image: Graph showing inervals of low CO2 concentrations in Antarctic ice cores correlating with major epidemics that decimated populations.
After: Ruddiman, William F., Plows, Plagues and Petroleum: How Humans took Control of Climate, p. 133.

1. VI century

In Britain, the period 535—555 experienced the worst weather of the 6th century. In Mesopotamia there were heavy falls of snow and in Arabia there was flooding follow by famine. In China, in 536, there was drought and famine and yellow dust rained down like snow. In Korea, AD535 and 536 were the worst years of that century in climatic terms with massive storms and flooding, followed by drought. It has also been suggested that the occurrence of the Justinian Plague, a pandemic which affected the Byzantine Empire, including its capital Constantinople, in the years 541–42 AD is linked to the climatic events

2. X-XIV century MWP (The Medieval Warm Period)

In Europe the warm conditions had positive effects. Summer after summer the harvests were good and the population increased rapidly. As a result thousands of hectares were cleared of woodland and farmers expanded their fields high into the hills and on mountain slopes. It was even possible to grow successfully grapes as far north as Yorkshire.

Under these conditions, art, literature and even science were developing apace and we see the height of medieval civilisation. The most visible achievements of this period are undoubtedly the construction of the many cathedrals all over Europe. The good harvests had made Europe rich and the good weather freed people from the burden of the struggle against the elements. It created the wealth and labour force to build cathedrals. It was a golden period for European Architecture and art.

3. XIV century - The Little Ice Age

Written records from the 14th century provide accounts of severe weather in the period from 1314 to 1317, which led in turn to crop failure and famine. This episode of failed harvests and its consequences is known as “The Great Famine”. Notwithstanding these ecological calamities, the population of northern Europe was at an all time high by the second quarter of the 14th century. 

4. 1340s-1350s

What catapulted the Black Death on the world stage? Recently it has been suggested that a climatic event similar to the 536 dust veil event is responsible. Based on comparing the chronologies of prices, wages, grain harvests and the corresponding chronologies of growing conditions and climactic variations, taking into consideration dendrochronology, the Greenland ice cores it has emerged that the episodes of the Black Death coincide with depressed temperatures.

Read more about this interesting (and often disregarded) aspect of history