Volcanic eruptions alter sky colours in a geoengineered world - Preprint

[Geoengineering News]

https://egusphere.copernicus.org/preprints/2026/egusphere-2026-3347/

Authors: Anna Lange, Ilaria Quaglia, Daniele Visioni, Alexei Rozanov, and Christian von Savigny

11 August 2026

Abstract

This study examines sky colour changes in a geoengineered world following a volcanic eruption, combining CESM2-(WACCM6) climate model simulations, SCIATRAN radiative transfer calculations, and colour modelling. Bridging a gap in existing research, this is the first study to analyse how sky colours respond when a volcanic eruption occurs in the context of an ongoing stratospheric aerosol injection (SAI) deployment. The SAI experiments consist of simulations with feedback-controlled sulphur dioxide injections amounting to 7.5 Tg per year at the time of the volcanic eruption, with eruption magnitudes of 10 and 50 Tg sulphur dioxide. The results show several optical phenomena, including Bishop's Rings near the solar horizon, anomalous greenish twilight colouration, and pronounced purple light. The latter is consistent with prior findings linking vivid purple colours to elevated aerosol loading. Despite variations in SAI scenario design, with Northern Hemisphere suspension in one scenario and complete suspension in the other, no significant differences in sky colour were found between the scenarios, months, and latitude investigated following the volcanic eruption with a magnitude of 10 Tg sulphur dioxide.

Source: EGUsphere