Late Antique Little Ice Age

Based on Wikipedia: Late Antique Little Ice Age

In the year 536, the sun went dark.

Not metaphorically. Not in some poetic sense. The Byzantine historian Procopius wrote that "the sun gave forth its light without brightness, like the moon, during this whole year." For eighteen months, a mysterious fog dimmed the sun across the Mediterranean world. Snow fell in China during summer. Crops failed from Ireland to Mesopotamia. And this was just the beginning of what scientists now call the Late Antique Little Ice Age—a century-long period of cooling that helped reshape the political map of the world.

A Climate Catastrophe Revealed in Tree Rings

The term "Late Antique Little Ice Age," sometimes abbreviated as LALIA, didn't exist until 2016. That's when a team of researchers led by Ulf Büntgen published a groundbreaking paper in the journal Nature Geoscience. By analyzing tree rings from across the Northern Hemisphere—those annual growth bands that reveal not just a tree's age but the conditions under which it grew—they documented a dramatic temperature plunge that lasted from roughly 536 to 660 AD.

This wasn't some subtle statistical blip. Summer temperatures in Europe crashed by as much as 2.5 degrees Celsius (about 4.5 degrees Fahrenheit) below normal. To put that in perspective, the global temperature increase since the Industrial Revolution that has scientists so alarmed today is around 1.2 degrees Celsius. Double that, flip the sign, and compress the change into a single year rather than two centuries—that's what people in 536 experienced.

Then it got worse.

Just three or four years later, in 539 or 540, another catastrophe struck. Temperatures dropped even further—2.7 degrees Celsius below normal. Then possibly again in 547. Three punches in quick succession, and the climate never fully recovered for over a century.

Volcanoes: The Culprits Hiding in Ice

What could cause such devastation? Scientists have proposed various explanations over the years—a meteorite impact, perhaps, or a comet fragment exploding in the upper atmosphere. But the evidence increasingly points to volcanoes. Not one, but a series of massive eruptions that pumped sulfur dioxide and ash high into the stratosphere, where it spread around the globe and blocked incoming sunlight.

The detective work has been painstaking. Researchers drill into glaciers, extracting ice cores that preserve thousands of years of atmospheric history layer by layer. Tiny glass particles in these cores can be matched to volcanic rocks from specific eruptions. In 2018, scientists found particles in Swiss ice cores that matched Icelandic volcanic rock, suggesting an eruption somewhere in Iceland or possibly North America triggered the 536 event.

The second eruption, the 539/540 event, likely came from the tropics. The prime suspect is Ilopango, a volcano in what is now El Salvador. When Ilopango erupts—and it has several times in human history—it does so with tremendous violence. The caldera lake that exists there today, a popular tourist destination, fills a crater formed by one of these ancient cataclysms. Evidence from tree rings near the volcano and from ice cores in both Greenland and Antarctica (eruptions near the equator leave signatures in both polar regions) points to Ilopango as the source.

There's a complication, though. Some researchers have dated the great Ilopango eruption to 431 rather than 540, which would mean another volcano, still unidentified, caused the second wave of cooling. The debate continues.

What we do know is that the 539/540 eruption, wherever it occurred, was enormous—larger than the 1815 eruption of Mount Tambora in Indonesia. That eruption caused what became known as the "Year Without a Summer" in 1816, when frost killed crops across New England and Europe in June, July, and August. The 6th-century eruptions were even more severe.

The Feedback Loop

Volcanic eruptions create what's called a volcanic winter. Sulfur dioxide combines with water vapor in the stratosphere to form tiny droplets of sulfuric acid that reflect sunlight back into space before it can warm the Earth's surface. This effect typically lasts a year or two before the particles settle out.

So why did the cooling persist for over a century?

The answer lies in feedback mechanisms—chains of cause and effect where the output of one process becomes the input of another. When temperatures dropped, sea ice expanded. Ice reflects more sunlight than open water (this property is called albedo), so more ice meant even less solar energy absorbed by the ocean. The ice also changed patterns of ocean circulation, which in turn affected weather patterns over land.

