Little Ice Age
The Little Ice Age was a period of regional cooling, particularly pronounced in the North Atlantic region. It was not a true ice age of global extent. The term was introduced into scientific literature by François E. Matthes in 1939. The period has been conventionally defined as extending from the 16th to the 19th centuries, but some experts prefer an alternative time-span from about 1300 to about 1850.
The NASA Earth Observatory notes three particularly cold intervals. One began about 1650, another about 1770, and the last in 1850, all of which were separated by intervals of slight warming. The Intergovernmental Panel on Climate Change Third Assessment Report considered that the timing and the areas affected by the LIA suggested largely independent regional climate changes, rather than a globally synchronous increased glaciation. At most, there was modest cooling of the Northern Hemisphere during the period.
Several causes have been proposed: cyclical lows in solar radiation, heightened volcanic activity, changes in the ocean circulation, variations in Earth's orbit and axial tilt, inherent variability in global climate, and decreases in the human population.
Areas involved
The Intergovernmental Panel on Climate Change Third Assessment Report of 2001 described the areas that were affected:The IPCC Fourth Assessment Report of 2007 discusses more recent research and gives particular attention to the Medieval Warm Period:
Dating
There is no consensus on when the Little Ice Age began, but a series of events before the known climatic minima have often been referenced. In the 13th century, pack ice began advancing southwards in the North Atlantic, as did glaciers in Greenland. Anecdotal evidence suggests expanding glaciers almost worldwide. Based on radiocarbon dating of roughly 150 samples of dead plant material with roots intact that were collected from beneath ice caps on Baffin Island and Iceland, Miller et al. state that cold summers and ice growth began abruptly between 1275 and 1300, followed by "a substantial intensification" from 1430 to 1455.In contrast, a climate reconstruction based on glacial length shows no great variation from 1600 to 1850 but a strong retreat thereafter.
Therefore, any of several dates ranging over 400 years may indicate the beginning of the Little Ice Age:
- 1250 for when Atlantic pack ice began to grow, a cold period that was possibly triggered or enhanced by the massive eruption of the Samalas volcano in 1257 and the associated volcanic winter.
- 1275 to 1300 for when the radiocarbon dating of plants shows that they were killed by glaciation
- 1300 for when warm summers stopped being dependable in Northern Europe
- 1315 for when rains and the Great Famine of 1315–1317 occurred
- 1560 to 1630 for when the worldwide glacial expansion, known as the Grindelwald Fluctuation, began
- 1650, not the start of the Little Ice Age, but the start of the coldest years midway through, i.e., the First Climatic Minimum
The 6th report of the IPCC describes the coldest period in the last millennium as: The definitions for the beginning and end of the LIA differ considerably, depending on the region and dataset used. The LIA in the Northern Hemisphere started between 1200 and 1400 AD. In the Southern Hemisphere the beginning of the LIA was delayed by about two centuries.
By region
Europe
Central Europe
In 2021, historian Christian Pfister and climatologist Heinz Wanner published a reconstruction of seasonal temperatures in Central Europe using temperature indices based on documentary data. After CE 1500, the reconstruction is based on an article by Czech geographer Petr Dobrovolny, which includes monthly, seasonal and annual temperature estimates for Germany, Switzerland and the Czech lands based on temperature indices up to 1759 and subsequent temperature measurements.Winter
Winters from 1000 to 1999 were generally cold until the end of the 19th century. A reconstruction of winter temperatures on a year-by-year basis from 1170 onward reveals a different picture of the Little Ice Age.The 13th century winters were predominantly cold only in the first third of the century, as well as between 1270 and 1280.
During the 14th century, cold winters were the norm, except for the 48 years between 1340 and 1377.
The 15th century was almost entirely cold, except for the 1470s. Until 1520, winters remained mostly cold.
The 16th century; cold and warm seasons were balanced until 1540. After that, cold winters became the norm, with particularly severe winters occurring between 1565 and 1573 and again from 1587 to 1595. Overall, winter seasons were around 0.9 °C below the 1961–1990 average.
The 17th century, temperatures were 1.2°C below average.
The 18th century, temperatures were 0.9°C below average.
The 19th century, temperatures were 1.2°C below average based on thermometric measurements.
The 20th century temperatures were 0.2°C below the 1961–1990 average, with positive values dominating after 1950.
Conclusion: The duration and intensity of cold spells in winter have increased since the 14th century, peaking in the 15th, 17th, and 19th centuries. The gradual decline in winter temperatures until the early 20th century, compared to the 1961–1990 measurement period, was one manifestation of the end of the Little Ice Age in Central Europe due to Global Warming.
Summer
14th century summers were slightly cooler than warm ones in the 14th century. The years from 1324 to 1340 and from 1380 to 1399 were predominantly warm, whereas the years from 1314 to 1322 and from 1355 to 1370 were mostly cold. The latter cold period triggered an advance of the Alpine glaciers, reaching its peak in the 1380s.Cold summers predominated in the 15th century. After a relatively warm period until 1424, the trend reversed. Seven cold summers occurred in the 1450s alone, presumably in connection with the eruption of a tropical volcano. Also notable is the sequence of three hot summers between 1471 and 1473.
In the 16th century, estimated temperatures were 0.2 °C below the 1961–1990 average. Due to ten hot and dry summers, temperatures from 1534 to 1567 were 0.3 °C above average, causing the glaciers to melt back somewhat. Subsequently, temperatures fell in conjunction with high summer precipitation, reaching a low point in the 1590s and triggering the widespread advance of Alpine glaciers.
