13th century volcano changed climate

Medieval texts record an abrupt cooling in the weather in the middle of the 13th century, including a terrible summer in 1258. Now a group of scientists believe they have found the source of the cooling: the eruption of the Samalas Volcano on Lombok Island, Indonesia.

"The evidence is very strong and compelling," Prof Clive Oppenheimer, from Cambridge University, UK, told the BBC's Science In Action programme. The 1257 eruption left ash traces in the ice of both the Arctic and the Antarctic, and medieval reports record failures of crops and mass burials.