The El Niño global climate cycle is triggering regular conflicts across the globe, new research suggests.
Its arrival every three to seven years boosts temperatures and cuts rainfall, doubles the risk of civil wars across 90 affected tropical countries, and could be behind as many as a fifth of worldwide conflicts during the past half-century, says the Columbia University team.
While climate has been linked with many historical conflicts, this is the first study to examine whether the connection exists today.
"The most important thing is that this looks at modern times, and it’s done on a global scale," says Solomon M Hsiang of the university's Earth Institute.
"This study shows a systematic pattern of global climate affecting conflict, and shows it right now.”
The El Niño-Southern Oscillation, or ENSO, is a periodic warming and cooling of the tropical Pacific Ocean, which affects weather patterns across much of Africa, the Middle East, India, southeast Asia, Australia, and the Americas. Half the world’s people live in the affected regions.
During the cool, or La Niña, phase, rain may be relatively plentiful in tropical areas; during the warmer El Niño, land temperatures rise, and rainfall declines in most affected places. On occasion, it brings scorching heat and multi-year droughts.
The scientists tracked ENSO from 1950 to 2004 and correlated it with the onset of civil conflicts that killed more than 25 people in a given year. The data included 175 countries and 234 conflicts, over half of which each caused more than 1,000 battle-related deaths.
And for nations whose weather is controlled by ENSO, they found that during La Niña, the chance of civil war breaking out was about three percent; during El Niño, that doubled to six percent. Countries not affected by the cycle remained at two percent, whatever the stage of the ENSO cycle.
Overall, the team calculates that El Niño may have played a role in 21 percent of civil wars worldwide — and nearly 30 percent in those countries affected by El Niño.
"No one should take this to say that climate is our fate," says Mark Cane of Columbia’s Lamont-Doherty Earth Observatory. "Rather, this is compelling evidence that it has a measurable influence on how much people fight overall."
It's pretty clear why. Some examples leap out of the data, says the team: in 1982, for example, a powerful El Niño destroyed crops in impoverished highland Peru; later that year, guerrilla attacks by the Shining Path movement kicked off a 20-year civil war.
Not everybody agrees.
"The study fails to improve on our understanding of the causes of armed conflicts, as it makes no attempt to explain the reported association between ENSO cycles and conflict risk," says Halvard Buhaug of the Peace Research Institute Oslo in Norway.
"Correlation without explanation can only lead to speculation."