“A great variety of information and data indicate there were major fluctuations in the global climate during the last 1000 years.”
By Dr. John J. Hidore
September 3, 2018—-A great variety of information and data indicate there were major fluctuations in the global climate during the last 1000 years. There were periods when it was warmer than now and others when it was colder. Fluctuating temperatures brought significant changes in the global environment.
The Medieval Warm Period or Little Climatic Optimum
One distinctive climatic period during this time is what is known as the Medieval Warm period or Little Climatic Optimum. The period extended from about 950 to 1250 AD. This time was unusually warm for the millennium and was warmer even by present global temperatures. With the increase in temperature came increased precipitation in many areas. This increased lake levels. The Caspian Sea rose by some 18 meters (59 feet).
The medieval warm period was a global phenomenon. Perhaps the best evidence of this was that sea level rose. This had a widespread impact on the human population at the time. The rise in sea level forced the migration of large numbers of people away from the coast and into areas already occupied. This resulted in clashes between different groups and cultures. There was an expansion of Eskimo cultures around the arctic. Central Asian cultures also expanded into areas they had not previously occupied.
Climate of the Western Arctic Basin
Contemporary literature from Iceland has aided in reconstructing of one of the most complete sequences of the Arctic Basin climate over the last thousand years. There is much data for Iceland from the following sources:
900-1590: information from Icelandic sagas about times of severe weather and related famine.
1591-1780: historical records combined with incomplete drift ice data.
1781-1845: a reconstruction of weather conditions as derived from the relative severity and frequency of drift ice near Iceland.
1846 to present: actual meteorological instruments.
Iceland and Greenland’s Changing Climate
The Vikings settled Iceland in the ninth century. Evidence of agriculture and other activities indicate the climate that existed at the time. When the Vikings settled Greenland, it was quite warm, as Eric the Red discovered in Greenland in 982 A.D. In 984 A.D. the Norse founded the colony of Osterbygd on Greenland. While an icy land, it supported enough vegetation (dwarf willow, birch, bush berries, pasture land) for settlement.
The settlers brought cattle and sheep that not only survived but thrived for a considerable period. They established two colonies and began to farm. The outposts thrived and regular communications existed with Iceland. Between 1250 and 1450 AD climate deteriorated over wide areas. Iceland’s population declined. Grains that grew there in the tenth century would no longer grow. Greenland became isolated from outside contact. Extensive drift ice prevented ships from reaching the settlements.
Europe’s Changing Climate
In Europe storminess resulted in the formation of the Zuider Zee and the excessively wet, damp conditions led to a high incidence of the disease St. Anthony’s Fire (ergotism.). Chronicles contain many references to weather conditions of the time, including the Arctic Basin. William of Malmsbury, writing in 1125 about the Gloucester region of England stated “the area exhibits a greater number of vineyards than any other county in England, yielding abundant crops of superior quality….they may also bear comparison with the growths of France.” What is significant about this statement is that by the fifteenth century there was no wine industry in England. The most probable reason is a cooling of the climate since the twelfth century.
Climate Changed in the Interior of North America
There is ample evidence that the warmer conditions affected continental areas as well. Research shows that Indians in the Great Plains of the United States migrated as a result of changes in precipitation. A study by archaeologists and climatologists show for example, that Indians of the Mill Creek culture of Iowa deserted a thriving community about 1200 A.D. Precipitation declined rapidly at the time.
The abandonment of settlements in the southwest United States probably was due to drought. The historic settlements of Chaco Canyon and Mesa Verde indicate that they supported large and prosperous communities. By 1300 A.D., these settlements were deserted.
Reasons other than drought certainly may account for the abandonment. However, tree-ring analysis shows that between 1276 A.D. and 1299 A.D, practically no rain fell in these areas.