Glaciers are one of the Earth's most sensitive indicators of climatic change. However, evaluating the significance of ice-marginal fluctuations is far from straightforward, as glaciers respond to climatic warming and cooling on different time scales. At the beginning of the new millennium, the majority of the Earth's mountain glaciers are undergoing recession, although there are some notable exceptions.

Along with the recession of glaciers comes the transfer of water stored on land to the sea, and with it the fear of rising global sea levels. Hence it is vitally important that we acquire data of the past and present response of glaciers to climatic change, in order to help us predict the future. As a step towards this goal, the World Glacier Monitoring Service assembles data on ice-marginal fluctuations for several hundred glaciers around the world.

Historical records, dating back to the eighteenth and nineteenth centuries, have been the prime source of information about glacier fluctuations, but there are few such records outside the Alps and Norway. In Europe this period was typified by the strongest advance of glaciers since the last ice age and became known as the Little Ice Age. It coincided with low average temperatures and widespread crop failure. In these and other regions dating of old ridges of glacial debris (moraines) by radiocarbon techniques has enabled scientists to determine glacier fluctuations on a time-scale of thousands of years.