I believe the climate started getting colder and more variable in the 14th century, which unfortunately also coincides with the arrival of the Bubonic plague. S

I believe the climate started getting colder and more variable in the 14th century, which unfortunately also coincides with the arrival of the Bubonic plague. Similar events also happened with the arrival of the bubonic plague during the reign of Justinian of the Roman Empire. It's probably responsible for bringing on what we think of the Middle Ages vs. the Late Antique. If anyone is interseted, there is a great podcast called "Tides Of History" The author goes into great detail about each period.