re: Real climate cataclysm: Scientists Can No Longer Ignore Ancient Flooding Tales (Netflix)

There is speculation that the Romans were smelting so much lead that it could have triggered the cold climate cycle that precipitated the fall of the Western Empire. Colder weather killed the grass lands that sustained the Huns, forcing them to move south and west in search of new grazing lands. Lower temperatures caused crop failures in Northern Europe that compounded by the Hunnic invasion displaced millions of barbarians east if the Rhine, sending them all crashing into Rome at a time when the Empire was already feeling the effects of lower crop yields. Rome, bankrupted from the increasing prices of the bread dole couldn’t afford to pay enough troops to fight the barbarians, and was eventually overwhelmed.

After the western Roman Empire was destroyed and largely depopulated by wars, invasion, and plague, we see the Medieval Warm Period as temperatures soared even higher than they are today. It is possible that the massive reduction in economic activity, particularly mining and smithing, following the death of Rome may have contributed to these harsh swings in climate.