Climate, Weather and the Civil War: A Correlation?

"Global climate change, war, and population decline in recent human history" in the Proceedings of the National Academy of Sciences (December 4, 2007) has the following 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. Findings of this research may lend an additional dimension to the classic concepts of Malthusianism and Darwinism.

The following graph shows average temperature in the northern hemisphere, from that paper.

The data indicate higher than average temperatures in the northern hemisphere in the 18th century, peaking about the time of the creation of the United States, followed by a drop in average temperatures through the first part of the 19th century.

I am not a meteorologist and the following are obtained from some brief surfing on the Internet. Indeed, 1860 was the very beginning of modern meteorology and the publication of weather records.

1859, the year before Lincoln was elected president seems to have been an unusual year. For example, here is one event, perhaps the hottest event in U.S. history:

"June 17, 1859 - The only 'simoon' ever to occur in the United States is reported by a United States Coast Survey vessel off Goleta (California). A northwest wind brings scorching temperatures of 133 degrees between 1:00 and 2:00 that afternoon. Birds fall from the sky, crops shrivel and cattle die under the shade of oak trees."

On September 1, 1859 the most powerful solar flare ever observed occurred, one that appears at least twice as large as any other in the last 500 years. Here is a report of the effects of that flare:

Just before dawn the next day, skies all over planet Earth erupted in red, green, and purple auroras so brilliant that newspapers could be read as easily as in daylight. Indeed, stunning auroras pulsated even at near tropical latitudes over Cuba, the Bahamas, Jamaica, El Salvador, and Hawaii.

Even more disconcerting, telegraph systems worldwide went haywire. Spark discharges shocked telegraph operators and set the telegraph paper on fire. Even when telegraphers disconnected the batteries powering the lines, aurora-induced electric currents in the wires still allowed messages to be transmitted.

A major hurricane struck the southern United States in August 1860, moving from the Atlantic coast to the Gulf coast. Maximum wind speed was estimated as high as 130 miles per hour. A huge outbreak of tornados occurred in June 1860 in what is now the mid west, killing many in what was then a sparsely populated land and causing great damage to a number of towns.

Could the low temperatures of the early 19th century have created conditions that exacerbated the disagreements that led to the Civil War? Could the anomalies of 1859 and 1860 have had a psychological impact? I don't know, but the question might be worth someone investigating.