There were a number of extremely large sunspots that year, some of which were visible to the unaided eye. A range of explanations for the weather cropped up in North America and Europe as well. Another theory at this time is that it had something to do with ice.
The 2015 episode covers a volcano eruption in Sumbawa, Indonesia in 1816, that combined with several other factors to create an unusual -- and catastrophic -- series of weather events.
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