European Palaeobotany and Palynology Conference 2026

Solar Energetic Particle (SEP) events can deplete stratospheric ozone and elevate surface UV-B radiation. The 774/775 CE event was the most extreme SEP of the past 11,000 years, yet evidence of its biological impact remains lacking. Here we present an unprecedented annually resolved reconstruction of variations in surface UV-B variability as detected via the analysis of UV-B absorbing compounds (UACs) from Pinus pollen recovered from varved lake sediments.

The record, spanning 764–783 CE, captures a sinusoidal pattern consistent with Schwabe cycle-modulated surface UV-B variability. Superimposed on this signal is an abrupt increase in UAC abundance in pollen recovered from samples dated to 776–777 CE, coinciding with 14C and 10Be anomalies associated with the SEP event. This UAC spike is likely explained by plants’ responses to short-term elevated surface UV-B driven by NOx-induced ozone depletion following the event, with effects persisting beyond a year. The timing of the event during a Schwabe cycle minimum supports recent studies suggesting its occurrence during a solar minimum rather than a solar maximum.