The year 1816 is called the Year Without a Summer because of strange weather patterns that made global temperatures drop by 0.4–0.7 °C (0.7–1 °F). In Europe, summer temperatures that year were the coldest recorded between 1766 and 2000. This led to failed crops and serious food shortages across the Northern Hemisphere.

Scientists believe the unusual weather was mainly caused by a volcanic winter. This happened after the huge eruption of Mount Tambora in the Dutch East Indies (now Indonesia) in April 1815. This was the largest eruption in at least 1,300 years, possibly bigger than the eruption that may have caused a volcanic winter in 536. The eruption of Mount Mayon in the Philippines in 1814 may have also contributed to the climate changes. Volcanic ash and gases from these eruptions blocked sunlight, causing the Earth to cool.

In countries like the United Kingdom of Great Britain and Ireland and France, people faced difficult times. Food shortages led to riots and famines. These problems were made worse because Europe was still recovering from the Napoleonic Wars, which added stress to the economy and society.

North America also had extreme weather. In the eastern United States, a thick "dry fog" blocked sunlight, causing cold and frost during summer. Crops failed in areas like New England, leading to food shortages and economic problems. Many families left their homes to find better farming areas, which helped push people westward across the continent.

Description

The Year Without a Summer was a major problem for farming. Historian John D. Post called it "the last great subsistence crisis in the Western world." The unusual weather in 1816 had the biggest effects on New England (United States), Atlantic Canada, and Western Europe.

The main reason for the Year Without a Summer was a volcanic winter caused by the April 1815 eruption of Mount Tambora on Sumbawa. This eruption had a volcanic explosivity index (VEI) of 7, which means it was very powerful. It sent at least 37 cubic kilometers of material into the atmosphere. This is the most recent confirmed VEI-7 eruption recorded.

Other large volcanic eruptions around this time included:
– A mysterious eruption in the southwestern Pacific Ocean in 1808
– La Soufrière on Saint Vincent in the Caribbean in 1812
– Awu in the Sangihe Islands, Dutch East Indies in 1812
– Suwanosejima in the Ryukyu Islands in 1813
– Mayon in the Philippines in 1814

These eruptions added a lot of dust to the atmosphere. This dust blocked sunlight, causing global temperatures to drop. A 2012 study by Berkeley Earth found that the 1815 Tambora eruption made Earth's average land temperature drop about one degree Celsius. Smaller drops were also recorded from eruptions in 1812–1814.

Earth had already been cooling for centuries, a period called the Little Ice Age, which began in the 14th century. This cooling had already caused problems for farming in Europe. The Tambora eruption happened near the end of the Little Ice Age, making the cooling even worse.

This time also overlapped with the Dalton Minimum, a period of low solar activity from 1790 to 1830. In May 1816, solar activity was at its lowest level since records began. However, scientists do not yet know if or how changes in solar activity affect Earth's climate.

There is no direct evidence about conditions in the Sahel region, but nearby areas suggest above-normal rainfall. Coastal regions of West Africa likely had less rain. Severe storms hit the South African coast during the Southern Hemisphere winter. On July 29–30, 1816, a strong storm near Cape Town, South Africa, brought heavy winds and hail, damaging ships.

In China, the monsoon season was disrupted, causing floods in the Yangtze Valley. Fort Shuangcheng reported crops damaged by frost, and some soldiers left their posts. Snow or mixed rain fell in Jiangxi and Anhui. In Taiwan, snow was reported in Hsinchu and Miaoli, and frost was reported in Changhua. A large famine in Yunnan weakened the Qing dynasty.

In India, delayed monsoon rains worsened the spread of cholera from Bengal to Moscow. Abnormal cold and snow were reported in Bengal during the winter monsoon.

In Japan, which had already suffered from a previous cold-related famine, crops were damaged by cold, but no major failures were reported, and population was not harmed.

