Солтүстік жарты шардағы жанартау атқыштарынан туған суыну дәуірі

Cooling period in Northern Hemisphere caused by volcanic eruptions

The volcanic winter of 536 was the most severe and protracted episode of climatic cooling in the Northern Hemisphere in the last 2,000 years. The volcanic winter was caused by at least three simultaneous eruptions of uncertain origin, with several possible locations proposed in various continents. Most contemporary accounts of the volcanic winter are from authors in Constantinople, the capital of the Eastern Roman Empire, although the impact of the cooler temperatures extended beyond Europe. Modern scholarship has determined that in early AD 536 (or possibly late 535), an eruption ejected massive amounts of sulfate aerosols into the atmosphere, which reduced the solar radiation reaching the Earth's surface and cooled the atmosphere for several years. In March 536, Constantinople began experiencing darkened skies and lower temperatures. Summer temperatures in 536 fell by as much as below normal in Europe. The lingering impact of the volcanic winter of 536 was augmented in 539–540, when another volcanic eruption caused summer temperatures to decline as much as below normal in Europe. There is evidence of still another volcanic eruption in 547 which would have extended the cool period. 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. The medieval scholar Michael McCormick wrote that 536 "was the beginning of one of the worst periods to be alive, if not the worst year."

Tree ring analysis by the dendrochronologist Mike Baillie, of the Queen's University of Belfast, shows abnormally little growth in Irish oak in 536 and another sharp drop in 542, after a partial recovery. Ice cores from Greenland and Antarctica show evidence of substantial sulfate deposits in around 534 ± 2, which is evidence of an extensive acidic dust veil.

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. The gold was possibly a sacrifice to appease the gods and get the sunlight back. Mythological events such as the Fimbulwinter and Ragnarök are theorised to be based on the cultural memory of the event. 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 Sassanid Empire, the collapse of the Gupta Empire, the rise of Islam, the expansion of Turkic tribes, and the fall of Teotihuacán. However, Keys and Wohletz's ideas lack mainstream acceptance. Reviewing Keys' book, British archaeologist Ken Dark commented that "much of the apparent evidence presented in the book is highly debatable, based on poor sources or simply incorrect. [ ] Nonetheless, both the global scope and the emphasis on the 6th century AD as a time of wide ranging change are notable, and the book contains some obscure information that will be new to many. However, it fails to demonstrate its central thesis and does not offer a convincing explanation for the many changes discussed". The philologist Andrew Breeze in a recent book (2020) argues that some King Arthur 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. Historian Robert Bruton argues that this catastrophe played a role in the decline of the Roman Empire.