The Little Ice AgeBy: Elly Sawicky

The Little Ice Age begins

• There is no agreed beginning year to the Little Ice Age, although there is a frequently referenced series of events preceding the known climatic minima.

• Starting in the 13th century, pack ice began advancing southwards in the North Atlantic, as did glaciers in Greenland.

• The three years of torrential rains beginning in 1315 ushered in an era of unpredictable weather in Northern Europe which did not lift until the 19th century.

• There is objective evidence of expanding glaciers almost worldwide.

Life during the Little Ice Age• When the ice cap in eastern

North America reached as far south as Pennsylvania, the world was about nine degrees cooler.

• In France, the harsh winter of 1788-89 added to the misery and discontent of the peasants, and cold and erratic weather patterns produced numerous crop failures in northerly areas such as Scotland and Norway.

• Native American tribes such as the Iroquois relocated their villages to escape the cold. These migrations stirred up political conflict among tribes.

• The hardest hit were the Norse settlements in Iceland and Greenland. The population of famine-ridden Iceland dwindled during the Little Ice Age to half its previous numbers.

What causedthe Little Ice Age?

• Most of the Little Ice Age occurred well before the Industrial Revolution and the widespread burning of fossil fuels, so scientists are confident that its climatic convulsions had purely natural causes.

• In the 1970s, scientists, noticed the correlation of sunspot numbers with major ups and downs in Earth's climate. For example, it was found that a period of low activity from 1645 to 1715 matched perfectly one of the coldest spells of the Little Ice Age.

• Scientists considered other possibilities such as shifts in ocean currents, heightened volcanic activity, and greenhouse gases -- mainly carbon dioxide and methane.

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 1-2°C (2-4°F) cooling events recurring every 1,500 years or so.

• The most recent of these cooling events was the Little Ice Age.

• 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 3-8°C (6-14°F).

The end of the Little Ice Age

• Beginning around 1850, the climate began warming and the Little Ice Age ended.

• Some global warming critics believe that Earth's climate is still recovering from the Little Ice Age and that human activity is not the decisive factor in present temperature trends, but this idea is not widely accepted.

• Mainstream scientific opinion on climate change is that warming over the last 50 years is caused primarily by the increased proportion of CO2 in the atmosphere caused by human activity.

• The clear message of science and history is that climate change has always been a natural phenomenon on Earth and a matter of vital human interest.

SOURCES

• Wikipedia, "Little Ice Age". Wikimedia Foundation, Inc., . August 9, 2010 <http://en.wikipedia.org/wiki/Little_ice_age.

• Cutler, Alan. "The Little Ice Age ". Washington Post. August 9, 2010 <http://www.geology.um.maine.edu/ges121/lectures/11-little-ice-age/little-ice-age.html>.