I am curious as to the connection between this cold period and the plague during Justinians reign. It is generally considered that the plague arrived from Egypt on grain ships.
When this topic went up, I thought, 'should be quick and easy to post the related FR topic links' from our fine selection of black death and plague. Yow, this will take a while. Long, related keywords, robot #1 (not Marco Rubio) is processing it now, then robot #2 will work it over, then a couple of sorts and duplicate removals, and I'll do a hand edit.
I'd guess that some years of extra cold would reduce crops in the more northern latitudes, thus necessitating the import from warmer climes.
The starting date of 536 ad is, I believe, the date of Cassiodorus report on the year with no sunshine. SC that is some list at #15, thanks. This period no doubt helped destroy the weakened Roman Empire. Bad growing conditions in the central Asian steppes would have played a part in driving the “barbarians” to the gates of Rome—the Vandals, Goths, Visigoths, Avars, Huns, etc.