Unpredictably unstable lunations. …
Originally posted by wikipedia:
The Year Without a Summer was 1816. Severe summer climate abnormalities destroyed crops in Northern Europe, the North-eastern United States and eastern Canada.
Historian John D. Post called this "the last great subsistence crisis in the Western world".
Most consider the climate anomaly to have been caused by a combination of low solar activity and a volcanic winter event; the latter caused by a succession of major volcanic eruptions capped off by the Mount Tambora eruption of 1815, the largest known eruption in over 1,600 years.
But what caused all these events?
They don't "just" happen. Everything in physics and chemistry has to have a root cause.
The same is true in biology. If one of your ancestors was a monkey, so are you. Nothing changes radically to turn a monkey into a fish. Monkeys don't grow up and suddenly decide to marry fish. The general trend is for future mothers to want a future husband more resembling dear old dad.
And it is the same with the last of the magic sciences: earthquakes, windstorms, tidal waves and volcanoes.
If you'd like to see a comparison of some pretty difficult to decipher lunar phases,
read the comments.