Volcanic winter of 536

The volcanic eruptions caused crop failures, and were accompanied by the Plague of Justinian, famine, and millions of deaths and initiated the Late Antique Little Ice Age, which lasted from 536 to 560.

[17][18][19][20] Tree ring analysis by the dendrochronologist Mike Baillie, of Queen's University Belfast, Ireland, shows abnormally little growth in Irish oak in 536 and another sharp drop in 542, after a partial recovery.

[26] This is strong evidence that a large explosive volcanic eruption caused the observed dimming and cooling, removing the need for an extraterrestrial explanation,[22][26] but an impact event around this time period cannot be ruled out.

[26][38] The 536 event and ensuing famine have been suggested as an explanation for the deposition of hoards of gold by Scandinavian elites at the end of the Migration Period.

[41] A book written by David Keys speculates that the climate changes contributed to various developments, such as the emergence of the Plague of Justinian (541–549), the decline of the Avars, the migration of Mongol tribes towards the west, the end of the Sasanian Empire, the collapse of the Gupta Empire, the rise of Islam, the expansion of Turkic tribes, and the fall of Teotihuacan.

[...] Nonetheless, both the global scope and the emphasis on the 6th century CE as a time of wide-ranging change are notable, and the book contains some obscure information that will be new to many.

[43] The philologist Andrew Breeze argues that some Arthurian events, including the Battle of Camlann, are historical, happening in 537 as a consequence of the famine associated with the climate change of the previous year.