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The Roman Empire's Worst Plagues Were Linked to Climate Change
(www.scientificamerican.com)
The reconstructions show that cooler periods—which had average temperatures as much as three degrees Celsius lower than the highs of preceding centuries for decades at a time—coincided with Roman reports of major pandemics
Obviously the cold air causes an excess of phlegm and threatens those with phlegmatic dispositions—Galen could have told you that. /s