John Maunder
Some of the answers to the complexities of the climate system are given in my recently published book Fifteen shades of climate… the fall of the weather dice and the butterfly effect. The following are extracts are from pages 197-201.
The Greenlandic Vikings’ Apogee
The Greenlandic Vikings’ apogee coincided with the Medieval Warm Period (also known as the Medieval Climate Anomaly), generally dated from about 950-1250; their disappearance followed the onset of the Little Ice Age, which ran from about 1300-1850. Both periods according to Wikipedia are firmly documented in European and Icelandic historical records. Thus, popular authors and some scientists have fixed on the idea that nice weather drew the settlers to Greenland, and bad weather froze and starved them. But there are no early historical climate records from Greenland. Recently, historians have proposed more complex factors in addition to, or instead of, climate: hostilities with the Inuit, a decline in ivory trade, soil erosion caused by the Vikings’ imported cattle, or a migration back to Europe to farms depopulated by the Black Plague.
The Medieval Warm Period (MWP), also called medieval warm epoch or little climatic optimum, was a brief climatic interval that is hypothesized to have occurred from approximately 950 to 1250 (roughly coinciding with the Middle Ages in Europe), in which relatively warm conditions are said to have prevailed in various parts of the world, though predominantly in the Northern Hemisphere from Greenland eastward through Europe and parts of Asia.
The Controversial Medieval Warm Period
John Rafferty (www.brittanica.com) has commented that the notion of a medieval warm period is highly controversial. Many paleoclimatologists claim that well-documented evidence for the phenomenon appears across the North Atlantic region, while others maintain that the phenomenon was global, occurring all over the world. Still other scientists insist that their data do not show appreciable changes in average temperature anywhere over the course of the interval. Meanwhile, global warming skeptics have used the MWP to bolster their position in the debate over the nature and effects of climate change.
Direct measurements of climate conditions collected by thermometers, barometers, rain gauges, and other equipment have been available since the 19th century. The climatic conditions of older periods, however, have to be “reconstructed” with the help of historical documents (which contain figures on food production, the length of growing seasons, and the duration of ice on bodies of water) and other indirect measures of climate (including “climate proxies” such as tree rings, ice cores, and sediment cores).
Many such studies suggest that Europe’s Middle Ages did see several multiyear stretches of relatively pleasant conditions and reliable weather. There is little evidence that such conditions prevailed on a global scale, however. Some climate proxies point to several periods of extended drought during the MWP in some locations, such as the Sierra Nevada mountains of North America, parts of Australia, and the Asian steppe, whereas other areas, such as northern China, experienced a mix of heavy rainfall and drought.
Many studies show that the amount of warming occurring during the MWP varied by season and region. Some provide evidence of relatively warm temperatures (most pronounced during the summer months) in several regions, including the North Atlantic, northern Europe, China, and parts of North America, as well as the Andes, Tasmania, and New Zealand. Other studies maintain that the temperature conditions of certain regions, such as the Mediterranean, South America, and other locations in the Southern Hemisphere, were essentially no different from those of the present day.
Only a few studies have attempted to assign a specific value to changes in average global temperatures during the MWP. In 1965 British climatologist Hubert Horace Lamb examined historical records of harvests and precipitation, along with early ice-core and tree-ring data, and concluded that the MWP was probably 1–2 °C (1.8–3.6 °F) warmer than early 20th-century conditions in Europe. Attempts to calculate global temperature changes during the MWP, even using modern instrumental and ice-core sampling techniques, have been inconclusive.
Vikings and Their Explorations
The website www.sunnysuffolk.edu has a very informative paper, written by Scott Mandia on February 3, 2017, on Vikings and their explorations in a warmer world. During the years 800-1200, Iceland and Greenland were settled by the Vikings. These people, also known as the Norse, included Norwegians, Swedes, Danes, and Finns. The warm climate during the MWP allowed this great migration to flourish. Drift ice posed the greatest hazard to sailors but reports of drift ice in old records do not appear until the thirteenth century. The Norse peoples travelled to Iceland for a variety of reasons including a search for more land and resources to satisfy a growing population and to escape raiders and harsh rulers.
One force behind the movement to Iceland in the ninth century was the ruthlessness of Harald Fairhair, a Norwegian King . Vikings travelling to Iceland from Norway during the MWP were probably encouraged by the sight of pastures with sedges, grasses and dwarf woodlands of birch and willow resembling those at home. Animal bones and other materials collected from archaeological sites reveal Icelandic Vikings had large farmsteads with dairy cattle (a source of meat), pigs, sheep and goats (for wool, hair, milk, and meat). Farmsteads also had ample pastures and fields of barley used for the making of beer and these farms were located near bird cliffs (providing meat, eggs, and eiderdown) and inshore fishing grounds. Fishing was primarily done with hand lines or from small boats that did not venture across the horizon.
