here’s part of a list I compiled for other purposes showing the volcanic eruptions from 0AD to 900AD and their VEI (St Hellens was VEI 5; each number greater is 10 times the previous expressivity). Each of those listed are 10 times greater than St Hellens.
• 0 A.D. - Carbon-14 Spike
• 50 A.D. - Ambrym, Vanuatu, Fiji Islands Erupts
Volcanic Explosivity Index (VEI) = 6+
• 60 A.D. - Churchill, Eastern Alaska Erupts
Volcanic Explosivity Index (VEI) = 6
• 180 A.D. - Taupo, New Zealand Erupts
Volcanic Explosivity Index (VEI) = 6+
• 240 A.D. - Ksudach, Kamchatka Peninsula, Russia Erupts
Volcanic Explosivity Index (VEI) = 6
• 426 A.D. - Dark Ages (Middle Ages) Begins
• 450 A.D. - Ilopango, El Salvador Erupts
Volcanic Explosivity Index (VEI) = 6
• 536 A.D. - Rabaul, Papua New Guinea Erupts
300 million tons of aerosols.
Volcanic Explosivity Index (VEI) = 6.
• 700 A.D. - Churchill, Eastern Alaska Erupts
Volcanic Explosivity Index (VEI) = 6
• 800 A.D. - • 1300 A.D. - The Medieval Warm Period
Somewhere in my search for more information I came across the information that Rabaul’s date was not 536, but had been corrected based on better dating methods. I think it was in the second link at Comment #48.