Hotter, drier weather brought about by the El Niño climate pattern has been linked to civil conflicts within poor tropical countries, according to a new study.

The study, released Wednesday, finds that the risk of internal conflicts in tropical countries affected by El Niño doubles as compared with the phenomenon's wetter, cooler counterpart, La Niña.

Formally known as the El Niño-Southern Oscillation (ENSO), it refers to the irregular warming of the surface of the Pacific Ocean near the equator. This affects the behavior of the ocean and the atmosphere, disrupting weather patterns around the planet. Normally wet regions dry out, and dry regions become wet. El Niño occurs roughly every four years, though it is not completely predictable, according to the National Oceanic and Atmospheric Administration.

The study looked at ENSOs from 1950 to 2004 and overlaid this data with civil conflicts or violence that had taken place within national borders. It examined 175 countries and 234 conflicts.

In countries whose weather cycles are determined by ENSO, the risk of civil conflict occurring during La Niña was about 3 percent; during El Niño, this doubled to 6 percent, the paper says. One out of five conflicts over the 54-year period were influenced in some way by El Niño, researchers said.

The incidence of strife in countries not affected by ENSO remained at 2 percent.

We believe this finding represents the first major evidence that global climate is a major factor in organized violence around the world, said Solomon Hsiang, the lead author of the study who conducted the research at Columbia University.

Researchers emphasized that that their findings did not mean that El Niño caused one in five conflicts, rather it contributes to one in five. It was an invisible influencing factor, though not the only one, in spurring internal conflict.

Hsiang, currently a postdoctoral researcher at Princeton University, said that it was the poorest countries that responded to El Niño with violence. Wealthy, partly tropical countries like Australia, which also experienced climatic fluctuations due to El Niño, did not lapse into violence.

Proposing that climatic fluctuations can contribute to violence in modern society is quite thought provoking. But researchers acknowledge that they have yet to explain how unusually warm sea surface temperatures are connected with violence. 

One of the theories put forth was that the effects of El Niño -- including droughts, crop losses, and hurricanes -- could fuel resentment and division in poorer societies already grappling with poverty, hunger and unemployment.

When people get warm and uncomfortable, they get irritated. They are more prone to fight, more prone to behave in ways that are, let's say, less civil, said Mark Cane, a study researcher with the Lamont-Doherty Earth Observatory of Columbia University, as per Livescience.com report.  I think all of these things contribute, and they are all quite real.

Hsiang compared El Niño's role in violence to that of winter ice on a road in a car accident, as stated in the Live Science report.  The ice alone doesn't cause the accident, but contributes to it.

According to the Collier-Hoeffler Model (a comprehensive studies of civil wars carried out by a team from the World Bank), there are many causes that might prompt armed rebellion. Poverty, inequality, increasing population are just some of the common factors.

Halvard Buhaug, a senior researcher at the Peace Research Institute in Oslo, said that even though many would be tempted to add climate or climate cycles to the causes of civil war, it would be premature to do so.

Buhaug, who was not involved in the study, said that while Hsiang and colleagues showed that El Niño and violent conflicts coincided, they needed to examine individual cases in order to precisely see how an unusual climatic event like El Niño led to a specific conflict.

Until we are able to do that, I don't think we are in a position to claim there is a causal relationship between climate and conflict, Buhaug told Live Science.

The research appears in the Aug. 25 issue of the journal Nature.