From Syrian President Bashar al-Assad to ISIS, many of the culprits are well known.
That's a question CNN reader Robert Goldschmidt, from University Park, Florida, asked recently as part of our network's Two Degrees series on climate change.
Specifically, he wanted to know if a record drought had "triggered" the crisis.
There are high-profile backers of this view, among them U.S. Secretary of State John Kerry.
"It's not a coincidence that immediately prior to the civil war in Syria, the country experienced its worst drought on record. As many as 1.5 million people migrated from Syria's farms to its cities, intensifying the political unrest that was just beginning to roil and boil in the region," Kerry said this week in a speech at Old Dominion University in Norfolk, Virginia.
While drought is not the only cause of the Syrian conflict, the idea is that it has helped drive up social unrest. It increased unemployment, exacerbated famine and water scarcity, and forced farmers from their homes and into cities, where violence began.
There's scientific evidence to support the case.
In a 2014 study published in the journal Weather, Climate and Society, climate expert Peter Gleick
wrote that "water and climatic conditions have played a direct role in the deterioration of Syria's economic conditions."
Furthermore, the idea that the drought, which was the worst ever recorded in the region, was worsened by climate change in the region was strengthened in another study published this year
. Researchers at the University of California, Santa Barbara, and Columbia University say the multiyear drought that helped drive the conflict was made "two to three times more likely" by man-made global warming.
According to the latest report from the Intergovernmental Panel on Climate Change
, the Middle East overall is expected to trend hotter and drier, which will make severe, multiyear droughts such as what occurred in Syria
more likely to occur.
The drought started in 2006, years before violence broke out in Syria. By 2009, yields of wheat and barley fell by about one-half and two-thirds
, respectively, and 800,000 people lost their basic food support. By 2011, the year violence erupted after a popular uprising against Assad
, the situation had worsened and more than 1 million Syrians were forced into food insecurity. With rising political tensions, and families no longer able to ensure their futures on rural agricultural land, more than 1.5 million people migrated to cities, including Aleppo, Damascus and Homs, where many deaths occurred.
While there is evidence to support the climate-violence link, not everyone agrees Syria's drought contributed to its civil war. One fact that casts doubt: Other droughts occurred in other countries such as Turkey and Iran
, which did not see the same mass migrations and social unrest. Others simply say the link between climate change and violence is prone to overstatement. And researchers stress the importance of acknowledging that war often emerges from many factors.
The U.S. Department of Defense takes the link seriously, though, calling climate change a "threat multiplier
." That means its effect is greatest in areas that are already environmentally and socially unstable.
Kerry and other officials stress the connection is real.
"It would be better for all of us if I was exaggerating the urgency of this threat, but the science tells us unequivocally that those who continue to make climate change a political fight put us all at risk," Kerry said.
Those comments -- and this discussion -- come at a critical time.
Negotiators from 195 countries will gather in Paris on November 30 to try to work toward an agreement to curb the rise in global temperatures. Perhaps that agreement, if successful, also could help reduce climate change's contribution to drought, and potentially violence, around the world.