Glaciers now occupy the center stage in the debate over causes and impacts of climate change.
The world has become far too hot for the aptly named Exit Glacier in Alaska.
Like many low-altitude glaciers, it's steadily melting, shrinking two miles over the past 200 years as it tries to strike a new balance with rising temperatures.
At the Kenai Fjords National Park south of Anchorage, managers have learned to follow the Exit and other glaciers, moving signs and paths to accommodate the ephemeral rivers of blue and white ice as they retreat up deeply carved valleys.
"Some of the stuff is changing fast enough that we now have signs on moving pedestals," said Fritz Klasner, natural resource specialist at Kenai Fjords.
The vast amounts of water stored in glaciers play crucial roles in river flows, hydropower generation and agricultural production, contributing to steady run-off for Ganges, Yangtze, Mekong and Indus rivers in Asia and elsewhere.
But many are melting rapidly, with the pace picking up over the past decade, giving glaciers a central role in the debate over causes and impacts of climate change.
That role has come even more sharply into focus after recent attacks on the U.N.'s climate panel, which included a wrong estimate for the pace of melting for Himalayan glaciers in a major 2007 report.
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