The annual death toll from war and interpersonal violence amounts to 0.5-1 million. Many factors ( social, political, economical, physiological) contribute to human conflict. Can climate changes be responsible too? Many disciplines have looked at relationship between climate changes and conflicts and this research is growing. This article provides the first quantitative summary of the existing findings. Solomon M. Hsiang, Marshall Burke and Edward Miguel from USA report an interesting association in the review.
A broad definition of “conflict,” ( that encompass a range of outcomes from individual- level violence and aggression to country-level political instability and civil war) was used to collect data. Quantitative studies that can reliably infer causal associations between climate variables and conflict outcomes were only included.Studies needed to account for unobservable confounding factors across populations, as well as for unobservable time- trending factors that could be correlated with both climate and conflict.
60 primary studies met the criteria. Large deviations from normal precipitation and mild temperatures systematically increased the risk of many types of conflict, often substantially, and that this relationship appears to hold over a variety of temporal and spatial scales.
Subjects are more likely to exhibit aggressive or violent behavior toward others if ambient temperatures at the time of observation are higher. Aggressive behaviors that respond to temperature range from horn-honking while driving and inter-player violence during sporting events to much more serious – e.g., the use of force during police training , domestic violence, and violent crimes such as assault or rape. Although physiological mechanism linking temperature to aggression remains unknown, the causal association appears robust across a variety of contexts.
In low-income settings, extreme rainfall events that adversely affect agricultural income are also associated with higher rates of personal violence and property crime .High temperatures are also associated with increased property crime but violent crimes appear to rise with temperature more quickly than property crimes.
1σ change in a location’s temperature is associated with an average 2.3% increase in the rate of interpersonal conflict and a 13.2% increase in the rate of intergroup conflict. Multiple mechanisms might contribute to the observed relationships and that different mechanisms could be dominating in different contexts. Decline in economic productivity, increasing inequality, displacements and migration etc are likely mechanisms by which climatic changes might be influencing human conflict.
Conclusions: Climatic changes can contribute to human conflict.The association between climatic events and human conflict is general i.e. it has been observed almost everywhere. Temperature increase is well associated with increased expression of conflictual behaviour.
Summary of the article:
Quantifying the Influence of Climate on Human Conflict Solomon M. Hsiang, Marshall Burke, Edward Miguel.Science. 2013. Ahead of print.