November 12, 2013

Climate Change and The Black Death (Update as of March, 2014)

Albeit a substantial killer by way of approximate body count, the plague was not the most destabilizing event of the Fourteenth Century. It may not have had a direct death toll, but climate change (different from the highly politicized ‘global warming’) could be considered as the first domino to fall in a series of traumatic and destabilizing events leading to what would be known as The Black Death.

During the fourteenth century, the Medieval Warm Period was transitioning into what would later be the Little Ice Age. During this period, Europe’s climate underwent substantial and sudden changes. The weather became wetter and cooler. Artist's renderings of the time have often depicted people wearing heavier clothing, as well as gray skies, and snow cover, providing clues as to the weather of the time.. With this climate change, came subsequent crop failures since the crops either froze or were drowned with the increase in precipitation. These crop failures led to the Great Famine, which persisted until the early 1320.  Grain stores were soaked and would rot, leaving less grain for the rodents to scavenge. This encouraged the rodents to move in to more densely populated areas looking for food while carrying their plague infested fleas with them to spread among the population. It would appear logical that in this sequence of events, that climate change was technically the most destabilizing event of the Fourteenth Century.

Further research into the physical evidence of such a connection came by way of a news item from the BBC. It cited recent research into the connection between climate change and the plague. The results put an interesting element of hard science to the argument, making a case that this sequence of events leading to the Black Death warranted more study.

In the article, a Dr. Thomas van Hoof and a team from Utrecht University, Netherlands, studied pollen grains and leaf remains collected from lake-bed sediments in the southeast Netherlands. They recorded the fluctuations in the abundance of cereal and tree pollen such as buckwheat and pollen from birch and oak trees. In doing so, the researchers were able to estimate changes in land-use between 1000C.E. and 1500C.E. Counting the stomata, or pores on ancient oak leaves provided the researchers a baseline with which to measure chances in the amount of atmospheric carbon dioxide during the Fourteenth Century. This is possible since leaves absorb carbon dioxide through their stomata, and their density varies as carbon dioxide goes up and down.

The researchers found an expected increase in cereal pollen from 1200 which reflected the agricultural expansion. However, this was followed by a sudden dive around 1347.  According to Dr. van Hoof, there is a noticeable decrease in stomata and a sharp rise in atmospheric carbon dioxide between 1200C.E. and 1300C.E. This is believed to be due to deforestation. This pattern appeared to reverse after 1350, suggesting that atmospheric carbon dioxide fell, perhaps due to reforestation following the plague.

The researchers theorize that the drop in carbon dioxide levels could help to explain why the climate started to cool so suddenly. This new data has given scholars a quantitative data point with which to base further study.  The new data adds weight to the theory that the Black Death could have played an important part in the changing of the climate, as opposed to the climate leading to the Black Death. Dr. Tim Lenton, an environmental scientist from the University of East Anglia, UK, said: "It is a nice study and the carbon dioxide changes could certainly be a contributory factor, but I think they are too modest to explain all the climate change seen."1. By contrast, Professor Richard Houghton, a climate expert from Woods Hole Research Center in Massachusetts, thinks that it may have been oceanic changes which led to climate change.

While there is no consensus, new scientific studies are being conducted to help better understand the causes behind both climate change and the Black Death so that we can avoid such future calamity. As it stands from my perspective, the Fourteenth Century was marked by a procession of traumatic events. However, I believe that it was climate change that set the procession into motion, thereby making it most deserving of the title; most destabilizing.
1. Ravilious, Kate. "BBC NEWS | Science/Nature | Europe's chill linked to disease." BBC News.