New SPARC activity on Hunga-Tonga stratospheric impacts

The Hunga Tonga-Hunga Haʻapai (HTHH)eruption in 2022 was the most explosive volcanic eruption in the satellite era, and the water-rich plume presents an opportunity to understand the impacts on the stratosphere of a large magnitude explosive phreatic eruption. The wide range of satellite observations of the early stratospheric plume and its dispersion to mid-latitudes will provide measurements to evaluate a range of models for their capabilities to represent stratospheric chemistry, aerosol and dynamics, in this case where both water vapour and aerosol are causing stratospheric ozone and radiative effects.

There are numerous HTHH eruption observational and modeling studies that have been published, preprints of submitted papers, and new research in early stages. As the plume continues to evolve and its impacts emerge, additional papers will be published. Because of the number and broad range of studies of the HTHH emissions and impacts, an international effort is required to provide a synthesis of studies in the published literature for the broader community and to coordinate multi-model assessments.

To do so, SPARC is welcoming a new Limited-Term Cross-Activity Focused Project in its portfolio of activities:

The new “Hunga-Tonga stratospheric impacts” SPARC activity, convening a team to co-ordinate and then write a special Hunga-Tonga impacts report, for publication in late-2025.

The report will directly feed into the upcoming 2026 UNEP/WMO Scientific Assessment of Ozone Depletion report, providing a benchmark synthesis of the impacts from the eruption. The HTHH SPARC activity will include defining a set of coordinated multi-model experiments for the report, coordinating with a number of existing community modelling activities to define potential modelling contributions to each chapter of the report (see outline structure). The report’s chapters will present consensus findings across both observational and modeling activities spanning a range of timescales, and provide knowledge for policy makers.

The activity is lead by Paul A. Newman, Bill Randel, Graham Mann and Yunqian Zhu.