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 lowest 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 from the huge eruption of Mount Tambora in the Dutch East Indies (now Indonesia) in April 1815. This eruption was the largest in at least 1,300 years. The 1814 eruption of Mayon in the Philippines may have made the climate effects worse. Volcanic ash and gases from Mount Tambora 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 recovering from the Napoleonic Wars, which added stress to the economy and society.

North America also had harsh 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 difficulties. 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 impact on New England (US), Atlantic Canada, and Western Europe.

The main reason for the Year Without a Summer is believed to be a volcanic winter caused by the eruption of Mount Tambora on Sumbawa in April 1815. This eruption had a volcanic explosivity index (VEI) of 7 and sent at least 37 km (8.9 cubic miles) of material into the atmosphere. It is 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 drop by about 1 degree Celsius. Smaller drops were also recorded from eruptions between 1812 and 1814.

The Earth had already been cooling for centuries, a period known as the Little Ice Age, which began in the 14th century. This cooling had already caused farming problems 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 weak solar activity from 1790 to 1830. In May 1816, the lowest solar activity recorded (Wolf number 0.1) was observed. However, it is still unclear how solar activity affects Earth’s climate.

No direct evidence about the Sahel region’s conditions has been found, but nearby areas showed signs of above-normal rainfall. Coastal regions in 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 brought heavy winds, hail, and damaged 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 rain fell in Jiangxi and Anhui. In Taiwan, snow was reported in Hsinchu and Miaoli, and frost was reported in Changhua. A major 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 was still recovering from the Great Tenmei famine of 1782–1788, cold weather damaged crops, but no major crop failures were reported.

Volcanic eruptions in the 1810s had already caused poor harvests for several years. The Tambora eruption in 1815 was the final major blow. Europe, still recovering from the Napoleonic Wars, faced widespread food shortages, the worst famine of the century. Low temperatures and heavy rains 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. Without knowing the cause, hungry people protested at grain markets and bakeries. Food riots were the most violent in Europe since the French Revolution.

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.

The Central England temperature record noted 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 saw brown-colored snow from volcanic ash, and red snow fell in northern Italy.

Flooding disrupted river navigation, including the movement of grain. In German-speaking areas, food prices rose, and though only Wurttemberg saw deaths exceed births, emigration caused more population loss. Austria avoided famine.

In Switzerland, famine was limited to the densely populated east. In western Switzerland, cold summers caused an ice dam to form below the Giétro Glacier in Val de Bagnes. The dam collapsed in 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 donated grain to western Europe.

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

Weather alone was not the main hardship for people used to long winters. Problems came from how the weather affected crops, reducing 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. On June 6, snow fell in Albany, New York, and Dennysville, Maine. In Cape May, New Jersey, frost lasted 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 unfit for animals. Food prices rose sharply in New England, Canada, and

Societal effects

Tephra in the air created a haze that stayed over the sky for years after the eruption, making sunsets appear very red. Paintings from before and after the event show that these bright red colors did not exist before Mount Tambora erupted. Earlier paintings often showed darker, more serious scenes, even during daylight and moonlight. Caspar David Friedrich’s 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 how much red paint artists used. Tephra in the air made sunsets look very bright during this time, as seen in the paintings of J. M. W. Turner. This may explain the yellow colors in his painting Chichester Canal (1828). Similar effects happened 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 creation of the draisine and velocipede, which were early versions of the bicycle.

Crop failures during the "Year without a Summer" may have influenced where people settled in the Midwestern United States. Many people left New England for western New York and the Northwest Territory to find better weather, soil, and growing conditions. Indiana became a state in December 1816, and Illinois became a state two years later. British historian Lawrence Goldman said that people moving into the burned-over district of upstate New York helped the abolitionist movement grow in that area.

According to historian L. D. Stillwell, Vermont lost between 10,000 and 15,000 people in 1816 and 1817, undoing seven years of population growth. Joseph Smith’s family was among those who left Vermont, moving 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, 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. During their time at Villa Diodati, they drank wine and used laudanum, an opium-based medicine, and had intellectual discussions. After one of these talks, Shelley imagined Victor Frankenstein kneeling over his creation, which inspired her to write Frankenstein. Byron wrote his poem Darkness after seeing birds roost at noon, as if it were midnight. The poem’s descriptions match the conditions of the Year Without a Summer.

Justus von Liebig, a chemist who experienced a 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 during the Late Pleistocene, which may have occurred after a volcanic eruption around 74,000 years ago.
• Climate changes between 1628 and 1626 BC are often connected to the Minoan eruption of Santorini.
• The Hekla 3 eruption, which happened around 1200 BC, occurred at the same time as the historical Bronze Age collapse.
• The Hatepe eruption, sometimes called the Taupō eruption, took place 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, located between modern-day North Korea and China, occurred around 969 (±20 years) and may have contributed to the downfall of Balhae.
• The Samalas eruption of Mount Rinjani on the island of Lombok happened in 1257.
• A mysterious eruption in 1452 or 1453 is linked to events surrounding the Fall of Constantinople in 1453.
• An eruption of Huaynaputina in Peru made 1601 the coldest year in the Northern Hemisphere for six centuries. This 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 (1783–1784). Long-lasting effects included poverty and famine, which 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, 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.