Year Without a Summer

1816 was called the Year Without a Summer due to the accumulation of volcanic ash (AUDIO: Mary's Story, TV: The Haunting of Villa Diodati) in the upper atmosphere after the eruption of Tambora in 1815. (AUDIO: Mary's Story) However, the Thirteenth Doctor pondered whether it was really something else which caused it. (TV: The Haunting of Villa Diodati)