The Krakatoa Catastrophe
The first telegram to arrive in Singapore on a Monday was sent from Batavia in the Dutch East Indies, now known as Jakarta, Indonesia. It reported “terrible explosions from Krakatoa (a volcanic island).” Shortly thereafter, another message stated, “Rocks are falling. A nearby village to Anjer has been destroyed.” The messages continued to pour in, detailing collapsed bridges, wrecked ships, and lighthouses that had “vanished.” By midday on Tuesday, the extent of the natural disaster was apparent: “Where Krakatoa once stood, the sea now stretches.”
Within days, the origin of the devastation became known globally. On the morning of August 27, 1883, a volcanic eruption had obliterated two islands in the strait between Java and Sumatra, along with most of a third island. Over 36,000 lives were lost, primarily due to the catastrophic tsunamis that followed the colossal explosion.
Thanks to the telecommunications of the Victorian era, this marked the first instance in history where people around the world could begin documenting, almost in real-time, the immediate and long-term effects of a catastrophic volcanic eruption. The knowledge gained in the ensuing years laid the groundwork for modern volcanology. This event revealed how significant eruptions can influence climate, agriculture, and even the trajectory of human history.
Global Climate Effects
In the months following the Krakatoa eruption, volcanic particles suspended in the upper atmosphere circled the globe, resulting in vividly coloured sunsets that artists of the time captured in their works, possibly including the psychedelic background of Edvard Munch’s “The Scream.”
The crucial component of the volcanic emissions that impacted the climate was the sulphur from the molten rock that fuelled Krakatoa. Once sulphur enters the atmosphere, it can form particles called aerosols that reflect sunlight and cool the Earth. In the months and years following the eruption, average summer temperatures dropped by 0.6 degrees Celsius (1.1 degrees Fahrenheit) in the non-tropical regions of the Northern Hemisphere.
More than a century later, researchers have come to understand that climatic changes, particularly rapid ones, have transformed societies by affecting agriculture, public health, and living conditions. Drawing on lessons from Krakatoa and other eruptions, volcanologists today identify catastrophic explosions from the past that may have contributed to historical events such as droughts, famines, epidemics, and social unrest.
Climate Anomalies of 536 AD
The first challenge in establishing connections between volcanic activity and societal impacts is to find physical evidence of past eruptions. In the year 536, scribes from Europe, the Middle East, and Asia documented strange weather phenomena, including a fog that obscured the sun for 18 months. Temperatures plummeted, crops failed, and within a few years, the first documented global plague began to spread.
These chronicles from the Early Middle Ages clearly indicate a significant volcanic eruption, but conclusive evidence lies deep within polar ice. Scientists can deduce that major eruptions occurred at certain times in the past by examining deposits of sulphur and ash in ice cores from Greenland and Antarctica. These cores, extracted from ice layers, preserve an annual record of everything that circulated in the Earth’s atmosphere and settled on the surface each year, allowing researchers to read these frozen layers as if turning the pages of a book.
It turns out that the polar ice cores contain substantial amounts of sulphur dating back to 536, a clear indication of a major eruption. However, the specific volcano that erupted at that time remains a mystery, as no written records exist from individuals living near the eruption—Iceland, where it may have occurred, was not yet populated.
Linking Eruptions to Historical Events
There is stronger evidence pointing to the volcano that may have contributed to the collapse of the Mongol Empire seven centuries later. Until 2013, researchers knew only that an eruption took place in 1257, the largest in millennia as measured by sulphur emissions. In 2013, an interdisciplinary team radiocarbon-dated ash, pumice, and other deposits around Samalas, a volcano in Indonesia, linking them to the 1257 eruption.
Tree ring studies, which analyse annual growth layers to determine years of favourable or adverse climate conditions, indicate widespread cooling across North America and Eurasia between 1257 and 1259. Among other impacts, poor harvests led to famines in England, while the cool and wet summer in Japan adversely affected rice production.
