“On scales the Romans could not even comprehend or imagine—from the microscopic to the universal—the fall of the empire was the triumph of nature over human ambition. Rome's destiny was the actors: emperors and barbarians, senators. and generals, soldiers and slaves. But it was bacteria and viruses, volcanoes and determined by solar cycles. It is only in recent years that we have acquired the scientific tools that allow us to understand, albeit often rapidly, the great drama of environmental changes unknown to the Romans…” Kyle Harper, “How the Roman Empire Collapsed. Climate, Disease and the Fall of Rome”
The fall of the Roman Empire is a classic theme. You might even say it's an obsession. For decades we've lived with this idea: barbarian invasions and internal political complications caused the fall of the Roman Empire.
Historian Kyle Harper offers another hypothesis. An explanation is due to solar radiation, microbes, volcanic eruptions and climate variations.
In his unanimously acclaimed book, he paints a climactic history of the empire's decline. A practice made possible by technological advances. Icebergs and tree rings are, in his own words, “natural archives,” new data that can be linked to stories.
Obviously, the story of the collapse of a superpower due to climate risks, it gives prime roles to a mini-ice age and epidemics that echo our times and our contemporary concerns, from global warming to the AIDS or Covid epidemics. But these “ecological” approaches to these works and history, even explaining cultural phenomena such as the revival of the cult of Apollo due to the Antonine plague, are subject to debate in the scientific community.
Harper is representative of an important movement that is paving its way in the field of history. This is why he was invited to lecture at the Collège de France and to hold a chair there, and this is why we invite him.
In the 6th century, Cassiodorus wrote that a blue sun had been seen. Procopius of Caesarea said it resembled the sun during an eclipse. So what were the effects of the sun on the fall of Rome? “This example is the most interesting in climate history. For decades, written accounts of the sun dimming were not taken seriously. It was NASA scientists who put the pieces of the puzzle together and took this human testimony seriously. In recent decades, much has been learned about this episode, triggered by volcanic eruptions. We don't know that there were two major volcanic eruptions. Explosions are the most powerful means of cooling. If you change the system by one or two degrees, in a very short period of time, the consequences are very unpredictable. In this case, climate episodes have been a major problem for communities. Harvests were poor, communities suffered, and within a few years, two or three years, a major epidemic developed. We know that these events, this climate episode and this pandemic are deeply connected. And the effects are intertwined. Ultimately, this was perhaps the greatest crisis the Roman Empire ever faced. By putting the pieces together and understanding the environment as a larger factor in human societies, that's what we've achieved..”
In this course he gave at the Collège de France, Harper explains that historians typically base their research on chronicles, letters, documents, and inscriptions. That is, archives left by humans. Today we can read history in layers of ice, wood, stone and sediment. Why can we only study them now? “The irony is that the impetus for this massive climate research is the human-caused crisis. The climate system changes somewhat naturally and we only measure relationships over a few hundred years. Thermometers were invented only in the 17th century. So how do we know, how do we know climate history without direct observation? Well, you have to look at natural records, indirect evidence. It is the history of the Earth reconstructed from data hidden in the polar caps, trees, truly extraordinary archives, minerals, ore deposits in caves, etc. in Greenland..”
Mix up the stories
Yet isn't there a danger inherent in Kyle Harper's approach, the danger of determinism, that is, of thinking that every climate event has an absolutely huge and unique impact on human history, on the destiny, of humanity? “As historians, we must always guard against environmental determinism. But we must also caution against discounting these environmental factors. I think the challenge for historians is to integrate human factors with environmental factors. Climate change did not cause the fall of the Roman Empire. But climate change has seriously stressed these communities. This is what makes history, along with human choices, human factors, political and tax systems, and the interaction between these systems..”
Antonine Plague and Political Changes
The climate seems to have initially favored the empire. We are talking about the Roman climate optimum. “Roman historians were not the inventors of the term. This is paleoclimatology. Earth system scientists have realized that during the last centuries before Christ, until the second century AD, there was an exceptionally stable phase when solar energy was high and constant. It appears to be one of the most definitive phases of the Holocene“Then we distinguish several phases in the decline of the empire. The first probably emerged under the reign of Marcus Aurelius, marking the first great difficulties of the empire. The period of the Antonine plague.”This is the first example of a clear link between a moment of climate change and a pandemic outbreak. An episode of infectious disease on a very large scale. A great plague broke out, with very high mortality. This is a very interesting phenomenon for historians, but we still don't know what caused it. This is one of the interesting mysteries we are still trying to solve. But the epidemic was so widespread that it shook this society so deeply that it caused and created a new era in Roman history.“How Did Roman Institutions Respond to Antonine Plague?”The Roman system survived these crises. The Roman Empire did not fall. This continued until the second century. There is a redistribution of power, which shows the accountability of the Roman army. Very quickly, they actually have more power and play a greater role in the selection of emperors, in the selection of emperors. The Empire is more inclusive. As the grip of a small Italian elite loosened, the empire was increasingly ruled from a few provinces. And this new method was activated by trauma.”
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