Volcanic winter
A paper written by Benjamin Franklin in the 1780s blamed the unusually cool summer of 1783 on volcanic dust coming from Iceland. The eruption of Laki volcano had released enormous amounts of sulfur dioxide, resulting in the death of much of the island's livestock and a catastrophic famine which killed a quarter of the population. Temperatures in the northern hemisphere dropped by about 1 °C in the year following the Laki eruption.