Volcanic monks – 08/04/2023 – Reinaldo José Lopes

Monks fascinated by the biblical book of Revelation are both villains and victims in Umberto Eco’s medieval detective novel “The Name of the Rose” (if you haven’t read it yet, read it, even if you have to skip the Latin paragraphs). In the real world, it cannot be denied that there were monks obsessed with the idea of ​​the end times, but their interest in the subject has just promoted a fruitful partnership between science and religion.

It turns out that observations of the night sky made by the religious between 900 years and 700 years ago helped a team from the University of Geneva to more accurately date the main volcanic eruptions of the time. The data obtained in this way can bring important advances on climate changes in the past and, consequently, also help to understand the climate crisis of our present.

Details about the monks who turned into accidental climatologists just appeared in the journal Nature. In work that was coordinated by Sébastien Guillet, from the Institute of Environmental Sciences at the Swiss university, the team scoured medieval astronomical annals in search of mentions of lunar eclipses.

The idea came from the fact that lunar eclipses are particularly dark, almost making the Earth’s satellite disappear completely from the sky, after large-scale volcanic eruptions. The clouds of particles released by powerful volcanoes into the atmosphere are enough to block what is left of lunar luminosity during an eclipse (without this, the Moon is still visible, albeit reddish, in the sky).

This is where the story gets even more curious, revealing the mix of scientific knowledge and mystical beliefs on the part of the monks. Unlike what many people imagine, in the Middle Ages all educated people already knew that the Earth was round. They also knew, at least roughly, the mechanism of eclipses, with the shadow of celestial bodies —in the case in question, that of the Earth—covering another object. There are schemes explaining this in medieval manuscripts.

However, there was also a belief that celestial phenomena could be divine signs and foreshadow tragedies. Many religious people were interested, for example, in a passage in the Apocalypse which states: “The sun became black like a sack of horsehair, and the whole moon like blood”. Since this is what happens in “normal” lunar eclipses, monks used to note the color of the Moon whenever they witnessed the phenomenon.

In the Swiss study, the team found that, of the 64 lunar eclipses visible in Europe between the years 1100 and 1300, the annals of monasteries recorded 51, and in five of these cases, there was a mention of the very dark appearance of the Moon. (It would be interesting to know whether the monks found this any more or less frightening than the “Blood Moon” of the Apocalypse, but it doesn’t seem to have been recorded.)

The dates match very well with eruptions that, until now, had only been inferred based on layers of volcanic ash that became trapped in the ice of Antarctica and Greenland. For Sébastien Guillet, the reconstruction can be an important clue to understanding how the Little Ice Age began, a period of falling global temperatures from the final centuries of the Middle Ages.

That’s because very strong volcanic eruptions tend to cool the atmosphere. There are even those who talk about imitating the process to temporarily curb global warming. It’s probably jerico’s idea, because there are a lot of side effects besides the temperature drop. Understanding what happened in the past is a good way to understand those consequences. Monks would probably say amen. Happy Easter for everyone!

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