In Alexandra Witze and Jeff Kanipe’s 2014 book, “Island on Fire: The Extraordinary Story of a Forgotten Volcano That Changed the World,” the devastating fate of Iceland amid the 1783 Laki volcanic eruption is portrayed through the priest Jón Steingrímsson’s well-documented accounts. 

“This, Jón thought, was the end,” the book describes. “The earthquakes that had shaken the ground over the last few days, some strong enough to frighten people out of their homes, had been but a clamorous prelude to something he had grimly foreseen.” 

The 42 billion tons of basalt lava that erupted over the course of eight months and the abundance of toxic gas that colored the Iceland sky, resulted in the deaths of more than 9,000 people according to Scientific American. 

But the horror didn’t stop at the regional boundaries of Iceland, not even of Europe. Laki was the largest high-latitude eruption of the past thousand years, and its climatic effects spanned all throughout the Northern Hemisphere. Over 3,000 miles away, the Inuit of Northwest Alaska was shaken by famine and death from extremely cold temperatures around the same time. Inuit oral history recalls it as the “Time Summertime Did Not Come,” according to a 1999 study. 

The culprit: sulfuric acid aerosols. High-volume volcanic eruptions like Laki tend to leave their mark worldwide due to the amount of sulfur dioxide they emit, which converts to sulfuric acid aerosols and saturates the stratosphere. 

“In that part of the atmosphere, they can cause cooling of the lower atmosphere because the sulfur will absorb and reflect some of the heat coming in from the sun,” Denison University volcanologist, Erik Klemetti, said.

While the global impact of Laki makes it a point of interest for scientists when studying just how interlinked our climate system is, no full picture has been painted. Past tree-ring analyses and climate models suggest that beginning in May, the entire Alaskan summer was unbelievably cold, despite the fact that the Laki volcano erupted in mid-June, halfway across the world. Julie Edwards, a Ph.D. student in the University of Arizona School of Geography, Development and Environment, wanted to address this enigma. 

In Dec. 2020, Edwards published a paper in the Journal of Geophysical Research with the goal of solving, once and for all, what the Laki eruption did to the Alaskan climate that year. Edwards explained that solving the uncertainties associated with Laki would not only give us a glimpse into the butterfly effects of our interconnected climate but could also inform one of the most widely debated climate change solutions: geoengineering.  

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To address these uncertainties, Edwards zoomed in past the level of tree-rings and looked at the cellular composition of Alaskan spruce trees through a process called Quantitative Wood Anatomy. Arx et al. define QWA as looking at variability within the cells and fibers of plant xylem, the tissue in trees transporting water and providing physical support. This paper is the first to ever use QWA to document climatic responses to volcanoes. 

Looking cell-by-cell, Edwards’ main finding was that for the most part, temperature conditions amid the summer of 1783 were relatively normal for Alaskan spruce trees. It was actually in late August when there was a quick, dramatic drop in Alaskan temperatures. This disproves past research, thus allowing the Alaskan cooling to be greater correlated with the Laki eruption since the timeline makes sense. 

“She solved the mystery, I would say,” said Kevin Anchukaitis, a UA associate professor and collaborator on this research. “We know now what happened and when it happened in Northwest North America.” 

According to Edwards, eruptions like Laki foreshadow the possible consequences of solar radiation management, a form of climate geoengineering. 

Climate geoengineering is a proposed remedy to extreme warming in which humans can directly manipulate atmospheric conditions to cool the Earth. Solar radiation management involves injecting large amounts of sulfuric aerosols into the stratosphere so that less solar radiation can reach the lower atmosphere. Although aerosol injection may be considered a last resort for when the climate grows too unbearable, many predict that it could negatively impact the water cycle, autotroph productivity and could even delay the healing of the Antarctic ozone hole, according to a 2018 study. 

“Volcanic eruptions cool the climate usually, and that’s something that is very attractive because currently, our climate is warming, so a lot of people who are interested in geoengineering look to sulfate-aerosol injection as a potential solution to global warming,” Edwards explained. 

Alan Robock, a Rutgers University climatologist, identified multiple ways in which studying volcanic eruptions like Laki informs the geoengineering debate. On one hand, past volcanic eruptions have clearly shown that spewing sulfur into the atmosphere will cool the climate and slow global warming. On the other hand, volcano-induced sulfurization has slowed precipitation in monsoon-dependent regions, depleted the ozone layer, whitened the sky and increased diffuse radiation. 

“Diffuse means if you have a cloudy sky, it’s cooler, but the sunlight comes in all directions and you don’t have shadows and that affects the biosphere,” Robock said. “It might really mess up ecosystems that depend on direct sunlight.” 

This lack of direct sunlight can also impact society’s ability to consume solar powered-electricity, explained Robock. After the 1991 Mount Pinatubo eruption in the Philippines, electricity generation among nine solar power facilities in California decreased by 34 percent the following summer, according to Robock’s 2013 paper. 

For Laki specifically, some of the worldwide climatic consequences of sulfur permeating the stratosphere included the failure of the African monsoon, a drying of the Nile River and agricultural consequences like rice crop collapse in Japan, according to Edwards.

Although there are some differences between volcanic eruptions and solar radiation management, the aforementioned Robock paper says that the study of volcanoes can help us answer questions like: How will aerosols transport throughout the atmosphere? How might they change temperature dynamics?

Volcanoes like the Laki eruption are really the “only natural experiment we have,” Anchukaitis said.

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