Review: Volcanic Eruptions Have Shaped Human History and Climate

Volcanoes have repeatedly rewritten human history from behind the scenes, functioning as a silent geologic force that triggers sudden climate cooling, crop failures, and widespread societal upheaval, according to a recent analysis published in the 2026 Annual Review of Earth and Planetary Sciences.

Key Clinical Takeaways:
• Researchers analyzed 38 large volcanic eruptions spanning from A.D. 1 to 1900 to measure their direct impacts on Northern Hemisphere climate and human society.
• On average, each major eruption induced approximately 0.5 degrees Celsius of surface cooling in the year following the event.
• Historical records demonstrate that climate shocks from eruptions frequently coincided with famines, disease outbreaks, and political unrest, though societal vulnerability and institutional responses heavily determined survival rates.

Mount Tambora and the Year Without a Summer

The bright sun was extinguished, and the icy earth swung blind and blackening in the moonless air. Those words from Lord Byron’s 1816 poem Darkness evoke a hellish apocalypse, but the poet may have been inspired by the fallout of a real cataclysm happening half a world away when Mount Tambora erupted in Indonesia in 1815. More than 71,000 people died in the immediate vicinity of the blast. Climate-cooling aerosols from the eruption ushered in extreme weather across the globe in subsequent years, destroying corn in New England, rice and buckwheat in China, and wheat, oats, and potatoes in Ireland. In some locations, rising bread prices sparked riots, while the disrupted conditions helped spread typhus. Observers dubbed 1816 “the year without a summer” or “the year of the beggars.” Clive Oppenheimer, a volcanologist at the University of Cambridge, noted that these climatic impacts were recorded without anyone realizing they stemmed from a volcanic eruption.

Oppenheimer Reviews Environmental and Societal Effects of 38 Eruptions

While Tambora remains the most thoroughly studied eruption in history, other cataclysms have similarly rattled the planet. Oppenheimer and his colleagues examined 38 large eruptions in their 2026 review for the Annual Review of Earth and Planetary Sciences, connecting geologic events with their environmental effects and potential societal fallout across food systems, economies, unrest, culture, and religion. Volcanic eruptions act as a heavy hammer blow to the climate system, according to Heli Huhtamaa, a climate and environmental historian at the University of Bern in Switzerland. Volcanoes spew sulfur-containing gases that react in the atmosphere over weeks to form particles capable of blocking sunlight. These particles persist aloft for months, riding jet streams around the globe. Because individual eruptions behave differently, understanding the climate response of one event does not mean understanding another, explains Ulf Büntgen, a paleoclimatologist at the University of Cambridge.

Tree Rings and Ice Cores as Historical Logs

Researchers uncover the footprints of past eruptions by examining ice cores drilled from Greenland and Antarctica, matching sulfur layers with tree ring data that record summer growing conditions. When cool summers impede final wood formation, chemical methods cause annual wood layers to turn blue under analysis. Büntgen and colleagues observed two rare blue rings around the year 1345—an occurrence never seen two years in a row prior—which coincided with the spread of the Black Death in Europe, a connection detailed in a 2025 study in Communications Earth & Environment. Expanding this detective work, the 2026 review calculated that the 38 largest eruptions between A.D. 1 and 1900 caused an average of 0.5 degrees Celsius of cooling in the year after each event, with recovery slowing down if the eruption occurred during already colder baseline periods.

Societal Vulnerability Versus Climatic Shock

Out of 17 large-scale famines in Europe from 1300 to 1800, 11 followed major eruptions, according to data in research. Beyond crop failure and famine, recurring societal responses included disease outbreaks, political turmoil, and migration. However, Huhtamaa emphasizes that human vulnerability matters more than the exact magnitude of temperature drop. Studying crop failures and farmstead desertions in Ostrobothnia—part of modern-day Finland—Huhtamaa and colleagues reported in 2022 in Climate of the Past that peasants fared better during an extremely cold eruption in 1695 than during milder eruptions earlier in the 17th century. Only about 7 percent of peasants lost their farmland in 1695, compared with 20 percent in earlier periods, largely because the crown provided tax relief to preserve its long-term tax base rather than out of humanitarian aid.

Eldgjá and the Christianization of Iceland

Volcanic catastrophes have also shaped religious and cultural shifts. Stanza 57 of the medieval Icelandic poem Vǫluspá describes the sun turning black, land sinking into the sea, and steam spurting up with high-flying flames, which researchers speculate records the A.D. 939 eruption of Iceland’s Eldgjá volcano. Oppenheimer and colleagues suggest that the poem Vǫluspá, which explained the eruption in terms of divine displeasure and foretold a fiery end to pagan gods replaced by one god, may have contributed to the island’s Christianization around 1000. Across centuries, the widespread climatic fingerprints of volcanoes have left tangible, lasting marks on human history.