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[♪ INTRO] For as long as people have existed on this
planet, volcanoes have been a kind of wildcard that
could change the course of human history with a single
explosion.
Mount Vesuvius is probably the most famous example of
this: It wiped out Pompeii and most of its inhabitants within
minutes in 79 CE.
In 1600 BCE, the eruption that created the famous caldera
on the Greek island of Santorini is thought to have
destroyed the Minoan civilization.
But not all volcanoes change history so quickly or
dramatically.
For decades, scientists have been exploring how volcanic
eruptions can alter the climate across the whole planet for
months, or even years.
Research suggests that these climate changes had major
effects on the societies that experienced them, leading to
things like famine, violence, and societal unrest.
While these brief periods of climate change are different
from the long-term and human-caused climate change
that’s going on today, they can still give us insight into how
human populations react to sudden environmental change.
And maybe that can help us predict how modern society might react to the climate crisis
that’s happening now.
Volcanoes are famous for the destruction they cause in
their immediate surroundings.
But their effects can reach way further.
Volcanic eruptions fill the air with ash, which blocks
sunlight and creates a cooling effect that can stretch
around the globe if the eruption is big enough.
And just like global warming, this global cooling can have
all sorts of consequences for ecosystems, weather
systems, and the people who depend on them.
. For instance, the land cools faster than water,
so global cooling can reduce the temperature
difference between the land and the sea.
In parts of Asia, that can weaken monsoon rains.
Less rainfall can lead to drought and smaller crop yields,
which can in turn lead to famines.
And at that point, societal unrest often isn’t far away.
And there are clear connections between environmental stress and societal unrest, both in the present
and the past.
And knowing this led some scientists to wonder how major
volcanic eruptions could be connected with historical
events.
One 2017 study on Ancient Egypt explored this question
by comparing the timing of eruptions to the water levels in
the Nile.
The authors found that major volcanic eruptions all over
the globe were linked with lower water levels in the Nile.
Flooding seems to have regularly decreased following
eruptions.
Less flooding would have been bad for crops, which
depended on floods to bring in water and nutrients every
year.
But that may not have been the only consequence.
The team took their analysis one step further and studied
Ancient Egyptian documents that held information about, like, what was going on in society
at the time.
They concluded that the environmental stresses caused by
the reduced water levels following volcanoes may have led
to riots during the time of Cleopatra.
In other words, according to their findings, social unrest
may have been directly related to faraway volcanoes that
they would not have even known about.
Now, not all scientists were totally convinced that the social
unrest in Ancient Egypt could be tied back to volcanoes,
but this idea was intriguing.
And in a 2022 study, one team of researchers from China
conducted a similar study, focusing on the effect of
volcanoes on Chinese history.
Specifically, they wanted to answer the question of whether
or not volcanic eruptions systematically topple governments.
To answer this question, they looked at a broad swathe of
Chinese history, covering most of the last two millennia.
Their first task was to find out around what year each
Chinese dynasty fell.
Fortunately, Chinese historical records are incredibly
comprehensive.
China is an old society, and recordkeepers took note of everything: historical events,
weather, climate, and even astronomical phenomena, going back
at least 3500 years.
So the researchers were able to pin down the approximate
date that each dynasty ended.
But figuring out the timing of nearby volcanic eruptions was
a little more complicated.
For this part, they turned to evidence that was preserved in
layers of ice in Greenland and Antarctica.
See, after volcanoes throw a bunch of ash into the air, it
eventually settles back down to Earth.
In most of the world, that ash mixes back in with the soil and disappears.
But in places where the ground is covered in ice,
that ash doesn’t go away.
It stays in the ice, and over time, new layers of ice cover up
the older ones.
So, today, scientists can drill into the ice and extract a long cylinder, known as an ice
core, which contains all these layers going way back in
time.
By looking at the amount of ash in different layers,
researchers can figure out approximately when significant
volcanic eruptions took place.
They can sometimes even figure out which volcano erupted.
That’s because each volcano has a different chemical signature, depending on what kinds
of materials it spews into the air, and this can serve as
a kind of volcanic fingerprint.
So, the authors of this study examined a set of ice cores
and searched and searched for eruptions that happened in
the Northern Hemisphere between year 1 CE and 1915, a
few years after the fall of China’s last dynasty and they
found 158.
