The climate can react to sudden shocks. The weather in 1816 was very strange.
Spring arrived, but then everything seemed to turn backward, as cold temperatures returned.
The sky seemed permanently overcast.
The lack of sunlight became so severe that farmers lost their crops. Food shortages were reported in Ireland, France, England, and the United States. 1816 became known as "The Year without a Summer" or "18-hundred-and-frozen-to-death".
It was over 100 years before anyone understood the reason for this weather disaster.
Volcanic events can cool the Earth for a few years.
The large eruption of Mount Pinatubo caused a dip in global temperatures in the early 1990s:
Mount Pinatubo 1991
In 1258 there was a European famine across many countries, and this is now linked to a major eruption in 1257 on Lombok in Indonesia - it has a much biggersulphate peak in the ice coresthan Tambora, so it was a bigger eruption.