El Niño
A farmer guides his carabao on dried and cracked farmland in San Juan town, Batangas province, south of Manila April 18, 2010. A mild dry spell brought about by the El Niño phenomenon damaged the Philippines' agriculture sector and caused power shortages due to low water levels at hydro power plants. REUTERS/Romeo Ranoco

The El Nino climate cycle brings not only high temperatures and dry weather, but also more chances of civil wars, a new study claims.

Between 1950 and 2004, the risk of civil wars doubled in 90 tropical countries when hit by El Nino, is the warm phase of the El Niño-Southern Oscillation, or ENSO, a periodic warming and cooling of the tropical Pacific Ocean.

While its partner La Nina is a cool, rainy period, El Nino brings high temperature and more scarce rainfall every three to seven years, impacting weather patterns across much of Africa, the Mideast, India, southeast Asia, Australia, and the Americas, which holds half the world's population.

Interacting with other factors including wind and temperature cycles over the other oceans, El Nino can vary dramatically in power and length. At its most intense, it brings scorching heat and multi-year droughts.

In the study published in Wednesday's Nature, scientists from Princeton University and Columbia University's Earth Institute used statistics to link global weather observations and outbreaks of violence.

The scientists correlated ENSO from 1950 to 2004 with onsets of civil conflicts that killed more than 25 people in a given year. The data included 175 countries and 234 conflicts, with over half of which each caused more than 1,000 battle-related deaths.

The findings suggest that the arrival of El Nino doubled the risk of civil conflict across 90 affected tropical countries, and may help account for a fifth of worldwide conflicts over the past half-century.

Remarkable links were found between El Nino patterns and civil unrest in Peru in 1982 and Sudan in 1963.

Further, a strong link between violence and El Nino were also found in El Salvador, the Philippines and Uganda in 1972; Angola, Haiti and Myanmar in 1991, and Congo, Eritrea, Indonesia and Rwanda in 1997.

This is the first major evidence that the global climate is a major factor in organized violence around the world, says Solomon M. Hsiang, the study's lead author, a graduate of the Earth Institute's Ph.D. in sustainable development.

While the study does not blame specific wars on El Nino, it confirms many scientists' speculation over the strong link between climate-conflict.

Just this July, the UN Security Council discussed on climate-driven conflicts. Secretary-General Ban Ki-moon noted that the possible adverse effects of climate change are not only exacerbates threats to international peace and security; it is a threat to international peace and security.

The most important thing is that this looks at modern times, and it's done on a global scale, said Hsiang. 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.

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 the co-author 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.

According to Cane, the poorest countries respond to El Nino with violence.

The natural El Nino cycle is different from manmade global warming which continuously ramps up the temperature and extreme weather, according to the researchers. Global warming would have even greater impacts than the El Niño, and is more likely to provoke conflicts, noted Cane.

El Nino patterns can be predicted up to two years ahead, the study may give room for pre-emptive action for some conflicts and reduce humanitarian suffering.