Note to general public:
My position on the current global warming is the same as the overwhelming majority of international climate scientists: the current rate of global warming is unprecedented and is being caused by humans. In no way can my summary of the research regarding the impact of regional climate change on the Viking civilization and Europe during the Little Ice Age be used to "prove" the current global warming is due to a natural cycle.
Please view Global Warming: Man or Myth which addresses many of the questions asked about the human impact on the current climate change in a very simple format. The climate change being observed today is unprecedented in modern times and can only be explained by the rapid increase of greenhouse gases by human activities. There are no known natural forces that could have caused the modern climate change.
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Western Europe experienced a general cooling of the climate between the years 1150 and 1460 and a very cold climate between 1560 and 1850 that brought dire consequences to its peoples. The colder weather impacted agriculture, health, economics, social strife, emigration, and even art and literature. Increased glaciation and storms also had a devastating affect on those that lived near glaciers and the sea.
Lamb (1966) points out that the growing season changed by 15 to 20 percent between the warmest and coldest times of the millenium. That is enough to affect almost any type of food production, especially crops highly adapted to use the full-season warm climatic periods. During the coldest times of the LIA, England's growing season was shortened by one to two months compared to present day values. The availability of varieties of seed today that can withstand extreme cold or warmth, wetness or dryness, was not available in the past. Therefore, climate changes had a much greater impact on agricultural output in the past.
Fig. 16 and 17 show the price of wheat and rye, respectively, in various European countries during the LIA.
Each of the peaks in prices corresponds to a particularly poor harvest, mostly due to unfavorable climates with the most notable peak in the year 1816 - "the year without a summer." One of the worst famines in the seventeenth century occurred in France due to the failed harvest of 1693. Millions of people in France and surrounding countries were killed.
The effect of the LIA on Swiss farms was also severe. Due to the cooler climate, snow covered the ground deep into spring. A parasite, known as Fusarium nivale, which thrives under snow cover, devastated crops. Additionally, due to the increased number of days of snow cover, the stocks of hay for the animals ran out so livestock were fed on straw and pine branches. Many cows had to be slaughtered.
In Norway, many farms located at higher latitudes were abandoned for better land in the valleys. By 1387, production and tax yields were between 12 percent and 70 percent of what they had been around 1300. In the 1460's it was being recognized that this change was permanent. As late as the year 1665, the total Norwegian grain harvest is reported to have been only 67 - 70 percent of what it had been about the year 1300 (Lamb, 1995.)
Fig. 18 shows a chronology of dearth and famine in Scotland during the LIA. Broken lines are years with reported dearth and full lines are years with reported famine.
Dots represent years with severe losses of stock (sheep and cattle), usually because of snow.
People keep records of their most important crops, grapes for wine-making being no exception. Ladurie (1971) notes that there were many "bad years" for wine during the LIA in France and surrounding countries due to very late harvests and very wet summers. The cultivation of grapes was extensive throughout the southern portion of England from about 1100-1300. This area is about 300 miles farther north than the areas in France and Germany that grow grapes today. Grapes were also grown in northern France and Germany at that time, areas which even today do not sustain commercial vineyards. At the time of the compilation of the Domesday Survey in the late eleventh century, vineyards were recorded in 46 places in southern England, from East Anglia through to modern-day Somerset. By the time King Henry VIIIth ascended the throne there were 139 sizeable vineyards in England and Wales - 11 of them owned by the Crown, 67 by noble families and 52 by the church (English-wine.com). In fact, Lamb (1995) suggests that during that period the amount of wine produced in England was substantial enough to provide significant economic competition with the producers in France. With the coming cooler climate in the 1400's, temperatures became too cold for grape production and the vineyards in southern England gradually declined.
German wine production also declined during the cooling experienced after the MWP and during the LIA. Between 1400 and 1700 German wine production was never above 53% of the production before 1300 and at times was as low as 20% of that production (Lamb, 1995.)
A study of the tree populations in forests of Southern Ontario by Campbell and McAndrews (1993) shows how the tree population in Europe might have been changed by the LIA. Their analysis of pollen demonstrated that after the year 1400, beech trees, the formerly dominant warmth-loving species, were replaced first by oak and subsequently by pine. Further, the forest under study appears to have remained in disequilbrium with the prevailing climate of today. That suggests that tree population distribution takes hundreds of years to recover from major climate changes.
