Two men on a remarkable journey high in the Himalayas investigate threats to global water and food supply.

Climate change will cause some of the world's largest glaciers to completely melt by 2030. What effect will this have on our daily lives, especially our water and food supply? With global warming falling low on a national list of American concerns, it's time to take a deeper look at what could be a global calamity in the making.

David Brancaccio and environmentalist Conrad Anker, one of the world's leading high-altitude climbers, trek to the Gangotri Glacier in the Himalayan Mountains, the source of the Ganges River, to witness the great melt and its dire consequences firsthand. The two also visit Montana's Glacier National Park to see the striking effects of global warming closer to home and learn how melting glaciers across the world can have a direct impact on food prices in the U.S.

Along the way, Brancaccio and Anker bathe in the River Ganges, view a water shortage calamity in India and see with their own eyes and cameras the tangible costs of climate change.

"We can't take climate change and put it on the back burner," warns Anker. "If we don't address climate change, we won't be around as humans."

Visit http://www.pbs.org/now/shows/516/  right now to watch an extended hour-long version of the program and to access David's 12-day photo-filled travel journal from their trek.