Global climate change, war, and population decline in recent history …

[nerdgirl 0]

That’s the title of a recently published article from the Proceedings of National Academy of Sciences (PNAS) by 5 authors from Hong Kong, USA, China, and UK.

Full text available at (free): http://www.pnas.org/cgi/reprint/104/49/19214.pdf

The authors found correlation of historical incidence of cooling climate periods across disparate geographical and cultural areas (i.e., Europe & China) and incidence of war.

The hypothesis is that long-term climate change has significant direct effects in land-carrying capacity that increases the likelihood of armed conflicts and population declines, which seems kind of obvious to me ... but need to the data and analysis to "prove" it.
By doing a meta-analysis integrating multiple databases, a correlation is observed that the authors assert represents the first time that a clear link between war and changing global temperatures has been identified in historical data: “Results showed a cyclic pattern of turbulent periods when temperatures were low followed by tranquil ones when temperatures were higher. The number of wars per year worldwide during cold centuries was almost twice that of the mild 18th century.”

It’s a really neat study with a multidisciplinary approach leveraging geography, political science, environmental engineering, and anthropology (& edited by a Stanford population biologist). There are a lot of similarities to Jared Diamond’s Guns, Germs, and Steel … although much shorter.
The idea that past climate changes (both natural and human-created) influenced/impacted human society is not new – seen with the Cahokia Native Americans of East St Louis, the Anasazi of southwest USA, ancient and modern Mesopatamia, Turkey's Catalhayuk, and the Vikings of Greenland, albeit most of those were very localized. It’s the correlation with incidence of armed conflict/war that's novel.

Extrapolating to severe anthropogenic global warming is not completely unambiguous, as the Northern hemisphere is currently at the height of a warm period, whereas historical correlations of war and population decline were observed during cooling periods, e.g., the Little Ice Age (~1450 – 1710 CE). We’re starting at the top of a curve, whether completely natural or natural + human impact is disputed.

The paper mentions the impact of technological and social advances in Europe that the authors assert help mitigate the impact of cooling periods in the more recent past. To me this argues for the importance of technological and social approaches, such as cooperative institutions like the UN and the non-tradtional institutional approaches that leverage the power of the free market.

For the primary data addicts Figure/graphs attached. Caption: “Fig. 1. Paleo-temperature variation, war frequency, and population growth rate, A.D. 1400–1900. (A) Temperature anomaly (°C) in the NH that is smoothed by 40-year Butterworth low pass filter. (B) Number of wars in the NH (bright green), Asia (pink), Europe (turquoise), and the arid areas in the NH (orange). (C) Number of wars worldwide as recorded by Wright (turquoise), Luard (orange), and Brecke (bright green). (D) Twenty-year population growth rate in Europe (turquoise), Asia (pink), and the NH (blue) and the NH 50-year fatality index (bright green). Cold phases are shaded as gray stripes. All war time series are in 10-year units, and the data are listed in S[upplemental] I[nformation] [nerdgirl] Table 1. The bright green curves correspond to the right y axis.”

VR/Marg

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Abstract: “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. Further analyses show that cooling impeded agricultural production, which brought about a series of serious social problems, including price inflation, then successively war outbreak, famine, and population decline successively. The findings suggest that worldwide and synchronistic war–peace, population, and price cycles in recent centuries have been driven mainly by long-term climate change. The findings also imply that social mechanisms that might mitigate the impact of climate change were not significantly effective during the study period. Climate change may thus have played a more important role and imposed a wider ranging effect on human civilization than has so far been suggested.”

Act as if everything you do matters, while laughing at yourself for thinking anything you do matters.
Tibetan Buddhist saying

[kschilk 0]

I realized that, a long time ago. Any extreme, hot or cold, makes people nasty. I was born and spent most of my time in the north but also lived in the south, for about 10 years. Southerners are, for the most part, much more pleasant and friendly. I can't recall a time when Jamaica or Bali were invading anyone and I don't think they're crankin' out terrorists. Nobody seems to be sweatin' Samoa, either....seems like, if they don't come from sand or snow....they're pretty tame.

In the north, when the weather gets colder and the daylight gets shorter, everyone gets even meaner. The amount of daylight, I think, also plays a large part in peoples' moods.

"T'was ever thus."

[lawrocket 3]

I would probably give more creedence to what grows and fails to grow in a different climate. If the US couldn't grow corn anymore, but those plow boys in Alberta have bumper crops, yeah, the odds of war increase.

People go where the food is. It's when people are already there that wars start.

My wife is hotter than your wife.