1 degree too cool and millions of people will starve, freeze, or otherwise die. Volcanoes erupt frequently and could easily be major SHTF.
Cold states such as Vermont lost a lot of population froze to death in 1816. Some hallucinated (saw the light?) and started Mormonism.
The year 1816 is known as the Year Without a Summer (also the Poverty Year, the Summer that Never Was, Year There Was No Summer, and Eighteen Hundred and Froze to Death), because of severe climate abnormalities that caused average global temperatures to decrease by 0.7–1.3 °F This resulted in major food shortages across the Northern Hemisphere
Cool temperatures and heavy rains resulted in failed harvests in Britain and Ireland. Families in Wales travelled long distances as refugees, begging for food. Famine was prevalent in north and southwest Ireland, following the failure of wheat, oats, and potato harvests. In Germany, the crisis was severe; food prices rose sharply. With the cause of the problems unknown, people demonstrated in front of grain markets and bakeries, and later riots, arson, and looting took place in many European cities. It was the worst famine of 19th-century Europe.
The effects were widespread and lasted beyond the winter. In western Switzerland, the summers of 1816 and 1817 were so cool, an ice dam formed below a tongue of the Giétro Glacier high in the Val de Bagnes. Despite engineer Ignaz Venetz’s efforts to drain the growing lake, the ice dam collapsed catastrophically in June 1818.
In China, the cold weather killed trees, rice crops, and even water buffalo, especially in the north. Floods destroyed many remaining crops. Mount Tambora’s eruption disrupted China’s monsoon season, resulting in overwhelming floods in the Yangtze Valley. In India, the delayed summer monsoon caused late torrential rains that aggravated the spread of cholera from a region near the River Ganges in Bengal to as far as Moscow.
The aberrations are now generally thought to have occurred because of the April 5–15, 1815, volcanic Mount Tambora eruption on the island of Sumbawa, Indonesia (then part of the Dutch East Indies, but under French rule during Napoleon’s occupation of the Netherlands), described by Thomas Stamford Raffles. The eruption had a volcanic explosivity index (VEI) ranking of 7, a supercolossal event that ejected immense amounts of volcanic ash into the upper atmosphere. It was the world’s largest eruption since the Hatepe eruption in 180 AD. That the 1815 eruption occurred during the middle of the Dalton Minimum (a period of unusually low solar activity) may also be significant, during the concluding decades of what has come to be called the Little Ice Age.
Other large volcanic eruptions (with VEIs at least 4) around this time were: • 1812, La Soufrière on Saint Vincent in the Caribbean
• 1812, Awu in the Sangihe Islands, Indonesia
• 1813, Suwanosejima in the Ryukyu Islands, Japan
• 1814, Mayon in the Philippines
These eruptions had already 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.
As a result of the series of volcanic eruptions, crops in the aforementioned areas had been poor for several years; the final blow came in 1815 with the eruption of Tambora. Europe, still recuperating from the Napoleonic Wars, suffered from food shortages. Food riots broke out in the United Kingdom and France, and grain warehouses were looted. The violence was worst in landlocked Switzerland, where famine caused the government to declare a national emergency. Huge storms and abnormal rainfall with flooding of Europe’s major rivers (including the Rhine) are attributed to the event, as is the August frost. A major typhus epidemic occurred in Ireland between 1816 and 1819, precipitated by the famine the Year Without a Summer caused. An estimated 100,000 Irish perished during this period. A BBC documentary using figures compiled in Switzerland estimated the fatality rates in 1816 were twice that of average years, giving an approximate European fatality total of 200,000 deaths.
New England also experienced major consequences from the eruption of Tambora. The corn crop was significantly advanced in New England and the eruption caused the crop to fail. In the summer of 1816 corn was reported to have ripened so badly, no more than a quarter of it was usable for food. The crop failures in New England, Canada, and parts of Europe also caused the price of wheat, grains, meat, vegetables, butter, milk, and flour to rise sharply.
The eruption of Tambora also caused Hungary to experience brown snow. Italy’s northern and north-central region experienced something similar, with red snow falling throughout the year. The cause of this is believed to have been volcanic ash in the atmosphere.
