Climate cycles are driving wars

By Clive Cookson in London

Researchers in the US have established the first strong statistical link between climate and conflict in the modern world.

El Niño, the cyclical warming of the equatorial Pacific ocean every few years, doubles the risk of armed conflict breaking out in the countries affected, according to analysis by Columbia University’s Earth Institute in New York.

The study, published on Thursday in the journal Nature, concluded that, between 1950 and 2004, El Niño played a role in 21 per cent of civil wars worldwide and 30 per cent of those in countries directly affected by the cycle.

Mark Cane, professor of climatology at Columbia, said that while climate alone could not trigger warfare – many political, economic and social factors were involved – “this is compelling evidence that it has a measurable influence on how much people fight overall.”

The study focused on the El Niño Southern Oscillation (Enso), which affects weather patterns across sub-Saharan Africa, south and south-east Asia, Australasia and Latin America. The continents generally become warmer and dryer during the El Niño phase and cooler and wetter during the opposite La Niña phase.

Though historians have built up much evidence for the influence of weather and climate – whether storms or long-term drought – on warfare and the fall of civilisations, the Columbia researchers say theirs is the first to make a statistical case for such destabilisation in the present day.

The data included all civil conflicts known to have killed more than 25 people in a given year: a total of 234 conflicts over more than half a century. For nations affected by Enso, the chance of conflict breaking out is 6 per cent in an El Niño year and 3 per cent in a La Niña year.

Examples of festering conflicts that have blown up during El Niños include Sudan (1963, 1976 and 1983); El Salvador, the Philippines and Uganda (1972); Peru (1982); Angola, Haiti and Burma (1991); and Congo, Eritrea, Indonesia and Rwanda (1997).

The study does not investigate the mechanism by which climate feeds conflict, though it is clear from the data that poorer countries are more vulnerable. “If you have social inequality, people are poor and there are underlying tensions, it seems possible that climate can deliver the knockout punch,” said Solomon Hsiang, lead author of the Nature paper. When crops fail, people may take up a gun simply to make a living, he added.

Nor does the research address directly the issue of long-term climate change. There is no clear evidence about whether future global warming would intensify or reduce the Enso fluctuations, though Prof Cane said a warmer world “would tend to be more El Niño-like”, whatever happens to the cycle.

Marshall Burke of the University of California, Berkeley, who was not involved in the study, said the Columbia authors gave “very convincing evidence” of a connection between climate and conflict, though he added: “People may respond differently to short-run shocks than they do to longer-run changes in average temperature and precipitation.”

Copyright The Financial Times Limited 2011.