While living in Paris in the spring of 1784, Benjamin Franklin wrote a remarkable essay in which he suggested that the "universal fog" and very cool temperatures that had affected western Europe and eastern North America for much of the previous year might have been caused, at least in part, by "the vast quantity of smoke, long continuing to issue... from Hecla [Mt. Hekla] in Iceland, and that other volcano [Mt. Reykjaneshryggur] which rose out of the sea near that island, which smoke might be spread by various winds, over the northern part of the world." Although he incorrectly identified the most important volcano to erupt in Iceland in 1783 as Hekla (it was actually Lakagigar) and was unaware of several other powerful eruptions around the world that year, Franklin's views on the possible impact of volcanic activity on global climate have been of great interest to modern researchers. Indeed, it is now clear, as a report from the American Geophysical Union has put it, that certain kinds of eruptions "can lead to a change in the radiation balance and temperature of the earth. Such a climatic 'forcing' by volcanic eruptions appears to be one of the most significant short-term changes imposed by nature." After reviewing some important recent research on this topic, this essay will explore the implications of that research for the study of East Asian and world history.