Then there's the sun itself. Through a cosmic coincidence, the 600s saw an unusually quiet period of solar activity. The sun's energy output varies slightly over cycles of roughly eleven years, and there are longer periods of reduced activity called grand solar minima. One of these minima occurred just when the Earth was most vulnerable to cooling, extending and deepening the freeze.

The Fall of Empires and the Rise of New Powers

Climate doesn't exist in a vacuum. The Late Antique Little Ice Age unfolded against a backdrop of political instability, epidemic disease, and mass migration. Its effects rippled through human societies in ways both dramatic and subtle.

The Roman Empire—or what remained of it—took a beating. By the 6th century, the western half had already collapsed, but the eastern half, which historians call the Byzantine Empire, still controlled vast territories around the Mediterranean. Emperor Justinian I harbored ambitions of reuniting the old empire. Instead, the climate catastrophe combined with the horrific Plague of Justinian, which began in 541 and eventually killed perhaps a quarter of the Mediterranean world's population, to drain Byzantine resources and manpower.

The plague's relationship to the climate crisis remains debated. Did the cooling somehow trigger or spread the disease? Perhaps. Climate stress can alter rodent populations (rats and their fleas spread the plague bacterium Yersinia pestis), change human migration patterns, and create food shortages that weaken immune systems. Or perhaps the timing was coincidental—two catastrophes that happened to overlap. Some scholars, like Haggai Olshanetsky and Lev Cosijns, argue that archaeological evidence shows no dramatic decline in the eastern Mediterranean during this period, suggesting both plague and climate change had more limited effects than sometimes claimed.

What is clearer is the role of climate in population movements. The Lombards, a Germanic people, invaded Italy in 568, establishing a kingdom that would last two centuries. The Slavs expanded dramatically during this period, settling across the Balkans and into territories that had been Roman. These migrations weren't random wanderings—they were responses to changing conditions that made some regions uninhabitable and others newly attractive.

Winners and Losers

Climate change creates losers, but it also creates winners. The Arabian Peninsula, surprisingly, may have benefited from the cooling.

Research by scientists at the Swiss Federal Research Institute suggests that the temperature drop brought increased rainfall to Arabia, turning marginal lands fertile. More food meant more people, and more people meant more potential soldiers and settlers. The Arab expansion out of the peninsula in the 7th century—the Islamic conquests that would transform the Middle East, North Africa, and beyond—coincided with this period of increased Arabian fertility and Byzantine and Persian weakness.

The timing is striking. The Muslim conquest of the Levant (the eastern Mediterranean coast, including modern-day Syria, Lebanon, Israel, and Jordan) occurred in the 630s. Egypt fell in the 640s. The vast Sassanid Persian Empire collapsed entirely by 651. Both the Byzantine and Persian empires had exhausted themselves fighting each other and coping with climate stress, plague, and internal unrest. The Arab armies that swept out of the peninsula encountered weakened opponents.

We should be careful about simple explanations. The rise of Islam and the Arab conquests had many causes—religious, political, military, economic. Climate was one factor among many. But it was a real factor, not just background noise.

The North Pays the Highest Price

If Arabia may have benefited from the cooling, northern Europe suffered most severely. The further north you go, the more marginal agriculture becomes, and the less margin for error exists in food production. A degree or two of temperature drop can be the difference between a successful harvest and starvation.

Scandinavia appears to have been devastated. Some estimates suggest that as many as half the population may have perished during this period. Evidence comes from abandoned farms, reduced pollen counts indicating less land under cultivation, and the haunted echoes that may survive in Norse mythology.

The Fimbulwinter. In Old Norse mythology, this is the terrible winter that precedes Ragnarök, the twilight of the gods and the end of the world. Three successive winters with no summer between them, when the sun grows dim and snow falls from all directions. The parallels to the actual conditions of 536-547 are impossible to ignore.

