We've already talked about how new technological advances over the centuries have led scientists to reconsider climate data. And thanks to this new technology, historians too are reinterpreting some of the most complex periods in human history, from the fall of the Ptolemaic Kingdom of Egypt to the birth of the Roman Empire and the decline of some of the most significant Chinese dynasties.
It's a well-known fact that volcanic eruptions have been the cause of disasters for various civilisations throughout history. There is consensus among most historians nowadays on accounts including the chronicle of the death of Pliny the Elder [1], who died in Stabiae (now Castellamare di Stabia) having suffocated due to the volcanic fumes of Vesuvius, as well as the explosion of the volcano Thera, which devastated the island of Santorini and inspired the myth of Atlantis [2].
In recent years, however, other theories relating to volcanic activity have taken their place alongside these reconstructions. The effect of volcanic eruptions doesn't seem to have been limited to their immediate and catastrophic impact on ancient civilisations; in fact, their primary consequence may be their medium and long-term effect on the climate.
One of the most important articles on the subject was published in the journal Nature back in 2015. By analysing the sediments found in various ice samples collected in Greenland and Antarctica, climatologists found a correlation between some of the largest volcanic eruptions of the last 2,500 years and periods of intense cold, sometimes with temperature drops lasting up to 10 years.
And that's not all. These violent eruptions – capable of spreading a thick layer of ash over hundreds of square miles – would have blocked out the sun and led to torrential rains, causing fully fledged famines on a global scale.
A 2020 study allowed researchers to analyse the eruption of the Okmok volcano, one of the largest volcanic eruptions of all time. According to scientists, this catastrophic event, which took place in Alaska in 43 BC, disrupted the climate of the entire northern hemisphere and led to temperature drops of up to 7° C in some areas of the Mediterranean.
Historical evidence describes the decade following the eruption as a real dark age that saw famines, epidemics, and political instability. The latter eventually resulted in the fall of Egypt's Ptolemaic Kingdom in 30 BC and the Roman Republic in 27 BC.
The decline of these two hugely important Mediterranean civilisations, until now correlated with the death of the great historical figures of the time, Cleopatra and Marc Antony (who died in 30 BC), can therefore now be seen in a new light that establishes climate change as one of the key factors.
But this isn't the only example. Year after year, these revelations are increasingly arousing the interest of both climatologists and historians, who work together to find the points where climate change and politics collide.
One famous case is a 2018 study that linked Napoleon's defeat at Waterloo to the eruption of a volcano in Indonesia [3]. Crazy? Not at all: the Belgian countryside in spring 1815 was sodden due to exceptional rain, which played a decisive role in limiting the movements of the French cavalry and neutralising the destructive effects of their artillery shells. The French tended to fire their cannons at a low angle so that the iron balls bounced several times along the dry ground, increasing their destructive effect. This technique was known as the bounce shot or ricochet. However, it was ineffective in this case due to the waterlogged ground, as the balls sank into the mud and failed to explode.
The exceptional levels of rain at the time were not simply down to the whims of Jupiter Pluvius. Instead, they were the result of dust and gases issued into the upper layers of the atmosphere by the most violent eruption in recorded history: the Tambora volcano eruption [4]. This volcano is located on the island of Sumbawa in the Indonesian archipelago of Sunda, about 7,500 miles (12,000 km) away from Waterloo. It began erupting on 5 April 1815, and the event was so violent that it led to effects whose reach is still being studied today.
The most recent study on the topic, meanwhile, was published in November 2021. It highlights “a systematic correlation between volcanic eruptions and the decline of the major Chinese dynasties over the last two millennia”, offering a scientific explanation for the periods of war and famine that are traditionally interpreted in China as a sign of divine disfavour towards the emperor [5].
The question is, therefore, if the history that we are taught in school – a tale often told through great historical figures, assassins and coups d'état – should be completely reconsidered in the light of these new scientific discoveries. As always, the answer is not quite that simple, and the debate among academics remains a heated one.
While there are those, like John L. Brooke – historian at Ohio State University and author of the book Climate Change and the Course of Global History: A Rough Journey – who claim that climate change plays a key role when it comes to interpreting historical information, there are also many authoritative critics of this approach who fear that it could lead to the social and political aspects of history being trivialised in favour of “climatic determinism”.
One thing is for sure: regardless of the role that these great volcanic eruptions played in the decline of ancient civilisations, we are increasingly coming to realise that the climate has an enormous influence on the history of humanity. These days, it's a good idea to keep that in mind!
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