Climatic and societal impacts in Scandinavia following the 536 and 540 CE volcanic double event

Abstract

In the Northern Hemisphere, the mid-6th century was one of the coldest periods of the last 2000 years, which was initiated by volcanic eruptions in 536 and 540 CE. Here, we study the effect of this volcanic double event on the climate and society in Scandinavia with a special focus on southern Norway. Using an ensemble of Max Planck Institute Earth system model transient simulations for 521–680 CE, temperature, precipitation, and atmospheric circulation patterns are analyzed. The simulated cooling magnitude is used as input for a growing degree day (GDD) model setup for three different study areas in southern Norway, representative of typical meteorological and landscape conditions. Pollen from bogs inside these study areas are analyzed at high resolution (1–3 cm sample intervals) to give insights into the validity of the GDD model setup with regard to the volcanic climate impact on the regional scale and to link the different data sets with the archeological records. We find that after the 536 and 540 CE double event, a maximum surface air cooling of up to 3.5 ∘C during the mean growing season is simulated regionally for southern Norway. With a scenario cooling of 3 ∘C, the GDD model indicates crop failures were likely in our northernmost and western study areas, while crops were more likely to mature in the southeastern study area. These results are in agreement with the pollen records from the respective areas. Archeological excavations show, however, a more complex pattern for the three areas with abandonment of farms and severe social impacts but also a continuation of occupation or a mix of those. Finally, we discuss the likely climatic and societal impacts of the 536 and 540 CE volcanic double event by synthesizing the new and available data sets for the whole Scandinavia.