Mythology is not history. We cannot prove that memories of the Late Antique Little Ice Age directly inspired the Fimbulwinter concept, which was recorded centuries later by Christian-era writers like Snorri Sturluson. But societies do remember catastrophes, and cultural trauma can echo through generations in transformed forms.

A City Dies in the Desert

One of the most poignant pieces of evidence for the climate catastrophe's human toll comes from the Negev Desert, in what is now southern Israel.

Elusa was a prosperous city on the ancient incense trade route, home to tens of thousands of people at its height. It had survived for centuries in a challenging environment, testament to the sophisticated water management and agricultural techniques of its inhabitants.

Around 540, the city began to decline. Israeli archaeologists have tracked this through a surprisingly intimate proxy: garbage. The amount of refuse a city generates correlates with its population and economic activity. At Elusa, garbage deposits shrank dramatically in the mid-6th century, indicating a population collapse. The city never recovered, fading into abandonment long before the Islamic conquest of the region in the 7th century.

Was the Late Antique Little Ice Age responsible? Climate change affects desert margins paradoxically—sometimes cooling means more precipitation, sometimes less, depending on shifting weather patterns. In Elusa's case, the disruption to established climate patterns may have been more damaging than the temperature change itself. A desert city survives by adapting precisely to local conditions. Change those conditions, and survival strategies that worked for generations suddenly fail.

Echoes in China

The cooling wasn't limited to the Mediterranean world. China, too, experienced political upheavals during this period, though the connections between climate and politics there are even harder to trace than in the West.

The 6th and early 7th centuries were a time of division and warfare in China. The north was ruled by non-Chinese dynasties of nomadic origin, while the south remained under Chinese control. The Sui Dynasty would eventually reunify the country in 589, followed by the Tang Dynasty in 618, which inaugurated one of China's golden ages. But the years of division and warfare that preceded reunification coincided with the worst of the Late Antique Little Ice Age.

Did climate stress contribute to political instability in China? Almost certainly. Food shortages breed unrest, and unrest breeds war. But China's political history in this period had many drivers—ethnic tensions, religious conflicts, the usual struggles for power and territory. Climate was one thread in a complex tapestry.

What We Still Don't Know

The Late Antique Little Ice Age was only formally identified in 2016. Research continues, and many questions remain unanswered.

We still don't know precisely where all the volcanic eruptions occurred. The 536 event might have been in Iceland, or North America, or somewhere else entirely. The 539/540 eruption was probably Ilopango, but that dating is contested. The 547 eruption remains a mystery.

We don't fully understand how the cooling spread and persisted. The feedback mechanisms involving sea ice and ocean circulation are still being modeled. The role of the solar minimum remains debated.

Most fundamentally, we don't know exactly how people experienced and responded to the crisis. Written records from this period are sparse and often unreliable. Archaeological evidence accumulates slowly. We can measure temperature drops in tree rings and ice cores, but reconstructing human lives—the fear, the hunger, the desperation, the adaptation, the resilience—requires imagination as well as data.

Lessons for Today

The Late Antique Little Ice Age matters because it demonstrates that climate can change rapidly and catastrophically, with profound consequences for human societies. The 6th-century cooling was triggered by volcanic eruptions—a natural cause beyond human control. But the vulnerability of societies to that cooling was shaped by human factors: political structures, food systems, trade networks, population densities.

Today we face a climate crisis of our own making. Global warming, driven by the burning of fossil fuels, is pushing temperatures in the opposite direction from the 6th-century cooling, but the fundamental lesson is the same. Climate is not just background scenery for human history. It is a driver of human history, capable of toppling empires and launching new ones, of emptying cities and filling graves.

The people of 536 saw the sun go dark and didn't know why. We know what's happening to our climate and why. What we do with that knowledge will shape the history of the centuries to come.