Has the Climate Changed Since Roman Times?
If you stand on the scoured uplands above Trawsfynydd in North Wales, face to the hammer of the wind, hunched like a beggar, horizontal rain and a Celtic Sea gale forcing the breath back down your throat and think to yourself, "This is AWESOME!" then, you, my friend, have good Welsh blood in you.
What blood the cavalrymen of the unknown auxiliary unit who built the Roman military complex at Tomen-y-Mur, up on that same mountainside, had in them isn't known. Neither is what they must have thought about this bleak, beautiful, damp, and brutal landscape. But it would have rained. A lot. It's Wales.
In Wales, we have a saying - If you can see the mountains, then it's going to rain, and if you can't see the mountains, then it's already raining.
Wherever they were from - Scythia, say - then they wouldn't have known anywhere like this. When it rains up there on the mynydd, it rains downwards and upwards at the same time. You get the urge to jump into the dark waters of Lake Trawsfynydd just to dry off. Apart from a foray or two out into the peat bogs to smash unwilling Ordovices over the head with something, there doesn't appear to have been much to do apart from stay dry. They filled their time building endless practice camps or honing their horsemanship on the vast parade grounds. In the far corner of the complex, they built themselves a minuscule yet perfect little arena, presumably so they could hunker together and find something to entertain their nights with. It's a wonderfully human and moving little touch.
Nothing has changed up there in terms of climate since the 1st Century Ad. The wind and the rain have spent millennia scouring the land flat. It's granite-old and tombstone grey. Up there on the mynydd, time never really mattered in the first place. The same rain that lashes the faces of hardy visitors today, ran down the lonely cheekbones of Roman soldiers 2,000 years ago.
The question we're faced with today, one proposed by a reader, is to do with climate and how it might have changed from Roman times. Were deserts more verdant? Was it hotter? That sort of thing.
Firstly, we have to be aware of the differences between climate and weather. There are many descriptions of the weather from ancient sources, but we'll need to take a broader overview to make some sort of conclusion about the climate in general. We could also look to science for help, and we can tell a lot about climate from tree ring data and sediment cores. However, this article is about history, so I'm going to skip over the boffinery as much as I can, just because that particular avenue feels like a whole other article in itself.
The climate of the Roman Empire 2,000 years ago was marked by the same variability as today, ranging from severe winters to warm summers. These conditions impacted the daily lives of Roman citizens, agriculture, trade, and urban planning. Ancient sources that describe these conditions, along with modern archaeological evidence, paint a picture of the dynamic nature of the empire's climate and how it shaped both local and regional developments.
Numerous accounts from ancient historians describe the severity of winters in various parts of the empire. One of the most notable examples comes from St. Augustine in his City of God, where he recalls a particularly harsh winter in Rome, stating:
"Then what shall I say of that memorable winter in which the weather was so incredibly severe, that in the Forum frightfully deep snow lay for forty days together, and the Tiber was frozen?"
(St. Augustine, City of God, Book III).
The freezing of the Tiber River and extended snowfalls would have disrupted both agricultural practices and daily life, as the city was ill-equipped to handle such extreme conditions.
Such harsh winters were not confined to Italy. Archaeological findings and historical records indicate that Roman Britain, the northern frontier of the empire, experienced similarly cold winters. The Roman historian Tacitus, in his Agricola, writes about the hardships faced by Roman soldiers stationed in Britain, where the extreme cold and wet conditions made military campaigns difficult and the terrain treacherous (Tacitus, Agricola, XXIII). These extreme weather patterns likely impacted Roman control over the region, hindering both military operations and trade.
In contrast to the severe winters, the summers in the Roman Empire were marked by unpredictable weather, including violent storms that posed significant challenges for coastal settlements and maritime trade. Pliny the Elder, in his Natural History, documented numerous storms that wreaked havoc on the Roman coastlines, destroying ships and disrupting the vital sea trade routes that the empire relied upon. In Natural History (II.XCVI), he notes: "storms were so fierce that they destroyed fleets and caused widespread damage to Roman cities along the Mediterranean coast." The unpredictability of summer storms further highlighted the vulnerability of the empire's transportation and communication systems.
