An estimated 200,000 Syrians have died since the onset of the country's civil war in 2011 and another three million have been forced to flee the country.
Complex political and social forces worked to drive the unrest. But, researchers from University of California Santa Barbara (UCSB) and Columbia University argue that a severe, multi-year drought spurred a massive migration to already stressed urban areas, agitating existing tensions — and that it was climate change that made the drought so bad.
"You can think of it as a natural drought that was made much worse by climate change," Colin Kelley, a climatologist at UCSB, told VICE News. "And because it was so severe, then you had this cascade of effects like the agricultural collapse and the mass migration and the population shock and the rise in crime and unemployment and nutrition-related diseases, and all that kind of stuff that happened just prior to the uprising."
The researchers' findings appear in the latest issue of the Proceedings of the National Academy of Sciences.
In 2008, Syria experienced the driest winter in the country's observed record, part of a drought that began in 2006 and ultimately became the worst ever recorded in Syria. The drought depleted the groundwater supply, used by farmers to irrigate land during normal dry seasons, and disrupted the country's wheat production, which made up about a quarter of the country's gross domestic product prior to the drought.
Farmers and their families began moving to urban areas in droves, a problem the government did little to alleviate, the paper argues. Ultimately, 1.5 million people migrated to cities that had already seen the arrival of nearly as many Iraqi refugees in the mid-2000s, creating levels of stress and corruption that president Bashar al-Assad failed to address.
"I think that this connection between drought and climate change is very real, and you can find it at work not just in Syria but also across the Sahel," Christian Parenti, author of Tropic of Chaos: Climate Change and the New Geography of Violence and a professor at New York University, told VICE News. "Although the connection between climate change, extreme weather, and local violence is attenuated, it is nonetheless real."
To tease out the influence of climate change on the recent drought, the researchers examined long-term trends in precipitation, temperature, and atmospheric pressure in Syria and the surrounding area, known as the Fertile Crescent, using 25 climate stations. They found that the data indicated trends of less rainfall and higher temperatures: the Fertile Crescent has seen a 13 percent reduction in winter rainfall since 1931, and every year from 1994 to 2009 saw temperatures higher than the 20th-century mean.
They then used experiments from two different sets of global climate models, one that included changes in carbon emissions during the 20th century and one that did not, to set a baseline of natural variability. They found that, when the trend toward warming was included, the likelihood of severe, multi-year drought increased two to three times.
"The climate models predict that if global warming continues, if climate change continues, on the trajectory that it has, then what we're going to see is continued drying and warming of this region throughout the 21st century," Kelley told VICE News. "And so that basically says the problem is only going to get worse."
The study adds to a growing body of evidence that changes in temperatures, precipitation patterns, and other aspects of the climate can lead to increased conflict. That can happen through a range of mechanisms, including disruption of agriculture and livelihoods, competition over increasingly scarce resources, like water, and negative affects of heat on the human psyche.
A review of published studies by the National Bureau of Economic Research found that an increase in hot temperatures can lead to an increase in both individual crimes, like road rage, and group crimes, like riots and wars.
"If this was the only study we had linking drought and hotter temperatures to conflict, maybe it would be less worrying and we'd be less inclined to believe it," Marshall Burke, an assistant professor of environmental Earth system science at Stanford and an author on the review, told VICE News. "But since we now have a whole set of studies throughout the world that make this link, the particular case of Syria is perhaps not so surprising."
Follow Laura Dattaro on Twitter: @ldattaro