Planet Earth Weekly

Climate Change and Renewable Energy: Saving Our Planet for Future Generations

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Climate Change over the last Millennium: The Medieval Warm Period

Global warming

Climate Change in the last 1000 years.

“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 Change

Global Warming over time.

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.

Climate Change

The earth’s overall temperatures are increasing every year.

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.

Global Greenhouse Gases

Climate Change

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.

Climate Change


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The Arctic Basin: Warming Faster than the Planet in its Entirety

Arctic Ocean

Melting of the Arctic Sea Ice

“The arctic basin is warming faster than most of the earth’s surface.”

By Dr. John J. Hidore
June 8, 2018—–The Arctic Basin consists of the Arctic Sea and the surrounding land. The climate of the basin is warming faster than any other area of Earth’s surface. Air temperature over the arctic has increased an average of nearly three degrees Celsius (five degrees Fahrenheit) over the last century. This is almost double that of the global average.

The Energy Exchange in Change of State Between Ice and Water

One very important feature of the energy balance distinguishes the Arctic Basin. Over 95% of the earth’s surface, the major change in the state of water in the environment is between liquid and gas. This entails evaporation and condensation. In the Arctic it is between solid and liquid. There is an energy exchange of about 80 calories per gram between solid and liquid. For the rest of the earth the energy exchange is much higher. The energy exchange between liquid and gas is 590 calories per gram. This is nearly seven times that of ice and water.

The implication of this is that melting or freezing takes place with relative small changes in heat added or heat lost in the environment!

The energy exchange in melting artic

Melting of the Arctic

Energy Exchange in the Tundra

Surrounding the Arctic sea is a grassland, generally known as the tundra. Such a grassland is found primarily only in the Northern Hemisphere. The southern margin of the tundra is delimited by the polar margin of a coniferous forest. Specific regions that contain tundra are the northern coast of North America, Iceland, Spitsbergen, coastal Greenland, and the Arctic borderlands of Eurasia.

A significant feature of the tundra is permafrost. Permafrost is permanently frozen ground. Extensive area of land in the basin are covered with it. Permafrost can vary from centimeters to many meters thick.

Ice and snow are highly reflective of solar radiation. However, in the summer months some of the solar radiation melts the permafrost. The surface layer of permafrost thaws leaving the deeper layer frozen. The result is that lakes and ponds are a characteristic of the tundra. Once the permafrost melts at the surface, the wet ground absorbs much more radiation and the thawing increases. However, except on the margins of the permafrost, there remains frozen ground beneath the surface.

How deep the permafrost melts will vary. The point is that once the surface thaws the solar energy that is absorbed goes up substantially. This in turn increases the rate of the thawing of the permafrost. As the earth’s atmosphere slowly warms this process is being accelerated.

climate change

The exchange of energy is causing rapid arctic melting.

Energy Exchange in the Arctic Sea

The Arctic Sea is a part of the world ocean that is frozen much of the year but increasingly is open during the summer months. The season when melting occurs has increased by three weeks since records began. At present, even in the summer, there is a large area that remains frozen. As the atmosphere slowly warms more of the ice cover melts. Open water absorbs much more radiation than the ice and this increases the temperature of the water which then increases melting of the ice. As a result, over recent decades, the sea ice has been thinning or melting entirely over large areas. Just as on land the conversion from sea ice to open water is increasing at an increasing rate.

Climate change

The rapidly melting artic

In summary, the arctic basin is warming faster than most of the earth’s surface. Part of the explanation lies in the fact that the amount of energy it takes to change the state of water between solid and liquid is much less than it takes to change the state between liquid to gas. There is thus a net gain in heat that is proportionately higher than that of the rest of the planet. As the summer season increases in length more heat is absorbed in the environment adding to the general global warming!

Warming of the Arctic