Speculating About the Weather: The Unusual Dry Fog of 1783

https://niche-canada.org/2017/10/02/speculating-about-the-weather-the-unusual-dry-fog-of-1783/

Let’s talk about the weather! In the summer of 1783 individuals in many parts of the northern hemisphere witnessed blood red sunsets and a peculiar, long-lasting dry fog. Speculation in the press was rife as to the cause. Many theories were put forward at the time but it was a century before the fog of ignorance was lifted. But what had caused this unusual weather?

“The summer of the year 1783 was an amazing and portentous one, and full of horrible phænomena; for besides the alarming meteors and tremendous thunder-storms that affrightened and distressed the different countries of this kingdom, the peculiar haze, or smokey fog, that prevailed for many weeks in this island, and in every part of Europe, and even beyond its limits, was a most extraordinary appearance, unlike anything known within the memory of man.”—Gilbert White

As illustrated by Gilbert White in his Natural History of Selborne, in the summer of 1783, Europeans had more than enough reasons to be concerned with the weather. A peculiar dry fog with an odd sulfuric smell cloaked Europe and remained for months, with neither wind nor rain managing to disperse it. The fog was not the only oddity these individuals were facing that summer: The sun had a blood red color when it set and rose; an unusual number of thunderstorms seemed to pass through; meteors were visible over western Europe, earthquakes occurred in Italy, and a new island emerged from the sea off the coast of Iceland. Speculation was rife as to the cause of all this.

Hekla, an Icelandic volcano, known in Europe since medieval times as the gate to hell, was thought to be a potential culprit. When referring to historical maps of Iceland, Hekla is usually pictured as erupting. Famously, Benjamin Franklin suggested that Hekla or Nyey, the newly emerging island, might have caused the dry fog. However, what is often forgotten in this context is that in the same paragraph, Franklin suggested “great burning balls” (meteors) might alternatively have caused it.

At the time a very fashionable explanation was electricity: Lightning was believed to fertilize the soil when it hit the ground. The numerous thunderstorms of the summer quickened the spread of the lightning rod, which had not yet had its breakthrough. The lightning rod was believed to withdraw the beneficial electricity from the atmosphere, which—so the theory went—caused the dry fog, as sulfuric odor had previously been consumed by the “electrical fire.”

There was yet another story making its rounds in the newspapers in July 1783: Not just one but two volcanic eruptions were described within the German territories. The Cottaberg near Dresden as well as the Gleichberg mountains near Hildburghausen were said to have roared to life and to be spitting fire. Both mountains are actually of volcanic origin—however, their last eruptions occurred 25 and 15 million years ago, respectively. The reports were retracted a few weeks later.

The most popular theory of the time suggested that earthquakes in Italy and this dry fog were directly related: people believed the earthquakes had opened a crack in the Earth, which released sulfuric odor from the Earth’s interior into the air. The concept of a subterraneous revolution plausibly explained the sulfuric smell, the fog, the earthquakes, and the newly emerging island.

Many more theories were put forward at the time. The natural sciences were not yet able to reliably identify the cause of the dry fog and the unusual weather of the summer. So, what had actually caused this lingering gas behemoth?

The Laki fissure (Lakagígar), a 27 kilometer long row of approximately 140 craters and vents, located in Iceland’s remote highlands, erupted over the course of eight months from June 1783 to February 1784 and released the largest volume of lava of any eruption in the last millennium. The gases produced by the eruption were transported from Iceland via the jet stream and dispersed over the northern hemisphere, where the gases became visible (as well as smellable) as a dry and sulfuric haze. At the time it took three months for the news about an Icelandic volcanic eruption to reach mainland Europe, during the summer of 1783, and Europeans were left alone to find an explanation.

It took another decade before the Icelandic naturalist and physicist Sveinn Pálsson discovered the Laki fissure in 1794, but his manuscript was not published in its entirety until 1945. The discovery of the volcano did not immediately lead to connecting the dots between the eruption and the dry fog. In 1883, one hundred years after the Laki fissure eruption, Krakatau in Indonesia roared to life. This colossal eruption and the invention of telegraphy made it possible to know about the eruption and simultaneously observe blood red sunsets and sunrises in the western world. It was only in retrospect that the dry fog and the other extraordinary phenomena such as the red skies of 1783 were connected to the Laki fissure eruption.

Many scholars are aware that tropical eruptions, such as the infamous 1815 Tambora eruption, can have far-reaching effects on the globe. High-latitude eruptions, however, can also affect the atmosphere and the weather in different parts of the northern hemisphere. In 2010 an Icelandic volcanic eruption brought international air traffic to its knees and the world (and the humanities) became aware that Iceland is volcanically active. Learning about the not always obvious effects of an Icelandic volcanic eruption can prove useful for European and North American environmental historians to be able to spot similar events in their sources from one of Iceland’s frequent (past or future) volcanic eruptions, or from eruptions originating in Alaska or the Cascades.