Web Presentation ES 767 Quaternary Geology Kurt Shobe July 15, 1999

Graphs taken from "Evidence of Little Ice Age", University of Washington, Http://www.atmos.washington.edu

The Little Ice Age

Our years are turned upside down; our summers are no summers; our harvests are no harvests: John King, 1595

The "Little Ice Age" was a period of unusual cooling which began after the demise of the Medieval Warm period and lasted nearly until the present time (~1200 AD to ~1900 AD), reaching its peak from 1550 to 1700. During this period, the average global temperature dropped between 1 and 2 degrees Celsius. This average temperature reduction, which lasted most of the millennium, resulted in advancing glaciers, widespread and recurrent crop failures, disease, displacement, and famine. Although the effects of the Little Ice Age are best documented in Europe, evidence points to a global reduction in temperature, with the corresponding negative results (Daley, 1998). Areas hardest hit by the cold were those situated at polar extremes or mountainous areas. Examples of areas effected include Greenland (which was actually green during the preceding medieval warm period), Iceland, the Himalayas, the Alps, and the Jiang-Xi region of China. One of the lasting effects of the Little Ice Age was the ruination of the 1816 Swiss summer vacation of poet Percy Shelley and his wife, Mary. The weather was so cold at Lake Geneva that most of the vacation was spent indoors, entertaining one another and friends with horror stories. Mary Shelley's contribution was Frankenstein, in which the monster and his creator meet their final fate in a cold Arctic wasteland.

SURFACE ALBEDO. Albedo can be described as a measure of the amount of solar radiation that does not reach the surface of the earth. High reflectivity is generally associated with snow and ice, however reflectivity can also be caused by material injected during a volcanic eruption, or an increase in the amount of cloud cover. Climatic cooling during the Little Ice Age resulted in the increase of glaciers and snow cover, producing higher reflectivity and in effect creating a "feedback loop" where further glacial increases produced further increases in reflectivity, and associated cooling. The increase in volcanic activity aided the cooling process once it started, and may have been one of the main drivers for the start of the cooling process, which then to some degree built upon itself. The period of cooling commonly referred to as the Little Ice Age extended roughly throughout most of the last millennium, though the exact beginning and end of the period is the subject of some debate. The effects of the period included advancing ice sheets, crop failures, famine, displacement, and disease. Causes of the Little Ice Age include increased volcanic activity, reduction in solar output, changes in the course of the Gulf Stream, and an increase in the reflectivity of incoming solar radiation. All of these effects, some of which are inter-dependant, conspired to bring about the long term cooling during this period.

BIBLIOGRAPHY AND FURTHER READING

Daley, Andrew, 1998 "The Little Ice Age; Was it Big Enough to be Global?" http://jrscience.wep.muohio.edu/ (5/8/98).

"Evidence of the Little Ice Age"; http://www.atmos.washington.edu/

Cutler, Alan, 1997, "the Little Ice Age: When Global Cooling Gripped the World". The Washington Post, August 13, 1997. http://www.vehicle.org/climate/cutler.html

Sigurdsson, H., and Carey, S., 1989, Plinian and co-igmibrite tephra fall from the 1815 eruption of Tambora volcano: Bulletin of Volcanology, v. 51, p. 243-270.