The year 1816 is known as the Year Without a Summer because of severe climate abnormalities that caused average global temperatures to decrease by . Summer temperatures in Europe were the coldest of any on record between the years of 1766 and 2000. This resulted in major food shortages across the Northern Hemisphere.
Evidence suggests that the anomaly was predominantly a volcanic winter event caused by the massive 1815 eruption of Mount Tambora in April in the Dutch East Indies (modern-day Indonesia). This eruption was the largest in at least 1,300 years (after the hypothesized eruption causing the volcanic winter of 536); its effect on the climate may have been exacerbated by the 1814 eruption of Mayon in the Philippines.
Description
The Year Without a Summer was an agricultural disaster. Historian John D. Post has called this "the last great subsistence crisis in the Western world". The climatic aberrations of 1816 had their greatest effect on most of New England, Atlantic Canada, and parts of western Europe.
The aberrations are now generally thought to have occurred because of the April 5–15, 1815, Mount Tambora volcanic eruption on the island of Sumbawa, Indonesia. The eruption had a volcanic explosivity index (VEI) ranking of 7, a colossal event that ejected at least of material. It was the world's largest volcanic eruption during historic times, comparable with the Minoan eruption in the 2nd millennium BC, the Hatepe eruption of Lake Taupō at around 180 AD, the eruption of Paektu Mountain in 946 AD, and the 1257 eruption of Mount Samalas.
Other large volcanic eruptions (with VEIs of at least 4) around this time were:
1808, the 1808 mystery eruption (VEI 6) in the southwestern Pacific Ocean
1812, La Soufrière on Saint Vincent in the Caribbean
1812, Awu in the Sangihe Islands, Dutch East Indies
1813, Suwanosejima in the Ryukyu Islands, Japan
1814, Mayon in the Philippines
These eruptions had built up a substantial amount of atmospheric dust. As is common after a massive volcanic eruption, temperatures fell worldwide because less sunlight passed through the stratosphere.
According to a 2012 analysis by Berkeley Earth Surface Temperature, the 1815 Tambora eruption caused a temporary drop in the Earth's average land temperature of about 1 °C. Smaller temperature drops were recorded from the 1812–1814 eruptions.
The Earth had already been in a centuries-long period of global cooling that started in the 14th century. Known today as the Little Ice Age, it had already caused considerable agricultural distress in Europe. The Little Ice Age's existing cooling was exacerbated by the eruption of Tambora, which occurred near the end of the Little Ice Age.
This period also occurred during the Dalton Minimum (a period of relatively low solar activity), specifically Solar Cycle 6, which ran from December 1810 to May 1823. May 1816 in particular had the lowest sunspot number (0.1) to date since recordkeeping on solar activity began. The physical mechanism that explains how changes in activity on the sun affect Earth's climate, if there is one, is unknown, and such episodes do not prove that lower sunspot numbers produce cooling.
Asia
In China, there was a profound famine. Floods destroyed many remaining crops. The monsoon season was disrupted, resulting in overwhelming floods in the Yangtze Valley. Fort Shuangcheng, now in Heilongjiang, reported fields disrupted by frost and conscripts deserting as a result. Summer snowfall or otherwise mixed precipitation was reported in various locations in Jiangxi and Anhui, located at around 30°N. In Taiwan, which has a tropical climate, snow was reported in Hsinchu and Miaoli, and frost was reported in Changhua.
In 1816, due to the abnormal climate caused by the volcanic eruption, there was a large-scale famine in Yunnan. This famine caused the Qing Dynasty to turn from prosperity to decline.
In India, the delayed summer monsoon caused late torrential rains that aggravated the spread of cholera from a region near the Ganges in Bengal to as far as Moscow.
In Japan, which was still exercising caution after the cold-weather-related Tenmei famine of 1782–1788, the cold damaged crops, but no crop failures were reported, and there were no adverse effects on population.