The El Niño/La Niña cycle has been correlated to periodic increases in warfare by researchers at Columbia University's Earth Institute.
Drought, crop losses, and other effects of the dry, hot El Niño climate conditions may destabilize already vulnerable nations. For example, the research notes the case of Peru. In 1982 a severe El Niño dried out the highlands of Peru and destroyed crops. That same year, attacks by the Sendero Luminoso, or Shining Path, guerrilla revolutionary movement escalated into full blown civil war.
Though El Niño can't be said to cause warfare, the research found a strong correlation between fluctuations in the El Niño Southern Oscillation (ENSO) and large-scale civil strife. ENSO is the collective term for the El Niño/La Niña cycles.
The research, published in the journal Nature, found that the arrival of El Niño doubles the risk of civil wars across 90 affected tropical countries. El Niño, which strikes every three to seven years, may partially account for a fifth of worldwide conflicts during the past half-century.
"The most important thing is that this looks at modern times, and it's done on a global scale," said Solomon M. Hsiang, the study's lead author. "We can speculate that a long-ago Egyptian dynasty was overthrown during a drought. That's a specific time and place, that may be very different from today, so people might say, 'OK, we're immune to that now.' This study shows a systematic pattern of global climate affecting conflict, and shows it right now."
The scientists examined ENSO (El Niño Southern Oscillation) from 1950 to 2004, alongside the onsets of civil conflicts that killed more than 25 people in a given year. They studied 175 countries and 234 conflicts, more than half of which caused in excess of 1,000 battle-related deaths each.
For nations where ENSO has little effect on the weather, the chances of a civil war stayed steady at 2 percent. In countries where ENSO influences the weather, La Niña increased the chance of civil war breaking out to about 3 percent.
But during El Niño, the chance doubled, to 6 percent. The Columbia researchers estimated that El Niño may have played a role in nearly 30 percent of the civil wars in those countries affected by El Niño, and 21 percent of all civil wars during the period studied.
Specifically the study mentions Sudan, first in 1963, then 1976, and finally in 1983. The fighting which started in 1983 continued for 20 years and resulted in 2 million deaths.
El Salvador, the Philippines, and Uganda were plunged into turmoil during a 1972 El Niño.
Angola, Haiti, and Myanmar experienced serious civil conflict starting in the 1991 El Niño year.
Congo, Eritrea, Indonesia, and Rwanda suffered deadly conflict during the 1997 El Niño.
Wealthier nations are better at keeping calm through disruptive El Niño events. Australia is influenced by ENSO, but has never had a civil war.
"But if you have social inequality, people are poor, and there are underlying tensions, it seems possible that climate can deliver the knockout punch," said Hsiang.
"No one should take this to say that climate is our fate. Rather, this is compelling evidence that it has a measurable influence on how much people fight overall," said coauthor Mark Cane, a climate scientist at Columbia's Lamont-Doherty Earth Observatory . "It is not the only factor–you have to consider politics, economics, all kinds of other things."
Currently, the Horn of Africa suffers serious drought as well as brutal and deadly civil conflict. Discovery News recently covered research correlating La Niña conditions with drought in Eastern Africa.
"Forecasters two years ago predicted that there would be a famine in Somalia this year, but donors in the international aid community did not take that forecast seriously," said Hsiang in a teleconference covered by the AFP.
"We hope our study can provide the international community and governments and aid organisations with additional information that might in the future help avert humanitarian crises that are associated with conflict."
IMAGE 1: An village in the Nuba mountains of Sudan, abandoned during the civil war. (Wikimedia Commons)
IMAGE 2: A casualty of the Salvadoran Civil War is carried back to his farm for burial (1982). (Gary Mark Smith, Wikimedia Commons)