Why was 1816 known as the year without summer?

Answer 1

On April 10, 1815, the largest explosive volcanic eruption since the beginning of recorded history ejected more than 24 cubic miles of magma into the atmosphere. Solar radiation could no longer penetrate the dense atmosphere to warm the earth. The next year crop-killing frosts occurred during the summer months in New England and 1816 was known as "the year without summer."

Answer 2

it took a year