Some researchers speculate that the eruption of Samalas may have sealed the fate of the Mongol Empire, which came to an end after the death of its last ruler during an epidemic in 1259, potentially linked to climate changes caused by the eruption.
The Black Death and Climate Connections
A century after Samalas, another intriguing connection between a volcanic eruption and disease was uncovered by volcanologists. Between 1346 and 1352, as much as half of the European population succumbed to the Black Death, caused by the bacterium Yersinia pestis, which was transmitted by fleas.
Historical records from Europe and Asia suggest that the skies were darker than usual during this period, possibly due to volcanic haze. Ice core records support this interpretation, documenting a major eruption—or perhaps several—around 1345, although the location remains unknown.
To ascertain how this volcanic activity may have affected the climate, an interdisciplinary team led by Ulf Büntgen, a tree ring specialist at the University of Cambridge, used tree ring data to confirm that the summers of 1345, 1346, and 1347 were unusually cold and wet in southern Europe.
Büntgen and his colleagues note that as crops failed due to adverse weather, Europeans imported grain from further east. Ships laden with grain arrived with rats carrying Y. pestis, leading researchers to argue that the mysterious volcano that erupted in 1345 may have triggered a chain of events that ultimately claimed the lives of millions.
Toxic Haze and Historical Perspectives
Establishing links between volcanoes and human events can be challenging even today; however, in 1784, an American ambassador in France, Benjamin Franklin, had the insight to connect an unusual haze that spread across the countryside the previous year to a distant eruption.
The source turned out to be Laki, an Icelandic fissure that expelled lava for eight months starting in June 1783. The eruption resulted in the death of at least one-fifth of Iceland’s population and much of its livestock due to toxic haze and climatic changes that devastated crops. While the event was well documented in Iceland, observers in England, France, and elsewhere in Europe who witnessed the volcanic haze and sometimes detected its odour could only speculate about what was happening in a disconnected world prior to the electronic era.
“They weren’t receiving news alerts on their mobile phones, nor were they watching live broadcasts of the eruption… they had no idea,” says Kleemann, who has studied the eruption.
Lessons from Tambora’s Eruption
Although it occurred just a few decades after Laki, one of the largest eruptions in human history provides a much clearer picture of how a volcanic-induced climatic disturbance can alter the course of history. In 1815, the Indonesian volcano Tambora erupted, releasing sulphur into the upper atmosphere and causing widespread climate changes.
The Tambora eruption led to cooling across much of Europe and North America, resulting in crop failures, with 1816 dubbed the “year without a summer.” The volcanic climate of that year trapped writer Mary Shelley during her travels in Switzerland, where she penned the novel “Frankenstein.”
The adverse weather resulted in famines in Switzerland, Ireland, and other regions; prices for grain and malnutrition surged in certain areas of Europe, prompting tens of thousands to emigrate to North America. Conversely, Eastern Europe and western Russia enjoyed relatively better growing conditions under the post-volcanic climate and sufficient grain for export to other countries. Port cities like London and Hamburg gained greater access to imported grains, while prices soared inland. These positive examples illustrate how access to transportation and trade networks can enhance societal resilience in the face of disasters.
Contemporary Relevance of Historical Eruptions
“Human society exhibits numerous susceptibilities and vulnerabilities,” states Clive Oppenheimer, a volcanologist at the University of Cambridge and co-author, along with Büntgen, of a paper published in 2026 in the Annual Review of Earth and Planetary Sciences on volcanoes, climate, and society. “Some climatic disturbances will come and go… At other times, the climatic disturbance will occur… when greater social vulnerabilities exist.”
These lessons may hold particular significance today, as researchers consider the historical consequences of past eruptions as clues to how humanity might respond to current climate change. While large volcanic eruptions cool the planet rather than warm it, they represent the same type of rapid global disturbances that societies face as the Earth warms.
As historical volcanology teaches us, the next major eruption is merely a matter of time. In the age of satellites and saturated social