On Climate Change and the Fall of the Roman Empire Redux

A couple of months ago we commented on a study that was making the rounds of assorted news agencies which suggested that there was a connection between climate change (as evidenced from tree ring samples) and barbarian migrations/fall of empires. At the time, the connection wasn’t clear to me and now there’s a followup story — with an actual Classical connection (well, fourth century) — that seems to cloud the issue even more. Here’s the incipit of an item in the Harvard Gazette:

Ancient Roman poetry and climate science may seem to have little in common, but a recent collaboration between a Harvard historian and European climate scientists highlights the potential for the two fields to illuminate each other and deepen the understanding of both nature’s and humankind’s past.

Michael McCormick, the Francis Goelet Professor of Medieval History, has collaborated with climate scientists three times in recent years, searching for witnesses to climate extremes gleaned from tree-ring data during the late Roman Empire and after, investigating the effect of volcanoes on climate and civilization during the time of Charlemagne, and, in an article soon to be published, looking at climate data and historical accounts in the centuries after the Roman Empire fell.

McCormick said he recently brought to class a precipitation chart developed in his work with a European team on the climate of the first millennium, published online by the journal Science in January. The class was studying a Roman poem from the year 371. The work mentions that a region of the Roman Empire was then very dry. McCormick showed students the chart, which has a deep, plunging spike denoting a drop in rainfall in the same region, around the same year.

“If you would have told me 10 years ago that I could walk into an undergraduate seminar, read a poem by one of the Roman Empire’s leading poets which describes a drought that he saw as he rode along a ridge and that literary specialists had dated to 371 — but couldn’t be sure — and then pulled out the chart of rainfall in that part of the Roman empire in 371 — it’s just extraordinary,” McCormick said. “This is a new world of historical investigation.”

• via: A match of climate and history | Harvard Gazette

This does sound potentially exciting … McCormick is one of a group of folks who were part of the study we previously mentioned. So anyway, yesterday I was wracking my brains for a bit trying to figure out what Roman poet might have written something around 371 which might contain something climate-related. I was thinking Prudentius, but nothing matched, and then Michael Chase came to my rescue (on the Classics list) and suggested they were probably referring to Ausonius‘ Mosella. The suggestion makes sense on numerous levels, not least of which is that it is the sort of poem which one might meet in an undergraduate classroom at some point and it is usually dated to around A.D. 371. As might be inferred, it is a poem praising the river Moselle. Here’s the intro (text and translation from the Hugh Evelyn-White Loeb edition at the Internet Archive :

TRANSIERAM celerem nebuloso flumine Navam,
addita miratus veteri nova moenia Vinco,
aequavit Latias ubi quondam Gallia Cannas
infletaeque iacent inopes super arva catervae.
unde iter ingrediens nemorosa per avia solum 5
et nulla human! spectans vestigia cultus
praetereo arentem sitientibus undique terris
Dumnissum riguasque perenni fonte Tabemas
arvaque Sauromatum nuper metata colonis :
et tandem primis Belgarum conspicor oris 10
Noiomagum, divi castra inclita Constantini.
purior hie campis aer Phoebusque sereno
lumine purpureum reserat iam sudus Olympum.
nee iam, coiisertis per mutua vincula ramis,
quaeritur exclusum viridi caligine caelura :

I HAD crossed over swift-flowing Nava’s cloudy
stream, and gazed with awe upon the ramparts lately
thrown round ancient Vincum where Gaul once
matched the Roman rout at Cannae, and where her
slaughtered hordes lay scattered over the countryside
untended and unwept. Thence onward I began
a lonely journey through pathless forest, nor did my
eyes rest on any trace of human inhabitants. I passed
Dumnissus,sweltering amid its parched fields, and
Tabernae, watered by its unfailing spring, and the
lands lately parcelled out to Sarmatian settlers.
And at length on the very verge of Belgic territory
I descry Noiomagus, the famed camp of sainted
Constantine. Clearer the air which here invests
the plains, and Phoebus, cloudless now, discloses
glowing heaven with his untroubled light. No
longer is the sky to seek, shut out by the green
gloom of branches intertwined :

So Ausonius is travelling from Vincum, which is modern-day Bingen (according to the notes in the text; if you track down the text online or ‘live’ there’s a map of the journey on p 222 of volume one), about 20 km through a very thick forest (apparently) until he gets to the ‘parched fields’ of Dumnissus, which is “probably Densen, near Kirchberg” according to the note and also seems to be what is being referred to by McCormick. Then another 20 or so km on to Tabernae (Berncastel), which doesn’t seem to have any water problems and Noiomagus (Neumagen). No indication of dryness here either. As the poem goes on, of course, it gets to the banks of the Moselle, which are verdant, vine-covered and just a joy for Ausonius to behold.

So here’s my problem with all this: clearly any ‘climate marker’ that can be tied to this poem can only be tied to the rather localized area of Dumnissus, which seems to be in between two points which aren’t having any water problems to speak of, nor is there any indication elsewhere in the poem that there are rainfall shortages or the like affecting the region. Would it not be more reasonable to think that the fields of Dumnissus were “parched” because of some incursion of the Alamanni (which Valentinian was dealing with in the late 360s) rather than some tree ring which may or may not come from that exact spot? It would be truly amazing if we could tie tree-ring data to literature, but I don’t think it quite works in this case. What is also interesting, of course, is that if there was this serious decline in rainfall (according to tree ring data), how do we account of the lushness of this region as described by Ausonius?