There was turmoil elsewhere also. In post-Roman Britain, King Arthur was killed in battle. The Anglo-Saxon Chronicle states that the sun was eclipsed and the stars appeared late in the morning. The cold cycle caused famine in Ireland where Celtic Christianity opened its great schism with Rome over when to celebrate Easter. The Celtic church lost.
Opinions are divided.
Some documents refer to huge earthquakes that killed a quarter million people in the Eastern Mediterranean and might have released volcanic eruptions that cooled the climate. Another hypothesis posits that a giant comet hit the earth, causing violent explosions that put dust into the atmosphere and produced a dramatic cooling. This view is supported by Dr. Baillie, based on the work of Oxford astrophysicist Victor Clube. His calculations show a major commentary bombardment between 400 and 600 AD by meteor showers from the breakup of the comet Biela. Dr. Bailey also cited the death of King Arthur, at about 540 AD, which Celtic myths link to fire from the sky.