Global climate change, war, and population decline in recent human history.

Although scientists have warned of possible social perils resulting from climate change, the impacts of long-term climate change on social unrest and population collapse have not been quantitatively investigated. In this study, high-resolution paleo-climatic data have been used to explore at a macroscale the effects of climate change on the outbreak of war and population decline in the preindustrial era. We show that long-term fluctuations of war frequency and population changes followed the cycles of temperature change.

The emotive causes of recurrent international conflicts.

Many international conflicts are recurrent, and many of these are characterized by periods of violence, including wars, that are hard to describe as planned products of rational decision-making. Analysis of these conflicts according to rational-choice international-relations theory or constructivist approaches has been less revealing than might have been hoped. We consider the possibility that emotive causes could better explain, or at least improve the explanation of, observed patterns.