Volcanic eruptions in the 1810s had already caused poor harvests for several years. The 1815 Tambora eruption was the final blow. Europe, still recovering from the Napoleonic Wars, faced severe food shortages, its worst famine of the century. Cold and heavy rain ruined harvests in Great Britain and Ireland. Famine was common in northern and southwestern Ireland after wheat, oat, and potato crops failed. Food prices rose sharply across Europe. People who did not know the cause of the problems gathered outside grain markets and bakeries, leading to violent food riots in many cities.

Between 1816 and 1819, typhus outbreaks occurred in parts of Europe, including Ireland, Italy, Switzerland, and Scotland. Over 65,000 people died from the disease as it spread beyond Ireland.

The Central England temperature record noted 1816 as the 11th coldest year since 1659, the third coldest summer, and the coldest July on record. Flooding of Europe’s major rivers and frost in August were linked to the event. Hungary had snow colored brown by volcanic ash, and red snow fell in northern Italy throughout the year.

Flooding made it hard to move grain along rivers like the Rhine. In German-speaking areas, food prices rose, and though only Wurttemberg saw deaths exceed births, emigration caused more population loss than deaths. Austria avoided famine.

In Switzerland, famine was limited to the east, which was more populated and industrialized. In western Switzerland, summers in 1816 and 1817 were so cold that an ice dam formed near the Giétro Glacier in Val de Bagnes, creating a lake. Engineer Ignaz Venetz tried to drain the lake, but the ice dam collapsed in June 1818, killing 40 people.

Harvests were not affected everywhere. In Scandinavia, the northern Baltic regions, eastern Europe, and western Russia, crops were mostly normal. Russian Emperor Alexander I even donated grain to western Europe.

In the spring and summer of 1816, a "dry fog" was seen in parts of the eastern United States. This fog made sunlight look red and dim, and sunspots were visible to the naked eye. The fog did not clear with wind or rain and was later called a "stratospheric sulfate aerosol veil" by scientist Clive Oppenheimer.

Cold weather itself was not the main problem for people used to long winters. The real issue was how the weather hurt crops, leading to less food and firewood. The hardest hit were high elevations, where farming was already difficult. In May 1816, frost destroyed crops in Massachusetts, New Hampshire, Vermont, and upstate New York. On June 6, snow fell in Albany, New York, and Dennysville, Maine. In Cape May, New Jersey, frost was reported for five nights in late June, damaging crops. Though fruit and vegetables survived in New England, corn ripened poorly, with less than a quarter usable for food. Much of it was moldy and not even fit for animal feed. Crop failures in New England, Canada, and parts of Europe caused food prices to rise sharply. In Canada, Quebec ran out of bread and milk, and Nova Scotians boiled foraged herbs for food.

Sarah Snell Bryant of Cummington, Massachusetts, wrote in her diary: "Weather backward." Nicholas Bennet of the Shakers near New Lebanon, New York, wrote in May 1816 that "all was froze" and the hills were "barren like winter."

Societal effects

High amounts of volcanic ash in the air after the eruption of Mount Tambora created a long-lasting haze over the sky for several years. This ash also made sunsets appear very red. Paintings from before and after the eruption show that these bright red colors were not seen earlier, and the artwork from that time often looked more somber and darker, even when showing sunlight or moonlight. For example, Caspar David Friedrich’s paintings The Monk by the Sea (around 1808–1810) and Two Men by the Sea (1817) show this change in mood.

A 2007 study looked at paintings made between 1500 and 1900 during times of major volcanic eruptions. It found that volcanic activity was linked to the use of more red colors in art. The volcanic ash in the air caused beautiful red sunsets, as seen in the paintings of J. M. W. Turner. This may also explain the yellow tones in his painting Chichester Canal (1828). Similar effects were seen after the 1883 eruption of Krakatoa and after the 1991 eruption of Mount Pinatubo on the West Coast of the United States.

