by AndrewMc | 8/24/2009 07:00:00 AM

According to research published in the August 13, 2009, edition of the journal Nature, paleotempestologists argue that the current upswing in hurricanes and cyclones is part of a long cycle stretching back more than a thousand years to the Middle Ages. That cycle peaked around the year 1000. The New York Times has a piece on the article, which for the most part argues that the medieval peak was a probably bigger than what we're seeing today.

Interesting field, paleotempestology. To some degree it relates to history in much the same way that dendrocrhonology does. Perhaps paleotempestology will contribute to some long-standing historical questions in the same way that dedrochronology helped us understand the Roanoke and Jamestown disasters a bit better.

I'm not a historian of the Middle Ages, but I teach Western Civilizations prior to 1648, and I use that period of climate change and some other events that occurred around the year 1000 as a way of tying together some themes that I use throughout the course. Briefly, I have my students think about the massive changes brought on by the agricultural revolution of thousands of years ago, and then place them in the context of the massive change in the medieval period in order to get them to think about change over time, historical context, contingency, etc.

The article in Nature got me to thinking about a comparison between the context of climate change in the medieval period, and the context of climate change today. The parallels aren't exact, but they are somewhat instructive.

Scientists sometimes refer to the period from 800 – 1300 as the “Medieval Warming Period.” While many believed that this was a global phenomenon, new research indicates that the warming effect may have been localized to Europe. Whatever the case, it is well-documented that temperatures rose in Europe, and that rainfall increased to some degree. The warmer, wetter weather made for better harvests.

At the same time that Europe was getting warmer and wetter, Europeans saw a number of “technological” changes that greatly improved their ability to grow food. Two of these improvements, in particular, went hand-in-hand.

The first advance was the gradual replacement of oxen with horses as draft animals. Horses may not seem like “technology,” but in a sense they are a kind of bio-technical improvement. Horses eat less than oxen, but can work faster, longer, and harder than can oxen. For farming they are a vast improvement over oxen, which are slower, require greater care, and eat more.

At the same time, Europeans finally discarded the old Roman-stye scratch plough—called an ard—in favor of an iron plough with a coulter. The scratch plough worked well in the Mediterranean area, where the soil was sandy. The plough, pulled by a team of oxen, scratched the surface, laying open a furrow which could be seeded. But in the heavy soil of Europe, the scratch plough was inadequate, and farmers often had to supplement the scratch plough with extra digging by hand. Use of the scratch plow also tends to cause "panning" where the soil below four inches becomes caked from the repeated disruption of the above soil. This can lead to less water absorption, and can restrict root growth to the shallower areas. Both effects reduce crop yields.

The iron plough—called a carruca—changed things dramatically. The coulter broke the tough soil while the ploughshare lifted the soil and flipped it over. It had the effect of aerating the soil and of bringing nutrients to the top. It was more labor intensive and required a larger team of animals (eight for a carruca, versus two for a scratch plough), but it vastly improved the quality of the soil.

The final improvement is less a kind of technology than a farming practice. Farmers had for many centuries practiced field rotation (not necessarily crop rotation), where crops were grown on one field while another lay fallow. This meant that any one time, half the fields were growing food. Beginning in the Middle Ages farmers began to practice three-field rotation. Spring crops would go in the first field, fall crops in the second field, and the third field would lie fallow. So in any year two-thirds of the fields would be under cultivation. During this period Europeans also greatly increased the amount of land available for farming by clearing vast forests.

So, the warmer, wetter weather in the Middle Ages was accompanied by—or perhaps better said, was coincidental to—a series of innovations and practices that greatly increased food production. The result was a population explosion. Figures are, of course, difficult to come by. But most estimates seem to agree that the population went from something like 30 million Europeans in the year 1000 to about 60 million in the year 1200. Accompanying this were a great number of societal changes that I won’t get into here.

But what about today? We have documented global warming. The scientific community is in near-total agreement that the earth is warming. We have also seen about a century or so of technological change that has fundamentally reordered human society. The big difference between the two is that in the 20th and 21st centuries technology isn’t accompanying global warming and environmental change—it is causing it. From increased carbon dioxide levels in the air and the oceans, to warmer weather worldwide, the planet is experiencing a warmer that seems unmatched in human history.

Aside from that, man-made technology, such as synthetic long chain polymers, is causing environmental changes that we don’t yet fully grasp. At the same time, other man-made chemicals in food, in manufacturing waste, and in other products, are causing changes in human DNA.

It’s hard to imagine that the changes of this confluence of technological and environmental change will be positive for humanity. Just as Europeans eventually suffered famines and the onset of the Black Death in the fourteenth century, 21st century humans seem headed for a hard fall.

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