At the outset of his new book, "Tropic of Chaos" author Christian Parenti suggests that the violent death of Kenyan farmer Ekaru Loruman -- and perhaps thousands of people like him living in the global south -- arose not just from the proximate cause of a bullet in the head, delivered by a rival tribe amid a conflict over resources, but also from a toxic cocktail of poverty, Cold War militarization and climate.
He calls it a "catastrophic convergence," in which large numbers of unemployed young men with ready access to weapons represent a tinderbox into which the match of global warming is thrown.
"You've already got a very volatile situation in these countries," Parenti said in an interview. Throw on top of that that crop failures, disruptions in fishing -- and even increases in grain prices and other vacillations in global trade -- and the economic shock of global climate change in the developing world, he suggests, can prove explosive.
It's not an entirely new idea, and numerous books and studies have sought to explore the complex connections between the environment and social friction. But the need to do so has gained increased currency -- and urgency -- not least because many climate scientists believe that the cyclical climate patterns driving weather in many of the world's less developed regions will become more frequent and more intense as average global temperatures rise.
That notion helped inspire a new study conducted by a team of researchers at Columbia University's Earth Institute. Indeed, what Parenti hypothesized anecdotally through Loruman's story and profiles of myriad other conflicts brewing across the globe, the researchers attempt to quantify statistically -- perhaps for the first time.
The analysis, to be published Wednesday in the journal Nature, reveals a striking connection between global climate and civil conflict -- though the underlying mechanism driving that connection remains something of a mystery. At the very least, the researchers suggest, the findings -- and future analyses based on them -- might provide an avenue for policymakers and humanitarian organizations to better prepare for years in which hostilities are likely to spike.
The researchers looked at the rhythms of a phenomenon dubbed ENSO (short for the El Niño-Southern Oscillation), which governs cyclical increases and decreases in temperature and precipitation for roughly half the world's population. They compiled data on ENSO patterns between 1950 and 2004 and paired this with data chronicling the onset of conflicts in which 25 or more people were killed in a given year.
The latter data set encompassed 234 separate conflicts in 175 countries. Half of these resulted in 1,000 or more deaths.
Controlling for a variety of other factors, the researchers discovered that in regions effected by El Niño, which delivers higher temperatures and reduced rainfall every three to seven years, the odds of civil conflict erupting increased twofold, to 6 percent, over cooler periods when El Niño's cousin, La Niña, prevails.
This does not mean that global climate patterns are the direct cause of increased violence, the researchers said, but like Parenti's catastrophic convergence, they likely play a significant role in sending populations with the right conditions over the edge.
In an interview, Solomon Hsiang, the lead author of the study, used car accidents as an analogy. "When you think about it, car accidents happen all the time," he said. "But they become more likely based on some environmental conditions, like when it's raining or icy."
The researchers also noted that they controlled for local temperature and rainfall amounts in individual countries, suggesting that the pattern of increased violence was not necessarily a function of weather on the ground, but in many cases could arise from the complex web of interdependent global trade, in which the impacts of El Niño at any one point can ripple though economies far and wide -- with particularly dire effects on fragile economies unable to endure shortages and price hikes.
The precise mechanics of the climate-conflict connection, Hsiang said, are fodder for future study, though he added that in practical terms, the ability to reliably predict the arrival of El Niño -- which modern technology now permits as much as two years out -- could already help aid agencies prepare resources ahead of periods when conflict and attending humanitarian crises are more likely to arise.
Still, not everyone is convinced. Halvard Buhaug, a senior researcher at the Center for the Study of Civil War in Norway said he was intrigued by the study's findings, but he said far more research was needed.
"All of us agree that climate is not going to be the sole driver of conflicts, and at best, it may contribute to some or even many," Buhaug said in an interview. "But I remain skeptical about the causal effect of climate on many conflicts."
He pointed in particular to the near instantaneous impact of El Niño on conflicts suggested in the new research. Disruptions in trade or agricultural under-performance -- and associated changes in state income -- Buhaug said, would likely take far longer to manifest than the findings suggest. He also said he was puzzled by the fact that the authors appeared to carefully, and correctly, eliminate the possibility that local changes in temperature and rainfall could fully account for any upticks in violence.
"What could it be that could have such an immediate effect but does not work through local changes in climate?" Buhaug wondered.
Hsiang said that's precisely what he and his fellow researchers hope to tease out in future analyses. He also suggested that because the effect was largely absent in areas not impacted by El Niño, as well as in El Niño-influenced countries with more developed economies and political structures, like Australia, the connection implied by the study was significant.
"What we found is quite a bit stronger than a mere correlation," Hsiang said.
Policy makers and security analysts won't likely be surprised.
Last year, the Pentagon noted for the first time in its Quadrennial Defense Review, a congressionally mandated evaluation of the nation's military doctrine, that climate change might play in global conflict.
"Assessments conducted by the intelligence community indicate that climate change could have significant geopolitical impacts around the world, contributing to poverty, environmental degradation, and the further weakening of fragile governments," the document stated. "Climate change will contribute to food and water scarcity, will increase the spread of disease, and may spur or exacerbate mass migration.
"While climate change alone does not cause conflict," it continued, "it may act as an accelerant of instability or conflict, placing a burden to respond on civilian institutions and militaries around the world."
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