Special One Hour Episode of NOW - On Thin Ice

Glaciers are receding, we know, but why should we be paying closer attention? Not only do glaciers store about 75 percent of the world's water supply, but they are not a renewable resource. NOW on PBS travels to Gangotri Glacier in the Himalayas with Conrad Anker, one of the world's leading high altitude climbers, in an HD one-hour special to show how the rapid disappearance of Gangotri, one of the world's largest glaciers, directly affects American food and water supply - not to mention the food and water of half a billion people in India and China.

Trekking with Anker to both Gangotri and Glacier National Park in Montana is NOW host David Brancaccio. Closer to home the ancient ice has nearly disappeared, leaving thousands of acres of rock and scree where the iconic American glaciers once reigned. Glacial retreat, which used to take millennia, has already had a significant effect on not just the global water supply but also on air temperatures, sea currents, wildlife, weather patterns, a steady rise in sea level - and now on human migration.

"On Thin Ice" airs Friday, April 17 at 8:30 on WGVU TV & WGVU HD.

Read NOW on PBS host David Brancaccio's journal from his trip to India.

See a slideshow from the same trip.