In the 17th century, estimated temperatures were 0.2°C lower than the average for the period 1961–1990. Until around 1630 and from 1670 to 1685, extremes of cold and warmth dominated, with warm summers occurring mid-century. After 1675, temperatures fell by an average of 0.6 °C until the turn of the century. Cod, which is sensitive to cold temperatures, disappeared from the waters around the Faroe Islands. The English climatologist and historian Hubert Lamb concluded that cold Arctic water had spread southwards.
Warm summers prevailed in the 18th century, particularly between 1718 and 1731. Temperatures remained relatively low between 1760 and 1779, triggering an advance of the Alpine glaciers.
Cold summers prevailed in the 19th century. Average temperatures in Central Europe were 0.6 °C below the 1961–1990 average. The first half of the century was predominantly cold, leading to glacier advances.
In the 20th century, summers in Central Europe remained cold until 1927. Temperatures then rose until the warm decade from 1943 to 1952, after which they fluctuated around the 1901–1960 average. The long-term process of glacier retreat began with the slow man-made warming of the late 19th century and accelerated with the more rapid warming that occurred after 1990.
Regional studies
, Iceland's northernmost glacier, reached its maximum extent during the LIA around 1665 or 1765.The Baltic Sea froze over twice, in 1303 and 1306–1307, and years followed of "unseasonable cold, storms and rains, and a rise in the level of the Caspian Sea". The Little Ice Age brought colder winters to parts of Europe and North America. Farms and villages in the Swiss Alps were destroyed by encroaching glaciers during the mid-17th century. Canals and rivers in Great Britain and the Netherlands were frequently frozen deeply enough to support ice skating and winter festivals. As trade needed to continue during the prolonged winter often spanning 5 months, merchants equipped their boer style boats with planks and skates, hence the iceboat was born. The first River Thames frost fair was in 1608 and the last in 1814. Changes to the bridges and the addition of the Thames Embankment have affected the river's flow and depth and greatly diminish the possibility of further freezes.
In early 1658, a Swedish army took advantage of the extremely cold winter to march through Denmark and across the Great Belt to attack Copenhagen from the west.
Sea ice surrounding Iceland extended for miles in every direction and closed harbors to shipping. The population of Iceland fell by half, but that may have been caused by skeletal fluorosis after the eruption of Laki in 1783. Iceland also suffered failures of cereal crops and people moved away from a grain-based diet.
After Greenland's climate became colder and stormier around 1250, the diet of the Norse Viking settlements there steadily shifted away from agricultural sources. By around 1300, seal hunting provided over three quarters of their food. By 1350, there was reduced demand for their exports, and trade with Europe fell away. The last document from the settlements dates from 1412, and over the following decades, the remaining Europeans left in what seems to have been a gradual withdrawal, which was caused mainly by economic factors such as increased availability of farms in Scandinavian countries. Greenland was largely cut off by ice from 1410 to the 1720s.
Between 1620 and 1740, the Yzeron Basin in the Massif Central of France witnessed a phase of decreased fluvial activity. This decline in fluvial activity is believed to be linked to a multidecennial phase of droughts in the western Mediterranean.
In southwestern Europe, a negative North Atlantic oscillation combined with increased aridity caused an increase in wind-driven sediment deposition during the LIA.
In his 1995 book, the early climatologist Hubert Lamb said that in many years, "snowfall was much heavier than recorded before or since, and the snow lay on the ground for many months longer than it does today." In Lisbon, Portugal, snowstorms were much more frequent than today, and one winter in the 17th century produced eight snowstorms. Many springs and summers were cold and wet but with great variability between years and groups of years. That was particularly evident during the "Grindelwald Fluctuation" ; the rapid cooling phase was associated with more erratic weather, including increased storminess, unseasonal snowstorms, and droughts. Crop practices throughout Europe had to be altered to adapt to the shortened and less reliable growing season, and there were many years of scarcity and famine. One was the Great Famine of 1315–1317, but that may have been before the Little Ice Age. According to Elizabeth Ewan and Janay Nugent, "Famines in France 1693–94, Norway 1695–96 and Sweden 1696–97 claimed roughly 10 percent of the population of each country. In Estonia and Finland in 1696–97, losses have been estimated at a fifth and a third of the national populations, respectively." Viticulture disappeared from some northern regions, and storms caused serious flooding and loss of life. Some of them resulted in the permanent loss of large areas of land from the Danish, German, and Dutch coasts.
The violinmaker Antonio Stradivari produced his instruments during the Little Ice Age. The colder climate may have caused the wood that was used in his violins to be denser than in warmer periods and to contribute to the tone of his instruments. According to the science historian James Burke, the period inspired such novelties in everyday life as the widespread use of buttons and button-holes, as well as knitting of custom-made undergarments for the better covering and insulating of the body. Chimneys were invented to replace open fires in the centre of communal halls to allow houses with multiple rooms to have the separation of masters from servants.
The Little Ice Age, by the anthropologist Brian Fagan of the University of California at Santa Barbara, describes the plight of European peasants from 1300 to 1850: famines, hypothermia, bread riots and the rise of despotic leaders brutalizing an increasingly dispirited peasantry. In the late 17th century, agriculture had dropped off dramatically: "Alpine villagers lived on bread made from ground nutshells mixed with barley and oat flour." Historian Wolfgang Behringer has linked intensive witch-hunting episodes in Europe to agricultural failures during the Little Ice Age.
The Frigid Golden Age, by the environmental historian Dagomar Degroot of Georgetown University, points out that some societies thrived, but others faltered during the Little Ice Age. In particular, the Little Ice Age transformed environments around the Dutch Republic and made them easier to exploit in commerce and conflict. The Dutch were resilient, even adaptive, in the face of weather that devastated neighboring countries. Merchants exploited harvest failures, military commanders took advantage of shifting wind patterns, and inventors developed technologies that helped them profit from the cold. The 17th-century Dutch Golden Age therefore owed much to its people's flexibility in coping with the changing climate.