The ice age that happened in the past had a major effect on the end of a Roman Empire.
By analysing tree-ring data for the past 2,000 years in Europe and Asia, scientists from the Swiss Federal Institute for Forest, Snow and Landscape Research WSL were able to precisely reconstruct the summer temperature for each year.
Scientists can analyse tree-ring widths in old trees to accurately predict temperatures.
By looking at these, they found that during the 6th century there was a drop in temperature of an average of three degrees celsius.
Ulf Büntgen, lead researcher on the project, said: “This was the most dramatic cooling in the Northern Hemisphere in the past 2,000 years.”
They believe that this climate change was triggered by three volcanic eruptions in 536, 540 and 547CE.
The team has dubbed this period the Late Antique Little Ice Age (LALLI).
This, they add, contributed to disease and famine to spread across the world.
They highlight the Justinian plague arose between 541 and 543CE which took the lives of millions of people over the ensuing centuries and contributed to the collapse of the Eastern Roman Empire.
This cooler period also allowed the Arab Empire to bloom in the Middle East as the Arabian Peninsula received more rain, meaning that more vegetation could grow which afforded them a larger army.
Additionally, more people migrated East towards China to escape famine and disease causing dramatic social shifts in Asia too.