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Climate Change and the Human Condition
Volume 11, Number 17: 23 April 2008

In the introduction to their illuminating paper, the authors say they previously studied "a long span of Chinese history and found that the number of war outbreaks and population collapses in China is significantly correlated with Northern Hemisphere temperature variations and that all of the periods of nationwide unrest, population collapse, and drastic change occurred in the cold phases of this period." In their current study, they write that they "extend the earlier study to the global and continental levels between AD 1400 and AD 1900." This they do by using high-resolution paleoclimate data to explore "at a macroscale" the effects of climate change on the outbreak of war and population decline in the pre-industrial era as discerned by analyses of historical socioeconomic and demographic data.

In describing their findings, the five scientists say their newest analyses, like their earlier ones, 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." And they suggest, as they put it, that "worldwide and synchronistic war-peace, population, and price cycles in recent centuries have been driven mainly by long-term climate change," wherein warm periods were supportive of good times and cooling led to bad times, some of which (in our opinion) could arguably be described as a descent into hell.

In response to "the gradual temperature drop and the increase in size of the cold area from the 'Medieval Warm Period' to the Little Ice Age," for example -- when they found that every sudden temperature drop would induce a "demographic shock" -- population growth rate "reached its lowest level in the 13-14th centuries, primarily because of epidemics, wars, and famines." In providing more detail for China, they say that "the invasion by the Mongols in the 13-14th centuries was related to the ecological stress caused by cooling, which reduced China's total population nearly by half (55 million decline)," while in Europe they report that the Black Death held sway, "accompanied by massive social unrest and economic collapse, which wiped out a quarter to one-third of the population in AD 1347-1353, the coldest period in the last several hundred years." Then, in the 17th century, which was the longest cold period of the Little Ice Age, they report that "more wars of great magnitude and the associated population declines in Europe and Asia followed." More specifically, they state that "the European population was devastated by possibly the worst war in its history in terms of the share of the population killed in AD 1618-1648, starvation, and epidemics." Likewise, they report that "in China, the population plummeted 43% (~70 million) because of wars, starvation and epidemics in AD 1620-1650."

Interestingly, after having presented an essentially ironclad case for their finding that warmer periods throughout human history have almost always been more conducive to good times than bad times throughout the majority of the Northern Hemisphere, Zhang et al. conclude their paper by suggesting just the opposite, i.e., that bad times would likely follow any future global warming that might occur, throwing all of their findings to the wind and listing as their reason for doing so the usual litany of unduly-catastrophic consequences that climate alarmists insist will follow any temperature increase that might occur, while stating that "the current high global average temperature (which has never been experienced in the last two millennia) is continuing to rise at an accelerated speed."

Apparently, Zhang et al. are not aware of the fact that the projected consequences of projected global warming (among which they list negative impacts on agriculture, sea level, tropical diseases, extreme weather and ice sheet status) are way overblown, as may be readily verified by perusing the various materials archived on our website that pertain to these subjects. And they are apparently equally unaware of the fact that the current global average temperature is not the highest of the last two millennia (see, for example, our Medieval Warm Period Project) and that earth's mean global temperature is not rising "at an accelerated speed." In fact, mean global temperature has not risen perceptibly over the entire past decade!

Clearly, Zhang et al.'s primary findings are right on the mark, but their abandonment of them in their concluding discussion in an attempt to remain politically correct should be an affront to all serious-minded people, as should their uncritical acceptance of standard climate-alarmist extremism and their two important factual errors.

Sherwood, Keith and Craig Idso

Zhang, D.D., Brecke, P., Lee, H.F., He, Y.-Q. and Zhang, J. 2007. Global climate change, war, and population decline in recent human history. Proceedings of the National Academy of Sciences, USA 104: 19,214-19,219.