Volcanic eruptions and the fall of the Roman Empire

Dendrochronology (or tree-ring dating) of the northern hemisphere now spans the past 7,600 years. Adverse weather conditions cause trees to grow slowly and that results in small tree rings. Various historical events, like volcanic eruptions, can be observed in those tree rings.

Vulcanic eruptions of AD 536 and 540 led to climate cooling and contributed to hardships of Late Antiquity societies throughout Eurasia, and triggered a major environmental event in the historical Roman Empire[1]. The period is known as Late Antique Little Ice Age (AD 536 – 660. Documents of that time describe the veiling of the solar radiation during and after AD 536, the sun was observed blue-colored, without brightness, spring without mildness and summer without heat[2].

A group of researchers has proposed the possibility of El Salvador's Ilopango, which is known to have erupted around 540 AD, but others think that there were two seperate erupting volcanoes.

[Ilopango - El Salvador]

What followed after these eruptions was a persistently low solar radiation in the entire northern hemnisphere that contributed to remarkably simultaneous outbreaks of famine and Justinianic plague in the eastern Roman Empire. An extended period of little light may make it difficult for humans to survive. The level of production of plants is dependent on the amount of available sunlight. Food production, i.e, farming and animal husbandry, rely on the same solar energy. Humans, meanwhile, become more prone to disease if they are not exposed to enough sunlight to produce vitamin D.

The new study tracks the correlation of carbon isotope variation and volcanic eruptions from the 19th century until recent years, and shows the dramatic reduction in available sunlight in AD 536 as well as between 541 and 544 AD. The unusually poor years coincide with the bubonic plague epidemic that devastated the Roman Empire. The epidemic caused by the Yersinia pestis bacterium began in 542 AD and killed approximately half of the inhabitants of what was then considered the Eastern Roman Empire. The plague spread through Europe, from the Mediterranean, possibly as far north as Finland, and had killed tens of millions of people by the 8th century.

Recent research shows that a vitamin D deficiency correlates with various infectious diseases[3]. Like Influenza or the plague.

[1] Helama et al: Volcanic dust veils from sixth century tree-ring isotopes linked to reduced irradiance, primary production and human health in Scientific Reports – 2018. See here.
[2] Stathakopoulos: Reconstructing the climate of the Byzantine world: State of the problem and case studies in People and Nature in Historical Perspective (pages 247–261) – 2003
[3] Gios et al: Vitamin D and Infectious Diseases: Simple Bystander or Contributing Factor? In Nutrients – 2017. See here.