A volcanic winter, set in place by the 1815 eruption of Mount Tambora, produced the coldest summer Europe had seen on record for the final quarter of the previous millennium. Average global temperatures plummeted by 0.7 - 1°F (0.4 - 0.7°C) and caused famine and unusual weather patterns throughout much of the world . The year that followed, which experienced exceptionally cooler weather, would be called “the Year Without a Summer”.
European Summer Temperature Anomaly for 1816. Courtesy of NOAA
Several ongoing phenomena helped contribute to the cooler temperatures seen globally during the first quarter of the 19th century. A centuries-long cool period dating back to the 14th century, now known as the Little Ice Age, had already caused periods of agricultural distress throughout Europe up to this point. The Sun, which sees cycles in its solar activity, was also experiencing a period of relatively low activity in the years leading up to 1816. A notable reduction of incoming solar energy would have compounded the issues produced by the volcanic eruptions of the early century.
Although several large volcanic eruptions had occurred in the years leading up to the unusual cooling period, it was the eruption of Mount Tambora in the spring of 1815 that set into motion the volcanic winter conditions.
The eruption of Mount Tambora, which spanned from the 5th to 15th of April, occurred on the Indonesian island of Sumbawa, part of the Dutch East Indies at the time. Over the ten-day span, at least 10 billion tons of ash and chemicals were released by the eruption, the largest volcanic eruption in over a millennium. Higher concentrations of dust in the atmosphere lessened the amount of sunlight that could pass through the stratosphere, cooling global temperatures as a result.
Impacts of the Year Without a Summer
The impacts of the volcanic winter became most evident during the summer of 1816. Cooler temperatures and heavier rainfall crippled the season’s harvest and spurred on famines in Europe that had only begun to recover following the Napoleonic Wars. Food scarcity helped inflame societal instability that had already been brewing on the continent in the preceding decades.
Across the pond in North America, observers in the young United States described various unusual phenomena during the spring and summer of 1816. Throughout the first half of the year, a dry fog was reported in the eastern portion of the country, its reddish hue dimming incoming sunlight. As a result of this, sun spots became visible to observers with the naked eye. Even wind or rainfall was reportedly unable to diminish the fog.
As the seasons passed, the effects of the volcanic winter became more apparent in the Americas. Winter seemed to linger longer than was typical, with frost being reported throughout much of New England as late as May and snow fell across Upstate New York in early June. As far south as Cape May, New Jersey even saw frosty nights into late June. Lake and river ice was seen at points in Pennsylvania during July and August with places as far south as Virginia seeing frost into late August. The continued frost/freeze events had a large impact on food production in the region, reducing yield and sharply increasing the price for select goods.
When summer did come (albeit substantially different than normal), the cool trend was not consistent throughout North America. Weather patterns were reported to have been all over the place with one resident of Cummington, Massachusetts writing in her diary: “Weather backward.” Dramatic changes in daily–even hourly–temperatures were often reported during the summer, with high temperatures occasionally reverting back to normal to above-normal levels. Some of the most dramatic swings saw temperatures rise to as high as 95°F (35°C) to freezing in the matter of hours.
An interesting aspect of this peculiar phenomenon is that its effects are recorded in history in more ways than one may initially suspect. Elevated levels of tephra, a material produced by volcanic eruptions, caused a haze to hang over the sky for several years after the Mount Tambora eruption. The lingering haze produced extraordinary sunsets that were well documented by painters at the time–even shifting the themes artists captured during this era. For instance, the two paintings below, both by German artist Caspar David Friedrich, showcase how different the skies were before and after the eruption. Landscape with Rainbow, dated to 1810, shows a more natural sky as one would expect to see on a typical summer day. A livelier, hopeful mood is portrayed whereas Two Men by the Sea, dated two years after the eruption, shows a darker, more despairing scene.
Landscape with Rainbow (1810)
Two Men by the Sea (1817)
Abnormal rainfall also impacted Europe during this period and helped shape modern literature, specifically the horror genre. Due to the incessant rainfall that hindered their summer holiday, author Mary Shelley and her fellow writer friends held a contest to see who could write the scariest story during their time spent indoors. It was during this time that Shelley wrote her renowned novel Frankenstein; or, The Modern Prometheus. It could be argued that if it wasn’t for the unseasonal summer of that year, the horror genre of today would look notably different.
In the years that followed the eruption of Mount Tambora and the subsequent volcanic winter, temperatures gradually returned to normal and harvests returned to their typical yield. Although it was only a short period of climatic changes that impacted the world two centuries ago, its effects are still apparent today. The harsh famines that resulted from the Year Without a Summer inspired German chemist Justus von Liebig, who had lived through the hardships as a child, to study plant nutrition and later introduce mineral fertilizers.
Now, with the prospect of future climate change one of the largest issues for the coming decades, it is intriguing to look back at the near past and learn from examples on how to face future challenges.