Their paper, published on 10 November in the journal Proceedings of the National Academy of Sciences, contradicts earlier studies that found that higher temperatures are a major risk factor in conflict.
For instance, last year a different group concluded that a shift towards hotter conditions by a single statistical unit known as a ‘standard deviation’ — equivalent to, for example, warming an African country by 0.4 degrees Celsius for a year — caused a four per cent rise in the likelihood of personal violence and a 14 per cent increase in conflict between groups.
“The effects of climate change on violence are actually quite modest compared to other factors.”
John O’Loughlin, University of Colorado
But now a team led by John O’Loughlin, a geographer at the University of Colorado Boulder in the United States, says that previous research may have overlooked other key triggers such as political instability, poverty and geographical conditions.
O’Loughlin’s team examined these factors alongside exceptionally hot or dry periods in Sub-Saharan Africa to assess the chances of increased violence. Breaking the area down into subregional grids, the researchers pinpointed 78,000 ‘conflict events’ from the past 33 years and matched them with weather conditions and social and geographical factors.
They found that conflicts such as riots, protests or violence against civilians were more common when temperatures were particularly high. But they also discovered an inconsistent relationship between temperature deviations on the one hand and different types of conflict and different subregions on the other.
And, more critically, they found that longer periods of higher temperatures and wet or dry conditions had less impact on conflict than other influences, such as recent nearby violence and a lack of democracy, says O’Loughlin.
“We were surprised to discover that the effects of climate change on violence are actually quite modest compared to other factors,” he says.
However, Tim Forsyth, an expert on the politics of environment and development at the London School of Economics and Political Science in the United Kingdom, says the paper also raises some questions.
“The problem with this approach is that there are many parts of the world experiencing climate change where violence doesn’t occur,” he says. “So instead of searching for linkage between climate change and violence, they should try to explain why certain places have conflict and others don’t.”
He believes that the approach taken will inevitably fail to explain the emergence of conflict in its complexity and help policymakers prevent it.
O’Loughlin agrees that other factors, such as conflicts over resources, play a major part in explaining conflict.
“Climate change is seen as a ‘threat multiplier’ that adds to the stresses and tensions over the distribution of resources in poor societies,” he says. “The scientific and public policy opinion is that it will be an indirect effect through this resource competition among groups.”
> Link to study in Proceedings of the National Academy of Sciences