From the Bulletin of the Atomic Scientists, a fascinating piece on climate change and drought as a cause of the Syrian uprising by Shahrzad Mohtadi:
From 1900 until 2005, there were six droughts of significance in Syria; the average monthly level of winter precipitation during these dry periods was approximately one-third of normal. All but one of these droughts lasted only one season; the exception lasted two. Farming communities were thus able to withstand dry periods by falling back on government subsidies and secondary water resources. This most recent, the seventh drought, however, lasted from 2006 to 2010, an astounding four seasons -- a true anomaly in the past century. Furthermore, the average level of precipitation in these four years was the lowest of any drought-ridden period in the last century.
While impossible to deem one instance of drought as a direct result of anthropogenic climate change, a 2011 report from the National Oceanic and Atmospheric Administration regarding this recent Syrian drought states: "Climate change from greenhouse gases explained roughly half the increased dryness of 1902-2010." Martin Hoerling, the lead researcher of the study, explains: "The magnitude and frequency of the drying that has occurred is too great to be explained by natural variability alone. This is not encouraging news for a region that already experiences water stress, because it implies natural variability alone is unlikely to return the region's climate to normal." The Intergovernmental Panel on Climate Change predicts that global warming will induce droughts even more severe in this region in the coming decades.
It is estimated that the Syrian drought has displaced more than 1.5 million people; entire families of agricultural workers and small-scale farmers moved from the country's breadbasket region in the northeast to urban peripheries of the south. The drought tipped the scale of an unbalanced agricultural system that was already feeling the weight of policy mismanagement and unsustainable environmental practices. Further, lack of contingency planning contributed to the inability of the system to cope with the aftermath of the drought. Decades of poorly planned agricultural policies now haunt Syria's al-Assad regime.