University of St Andrews
Earth and Environmental Sciences

Tracing how volcanic sulphur shapes global cooling

Large volcanic eruptions can cool the planet by sending sulphur high into the atmosphere. There, sulphur gases oxidise to form sulphate aerosols that reflect incoming sunlight. However, climate models assume that volcanic sulphur dioxide is oxidized entirely by OH radicals but recent work suggests that OH can be depleted and that alternative pathways may be critical. This weakens our ability to predict how long sulfur aerosols remain in the atmosphere and the impact of anthropogenic and volcanic sulfur emissions on climate.

Ally’s project will investigate the atmospheric chemistry of six major volcanic eruptions by combining sulphur measurements from volcanic rocks with isotope records from Greenland ice cores. Volcanic rocks will reveal how much sulphur was released and its isotopic signature, while ice cores will provide evidence of how it was processed in the atmosphere. Using isotope modelling, the research will identify which chemical pathways best explain these records and how they vary between eruptions.

The findings could improve how sulphur oxidation and aerosol formation are represented in climate models, moving beyond existing approaches that focus primarily on a single chemical pathway. This could strengthen predictions of the climate impacts of future volcanic eruptions, with wider relevance for understanding human-caused aerosol emissions and assessing climate intervention strategies.