The 1286 eruption really happened in 1285
A big two-pole sulfur signal, yet a bright, colourful eclipse over England and Italy in October 1287. We first offered two explanations: the eruption came early (1285) so the veil had thinned by October 1287, or the volcano was southern and its veil stayed south.
Tested 24 October 2026 with the monthly ice-core data published with Guillet et al. 2023. The southern-veil idea is weakened: Greenland received about as much extra sulfur as Antarctica. The Greenland record lags by over a year, but it does that after other eruptions too, so it is a dating drift, not a clue. The early idea is supported: Antarctic sulfur starts climbing in August 1285 and peaks in September 1286, so the eruption most likely happened in the first half of 1285, about two years before the bright eclipse. That is long enough for a veil to thin, though not certainly long enough to vanish.
No eclipse descriptions survive for 1284 to 1286 in the study's European or Japanese datasets, and the East Asian aurora catalogue has nothing from 1280 to 1287 either. So the remaining test is any written record of a dim sun, red twilights or a dark eclipse in 1285.
What to check next
- Korean and Chinese records of a dim or reddish sun in 1285 (the Goryeosa five-elements treatise, the Yuanshi)
- Total lunar eclipses visible in East Asia: 4 January 1284 and 29 April 1287; look for colour notes
- Ask whether the 1285 timing matches any undated young caldera in the tropics