How a sixth-century bishop documented the world's most mysterious climate catastrophe

Ideas & Philosophy · Published 3 October 2026 Swipe more like this →

In short: John of Ephesus was a prominent Miaphysite bishop and historian whose writings provide a rare, firsthand account of the Plague of Justinian. Beyond his ecclesiastical duties, his observations of a sun that dimmed for eighteen months in 535 AD have become essential evidence for modern research into the Late Antique Little Ice Age.

Born around 507 AD in Amida, John of Ephesus lived through a period of profound religious and environmental upheaval. A dedicated leader of the Miaphysite Church, he spent much of his life in Constantinople, where he gained the favor of Emperor Justinian I. This relationship allowed him to manage the church's revenues and undertake imperial missions, including a campaign to convert pagans in Asia Minor, where he claimed to have baptized 70,000 people. However, his fortunes shifted dramatically under Justin II, leading to his imprisonment and the confiscation of his property.

It was during his imprisonment in Constantinople that John composed the third part of his Ecclesiastical History. This work, along with his collection of biographies of Eastern saints, serves as a vital record of the sixth century. His writing is characterized by a narrow focus on Miaphysite orthodoxy, yet it remains a crucial contemporary source for the political and religious tensions of the era. He documented the devastation of the great plague and the intense persecutions directed at his faith, providing a detailed, if sometimes stylistically uneven, account of these events.

John’s most striking contribution to modern science lies in his description of the years 535 and 536 AD. He recorded that the sun became dark, casting only a feeble shadow for eighteen months. While these accounts were once viewed as purely symbolic or localized phenomena, 2010 research linked them to volcanic eruptions that triggered a decade-long cooling period known as the Late Antique Little Ice Age. By aligning his historical observations with dendrochronological data from ancient tree rings, scientists have confirmed that John was witnessing a global climate event of massive proportions.

His legacy persists through his surviving manuscripts, such as the seventh-century British Museum manuscript Add. 14640. Although the first part of his history is lost, the remaining sections continue to be studied for their insight into the Byzantine world. John’s commitment to his faith, his role in the administration of the church, and his meticulous, if biased, documentation of his times ensure his place as one of the most important historians to write in Syriac.

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