Today, more people than ever live in close proximity to or even on volcanoes. While these mighty giants sleep, cities keep growing, seemingly safe. But what effects can a local eruption have on the global climate? Is it possible that a single event could change the course of human history? In the 6th century AD, large parts of the world were devastated by such a climactic shift; global cooling, crop failures and famine; Europe gripped in the cold mercy of the Bubonic plague. All thanks to an eruption on the other side of the world.