In China, unusually low temperatures in summer and fall devastated rice production in Yunnan, resulting in widespread famine. 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.
Hong Kong sunset circa 1992
High levels of tephra in the atmosphere led to unusually spectacular sunsets during this period, a feature celebrated in the paintings of J. M. W. Turner. This may have given rise to the yellow tinge predominant in his paintings such as Chichester Canal circa 1828. Similar phenomena were observed after the 1883 eruption of Krakatoa, and on the West Coast of the United States following the 1991 eruption of Mount Pinatubo in the Philippines.
The lack of oats to feed horses may have inspired the German inventor Karl Drais to research new ways of horseless transportation, which led to the invention of the draisine or velocipede. This was the ancestor of the modern bicycle and a step toward mechanized personal transport.
The crop failures of the “Year without a Summer” may have helped shape the settling of the “American Heartland”, as many thousands of people (particularly farm families who were wiped out by the event) left New England for what is now western and central New York and the Midwest (then the Northwest Territory) in search of a more hospitable climate, richer soil, and better growing conditions.
Chichester Canal circa 1828 by J. M. W. Turner
According to historian L.D. Stillwell, Vermont alone experienced a drop between 10,000 and 15,000 people, erasing seven previous years of population growth.
Among those who left Vermont were the family of Joseph Smith, who moved from Norwich, Vermont (though he was born in Sharon, Vermont) to Palmyra, New York.
This move precipitated the series of events that culminated in the publication of the Book of Mormon and the founding of the Church of Jesus Christ of Latter-day Saints.
In June 1816, “incessant rainfall” during that “wet, ungenial summer” forced Mary Shelley, John William Polidori, and their friends to stay indoors at Villa Diodati overlooking Lake Geneva for much of their Swiss holiday. They decided to have a contest to see who could write the scariest story, leading Shelley to write Frankenstein, or The Modern Prometheus and Lord Byron to write “A Fragment”, which Polidori later used as inspiration for The Vampyre — a precursor to Dracula. In addition, Lord Byron was inspired to write a poem, “Darkness”, at the same time.
Justus von Liebig, a chemist who had experienced the famine as a child in Darmstadt, later studied plant nutrition and introduced mineral fertilizers.
• Toba catastrophe 70,000 to 75,000 years ago
• The 1628–26 BC climate disturbances, usually attributed to the Minoan eruption of Santorini
• The Hekla 3 eruption of about 1200 BC, contemporary with the historical Bronze Age collapse
• The Hatepe eruption (sometimes referred to as the Taupo eruption), around 180 AD
• Extreme weather events of 535–536 have been linked to the effects of a volcanic eruption, possibly at Krakatoa, or Ilopango in El Salvador.
• The Heaven Lake eruption of Paektu Mountain between North Korea and the People’s Republic of China, in 969 (± 20 years), is thought to have had a role in the downfall of Balhae. • An eruption of Mount Rinjani on the island of Lombok in Indonesia, in 1257
• An eruption of Kuwae, a Pacific volcano, has been implicated in events surrounding the Fall of Constantinople in 1453.
• An eruption of Huaynaputina, in Peru, caused 1601 to be the coldest year in the Northern Hemisphere for six centuries (see Russian famine of 1601–1603); 1601 consisted of a bitterly cold winter, a cold, frosty, late (possibly nonexistent) spring, and a cool, wet summer.
• An eruption of Laki, in Iceland, caused thousands of fatalities in Europe, 1783–84.
• The eruption of Mount Pinatubo in 1991 led to odd weather patterns and temporary cooling in the United States, particularly in the Midwest and parts of the Northeast. An unusually mild winter and a warm, early spring were followed by an unusually cool, wet summer and a cold, early autumn in 1992. Enhanced rainfall occurred across the West Coast of the United States, particularly California, during the 1991–92 and 1992–93 rainy seasons.
• Global cooling
• Little Ice Age
• New England’s Dark Day
• Timetable of major worldwide volcanic eruptions
• White Christmas in the Southern Hemisphere