Remarkably sane article in Science: Warm periods are good, cold periods are bad

Got War? Blame the Weather - ScienceNOW

As the Thirty Years' War between Europe's ruling dynasties dragged on during the 17th century, soldiers suffered through the coldest few decades Europe had experienced for some time. Far to the east, armies from Manchuria (present day northern China) swept down from the snowy north and breeched the Great Wall of China. Not long after, a plague swept Europe. Why so much tumult? A controversial new study suggests that most of humankind's maladies—from wars to epidemics to economic downturns—can be traced to climate fluctuations.
...a 100-year cold period beginning in 1560 caused shortened crop growing seasons. The researchers found a causal linkage with a decline in average human height by nearly an inch during this period, and the century was rife with disease and conflict. But the world began to warm in 1650; when Charles II was crowned king of England in 1660, the coronation sparked the Enlightenment era in Europe.
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Zhang says that's hard to predict. "We've never experienced how hot the climate [has to be] to create human disasters," he says. "We know current temperatures may be the hottest for 2 millennia," but the evidence that this will cause wars is "not much."