http://www.sciencenews.org/view/generic/id/341497/title/13th_century_volcano_mystery_may_be_solvedScience News is reporting that the volcano which apparently erupted in 1257/1258 and caused a period of global cooling has been identified. Rinjani, a volcano on he Indonesian island of Lombok will probably be named in an upcoming Science article which will present evidence that the chemistry of its rocks matches the world-wide ice-core sulfur deposits that indicate a massive volcanic eruption at this time - the largest in 7,000 years.
That's really interesting! It would be interesting to know exactly how much of an impact that the cooling had on global politics. For example, Henry III was having some… erm… trouble with Barons. Not unusual for his reign, but I wonder if bad crops etc might have made it even worse.