Cassiodorus

Flavius Magnus Aurelius Cassiodorus was a Roman aristocrat who served the Ostrogothic kings of Italy, starting under Theodoric the Great. He held high offices including consul in 514 and praetorian prefect, the chief civil post. Around 540 he retired and founded the monastery of Vivarium in southern Italy, where monks copied both Christian and classical texts, an example that helped preserve ancient literature through the Middle Ages.

His Variae, published in 537, collects 468 official letters and documents he drafted. One letter, written as prefect to his deputy, describes the strange weather of 536 to 537: the sun appeared bluish, the moon lacked its glow even when full, the seasons seemed confused, summer had no warmth and crops were failing from cold.

Together with Procopius in the east, his letter is a key written witness to the 536 cooling that scientists now link to volcanic eruptions.