'overwhelming' consensus for manmade warming: , page-45

In 1815, the Indonesian volcano Tambora propelled more ash and volcanic gases into the atmosphere than any other eruption in history and resulted in significant atmospheric cooling on a global scale, much like Krakatau a few decades later. New England and Europe were particularly hard hit, with snowfalls as late as August and massive crop failures. The cold, wet, and unpleasant climatic effects of the eruption led 1816 to be known as "the year without a summer," and inspired Lord Byron to write:

"The bright Sun was extinguish¿d, and the stars
Did wander darkling in the eternal space
Rayless and pathless, and the icy earth
Swung blind and blackening in the moonless air;
Morn came and went¿and came,
And brought no day¿"

--Lord Byron, "Darkness"
There is a story that Byron invited some of his friends to his home in Switzerland that summer to relax by the shores of Lake Geneva. The lack of sun and warm summer weather led the group to hold a competition writing ghost stories to keep themselves entertained. One of the guests, Mary Shelley, wrote the famous novel Frankenstein for this contest, revealing that in addition to major climatic effects, volcanic eruptions can have some unexpectedly far-reaching results.

Answer originally published April 15, 2002.