Climate Change and Global Conflicts

"Cold" wars have existed throughout history; now we may see heat wars.

Traumatic climate cooling may have launched wars in the past, like the Little Ice Age of the mid-sixteenth through mid-nineteenth centuries. Cold-induced stresses on agriculture led to wars, famines, and population declines, an international team of researchers believes. Now, they warn that future climate change that turns up the heat could also increase conflicts.

Sudden changes in temperature don't directly cause conflict, but they do disrupt water and food supplies. Shortages of such critical resources can lead people to rise against their governments or invade neighboring countries, according to research led by University of Hong Kong geographer David Zhang and published by the Proceedings of the National Academy of Sciences.

To study the relationship between climate and conflict, the researchers collected data on temperature change and wars from A.D. 1400 to 1900. They discovered that cycles of turbulence followed historic low temperatures, with tranquility restored during more-temperate times. Sources for the study included a database of 4,500 wars, assembled by co-author Peter Brecke of Georgia Tech, and climate records reconstructed by paleontologists from historical documents.

The researchers found that there were nearly twice as many wars per year worldwide during cold centuries as there were during the milder eighteenth century. More than 80% of countries around the world experienced more wars in a cold climate, according to Zhang.

The researchers reason that the link between climate shock and conflict is the supply of food: Decreases in agricultural production trigger increases in food prices, and when grain prices reach a certain level, wars erupt.

Population growth and decline are also affected by these climate change driven conflicts, the researchers believe. After peak periods of war in Europe and Asia, such as during the frigid seventeenth century, populations declined. In China, population dropped by 43% between 1620 and 1650, then rose dramatically between 1650 and 1800, when the next cooling period began, bringing another global demographic shock.

"Climate change may have played a more important role on human civilization than has so far been suggested," says Zhang. The depletion of resources on which livelihoods are based is the most critical effect of such change and is "the root cause of human miseries—e.g., wars, famines, and epidemics."

Abrupt global warming is upon us now, they warn, and may pose just as dire threats to resource supply and demand as did global cooling in centuries past.

"The speed of global warming is totally beyond our imagination," says Zhang. "Such abnormal climate will certainly break the balance of human ecosystem. At the moment, scientists cannot accurately predict the chain of ecological effects induced by climate change. If global warming continues, we are afraid that the associated shortages of livelihood resources such as freshwater, arable land, and food may trigger more armed conflicts (e.g., Darfur in Africa) or even general crises in the world."

As Brecke of Georgia Tech points out, global warming may have some beneficial effects in the short term, but "with more droughts and a rapidly growing population, it is going to get harder and harder to provide food for everyone and thus we should not be surprised to see more instances of starvation and probably more cases of hungry people clashing over scarce food and water."

Human beings are unlikely to sit still with such dire prospects before them, notes Zhang. Responses to resource shortages extend beyond fighting over dwindling crumbs of bread and drops of water, but include economic change, trade, technological and social innovation, and peaceful resource distribution. In eighteenth century China, for instance, the frequency of war decreased "because the Qing emperors had united all troublesome tribal states in the western and northern marginal areas," the authors write. "We hope that positive social mechanisms that are conducive to human adaptability will play an ever more effective role in meeting the challenges of the future."--Cynthia G. Wagner

Sources: "Global Climate Change, War, and Population Decline in Recent Human History" by David D. Zhang et al. Proceedings of the National Academy of Sciences (November 20, 2007).

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March-April 2008. Vol 42 No. 2

Climate Change and Global Conflicts