Agriculture was crucial to the Roman Empire, and the climate played a pivotal role in shaping agricultural productivity. The Mediterranean region, with its hot, dry summers and mild, wet winters, provided an ideal environment for growing crops such as wheat, barley, olives, and grapes—key staples of the Roman diet. The Mediterranean climate facilitated extensive agricultural trade, including the well-known Roman wine trade, which spanned much of the empire.
However, other regions of the empire, particularly Roman Britain, presented challenges for certain types of agriculture, such as viticulture. The cooler climate and shorter growing seasons in Britain made it difficult to cultivate the same grape varieties found in warmer regions like Gaul, Spain, or Italy. Archaeological evidence, including the discovery of Roman wine presses, indicates that while wine production did occur on a limited scale in Britain, it could not match the productivity or quality of wine produced in more temperate regions (Wilson, 2008). Despite these challenges, Roman agricultural practices, including crop rotation, irrigation systems, and the selection of suitable crops, allowed the empire to adapt to different climates.
Droughts and floods also had a significant impact on grain production, which was essential for feeding the empire's growing population. Tree-ring data from the Mediterranean region reveals periods of prolonged drought, making it difficult to sustain large-scale grain production. In such times, the Romans relied on their extensive trade networks to import grain from Egypt and North Africa, although these supplies were vulnerable to disruption. Notably, during the reign of Emperor Tiberius (AD 14–37), food shortages triggered the Grain Riots in Rome, illustrating the social unrest that could arise from poor harvests (Lendon, 2005).
The climate and landscape of Roman Britain were also shaped by climatic changes over time. Studies have shown that sea levels were lower during the Roman period than they are today, due to the effects of isostatic rebound following the last Ice Age. As glaciers melted, the Earth's crust in northern Europe began to rise, altering the coastal geography. Roman-era ports that were once directly on the coast are now inland, a clear indication of these long-term shifts (Rippon, 2012).
Roman infrastructure, including roads and settlements, was designed to cope with unpredictable weather conditions. The adaptability of Roman architecture and planning helped ensure the movement of goods, soldiers, and people despite the challenges posed by a fluctuating climate.
In addition to fluctuating weather patterns, the Roman Empire's agricultural practices in North Africa were impacted by long-term climatic shifts. The region, particularly the Sahara Desert, has undergone significant changes in climate since Roman times. Archaeological evidence suggests that the Sahara was once a greener, more habitable region, with lakes, rivers, and agricultural settlements, as shown by findings in modern-day Algeria, Libya, and Egypt. This wetter period allowed for Roman agricultural settlements and irrigation systems to thrive (Harrison, 2020).
However, starting around the 4th and 5th centuries AD, the Sahara began to dry, leading to desertification. The decline of the Roman Empire coincided with the degradation of the region's environment, as large-scale agriculture and deforestation contributed to the spread of desert conditions. The collapse of Roman irrigation systems further exacerbated this process, resulting in the expansion of deserts in North Africa (Jones, 1997).
The climate of the Roman Empire was dynamic, with fluctuations in temperature and precipitation influencing both the natural environment and human activity. The adaptability of the Romans—demonstrated through their agricultural practices, infrastructure, and trade networks—enabled the empire to thrive in diverse climates. Yet, climatic challenges such as tough winters, unexpected storms, and droughts had profound effects on agriculture, trade, and social stability.
References
Augustine, St. City of God, Book III.
Harrison, P. (2020). "The Changing Climate of North Africa: Evidence of Shifting Desert Boundaries." Journal of Ancient Environmental Studies.
Jones, D. (1997). Roman Agricultural Practices in North Africa. Cambridge University Press.
Lendon, J. E. (2005). Soldiers and Ghosts: A History of Battle in Classical Antiquity. Yale University Press.
Pliny the Elder. Natural History, II.XCVI.
Rippon, S. (2012). Roman Rural Settlement in the West Midlands. Oxford University Press.
Tacitus, Agricola, XXIII.
Wilson, A. (2008). The Romans in Britain: A History. Routledge.
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