Study aims to scientifically link climate change to societal upheaval.
Brian Handwerk, for National Geographic News
Published October 3, 2011
Pockmarked with wars, inflation, famines and shrinking humans, the 1600s in Europe came to be called the General Crisis.
But whereas historians have blamed those tumultuous decades on growing pains between feudalism and capitalism, a new study points to another culprit: the coldest stretch of the climate change period known as the Little Ice Age.
The Little Ice Age curbed agricultural production and eventually led to the European crisis, according to the authors of the study—said to be the first to scientifically verify cause-and-effect between climate change and large-scale human crises.
Prior to the industrial revolution, all European countries were by and large agrarian, and as study co-author David Zhang pointed out, “In agricultural societies, the economy is controlled by climate,” since it dictates growing conditions.
A team led by Zhang, of the University of Hong Kong, pored over data from Europe and other the Northern Hemisphere regions between A.D. 1500 to 1800.
The team compared climate data, such as temperatures, with other variables, including population sizes, growth rates, wars and other social disturbances, agricultural production figures and famines, grain prices, and wages.
The authors say some effects, such as food shortages and health problems, showed up almost immediately between 1560 and 1660—the Little Ice Age’s harshest period—during which growing seasons shortened and cultivated land shrank.
As arable land contracted, so too did Europeans themselves, the study notes. Average height followed the temperature line, dipping nearly an inch (two centimeters) during the late 1500s, as malnourishment spread, and rising again only as temperatures climbed after 1650, the authors found.
Others effects—such as famines, the Thirty Years’ War (1618-48), or the 164 Manchu conquest of China—took decades to manifest. “Temperature is not a direct cause of war and social disturbance,” Zhang said. “The direct cause of war and social disturbance is the grain price. That is why we say climate change is the ultimate cause.”
The new study is both history lesson and warning, the researchers added.
As our climate changes due to global warming (see interactive), Zhang said, “developing countries will suffer more, because large populations in these countries [directly] rely on agricultural production.”