The Frozen Thames, 1677
The
Little Ice Age (LIA) was a period of cooling that occurred after the
Medieval Warm Period. While not a true
ice age, the term was introduced into scientific literature by François E. Matthes in 1939. It is conventionally defined as a period extending from the 16th to the 19th centuries, though climatologists and historians working with local records no longer expect to agree on either the start or end dates of this period, which varied according to local conditions. It is generally agreed that there were three
minima, beginning about 1650, about 1770, and 1850, each separated by intervals of slight warming.
Several causes have been proposed:
cyclical lows in solar radiation, heightened
volcanic activity, changes in the
ocean circulation, an inherent variability in global climate.
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 anecdotal evidence of expanding
glaciers almost worldwide. In contrast, a climate reconstruction based on glacial length shows no great variation from 1600 to 1850, though it shows strong retreat thereafter.
For this reason, any of several dates ranging over 400 years may indicate the beginning of the Little Ice Age:
- 1250 for when Atlantic pack ice began to grow
- 1300 for when warm summers stopped being dependable in Northern Europe
- 1315 for the rains and Great Famine of 1315-1317
- 1550 for theorized beginning of worldwide glacial expansion
- 1650 for the first climatic minimum.
The prevailing scientific view is that the Little Ice Age ended in the latter half of the 19th century or early in the 20th century.
Timothy Ball and
Syun-Ichi Akasofu, founder of the
International Arctic Research Center at the
University of Alaska believe that Earth's climate is still recovering from the Little Ice Age.
Little Ice Age - Wikipedia, the free encyclopedia
This image is a comparison of 10 different published reconstructions of mean temperature changes during the last 2000 years. More recent reconstructions are plotted towards the front and in redder colors, older reconstructions appear towards the back and in bluer colors. An instrumental history of temperature is also shown in black. The
medieval warm period and
little ice age are labeled at roughly the times when they are historically believed to occur, though it is still disputed whether these were truly global or only regional events. The single, unsmoothed annual value for 2004 is also shown for comparison:
Little Ice Age - Wikimedia Commons
