Upcoming presentations: Ice cores and dendochronology correlate climate change to human conflict in the ancient world

A history resource article by Mary Harrsch © 2015

I received an announcement of two upcoming presentations from researchers at the Yale Climate and Energy Institute (YCEI) that sound really fascinating.  On Monday, November 16, 2015 Francis Ludlow will present information he has gleaned from the study of tree-ring growth in Ireland and ice core samples then compared to Irish chroniclers' records of severe frosts, droughts, dried rivers and discolored sunsets that shows how short term climate change appears to be a driver of historical conflict and violence using medieval Ireland as an example.

Eric Ellman of the YCEI, explains:

Bloody battles, slave and cattle raids, burning of crops and settlements, and the killings of secular and ecclesiastical elites feature prominently in Ludlow’s review of 1200 years of Irish chroniclers’ accounting of yearly events.  When mapped against tree ring and ice core records he has begun to see a recurring link to between periods of climatic stress and extreme weather, and an increased reporting of violence and conflict [see Figure 1 for one example]. The pathways connecting climate to violence are undoubtedly complex, with cultural and political factors playing a large role and mediating any influence of weather and climate. But the Irish chronicles make abundantly clear how conflict and violence can be triggered by the consequences of extreme weather, with the Annalsof Connacht reporting in 1465 CE how “Exceeding great frost and snow and stormy weather [occurred] this year, so that no herb grew in the ground and no leaf budded on a tree until the feast of St. Brendan [16^th May], but a man, if he were the stronger, would forcibly carry away the food from the priest in church…”. As Ludlow remarks, “it is time to take climatic pressures seriously as a recurring factor in human history.”

Figure 1. Deaths recorded in conflict in the medieval Irish Annals of Ulster, for the years 728 to 748 CE. A notable jump in the death in conflict of members of Irish societal elites coincides with severely depressed Irish oak tree-ring growth in 738 CE, signifying severe drought conditions. 738 CE was also the year of the historically pivotal battle of Áth Senaig (Co. Kildare) that helped re-write the Irish political landscape for centuries to come. (F. Ludlow).

On Tuesday, November 17, 2015 Joseph Manning will present his studies of volcanic eruptions that indicate they triggered revolt and suppressed interstate conflict in Hellenistic Egypt.  

"Manning always suspected that shocks lay behind the problems that the Ptolemaic kings faced in the 3rd century BCE," Ellman observes.  

'We always knew that the Nile deeply effects Egyptian civilization in every way.  But in terms of social dynamics,' Manning says, 'it wasn’t so easy to see.'

Ellman continues, "Until Manning met Ludlow through the YCEI and Whitney Humanities-funded Climate History Initiative.  Ludlow showed him how sulfate levels in ice cores recorded some of the largest volcanic eruptions in human history.  'To my astonishment,' Manning says, 'dozens of them aligned with Egypt’s years of greatest hardship.' 

"The observation complemented historical references to failures of Nile flooding that Manning had collected in a shoebox over his career. Further investigation with atmospheric scientists Bill Boos and Trude Storelvmo suggest a linkage between high-latitude eruptions and Nile flow."

"New precision regarding dates of climate disturbance -- along with other technological advances including the ability to now read charred papyrus records – reveals untold chapters of Egypt’s history.  The 'Revolt of the Shepherds,' the only revolt in Roman Egypt, appears linked to an eruption in AD 168, subsequent cooling and a devastating plague."

"'The new chronology of volcanism,' says Manning, 'opens our eyes to a past we’ve been pretty blind to.' Combined with written archives from the Greco-Roman period, he says, fresh understanding of climate’s history helps to explain food crises, social unrest, political bargaining, and major wars through a new lens."

I wished I lived closer to Yale so I could hear these presentations.  Hopefully, I can obtain a transcript of each of them and share it with you in a future post.