Today is the Feast of the Presentation of Christ at the Temple, otherwise known as Candlemas. In the reading from Luke’s gospel, Simeon calls Jesus “a light for revelation to the Gentiles and for glory to your people Israel.” (Luke 2:32; NRSV), hence presumably the practice in the western church of blessing the candles for use in the church throughout the year, and the name ‘Candlemas’.

Originally, the feast was a minor celebration. But in 541 AD, bubonic plague broke out in Constantinople, killing thousands. Emperor Justinian I, in consultation with the Patriarch of Constantinople, ordered a period of fasting and prayer throughout the Eastern Empire, culminating in processions and a prayer service asking for deliverance on Candlemas in 542, whereupon the plague ceased. In thanksgiving, Justinian elevated the feast to a more solemn celebration.

Sometime in my first couple of years at the Met Office, I went to a lecture on dendrochronology-palaeoecology. Dendrochronology is the scientific method of dating based on the analysis of patterns of tree-rings, which is then used to determine certain aspects of past ecologies. In areas where the climate is reasonably predictable, trees develop annual rings of different properties depending on weather, rain, temperature, soil acidity, plant nutrition, carbon dioxide concentration, and so on.

In 540 AD, there was a major eruption of the Rabaul caldera near Papua New Guinea, of roughly the same magnitude as Mount Pinatubo in 1991 or Krakatoa in 1883. These sort of events fling huge quantities of ash and sulphur dioxide into the atmosphere (Eyjafjallajökull in 2010 pales into insignificance), and appear in the palaeoecology record as ash strata in ice cores and the narrow tree rings resulting from global cooling. The lecturer was relating the science to all sorts of historical events and art, the really fascinating stuff you can get to in science, but only after paying your dues by painstaking counting of gazillions of tree-rings to assemble large enough datasets. He considered the global cooling following the 540 eruption as one of the contributions to the outbreak of plague; cooling would have affected grain crops, leading to famine, greater trade in grain, and hence in rats and fleas, and reduced resistance to disease.

By 542, the atmosphere was recovering, the sun returning and harvests improving. The lecturer didn’t go as far as linking the return of the sun with Justinian’s establishment of the feast celebrating the light for revelation to the nations – that was something I realised after the lecture. Probably there was no such link, but I liked the idea.

This is a repost from my Mucknell Abbey blog. Well, it is Groundhog Day after all!