Mega Volcanic Eruptions in 536 and 540 CE and Aftermath Caused the Collapse of Multiple Societies and Massive Deaths

"...the volcanoes decreased average global temperatures by as much as 3.6 degrees Fahrenheit. Crops in northern Europe and elsewhere failed, likely triggering starvation and disease."

I zeroed in on that 36 degrees F decrease in temperature, because a few days ago, I read an article at The Washington Post about the recent average 2 degrees Centigrade increase in temperatures in the United States - which equates to 3.6 degrees F.  If a drop of less than 4 degrees F caused massive crop failures and famines around the globe, triggering societal collapses in one area after another and roving groups of bandits and invaders looking for food, water and animals - what do you think a 3.6 degrees F rise in temperature on average may do to crop production, local ecosystems and their plants and animal life?  

The "disease" the quote above refers to is the plague of Justinian, which killed "tens of millions of people" starting in 541, arguable the worst year of the combined sustained impact of the catastrophic volcanic eruptions in 536 and 540.

This scares the bejesu out of me!  The climate change in the 6th century CE was "mini" (it lasted about 10 years) compared to what we can expect to get worse and deepen from now into the foreseeable future - and beyond that. 

If you want to read the articles I did, here they are:

"2 Degrees Centigrade Beyond the Limit
Extreme Climate Change Has Arrived in America"
Steven Mufson, Chris Mooney, Juliet Eilperin and John Muyskens
Photography by Salwan Georges
August 13, 2019"
The Washington Post Online

"The Global Cooling Event of the Sixth Century.  Mystery No Longer?"
Dr. Tim Neufield, Princeton University
May 1, 2016
Historical Climatology Blog
(This is the first article I read about the period in the 6th century CE called the "Mini-Ice Age."  It can get a little bit technical in places, but not overly so).  

"Colossal volcano behind 'mystery' global cooling finally found"
Michael Greshko
August 23, 2019
National Geographic Online
(While this article does not pinpoint the location of the massive volcanic eruption that occurred in 536 CE, it does refer to it.  The article itself is about the eruption in 540 CE and how researchers eventually narrowed the eruption site down to a volcano in Central America).