Kyle Harper

In this case, the sixth century, we know the cause, that there was a series of really significant volcanic eruptions.

Volcanoes are very powerful, short-term climate forcing mechanism.

It ejects sulfur into the stratosphere.

It aerosolizes and sort of creates reflective shields that scatters the radiation entering the atmosphere.

And so it leads usually to short-term cooling.

And in this case, you had a series of really significant volcanic eruptions that cooled the climate for several decades and in some ways with the later series of eruptions even like a century and a half.

And it wasn't just a little bit cooler.

It was like a degree to two degrees cooler.

which we all kind of know now, like two degrees, this isn't weather, this is climate.

So like two degrees doesn't affect your day, but two degrees globally is a pretty different globe.

And so all of a sudden in the late Roman world, it's much, much cooler.

probably areas that have been wetter are now drier, places that are drier may be wetter.

It changes the hydrological cycle as well, which is more complicated.

In addition to the shock of the plague, you have this simultaneous and probably not unrelated shock to the climate system.

We know that it was essentially challenging for agriculturalists.

That when the sun is blocked and it's really, really cold and the wheat doesn't grow, your society then starves.

And so the Romans get this like wham, bam, double shock of climate change, famine and plague.

And so back to how people explain this.

Yes, like apocalyptic thought is one of the principal sort of ways people frame it.

To them, nature is going crazy.