Throughout the ages, human societies have similarly been in flux, with repeated wars, migrations, and power shifts leading to the rise or fall of nation-states.
But to what extent are these across the lines of human history—climate change and conflict—related to each other?
“Most of the time, we think of climate change as something very new, something that people don’t know how to deal with,” he says. Nancy KanianKellogg Professor of Managerial Economics and Decision Sciences. “But in reality, climate is always changing, and this interaction between climate and society, economy, politics and conflict is a story as old as time.”
To shed light on the historical relationship between climate change and political instability, Qian teamed up with Murat Iyigun of the University of Colorado Boulder and Joris Mueller of the University of Singapore. They analyzed the relationship between regional conflicts and regional changes in temperature and rainfall that occurred several hundred years ago during the so-called Little Ice Age.
The researchers’ analysis revealed that while sudden and severe cold disturbances within a 50-year period were not associated with increased conflict, fighting appeared to escalate in areas that experienced two consecutive 50-year cooling spells.
Human ingenuity may have allowed populations to successfully adapt to climate change in the short term (ie, less than 50 years), Qian says. But when climate change intensified and compounded over longer periods of time, societies were pushed into conflict.
“We have to appreciate that climate change is a very long process and can affect generations of people,” Qian says.
“Today’s climate change will be a complex and long-term process, with necessary economic changes, social changes, cultural changes and human migration changes,” he adds. “We have to start thinking about it now.”
Climate cues in nature
Qian, Iyigun and Mueller focused their research on the Little Ice Age, a period of widespread cooling from the early 14th century to the mid-19th century that was particularly intense in areas around the northern Atlantic Ocean.
Significant cooling during this period extended the footprints of glaciers and freezing seas as far as modern Turkey. Temperature shifts have also led to increased rainfall variability. This in turn led to drought, regional agricultural disturbances and famines, which weakened states and opened the door to conflict and invasion.
For their study, Qian and his colleagues created a dataset of wars and battles fought between 1400 and 1900 in Europe, the Near East and North Africa. Their final sample included 2,792 skirmishes. The researchers cross-referenced this dataset with historical climate data constructed by geologists and climatologists using subtle clues from nature, such as tree rings and fossilized pollen, as well as written documentation of weather events recorded by travelers and traders of the period.
The research team then divided the area into 400km by 400km cells on a grid and plotted the conflicts and climate shifts in their respective locations to see what patterns might emerge.
Condensation of challenges
When a land cell experienced two consecutive cooling periods, the collision incidence increased by 3.86%, the researchers found. Additionally, locations heavily dependent on agriculture were more likely to see fighting between 1401 and 1450, as were cells where two different territories or states shared a border. Dependence on agriculture and proximity to other groups appears to have primed these areas for political instability, making them more susceptible to conflict as weather changes continue.
“Our interpretation is that collisions compound,” Qian says. He hypothesizes that as the weather cooled and a society’s usual agricultural practices became unsustainable, the society adapted and looked to new approaches. But if climate change continued for more than five decades or so, society might have to consider more desperate and disruptive adaptations—perhaps through migration or the fight for resources.
It wasn’t just that there was a certain low temperature threshold at which food supply became impossible, according to Qian. The researchers ruled out this possible explanation by controlling for temperature level in their study. Qian believes that, instead, what explains the spike in fighting is the stress of having to repeatedly find new ways to cope with an increasingly cold life.
After all, even today we can see how decades of conflict (not necessarily related to climate change) are reshaping societies and cultures.
“If you only have problems for a few years, those problems are easily mitigated,” he says. “But if you have generations of discomfort, those sections get deeper and deeper, and it’s very difficult to get out of.”
Better future casting
Qian hopes that as the technology and available data sets continue to improve, researchers will be able to form a more detailed understanding of how climate change has historically shaped society—and how it may do so in the future. This type of research could help create key strategies to ameliorate the negative impacts of a changing climate on society.
“When we look at countries on the front lines of climate change – particularly those that don’t have the financial resources of the US or Northern Europe – we hear about many possible solutions, from improving education to gender equality,” says Qian. While these approaches are important, “they ignore the fundamental issue: many people today no longer have land that produces food. They will remain poor and continue to struggle, until this is addressed.”
