Dr. Franklin and the Volcano

In May 1784, Benjamin Franklin published an essay titled “Meteorological Imaginations and Conjectures.”

In it Franklin observed that “the winter of 1783-84, was more severe than any that happened for many years.” Though he was writing in and about Europe, such American planters as George Washington and James Madison also complained about that season.

Franklin attributed the harsh winter to “a constant fog over all Europe” in the summer of 1783, though those months had been unusually hot. As for the nature of that haze in the atmosphere, Franklin saw different possibilities, including meteors and

the vast quantity of smoke, long continuing to issue during the summer from Hecla, in Iceland, and that other volcano which arose out of the sea near that island, which smoke might be spread by various winds over the northern part of the world

The eruptions on Iceland and the ensuing livestock deaths and crop failures reportedly killed a fifth of the population on that island. Even in Britain, people blamed the unhealthy atmosphere for thousands of deaths. But Franklin was apparently the first person to suggest that a volcanic eruption might affect the winter months later.

In 2011, as reported by the website phys.org, Geophysical Research Letters published a paper by Rosanne D’Arrigo and colleagues which concluded the “1783-84 weather was most likely the result of a rare confluence: A warm tropical eastern Pacific Ocean—El Niño—combined with a strong negative pressure in the North Atlantic Ocean.” The same effect occurred in 2009-10, the team wrote. They therefore didn’t think the volcano was a necessary part of the explanation (and no one talks about Franklin’s meteor hypothesis).

However, this month a paper in the Journal of Geophysical Research with Brian Zambri as lead author took another look at the eruption, which was huge:

The eight-month eruption of the Laki volcano, beginning in June 1783, was the largest high-latitude eruption in the last 1,000 years. It injected about six times as much sulfur dioxide into the upper atmosphere as the 1883 Krakatau or 1991 Pinatubo eruptions…

Using computer models, these authors tried to isolate the volcano’s effect. They concluded that it didn’t make the summer of 1783 unusually warm; in fact, “It would have been even warmer without the eruption.” But the following winter was definitely colder because of Laki, as Franklin had guessed.