The cooler climate during the LIA had a huge impact on the health of Europeans. As mentioned earlier, dearth and famine killed millions and poor nutrition decreased the stature of the Vikings in Greenland and Iceland.
Cool, wet summers led to outbreaks of an illness called St. Anthony's Fire. Whole villages would suffer convulsions, hallucinations, gangrenous rotting of the extremities, and even death. Grain, if stored in cool, damp conditions, may develop a fungus known as ergot blight and also may ferment just enough to produce a drug similar to LSD. (In fact, some historians claim that the Salem, Massachusetts witch hysteria was the result of ergot blight.)
Malnutrition led to a weakened immunity to a variety of illnesses. In England, malnutrition aggravated an influenza epidemic of 1557-8 in which whole families died. In fact, during most of the 1550's deaths outnumbered births (Lamb, 1995.) The Black Death (Bubonic Plague) was hastened by malnutrition all over Europe.
One might not expect a typically tropical disease such as malaria to be found during the LIA, but Reiter (2000) has shown that it was an important cause of illness and death in several parts of England. The English word for malaria was ague, a term that remained in common usage until the nineteenth century. Geoffrey Chaucer (1342-1400) wrote in the Nun's Priest Tale:
You are so very choleric of complexion.
Beware the mounting sun and all dejection,
Nor get yourself with sudden humours hot;
For if you do, I dare well lay a groat
That you shall have the tertian fever's pain,
Or some ague that may well be your bane.
In sixteenth century England, many marshlands were notorious for their ague-stricken populations. William Shakespeare (1564-1616) mentioned ague in eight of his plays. Oliver Cromwell (1599-1658) died of ague in September 1658, which was one of the coldest years of the LIA.
Five indigenous species of mosquito are capable of transmitting malaria in England where they prefer the brackish water along river estuaries. The anaerobic bacterial flora of saline mud produces a strong sulfur odor that was widely believed to be the cause of agues in salt marsh areas (i.e. Shakespeare's "unwholesome fens.") The term malaria comes from the Italian term "mala aria" meaning "bad air."
In addition to increasing grain prices and lower wine production, there were many examples of economic impact by the dramatic cooling of the climate. Due to famine, storms, and growth of glaciers ,many farmsteads were destroyed, which resulted in less tax revenues collected due to decreased value of the properties (Lamb, 1995.)
Cod fishing greatly decreased, especially for the Scottish fisherman, as the cod moved farther south. The cod fishery at the Faeroe Islands began to fail around 1615 and failed altogether for thirty years between 1675 and 1704 (Lamb, 1995.) In the Hohe Tauern mountains of the Austrian Alps, advancing glaciers closed the gold mines of the Archbishop of Salzburg who was one of the wealthiest dukes in the empire. The succession of two or three bad summers where the miners could not rely on work in the mines caused them to find employment elsewhere, which resulted in an abrupt end to the mining operations (Bryson, 1977.)
Not all of the economic impact was bad. The fertile fishing grounds of the present day Newfoundland Banks were thought to have been found by fisherman in the late 1400's who were looking for the fish stocks that had deserted their former grounds as the result of the movement of colder waters from the north (Lamb, 1995.)
English fisherman benefited by the southern movement of herring normally found in the waters off Norway. This increase in deep-sea fishing helped to build the maritime population and strength of the country (Lamb, 1995.) The failure of crops in Norway between 1680 and 1720 was a prime reason for the great growth of merchant shipping there. Coastal farmers whose crops failed turned to selling their timber and to constructing ships in order to transport these timbers themselves (Lamb, 1995.)
Conditions during the LIA led to many cases of social unrest. The winter of 1709 killed many people in France. Conditions were so bad, a priest in Angers, in west-central France, wrote: "The cold began on January 6, 1709, and lasted in all its rigor until the twenty-fourth. The crops that had been sewn were all completely destroyed.... Most of the hens had died of cold, as had the beasts in the stables. When any poultry did survive the cold, their combs were seen to freeze and fall off. Many birds, ducks, partidges, woodcock, and blackbirds died and were found on the roads and on the thick ice and frequent snow. Oaks, ashes, and other valley trees split with cold. Two thirds of the vines died.... No grape harvest was gathered at all in Anjou.... I myself did not get enough wine from my vineyard to fill a nutshell." (Ladurie, 1971) In March the poor rioted in several cities to keep the merchants from selling what little wheat they had left.
