As the Obama administration undertakes a highly public, multilateral campaign to degrade and destroy the militant jihadists known as ISIS, ISIL and the Islamic State, many in the West remain unaware that climate played a significant role in the rise of Syria's extremists. A historic drought afflicted the country from 2006 through 2010, setting off a dire humanitarian crisis for millions of Syrians. Yet the four-year drought evoked little response from Bashar al-Assad's government. Rage at the regime's callousness boiled over in 2011, helping to fuel the popular uprising. In the ensuing chaos, ISIS stole onto the scene, proclaimed a caliphate in late June and accelerated its rampage of atrocities including the recent beheadings of three Western civilians. 

While ISIS threatens brutal violence against all who dissent from its harsh ideology, climate change menaces communities (less maliciously) with increasingly extreme weather. Most of us perceive these threats as unrelated. We recycle water bottles and buy local produce to keep the earth livable for our children -- not to ward off terrorists. Yet environmental stressors and political violence are connected in surprising ways, sparking questions about collective behavior. If more Americans knew how glacial melt contributes to catastrophic weather in Afghanistan -- potentially strengthening the Taliban and imperiling Afghan girls who want to attend school -- would we drive more hybrids and use millions fewer plastic bags? How would elections and legislation be influenced?

The drought that preceded the current conflict in Syria fits into a pattern of increased dryness in the Mediterranean and Middle East, for which scientists hold climate change partly responsible. Affecting 60 percent of Syria's land, drought ravaged the country's northeastern breadbasket region; devastated the livelihoods of 800,000 farmers and herders; and knocked two to three million people into extreme poverty. Many became climate refugees, abandoning their homes and migrating to already overcrowded cities. They forged temporary settlements on the outskirts of areas like Aleppo, Damascus, Hama and Homs. Some of the displaced settled in Daraa, where protests in early 2011 fanned out and eventually ignited a full-fledged war. 

Drought did not singlehandedly spawn the Syrian uprising, but it stoked simmering anger at Assad's dictatorship. This frustration further destabilized Syria and carved out a space in which ISIS would thrive...