Climate changes of 535–536

The extreme weather events of 535–536 were the most severe and protracted short-term episodes of cooling in the Northern Hemisphere in the last 2000 years. The event is thought to have been caused by an extensive atmospheric dust veil, possibly resulting from a large volcanic eruption in the tropics, or debris from space impacting the Earth. Its effects were widespread, causing unseasonal weather, crop failures and famines worldwide.

The Byzantine historian Procopius recorded of 536, in his report on the wars with the Vandals, "during this year a most dread portent took place. For the sun gave forth its light without brightness... and it seemed exceedingly like the sun in eclipse, for the beams it shed were not clear".

The Gaelic Irish Annals record the following:

Further phenomena were reported by a number of independent contemporary sources:

Tree ring analysis by 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. Similar patterns are recorded in tree rings from Sweden and Finland, in California's Sierra Nevada and in rings from Chilean Fitzroya trees.Ice cores from Greenland and Antarctica show evidence of substantial sulfate deposits in around 533–534 ± 2, which is evidence of an extensive acidic dust veil.

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