If the cold period began in 500 A.D., it was too late to bring down the Western Roman Empire. Romulus Augustulus, the last official Western Roman Emperor, was deposed in 476. By the 500s, the last people claiming to be Western emperors were gone, except for the local king of a mini-state in western Algeria. It looks like the Eastern Roman Empire WAS badly affected by the colder weather and Justinian’s plague, but I figured we all believed in that by now.
Yup. Plus, the Roman/Byzantine Empire didn’t fall until 1453. :^)