The Effect of Japanese Volcanic Activity To The Irish Summer
Irish summers have a certain reputation, so a manuscript telling of “heavy rain and bad weather in the summer and autumn” of 1109 might not seem remarkable – except for the fact that the likely culprit was an eruption thousands of miles away in Japan.
Medieval records reveal that bad weather brought famine and hardship to Europe between the years 1109 and 1111. French monks described how continuous and excessive rainfall during the summer and autumn of 1109 “drowned the crops, the barrenness of the earth cried aloud, and the grape harvest was an almost total failure”.
In France, the loss of a season’s wine led to mourning, while in Ireland, people observed fastings and abstinence and gave alms to dispel the heavy rain and bad weather in the summer and autumn, as documented in the Annals of Inishfallen. Observers in Germany, Belgium, Northern Spain, and Britain documented poor conditions similarly.
And apart from the constant rain, it was also much cooler than usual. Scientists have figured out that the summer of 1109 was one of the coolest in the past 1500 years. The likely cause was a dust veil hanging over Europe, formed by volcanic particles thrown high up into the stratosphere caused by volcanic activity.
Poor weather conditions caused crop shortages and rising food prices, according to sources written at the time. In France, for example, wheat prices doubled between the autumn of 1108 and the summer of 1109. According to one source, “terrible famine decimated human beings everywhere”. Similar conditions were felt throughout Europe, including Ireland.
Piecing the Story Together
By integrating data from medieval texts with tree-ring and ice core records, researchers were able to reconstruct a scenario of significant volcanic activity during this period. Fujiwara no Munetada, a Japanese courtier, documented the Mount Asama eruption in Japan during the autumn of 1108 in his diary. In his writings, he noted:
On August 29, a fire erupted at the summit of the volcano, leaving a heavy coating of ash in the governor’s garden. The fields and rice paddies have become unsuitable for cultivation, which is an unprecedented and unusual occurrence in the area.
But scientists believe Mount Asama alone wasn’t responsible for the impact on Europe. They think several large eruptions occurred within a short space of time. At least one was in the Northern hemisphere, with another in the Southern hemisphere or near the equator.
Another vital piece of evidence helped scientists to piece the story together. It was an eyewitness account of an exceptionally dark lunar eclipse in May 1110. Volcanic dust has impacted the brightness of all the darkest total lunar eclipses in the last 400 years, correlating with volcanic activity.
The moon was shining brightly in the evening on the fifth night of May, and then its brightness gradually faded. As night fell, it vanished completely, with no visible light, orb, or any trace at all.
So, instead of complaining about the Irish summer, consider the positive side. At least we are spared from dealing with a volcanic dust cloud that could make it even worse. Let’s hope the weather cooperates with us in 2020.
