from the National Center for Atmospheric Research, the University of Leeds, and the University of Maryland, Baltimore County. Lizzy Asher, Ewa Bednarz, and Alex Baron from CIRES also contributed to the report. 

“The Hunga eruption was unlike anything observed before,” Zhu said. “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.”

Key scientific findings

The 2022 Hunga eruption, a high-magnitude submarine explosion, was unique in that it injected vast quantities of water vapor into the stratosphere. The eruption increased global stratospheric water content by about 10 percent, much of which remains in the atmosphere to this day. Unlike past eruptions that have caused stratospheric warming, Hunga’s water vapor led to cooling of the mid-to-upper stratosphere and mesosphere.

"The Hunga volcanic eruption cooled the stratosphere by 0.5-1K, which is in contrast with other previous major volcanic eruptions, where aerosols led to stratospheric warming," said Xin-Yue Wang, a CU Boulder professor of atmospheric and ocean sciences who also contributed to the report. 

However, the report emphasizes that record-high global temperatures in 2023 and 2024 were not due to the eruption. Model simulations indicate that Hunga’s surface cooling influence (about 0.05 degrees Celsius) was indistinguishable from natural climate variability.

The eruption also led to localized ozone depletion in the Southern Hemisphere in the months following, but its overall effects on the Antarctic ozone hole and surface climate were minor.

CIRES and NOAA researchers were able to collect critical observations of the plume just days after the eruption.  

"Our rapid response balloon-borne measurements, taken within one week of the eruption, enabled us to directly observe large water vapor enhancements and a rapidly forming aerosol layer, colocated with ozone anomalies, and verify global climate model simulations of this anomalous event," said CIRES researcher Lizzy Asher. 

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.