The year 1816 is called the Year Without a Summer because of extreme weather changes 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, leading to failed crops and serious food shortages across the Northern Hemisphere.

Scientists believe this unusual cold was mainly caused by a volcanic winter 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 one that caused a volcanic winter in 536. The eruption may have been made worse by another volcanic event in the Philippines in 1814. Volcanic ash and gases from Mount Tambora entered the atmosphere and blocked sunlight, causing the world to cool.

In countries like the United Kingdom of Great Britain and Ireland and France, people faced serious problems, including food riots and famine. These issues were made worse because Europe was still trying to recover from the Napoleonic Wars, which added to economic and social challenges.

North America also had extreme weather. In the eastern United States, a thick, dry fog blocked sunlight, causing unusual cold and frost during the summer. Crops failed in areas like New England, leading to food shortages and economic hardship. These conditions forced many families to leave their homes to find better farming opportunities, which helped push people to move westward.

Description

The Year Without a Summer was a major disaster 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 impact on New England (United States), Atlantic Canada, and Western Europe.

The main cause of 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 and sent at least 37 cubic kilometers (8.9 cubic miles) of material into the atmosphere. It remains the most recent confirmed VEI-7 eruption.

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, which blocked sunlight and caused global temperatures to drop. A 2012 study by Berkeley Earth found that the 1815 Tambora eruption caused Earth’s average land temperature to fall by about one degree Celsius. Smaller drops were also recorded from eruptions between 1812 and 1814.

Earth had already been cooling for centuries, a period called the Little Ice Age, which began in the 1300s. This cooling had already caused serious problems for farming in Europe. The Tambora eruption happened near the end of the Little Ice Age, making the cooling 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 recorded. However, it is not clear how solar activity affects Earth’s climate, and this connection does not prove that lower solar activity causes cooling.

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 than usual. 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 frost damaging crops and soldiers leaving their posts. Snow or mixed precipitation was reported in Jiangxi and Anhui. In Taiwan, snow fell in Hsinchu and Miaoli, and frost was reported in Changhua. A major famine in Yunnan weakened the ruling Qing dynasty.

In India, late 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 recovered from the Great Tenmei famine of 1782–1788, cold weather damaged crops, but no major crop failures were reported, and the population was not affected.

The eruptions of the 1810s caused poor harvests for several years. The final problem came in 1815 with the Tambora eruption. Europe, still recovering from the Napoleonic Wars, faced widespread food shortages, the worst famine of the century. Low temperatures and heavy rain ruined crops in Great Britain and Ireland. Famine was common in northern and southwestern Ireland after wheat, oat, and potato harvests failed. Food prices rose sharply across Europe. People protested at grain markets and bakeries, and violent food riots occurred in many cities.

Between 1816 and 1819, typhus epidemics spread in parts of Europe, including Ireland, Italy, Switzerland, and Scotland. More than 65,000 people died from the disease.

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 brown-colored snow from volcanic ash, and red snow fell in northern Italy.

Flooding disrupted river travel, including the movement of grain. In German-speaking areas, prices rose, and while 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 densely populated and industrialized. In western Switzerland, the summers of 1816 and 1817 were so cold that an ice dam formed near the Giétro Glacier, creating a lake. The dam collapsed in June 1818, killing 40 people.

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

In the eastern United States, a persistent "dry fog" was seen in spring and summer 1816. The fog turned sunlight red and dim, making sunspots visible. This fog was later described as a "stratospheric sulfate aerosol veil."

Cold weather did not harm people used to long winters, but it hurt crops and reduced food and firewood supplies. The hardest hit were higher elevations, where farming was already difficult. In May 1816, frost destroyed crops in Massachusetts, New Hampshire, Vermont, and upstate New York. Snow fell in Albany, New York, and Dennysville, Maine, in June. In Cape May, New Jersey, frost damaged crops for five nights in late June. In New England, corn ripened poorly, with less than a quarter usable for food. 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 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

Societal effects

High levels of volcanic ash in the atmosphere caused a haze to remain in the sky for several years after the eruption, which made sunsets appear very red. Paintings from before and after the eruption show that these bright red colors were not seen before the Mount Tambora eruption. These paintings also show darker and more serious scenes, even during daylight and moonlight. Caspar David Friedrich’s The Monk by the Sea (about 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 how much red color was used in paintings. The volcanic ash in the air created bright sunsets during this time, 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 search for new ways to move without horses. This led to the invention of the draisine and velocipede, which were early models of the bicycle.

The poor harvests during 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 the "burned-over district" of 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" forced Mary Shelley, Percy Bysshe Shelley, Lord Byron, John William Polidori, and their friends to stay 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 led Shelley to write Frankenstein and Byron to write "A Fragment," which Polidori later used to create The Vampyre, a story that influenced Dracula. These days at Villa Diodati included drinking wine, using laudanum (a type of opium medicine), and having intellectual discussions. After listening to one of these conversations, Shelley imagined Victor Frankenstein kneeling over his creation, which inspired her to write Frankenstein. Byron was inspired to write the poem "Darkness" after seeing birds roost 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 experienced the famine as a child in Darmstadt, later studied how plants grow and introduced mineral fertilizers.

Comparable events

• The Toba catastrophe refers to a possible cooling event that occurred during the Late Pleistocene, following a major eruption about 74,000 years ago.
• Climate disruptions between 1628 and 1626 BC are often linked to the Minoan eruption of Santorini.
• The Hekla 3 eruption, around 1200 BC, happened at the same time as the collapse of Bronze Age civilizations.
• The Hatepe eruption, also called the Taupō eruption, occurred around AD 180.
• The winter of 536 is connected to the effects of 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, around 969 (±20 years), may have contributed to the fall of Balhae.
• The Samalas eruption of Mount Rinjani on Lombok in 1257.
• The 1452/1453 mystery eruption is associated with events leading to the Fall of Constantinople in 1453.
• The eruption of Huaynaputina in Peru caused 1601 to be the coldest year in the Northern Hemisphere for six centuries. This year had an extremely cold winter, no spring, and a cool, wet summer.
• The Laki eruption in Iceland led to hundreds of thousands of deaths across the Northern Hemisphere, including over 25,000 in England. It also caused one of the coldest winters ever recorded in North America (1783–1784). Long-term effects included poverty and famine that might have helped cause the French Revolution in 1789.
• The 1883 eruption of Krakatoa caused summer temperatures in the Northern Hemisphere 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 usual. The West Coast, particularly California, received more rain than normal during 1991–1992 and 1992–1993. 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.