The Worst Year For Humanity?

The medieval scholar Michael McCormick has said that 536 was likely "the worst year to be alive".

The volcanic winter of 536, caused by an eruption, was a severe episode of climatic cooling.

Sulfate aerosols and ash released into the atmosphere blocked the sun's rays from reaching the Earth's surface. 

Temperatures dropped and crops failed. 

Roman statesman Cassiodorus wrote in a letter in 538:

The sun's rays were weak, and it appeared a "bluish" colour.

At noon, no shadows from people were visible on the ground.

The heat from the sun was feeble.

The moon, even when full, was "empty of splendour"

"A winter without storms, a spring without mildness, and a summer without heat"

The seasons "seem to be all jumbled up together"

The Irish Annals recorded: 

A failure of bread in the year 536 AD" – the Annals of Ulster

"A failure of bread from the years 536–539 AD" – the Annals of Inisfallen

Snow reportedly fell in the summer in China, along with crop failures.

The 536 volcanic winter coincided with the Plague of Justinian, which began in 541. One of the deadliest pandemics in history. An estimated 15–100 million people died during two centuries of recurrence.

The disease afflicted the entire Mediterranean Basin, Europe, and the Near East.

The climatic cooling led to famine and conflict, perhaps leading to the migrations of the Lombards and the Slavs into Roman territory. The Barbarian Invasions (according to the Roman and Greeks) contributed to the breakdown of central power and the conquest of Rome by the Lombards in 568.

Lower temperatures in Arabia, however, increased the supply of crops and may have contributed to the expansion, invasions and Islamic conquests.

St Sebastian pleading for the life of a gravedigger afflicted with plague during the 7th-century Plague of Pavia.