Generally speaking, when they compared these eruption
dates to Chinese historical records, they found that
eruptions in the Northern Hemisphere tended to be
followed by hard times in China.
Chinese society often faced issues such as severe
drought, flood, frost, and even outbreaks of plagues and
locusts happening shortly after an eruption event.
Eruptions were also marked by less rain during the
monsoon season, which is essential to Chinese agriculture.
Out of all the eruptions they identified, the researchers
then looked for any that happened up to ten years before
or two years after the official date of a dynastic collapse.
And they chose this window because the dates in historical
records are only approximations, so there’s some
uncertainty of up to two years on some of them.
And they looked at the whole 10 years before a collapse
because not all regimes fall quickly, right?
Sometimes, hard times don’t immediately topple a regime,
but can lead to years of civil unrest before the government
cedes power.
Within these windows, they found something remarkable.
They observed that 62 out of 68 dynastic collapses were
accompanied by an eruption event in the same window of
time.
In other words, they found that more than nine out of 10 of
all Chinese dynasties’ fall was associated with a volcanic
eruption.
In some cases, they were even able to connect specific
eruptions to a dynasty’s collapse.
For example, the 1641 eruption of Mount Parker in the Philippines
was followed closely by the collapse of the Ming dynasty
in 1644.
Now, previous researchers had picked up on the fact that
certain dynasties had collapsed during tough environmental times.
Both the Tang dynasty and the Yuan dynasty collapsed
during periods of cold and drought.
But prior to this 2022 study, the idea that climate change
and extreme weather could play a role in the fall of
governments was pretty controversial because there just
wasn’t a lot of hard evidence.
What sets this study apart is that it wasn’t just looking at
one or two events in history.
It was the first to really look at the effect of climate on history, on a large
scale.
It included enough examples that the authors could use
statistics to estimate the probability of these events
aligning by chance.
And they found that there was only a 1% chance their
results could have come up randomly.
So, this study offers the strongest evidence yet that there
is a significant link between volcanic activity and human
society.
But there’s one curious detail in all this.
And that is that not every eruption on the record was linked to
social unrest or a dynastic collapse.
In 1815, Mount Tambora erupted in Indonesia.
This eruption was the strongest recorded in human
history.
It cooled the summer across the Northern Hemisphere
by half a degree Celsius, and in Europe, 1815
became known as “the year without a summer.”
Despite well recorded climate changes all over the
Northern Hemisphere, this disruptive event did not cause
any social upheavals in Chinese history.
Researchers believe that this is because Chinese society
was stable in 1815.
When Mount Tambora erupted, there was no large-scale warfare or social unrest.
So, the researchers suspect that the Chinese people were
able to weather the hard times without any regime change.
If this interpretation is right, the researchers’ finding
suggests that climate change doesn’t have to cause
social unrest.
Like, if the extreme weather happens in a place that’s
stable, with support systems or food reserves in place,
environmental stressors might not disrupt society too
much.
And even though this study was all about events that
happened in the past, it may have some interesting insights for us now that we’re in an era
of global climate change, with more changes on the way.
Because climate change is already disrupting societies by
causing problems like droughts and food shortages, especially in the Global South.
But by investing in systems that make vulnerable societies
strong and resilient, we may have a better chance at
making it through challenges like these.
In the past two centuries, there have been relatively few
destructive volcanic eruptions.
But, as advanced as societies have become, there is no escaping
the fact that climate and society are intertwined.
In fact, sometime around the end of 2022 or in 2023,
scientists are expecting to see a dip in temperatures caused by the massive explosion of the Tonga
volcano in January of 2022.
This won’t make a dent in human-caused climate change
in the long term, but it will still be a measurable effect.
The thing is, whether or not environmental stress is caused
by volcanoes, it can wreak havoc on human society.
And as the planet warms, every part of the globe
is going to experience certain environmental stresses.
While most of the planet will rise in temperature rather than
fall, these changes will likely be similar to the ones caused
by volcanic eruptions.
The difference is, while volcanoes only affect the climate
for a couple of years, the crisis of anthropogenic climate
change will create longer-term disturbances.
But now that we have research to give us an idea how
these changes may affect society, we’re in a better position
than anyone else in history to prepare ourselves for the
changes that are coming.
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thank you for watching!
And also thanks to all those emperors out there who everybody thought it
was there fault but it turns out just some volcano half
way across the world really messed things up for them.
[♪ OUTRO]