On the basis of archaeological findings and dendrochronologic evidence, scientists state that in AD 536-537 a thick veil of dust covered the territories between Europe and Asia Minor for a period of 12-18 months and blocked the sun out. As a result of this climatic phenomenon the temperatures dropped and there was drought and famine. About 1/3 of the European population was exterminated by a combination of the climate and the smallpox plague at the time. In some parts of China up to 80% of the people starved while the Scandinavian region lost between 75 and 90% of its population.
There are both physical evidence and historical documentation of this phenomenon, though its cause is still not defined for certain. Some scientists claim the dust veil was caused by a severe volcanic eruption while others believe it was due to an impact with a comet leading to the creation of a dust cloud consisting of smoke, dust particles and sulphuric acid.