A shortage of oats to feed horses may have led the German inventor Karl Drais to find new ways to move without horses. This led to the invention of the draisine and velocipede, which were early versions of the bicycle.

The poor harvests of the "Year without a Summer" may have influenced people to move to the Midwestern United States. Many people left New England for western New York and the Northwest Territory because they wanted better weather, richer soil, and better farming conditions. Indiana became a state in December 1816, and Illinois became a state two years later. British historian Lawrence Goldman suggested that people moving to upstate New York helped make that area a center for the abolitionist movement.

According to historian L. D. Stillwell, Vermont lost between 10,000 and 15,000 people in 1816 and 1817, ending seven years of population growth. Among those who left was the family of Joseph Smith, who moved from Norwich, Vermont, to Palmyra, New York. This move led to events that eventually resulted in Smith founding The Church of Jesus Christ of Latter-day Saints.

In June 1816, heavy rain during the "wet, ungenial summer" kept Mary Shelley, Percy Bysshe Shelley, Lord Byron, John William Polidori, and their friends indoors at Villa Diodati for much of their Swiss vacation. Inspired by German ghost stories they had read, Lord Byron suggested a contest to write the scariest story. This inspired Mary Shelley to write Frankenstein and Lord Byron to write "A Fragment," which Polidori later used for The Vampyre—a story that influenced Dracula. These days at Villa Diodati included drinking wine and using laudanum, a type of opium, and having intellectual discussions. After one of these conversations, Mary Shelley imagined Victor Frankenstein kneeling over his creation and wrote Frankenstein. Lord Byron was inspired to write the poem Darkness after seeing animals go to sleep at noon, as if it were midnight. The poem’s descriptions closely match the conditions of the Year Without a Summer.

Justus von Liebig, a chemist who had experienced a famine as a child in Darmstadt, later studied how plants grow and introduced mineral fertilizers to improve soil health.

Comparable events

• The Toba catastrophe is a theory that suggests a major cooling event occurred during the Late Pleistocene after a volcanic eruption 74,000 years ago.
• Climate changes between 1628 and 1626 BC are often linked to the Minoan eruption of Santorini.
• The Hekla 3 eruption, around 1200 BC, occurred during the same time as the collapse of the Bronze Age.
• The Hatepe eruption, also called the Taupō eruption, happened around AD 180.
• The winter of 536 is believed to have been caused by a volcanic eruption, possibly from Krakatoa or Ilopango in El Salvador.
• The Heaven Lake eruption of Paektu Mountain, between modern-day North Korea and China, in 969 (±20 years), may have contributed to the fall of the Balhae kingdom.
• The 1257 Samalas eruption of Mount Rinjani on the island of Lombok occurred in 1257.
• A mysterious eruption in 1452 or 1453 is thought to have influenced events during the Fall of Constantinople in 1453.
• An eruption of Huaynaputina in Peru made 1601 the coldest year in the Northern Hemisphere for six centuries. The year had an extremely cold winter, no spring, and a cool, wet summer.
• An eruption of Laki in Iceland caused hundreds of thousands of deaths across the Northern Hemisphere, including over 25,000 in England. It also led to one of the coldest winters ever recorded in North America during 1783–1784. Long-term effects included poverty and famine that may have contributed to the French Revolution in 1789.
• The 1883 eruption of Krakatoa caused Northern Hemisphere summer temperatures to drop by up to 1.2 °C (2.2 °F). This was followed by one of the wettest rainy seasons in California’s history during 1883–1884.
• The 1991 eruption of Mount Pinatubo caused unusual weather patterns and temporary cooling in the United States, especially in the Midwest and parts of the Northeast. Every month in 1992 except January and February was colder than normal. The West Coast of the United States, particularly California, received more rain than usual during the 1991–1992 and 1992–1993 rainy seasons. The American Midwest experienced heavy rain and major flooding during the spring and summer of 1993. This may have also contributed to the historic "Storm of the Century" on the Atlantic Coast in March 1993.