Erik the Red
In 960, Thorvald Asvaldsson of Jaederen in Norway killed a man. He was forced to leave the country so he moved to northern Iceland. He had a ten year old son named Erik, or Erik the Red. Erik too had a violent streak and in 982 he killed two men. Erik the Red was banished from Iceland for three years so he sailed west to find a land that Icelanders had discovered years before but knew little about. Erik searched the coast of this land and found the most hospitable area, a deep fiord on the southwestern coast. Warmer Atlantic currents met the island there and conditions were not much different than those in Iceland (trees and grasses). He called this new land “Greenland” because he “believed more people would go thither if the country had a beautiful name,” according to one of the Icelandic chronicles; although Greenland, as a whole, could not be considered “green.” Additionally, the land was not very good for farming.
Norse, or Vikings, led by Erik the Red, first sailed from recently settled Iceland to southwestern Greenland around 985, according to Icelandic records. Some 3,000 to 5,000 settlers eventually lived in Greenland, harvesting walrus ivory and raising livestock. But the colonies disappeared between about 1360 and 1460, leaving only ruins, and a longstanding mystery as to what happened. The native Inuit remained, but Europeans did not re-inhabit Greenland until the 1700s.
The Greenland Vikings
The Greenland Vikings lived mostly on dairy produce and meat, primarily 200 Fifteen Shades of Climate Lessons from history 201 from cows. The vegetable diet of Greenlanders included berries, edible grasses, and seaweed, but these were inadequate even during the best harvests. During the MWP, Greenland’s climate was so cold that cattle breeding and dairy farming could only be carried on in the sheltered fiords. The growing season in Greenland even then was very short. Frost typically occurred in August and the fiords froze in October. Before the year 1300, ships regularly sailed from Norway and other European countries to Greenland bringing with them timber, iron, corn, salt, and other needed items.
The Gift of a Cargo of Wine
Trade was by barter. Greenlanders offered butter, cheese, wool, and their frieze cloths, which were greatly sought after in Europe, as well as white and blue fox furs, polar bear skins, walrus and narwhal tusks, and walrus skins. In fact, two Greenland items in particular were prized by Europeans: white bears and the white falcon. These items were given as royal gifts. For instance, the King of Norway-Denmark sent a number of Greenland falcons as a gift to the King of Portugal, and received in return the gift of a cargo of wine. Because of the shortage of adequate vegetables and cereal grains, and a shortage of timber to make ships, the trade link to Iceland and Europe was vital.
One study undercuts the idea that the MWF was global and that Vikings may not have colonized Greenland in nice weather. Vikings colonized Greenland and possibly neighbouring Baffin Island during what has been assumed to be – perhaps mistakenly – a temporary warm period. They disappeared in the 1400s. Southern Greenland’s Hvalsey church is the best preserved Viking ruin. (Wikimedia Commons). A new study questions the popular notion that 10th-century Norse people were able to colonize Greenland because of a period of unusually warm weather. Based upon signs left by old glaciers, researchers say the climate was already cold when the Norse arrived–and that climate thus probably played little role in their mysterious demise some 400 years later. On a larger scale, the study adds to building evidence that the socalled MWP, when Europe enjoyed exceptionally clement weather, did not necessarily extend to other parts of the world. “It’s becoming clearer that the MWP was patchy, not global,” said lead author Nicolás Young, a glacial geologist at Columbia University’s Lamont-Doherty Earth Observatory. “The concept is Eurocentric–that’s where the best-known observations were made. Elsewhere, the climate might not have been the same.” Climate scientists have cited the MWP to explain anomalies in rainfall and temperature in far-flung regions, from the U.S. Southwest to China. The study appears in the journal Science Advances in 2015.
Glaciers usually advance during cold times and recede during warm ones. Two glaciers in western Greenland are now retreating from where they may have been when the Vikings arrived. In the new study, the scientists sampled boulders left by advancing glaciers over the last 1,000-some years in southwest Greenland, and on neighbouring Baffin Island, which the Norse may also have occupied, according to newly uncovered evidence. Glacial advances during the Little Ice Age have wiped out most evidence of where the glaciers were during the Norse settlement. Young and his colleagues were able to find traces of a few moraines–heaps of debris left at glaciers’ ends–that, by their layout, they could tell predated the Little Ice Age advances. Using newly precise methods of analyzing chemical isotopes in the rocks, they showed that these moraines had been deposited during the Viking occupation, and that the glaciers had neared or reached their later maximum Little Ice Age positions between 975 and 1275. The strong implication: it was at least as cold when the Vikings arrived as when they left. “If the Vikings travelled to Greenland when it was cool, it’s a stretch to say deteriorating climate drove them out,” said Young.
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