While it's not clear yet that these changes are the result of human-induced greenhouse warming, scientists say, the rate of change has accelerated markedly in recent decades.
Researchers discussed recent developments at high latitudes and their possible implications for sea level-rise at a session entitled "Deciphering the Complex Changes in Snow and Ice," at the AAAS Annual Meeting.
The world's glaciers and ice caps have been shrinking faster since the 1980s than they did during the last several millennia, according to estimates by Mark Meier of the University of Colorado at Boulder. Meier analyzed information about glacier volumes worldwide, from several thousand years ago to the present, and studied the last 40 years in more detail. He estimates that sea level is likely to rise perhaps twice as much as the International Panel on Climatic Change (IPCC) recently predicted.
"The IPCC's projections are too low for several reasons," he said.
According to Meier, the projections don't consider that glaciers seem to be growing increasingly sensitive as air temperatures get warmer. In addition, smaller glaciers melt faster than large ones because a greater percentage of their surface area is at lower altitudes. Finally, as temperatures increase, large glaciers that are currently not contributing to sea-level rise will begin to do so.
Meier also analyzed measurements of glacier runoff and precipitation, and found that the increase in melting seems to have intensified the hydrological cycle at high altitudes. That is, the amount of water evaporating from the Earth's surface and returning as precipitation has also amplifi
Contact: Monica Amarelo
American Association for the Advancement of Science