Using computer simulations and historical measurements of the Nile River, Ludlow, Manning, and their colleagues discovered that poor flood years on the Nile lined up over and over again with major volcanic eruptions around the world. The evidence suggests that the volcanic activity cooled the atmosphere, suppressing rainfall and preventing the Nile from flooding.
Digging even deeper into the historical record, Manning was able to determine that volcanic eruptions preceded several major political and economic events during the Ptolemaic period. For instance, a major eruption in 247 BC was followed by a revolt that caused the army of Ptolemy III to withdraw from a Middle Eastern campaign and return home. The revolt was likely due to crop failure, which was almost certainly caused by the Nile failing to flood.
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A similar scenario occurred in 44 BC, which led to an outbreak of famine and disease that weakened the rule of Cleopatra.
The researchers are quick to note that much of the cause-and-effect linkage is supposition, and that climate changes are just one of many factors that can contribute to major events in history.
“Connecting climatic changes to complex social and political events like the collapse of a dynasty needs to be done cautiously and with a full recognition of the historical context in which many other factors will also inevitably have played an important role,” Ludlow said.
Still, the concurrence of volcanic activity with Nile river failures — and subsequent civil unrest — is remarkably precise and very unlikely to be simple coincidence, researchers said. The trick is in noticing them in the first place. All the clues were there in the historical record, Manning said, but it took a team of scholars to piece them together.
“It's important to work in this truly interdisciplinary way in order to make progress,” Manning said.
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Ludlow and Manning intend to continue their collaboration, looking into Egypt during the Roman and Byzantine periods, and perhaps branching out to the Near East and India. The researchers note that their work could have implications in the modern era, as well.
“The 21st century has been lacking in explosive eruptions… but that could change at any time,” Ludlow said. “The potential for this needs to be taken into account in trying to agree on how the valuable waters of the Blue Nile are going to be managed between Ethiopia, Sudan, and Egypt.”
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