Over 68 percent of the Earth's freshwater is locked in glaciers and the polar ice caps. Glaciers are important features in the water cycle and affect the volume, variability, and water quality of runoff in areas where they occur (ga.water.usgs.gov/edu/).
Global Warming Today
Since the end of the 19th century, the average temperature has risen 0.7 degrees C. To see the changes this rise in temperature has caused, compare the before and after photographs of glaciers below.
Photograph Credits: Global Warming ArtClimate change, through either global warming or cooling, has catastrophic effects on the Earth and its inhabitants. For 1000 years, the average temperature on Earth was relatively constant.
Past Warming Trend
Between the 10th and 14th centuries, the Earth warmed by 1 degree C. This is when wineries flourished in England, citrus trees grew in northern China, the passes in the Alps between Italy and Germany were navigable, and Iceland and Greenland were settled as the Arctic ice pack retreated.
Past Cooling Trend
The Earth underwent a Little Ice Age between the 15th and 19th centuries, when the average temperature was between 1-2 degrees C. cooler than today. The Alpine glaciers descended, the River Thames froze solid, sea ice expanded, thus sealing the fate of the Viking colony in Greenland. Spring melt brought flooding to lowland area in Europe, causing crop failure and increasing famine.
This post made in support of Blog Action Day 2009.