A study by researchers at Trinity College Dublin has concluded volcanic eruptions leading to short-term climate change may have been responsible for triggering major upheaval in ancient Egypt.
The research found that summer flooding of the Nile may have been prevented by the eruption, leading to economic and political unrest caused by disruption to the region’s agriculture.
The historical research has modern day resonance, as countries around the world face into the need to adapt to a changing climate caused by increased greenhouse gas emissions.
The famous Ptolemaic era (305-30BCE) of ancient Egypt is well known for its cultural and material progress as well as its prosperity.
But it was also a time of political upheaval including revolts against the ruling Ptolemaic family and the ending of major inter-state wars.
Why that happened, however, has remained a mystery, despite rich documentation of the period.
Now, in a paper published in Nature Communications, a team from Trinity College Dublin working with colleagues in Yale University in the US, has set out what it thinks caused the change.
They used a combination of climate modelling of large volcanic eruptions, Nile summer flooding records, ancient Egyptian writings and polar-ice core records to build a picture of what happened at the time.
They conclude that large volcanic eruptions disrupted the African summer monsoon and as a result this lowered the flow of the Nile river.
Economic and political instability was set off as a consequence, in particular acting to trigger revolts against Ptolemaic rule of Egypt and limiting the Ptolemaic state’s ability to wage warfare.
The study also found that sales of family owned land increased following the eruptions, creating further upheaval.
"To fully understand how sudden environmental pressures could act to destabilise society, the historical context is key," said study co-lead, Dr Francis Ludlow, Marie Sklodowska-Curie Individual Fellow in Trinity's School of Histories and Humanities.
"And in this case included pressures from high levels of taxation and ethnic tensions that likely coalesced to trigger revolt at times of agricultural failures from insufficient floodwaters."
According to the authors, the research can also help to inform current analysis of the consequences of responding to climate change and the impact on communities of volcanic eruptions.
"A lot of volcanoes erupt each year but they are not affecting the climate system on the scale of some past eruptions," said Dr Ludlow.
"There hasn’t been a truly large eruption affecting the global climate system since Mount Pinatubo in the Philippines in 1991."
"Sooner or later we will experience a large volcanic eruption, and perhaps a sequence of them, that will act to exacerbate drought in sensitive parts of the world."
"Our research points to the need for further study into the effects of volcanic climate disturbances on modern societies worldwide."