Filippo Lippi painting of St. Fridianus redirecting the course of the Serchio River
St. Fridianus is credited with diverting the course of the Serchio, a Tuscan river, in the 6th century—a period during which the North Atlantic Oscillation was particularly intense. Credit: Filippo Lippi/Uffizi Gallery, public domain

In early medieval Italy (then a troubled peninsula transitioning from the collapse of Roman rule) a group of monks at a mountaintop monastery had a water problem. To fetch their supply, they needed to descend from the monastery’s steep and rocky perch. To their aid came St. Benedict, who spontaneously brought water to the summit in the form of a spring.

According to a new study, this account does more than relay the performance of a miracle. It also suggests that climate change played a previously unassociated role in societal shifts long recognized by historians.

“Even when climate is not causing the economic or social system to collapse, there might be some impact on other levels of human functioning.”

The study, published in the journal Climatic Change, brought together an international group of geoscientists and historians led by researchers at the University of Warsaw and the University of Pisa. Authors examined both paleoclimatological proxy data and historical records to gain a fuller picture of the impact that a prolonged period of increased rainfall had on Italian society in the 6th century. Their findings indicate that contemporaneous water-related miracle stories go beyond the anecdotal to reveal one way local Christian leaders responded to a period of climate extremes.

A Stormy Century

After the collapse of the Western Roman Empire in the late 5th century, central and northern Italy came under siege by invading forces, and decades of war left the peninsula hobbled and depopulated. Into this maelstrom swept a century-long spell of bad weather, a circumstance that provided rich material for Pope Gregory I (Gregory the Great), whose Dialogues on the Miracles of the Italian Fathers, written in the 590s, included descriptions of holy figures bringing forth storms, conjuring new water sources, and rerouting troublesome rivers.

Hagiographical accounts are generally considered anecdotal or derivative. But when combined with proxy data, the Dialogues’ water-related stories, along with those of other 6th century writings, may demonstrate that the society affected by the century’s changing weather patterns also responded to attempts to explain or contextualize them.

Schematic outlining the influence of increased precipitation on accounts of water miracles in 6th century Italy
This schematic representation shows the network of relationships between increased precipitation and social change in 6th century Italy. Credit: Drawing by Michelle O’Reilly, MPI SHH; design by Adam Izdebski,, CC BY 4.0

“Even when climate is not causing the economic or social system to collapse, there might be some important influences, some impact on other levels of human functioning…on our thinking and our behavior,” said study coauthor Adam Izdebski, independent research group leader at the Max Planck Institute for the Science of Human History. It can be as simple, he said, as people noticing the weather and leaders taking advantage of that awareness. For Gregory, it was an opportunity to move the cultural tide in the church’s favor.

“Hagiographical sources show us the world as the people who produced them saw it,” said Samantha Kahn Herrick, an associate professor of history at Syracuse University who was not involved in the study. “They reveal how people made sense of what was happening. Even historical sources that seem much more banal and straightforward are always shaped by their authors’ sense of what’s possible and what’s important.”

A Layered Story

Researchers obtained climate data by analyzing a stalagmite collected from Renella cave, located near the town of Lucca in northern Tuscany. By measuring oxygen isotope ratios in the stalagmite’s layers, researchers were able to determine whether environmental conditions were wet or dry when the layers were formed. They then used uranium-thorium dating to pinpoint when those conditions occurred. The stalagmite provided nearly a thousand years of data from the period before 900 CE and showed that northern and central Italy experienced hydrological extremes during the 6th century.

The culprit, according to study authors, was likely a negative phase of the North Atlantic Oscillation (NAO), a winter weather pattern that brings moisture from the Atlantic Ocean to parts of Mediterranean Europe, in this case resulting in decades of increased precipitation during the colder months. Researchers analyzing the stalagmite from Renella found that in the 6th century, precipitation in the region was distinguished by a particular isotopic trace that’s left by moisture from the Atlantic.

The Saints Go Marching In

In Lucca, local legend credits St. Fridianus, a 6th century bishop, with redirecting the flood-prone Serchio River away from town, a story that appeared in—and may have originated with—the Dialogues. By directly addressing a preoccupation of the times, accounts of miracles like those performed by Benedict and Fridianus would have served to strengthen the cult of saints, then a relatively new phenomenon, and concentrate power in the hands of local bishops, keepers of sacred relics that could bring protection against demons, illness, fire—and floods.

To analyze whether such stories went beyond the application of familiar literary motifs, researchers mined works contained in the Cult of Saints in Late Antiquity Database, a collection of texts spanning around five centuries that an Oxford-based team has been working to catalog since 2014. Study authors found that hagiographies from the eras immediately preceding and following the study period had nearly no mention of water miracles, nor did such stories appear significantly in the contemporaneous works of the Frankish historian and bishop Gregory of Tours, who chronicled events outside the area that would have been affected by the negative NAO. In addition, only some of the water miracles related in the Dialogues echo earlier works in the genre. Others scenarios are, as researchers wrote, “either new or strangely overrepresented.”

Nonhagiographical works written during or about northern and central Italy in the 6th century—such as the letters of Roman official Cassiodorus and Paul the Deacon’s History of the Lombards—also reveal evidence of increased precipitation through passing remarks about flooding and torrential rain. “They confirm the impression we have from Gregory’s Dialogues,” said Robert Wiśniewski, a study coauthor and historian from the University of Warsaw.

According to Wiśniewski, Gregory’s body of work indicates that he was unlikely to tell stories that wouldn’t influence his audience. Therefore, his uncommon inclusion of a relatively large number of water miracles in his Dialogues—they make up 20% of the text—suggests that he was aware of how the changing climate had affected the population and that he used the stories as tools to demonstrate the ability of the church, and saints in particular, to offer solutions.

Better Together

The study’s interdisciplinary approach was key to making connections that “are very unusual and far from obvious.”

The study’s interdisciplinary approach was key to making connections that, according to Izdebski, “are very unusual and far from obvious.” Working separately, neither the team of geoscientists at Renella cave nor the study’s historians might have been able to access or interpret the data needed to draw their conclusions.

“The way they put all of these different data into conversation was valuable both in terms of their conclusions and in terms of showing that historical evidence could influence interpretation of the scientific data,” said Herrick. And the impact goes both ways. “Perceptions of reactions to climate change are going to be fundamentally shaped by the culture, as well as the political and economic and social structures of a society, which I think is an important thing for scientists to recognize.”

—Korena Di Roma Howley (@KDRHowley), Science Writer


Howley, K. D. R. (2021), Holy water: Miracle accounts and proxy data tell a climate story, Eos, 102, Published on 10 May 2021.

Text © 2021. The authors. CC BY-NC-ND 3.0
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