Role of stratospheric water vapor in long-term atmospheric chemistry and dynamics

Develop a detailed understanding of how stratospheric water vapor modulates long-term atmospheric chemistry and dynamics, particularly in the aftermath of major volcanic eruptions that inject substantial water into the stratosphere.

Background

The paper considers the possibility that recent temperature anomalies may have been influenced by volcanic activity, including aerosol and water vapor injections into the stratosphere. While the temporal sequence of cooling by aerosols and subsequent warming by stratospheric water vapor is noted, the authors emphasize that current understanding is incomplete.

Specifically, they point out that a comprehensive, mechanistic understanding of stratospheric water vapor’s role in modulating long-term atmospheric chemistry and dynamics is still lacking, underscoring the need for improved models and observational constraints.

References

While the expected time-ordering of a cooling effect of aerosols through the first months after eruption and the warming effect of water vapour in the following years would fit well to the steep temperature increase in 2023-24, and the slow decline in 2025, a detailed understanding of the role of stratospheric water vapor in modulating long-term atmospheric chemistry and dynamics is still pending.

— Solar and anthropogenic climate drivers: an updated regression model and refined forecast  (2601.11285 - Stefani, 16 Jan 2026) in Introduction, footnote on volcanic impacts and recent temperature anomalies (following discussion of the Hunga eruption and references to Bednarz et al. 2025 and APARC 2025)