What Caused the ‘Year Without A Summer’?

Depiction of the eruption of Mt. Tambora, imagined by Leon Sonrel, 1821

Who doesn’t love warm summer weather? Summer is the perfect time for walking barefoot in the grass, outdoor picnics and going to the beach.

But in some place in the U.S. and around the world this summer, wildfires are raging and heat records are shattering.

Climate change, due to the “greenhouse effect” caused by burning fossil fuels, is the most likely culprit for these climate abnormalities.

But climate change can have other causes and effects. For example, there was a year during the Regency when people suffered because the sun wouldn’t shine and temperatures plummeted. The sky was dark and the world was cold.

It was 1816, known as the year without a summer.

The Eruption of Mt. Tambora

The reason for the “year without a summer” was another climate disaster – a massive volcanic eruption. And this disaster had lasting repercussions.

Sumbawa, a small island in Indonesia (known as the Dutch East Indies during the Regency) is approximately 10,000 miles from Boston, Massachusetts, and almost 8,000 miles distant from London, England. I’d guess that most people living in the United States and the United Kingdom at that time were scarcely aware of the island’s existence.

But on April 5, 1815, a volcano on Sumbawa, Mt. Tambora, erupted violently with a series of blasts. Sir Thomas Stamford Raffles, the Lt. Governor of Java, was at his post 800 miles away when he heard what he thought was a volley of cannon fire.

Sailors onboard ships at sea heard the blasts, and believed a battle was taking place. Fields composed of pumice, some as large as three miles wide, covered the South Indian Ocean like icebergs.

Then, five days later Mt. Tambora erupted again, and this time the blast was even worse. Three huge columns of fire rose in the air, coming together at the top, spewing ash, debris and molten rock while lava streamed down the mountainside.

A top-side view of Mt. Tambora’s enormous caldera, taken by NASA in 2009.

About 12,000 people lived close to the mountain, and almost all were dead within 24 hours. Twenty miles away from the blast site, villages were covered in ash that was 40 inches thick. Hundreds of miles away, layers of dust ruined crops, killed cattle, fish and other wildlife, and poisoned water.

Famine and disease came next, causing even more destruction, until the death toll in Indonesia reached at least 90,000 people.

All told, the eruption of Mt. Tambora in 1815 killed hundreds of thousands of people, either directly or indirectly. It is still the largest volcanic eruption ever witnessed or recorded, ten times more violent than the eruption of Mt. Krakatoa in 1883. The Mt. Tambora eruption released a burst of volcanic energy equal to exploding 33 gigatons of TNT.

Climate Effects

When Mt. Tambora blew, about three to four thousand feet blasted right off the top of the mountain. Ash and tephra (fragments of magma and other minerals) from the eruption shot into the earth’s stratosphere and were dispersed by winds around the globe, forming an almost invisible aerosol veil that scattered sunlight, effectively blocking the sun’s rays and lowering temperatures around the world.

Although the aerosol veil reflected only about one-half to one percent of the incoming energy of the sun, that percentage was enough to cool temperatures in the Northern Hemisphere by approximately three degrees Fahrenheit. And that 3-degree reduction was enough to change weather patterns and wreak agricultural destruction on both sides of the Atlantic Ocean.

But the effects of the Mt. Tambora eruption were not felt in Europe and North America for many months. It wasn’t until the spring and summer of 1816 that the change in climate began to become quite noticeable.

Popular beliefs 

Persistent rain, flooding, frost and snowfall during the summer months in Europe and North America were some of the climate abnormalities caused by the volcanic blast.

Other effects included drought and raging forest fires, crop failures and famine. To people living in the Northern Hemisphere in 1816, the world must have seemed as though it were turned upside down.

Two paintings by Caspar David Friedrich, a German Romantic landscape artist, vividly illustrate the atmospheric changes observed in Europe following the eruption of Mt. Tambora.

The first was painted in 1809. Notice how clear the sky is.

Monk by the Sea, by Caspar David Friedrich, 1809.

The second painting is set in roughly the same location, but it was painted eight years later. The yellowish-grey sky recorded by the artist attests to the lingering atmospheric effects of the volcanic eruption.

Two Men by the Sea,  by Caspar David Friedrich, 1817.


Next: The long-lasting effects that “the year without a summer” had on science, literature, and the settling of the American West.

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Sources for this post include:

The Year Without Summer: 1816 and the Volcano That Darkened the World and Changed History, by William K. Klingaman and Nicholas P. Klingaman, St. Martin’s Press, New York, 2013

The Regency Years, During Which Jane Austen Writes, Napoleon Fights, Byron Makes Love and Britain Becomes Modern, by Robert Morrison, W.W. Norton & Company, New York and London, 2019

“Mount Tambora and the Year Without a Summer,” UCAR Center for Science Education

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Images courtesy of Wikimedia Commons

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