Kyle Harper: commitment

Transcript context

…Yeah. Okay, one of the things I found really interesting was you were discussing the firsthand accounts as this big... and feel free to explain the cold snap as well as it's happening. But the firsthand accounts of people who are experiencing this, some of whom come from this burgeoning Christian faith, which already lends itself to millenarianism and apocalyptic thinking. I'm curious basically how did different people try to make sense of this once in a 1,000-year event that's super intense? Clearly, people have to try and explain, within the elements of a worldview that they have, how something like this could happen. They don't have modern science. They don't have germ theory. They don't think of it in terms of a biological event or climatic event. Since that's come up and you've invited, I'll say a little bit about that. This is one of the other really exciting frontiers where we're learning new things about the human past that we just didn't know 10 or 15 years ago. In this case, we now have really cool paleo climate data that helps us understand that this period of the sixth and seventh century was also a period of really abrupt and significant natural climate change. We're all familiar with anthropogenic climate change, that carbon emissions stay in the atmosphere, trap heat. Humans are changing the climate. That's a big problem and we can talk about it if you want. I just want to clarify, that view is not incompatible with the reality that the climate does also change for natural reasons on every timescale, from long geological timescales to much shorter timescales. We live in the Holocene. The last 11,700 years have been pretty stable, pretty warm. It's an interglacial. We're literally between Ice Ages right now. It's been really stable in the big picture. Yet even within that stability, there are smaller scale climate variations and climate changes. Because we need to understand how the earth system works, how the climate system works in order to be able to model what's happening, we need an empirical record of what the climate has done. For historians, this is great news because now we have a huge number of sometimes even pretty high resolution climate reconstructions for historical periods across the Holocene. We now know, like we did not know this 20 years ago when I started graduate school, that the Roman period experienced some really abrupt episodes of climate change. In this case, the sixth century, we know the cause: there was a series of really significant volcanic eruptions. Volcanoes are a very powerful short-term climate forcing mechanism. They eject sulfur into the stratosphere. It aerosolizes and creates a reflective shield that scatters the radiation entering the atmosphere. It leads usually to short term cooling. In this case, you had a series of really significant volcanic eruptions that cooled the climate for several decades. In some ways, the later series of eruptions even like a century and a half. It wasn't just a little bit cooler, it was like a degree to two degrees cooler, which we all kind of know now: two degrees isn't weather, this is climate. Two degrees doesn't affect your day, but two degrees globally is a pretty different globe. 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. 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. When the sun is blocked and it's really cold and the wheat doesn't grow, your society then starves. The Romans get this wham bam double shock of climate change, famine, and plague. So back to how people explain this. Apocalyptic thought is one of the principle ways people frame it. To them, nature's going crazy. Huge amounts of the population are dying of this horrible sudden disease and the crops don't grow. You don't have microbiology and you don't have climatology. So you explain it with the resources of the worldview you have. There's a huge burst of apocalyptic thought in the sixth and seventh century, which is always kind of there. You mentioned that Christianity is eschatological. It is, yes, fundamentally, but that comes out in different ways with different emphases in different time periods. This is a period, the sixth century, when there's a really sharp emphasis on eschatology in Christian thought.…

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