The Little Ice Age Theories
Examining Climatology Records for Evidence of Climate Change
The Little Ice Age caused decreased winter temperatures, resulting in sea ice, glacier advances, and crop failures. Discover what caused this abrupt change in climate.
The Little Ice Age occurred from the early 1400s until the late 1800s, affecting many areas of the Northern Hemisphere. Regions of North America and Europe experienced the lowest temperature values of the last millennium, according to the climatology records. Winter temperatures dipped by 2 to 3 degrees Fahrenheit, or 1-1.5 Celsius.
This slight decrease in winter temperatures, caused rivers and oceans to freeze, sea ice to form and glaciers to expand and advance. Records mention that Greenland was cut off by ice for over 300 years, until the 1720s. Holland’s canals froze solid. Rivers in Europe and North American froze over, which were previously noted as ice free. Paintings of this era, depict ice sports being played on these frozen rivers.
What Caused the Little Ice Age?
Scientists are still developing and reworking theories on what caused the Little Ice Age. One of the main theories states that low solar activity caused the atmospheric changes, triggering the Little Ice Age. Astronomers during this time period, recorded the sun’s activity, counting the number of sunspots for a 30 year period. Normal sun activity recorded 40-50,000 sunspots in a 30 year period. During the coldest portion of the Little Ice Age, from 1645 to 1715, astronomers observed about 50 sunspots for a 30 year period, which points to a definite decline in solar activity. This period is known as the Maunder Minimum.
Another theory points to increased volcanic activity as the cause for abrupt climate changes. In 1815, Tambora erupted in Indonesia, causing millions of tons of ash and dust to be launched into the atmosphere. The dark clouds circled the globe, moving with the wind. The eruption of Tambora is known as “the largest eruption in historic time.” The following year is referred to as the “Year Without a Summer” because the dark clouds from Tambora, blocked essential sunlight. This caused changes in agricultural production, causing crop failures and famine.
A final theory, developed by Milutin Milankovitch, explains the climate shift was due to changes in the Earth’s tilt. This Milankovitch Theory points to the coming and going of ice ages caused by the Earth’s orbital shift.
What Evidence is Found
Evidence used to develop these theories includes climatology records such as:
- ice cores
- tree rings
- temperature records found in weather diaries
- glacier movement
- sea ice
- records of harsh winters.
Scientists have also found evidence in marshes of New York’s Hudson Valley, examining sediment samples and pollen records. Research by NASA and Columbia University in this area have found evidence of the Little Ice Age.
Effect on Climate
The Little Ice Age not only caused decreased winter temperatures but also diminished the winds of the jet stream, which transports warm air from the ocean. The changes in climate caused by the Little Ice Age, resulted in decreased agriculture and ultimately famine in some areas. The Little Ice Age followed periods of drought, occurring during the Medieval Warm period from 800 to 1300 AD.
Sources:
NASA
National Climatic Data Center
