| 11 Aug 2026
Volcanic eruptions alter sky colours in a geoengineered world
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.
With respect to the 1883 Krakatau eruption, I want to make two small comments:
1. The correct spelling is Krakatau, and not Krakatoa. Even though the British spelled it wrong, it should be spelled the way the Indonesians spell the name of their own volcano.
2. I recommend you consider this paper, which is relevant to your paper. One idea, which I support, is that the sky in The Scream was based on what Munch saw after the Krakatau eruption, and the paper goes into detail about volcanic sunsets.
Prata, Fred, Alan Robock, and Richard Hamblyn, 2018: The sky in Edvard Munch’s The Scream. Bull. Amer. Meteorol. Soc., 99, 1377-1390, doi:10.1175/BAMS-D-17-0144.1.