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Little Ice Age

Retrieved from the Wikipedia, the free encyclopedia on 10/10/2005. Edited for length by B.Rick.

The Little Ice Age (LIA) was a period of cooling lasting approximately from the 14th to the mid-19th centuries, although there is no generally agreed start or end date: some confine the period to 1550-1850. This cooler period occurs after a warmer era known as the Medieval climate optimum.[1].

The Intergovernmental Panel on Climate Change (IPCC)... describes the LIA as a modest cooling of the Northern Hemisphere during this period of less than 1°C, and says current evidence does not support globally synchronous periods of anomalous cold or warmth over this timeframe. The reconstructed depth of the Little Ice Age varies between different studies.

Dates of the Little Ice Age

There is no agreed beginning year to the Little Ice Age, although there are a frequently referenced series of events preceding the known climactic minima. Starting in the 13th century, pack ice began advancing southwards in the North Atlantic, as well as glaciers in Greenland. The three years of torrential rains in 1315 ushered in an era of unpredictable weather in Northern Europe which did not lift until the 19th century. Finally, expanding glaciers are recorded almost worldwide (including the Andes, China, and New Zealand) starting in the mid-17th century (Brian Fagan, The Little Ice Age, 2000).

For this reason, scholars tend to use any of several dates ranging over 400 years for the beginning of the Little Ice Age:

In contrast to its vague beginning, there is an almost undisputed consensus that the end of the Little Ice Age was in the mid-19th century.

Northern Hemisphere

The Little Ice Age brought bitterly cold winters to many parts of the world, but is most thoroughly documented in Europe and North America. In the mid-17th century, glaciers in the Swiss Alps advanced, gradually engulfing farms and crushing entire villages. The River Thames and the canals and rivers of the Netherlands often froze over during the winter, and people skated and even held frost fairs on the ice. In the winter of 1780, New York Harbor froze, allowing people to walk from Manhattan to Staten Island. Sea ice surrounding Iceland extended for miles in every direction, closing that island's harbors to shipping. The Arctic pack ice extended so far south that there are six records of Eskimos landing their kayaks in Scotland [2].

The severe winters affected human life in ways large and small. The population of Iceland fell by half, and the Viking colonies in Greenland died out. In North America, Native Americans formed leagues in response to food shortages [3].

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. Many springs and summers were outstandingly cold and wet, although there was great variability between years and groups of years. Crop practices throughout Europe had to be altered to adapt to the shortened, less reliable growing season, and there were many years of death and famine. Violent storms caused massive flooding and loss of life. Some of these resulted in permanent losses of large tracts of land from the Danish, German, and Dutch coasts [4].

In China, warm weather crops, such as oranges, were abandoned in Jiangxi Province, where they had been grown for centuries. In North America, the early European settlers also reported exceptionally severe winters. For example, in 1607-8 ice persisted on Lake Superior until June [8].

The Little Ice Age can be seen in the art of the time; for example, snow dominates many village-scapes by the Flemish painter Pieter Brueghel the Younger, who lived from 1564 to 1638. The famous winter paintings by Pieter Brueghel the Elder (e.g. Hunters in the Snow) appear to all have been painted in 1565.

Another famous person to live during the LIA was Antonio Stradivari, a violin maker. The colder climates of the time caused the wood from the trees he used to be denser; the superb tone of Stradivari's creations has been partially attributed to this.

Tropical Pacific coral records indicate the most frequent, intense ENSO activity occurred in the mid-17th century, during the Little Ice Age [15].

Climate patterns

In the North Atlantic, sediments accumulated since the end of the last ice age nearly 12,000 years ago show regular increases in the amount of coarse sediment grains deposited from icebergs melting in the now open ocean, indicating a series of 1-2ºC (2-4°F) cooling events recurring every 1,500 years or so. The most recent of these cooling events was the Little Ice Age. These same cooling events are detected in sediments accumulating off Africa, but the cooling events appear to be larger, ranging between 3-8ºC (6-14°F) [16].

Causes

Scientists have identified two causes of the Little Ice Age from outside the ocean/atmosphere/land systems: decreased solar activity and increased volcanic activity. Research is ongoing on more ambiguous influences such as internal variability of the climate system, and anthropogenic influence (Ruddiman). Some have also speculated that depopulation of Europe during the Black Death and the resulting decrease in agricultural output may have prolonged the Little Ice Age.

One of the difficulties in identifing the causes of the Little Ice Age is the lack of consensus on what constitutes "normal" climate. While some scholars regard the LIA as an unusual period caused by a combination of global and regional changes, other scientists see glaciation as the norm for the Earth and the Medieval Warm Period ... as the anomalies requiring explanation (Fagan).

Solar activity

During the period 1645-1715, right in the middle of the Little Ice Age, solar activity as seen in sunspots was extremely low, with some years having no sunspots at all. The precise link between low sunspot activity and cooling temperatures has not been established.

Volcanic activity

Throughout the Little Ice Age, the world also experienced heightened volcanic activity. When a volcano erupts, its ash reaches high into the atmosphere and can spread to cover the whole earth. This ash cloud blocks out some of the incoming solar radiation, leading to world-wide cooling that can last up to two years after an eruption. Also emitted by eruptions is sulfur in the form of SO2 gas. When this gas reaches the stratosphere, it turns into sulfuric acid particles, which reflect the sun's rays, further reducing the amount of radiation reaching the earth's surface. The 1815 eruption of Tambora in Indonesia blanketed the atmosphere with ash; the following year, 1816, came to be known as the Year Without A Summer, when frost and snow were reported in June and July in both New England and Northern Europe.

End of Little Ice Age

Beginning around 1850, the world's climate began warming again and the Little Ice Age may be said to have come to an end at that time. Some scientists believe that the Earth's climate is still recovering from the Little Ice Age. Others believe that human-induced warming may be the reason for the end of the Little Ice Age.