This combination image shows a 1921 view of the Main Rongbuk Glacier, Northern Slope of Mount Everest, Tibet Autonomous Region, China by George L. Mallory, courtesy of Royal Geographical Society (left) and a 2007 view of the Main Rongbuk Glacier, Northern Slope of Mount Everest, Tibet Autonomous Region, China by David Breashears, courtesy of Glacier Works. When legendary British climber George Mallory took his iconic 1921 photo of the north face of Mount Everest, the mighty, river-shaped glacier snaking past his feet seemed eternal. Decades of pollution and global warming later, modern mountaineer David Breashears has taken his own picture at the same spot - and proved an alarming reality. Instead of the powerful, white, S-shaped sweep of ice witnessed by Mallory before he died on his conquest of Mount Everest, today's Rongbuk glacier is shrunken and withered.