While the Year Without a Summer , in 1816 , occurred during the Dalton Minimum , the prime reason for that year 's cool temperatures was the highly explosive 1815 eruption of Mount Tambora in Indonesia , which was one of the two largest eruptions in the past 2000 years . One must also consider that the rise in volcanism may have been triggered by lower levels of solar output as there is a weak but statistically significant link between decreased solar output and an increase in volcanism
Year Without a Summer
Year Without a Summer
Dalton Minimum