The winter of 1739-40 was also a bad one. After that there was no spring and only a damp, cool summer which spoiled the wheat harvest. The poor rebelled and the governor of Liège told the rich to "fire into the middle of them. That's the only way to disperse this riffraff, who want nothing but bread and loot." (Ladurie, 1971)
Lamb (1995) reports the occurrence of cattle raids on the Lowlanders by Highlanders who were stressed by the deteriorating climate. In 1436, King James I of Scotland was murdered while hunting on the edge of the Highland region near Perth. The clan warfare grew so bad that it was decided that no place north of Edinburgh Castle was safe for the king so Edinburgh became the capital of the country.
In England, the effect of starvation and the poor condition of the country encouraged men to enlist during the War of the Roses (1455-1485.) As tillable land was converted to other uses such as sheep rearing, the landlords who organized the conversions became the focus of many hostilities.
One group in particular suffered from the poor conditions - people thought to be witches (Behringer, 1999.) Weather-making was thought to be among the traditional abilities of witches and during the late fourteenth and fifteenth centuries many saw a great witch conspiracy. Extensive witch hunts took place during the most severe years of the LIA, as people looked for scapegoats to blame for their suffering.
One of history's most notorious quotes might have been due in part to a rare extremely warm period during the LIA. In northern France in 1788, after an unusually bad winter, May, June, and July were excessively hot, which caused the grain to shrivel. On July 13, just at harvest time, a severe hailstorm (which typically occurs when there is very cold air aloft) destroyed what little crops were left. From that bad harvest of 1788 came the bread riots of 1789 which led to Marie Antoinette's alleged remark "Let them eat cake," and the storming of the Bastille.
Writers and artists were also influenced by the great change in climate. In 1816, "the year without a summer," many Europeans spent their summers around the fire. Mary Shelley was inspired to write Frankenstein, and Polidori, The Vampire. Both authors, together with Byron and Percy Shelley, were in Switzerland, near Lake Geneva where Byron said "We will each write a ghost story." Percy Shelley also referred to a glacier in his poem "Mont Blanc" when he wrote "…and wall impregnable of beaming ice. The race of man flies far in dread; his work and dwelling vanish…"
Neuberger (1970) studied more than 12,000 paintings in 41 art museums in the United States and eight European countries to test his hypothesis that paintings would accurately reveal the climate record. These paintings covered the period from 1400 to 1967. He categorized the blueness of the sky into a three-step scale consisting of pale blue, medium blue, and deep blue. Cloudiness was estimated according to the U.S. airways code: clear (less than 10 percent coverage), scattered (10 to 50 percent), broken (60 to 90 percent), and overcast (more than 90 percent cloud coverage.) In addition, the types of clouds were observed according to four families: high, middle, low, and convective (vertically-developed) clouds. Neuberger separated his data into three epochs. According to the data in Fig. 19 below, during the second epoch when the LIA was at its peak, cloudiness and darkness prevailed.
Neuberger suggests that the similarities between the second and third epochs have more to do with a stylistic change in the third epoch to impressionism which produced hazy atmospheres and also to an increase in industrial pollution.
Fig. 20 shows the number of reported severe sea floods per century in the North Sea region.
During the LIA, there was a high frequency of storms. As the cooler air began to move southward, the polar jet stream strengthened and followed, which directed a higher number of storms into the region. At least four sea floods of the Dutch and German coasts in the thirteenth century were reported to have caused the loss of around 100,000 lives. Sea level was likely increased by the long-term ice melt during the MWP which compounded the flooding. Storms that caused greater than 100,000 deaths were also reported in 1421, 1446, and 1570. Additionally, large hailstorms that wiped out farmland and killed great numbers of livestock occurred over much of Europe due to the very cold air aloft during the warmer months. Due to severe erosion of coastline and high winds, great sand storms developed which destroyed farmlands and reshaped coastal land regions.
During the post-MWP cooling of the climate, glaciers in many parts of Europe began to advance. Glaciers negatively influenced almost every aspect of life for those unfortunate enough to be living in their path. Glacial advances throughout Europe destroyed farmland and caused massive flooding. On many occasions bishops and priests were called to bless the fields and to pray that the ice stopped grinding forward (Bryson, 1977.) Various tax records show glaciers over the years destroying whole towns caught in their path. A few major advances, as noted by Ladurie (1971), appear below: