Glaciers in China's bleak, rugged Qilian mountains are disappearing at a shocking rate as global warming brings unpredictable change and raises the prospect of crippling, long-term water shortages, scientists say. The largest glacier in the 800-km (500-mile) mountain chain on the arid northeastern edge of the Tibetan plateau has retreated about 450 metres since the 1950s, when researchers set up China's first monitoring station to study it. The 20-square kilometre glacier, known as Laohugou No. 12, is criss-crossed by rivulets of water down its craggy, grit-blown surface. It has shrunk by about 7% since measurements began, with melting accelerating at a record pace in recent years, scientists say. Equally alarming is the loss of thickness, with about 13 metres (42 feet) of ice disappearing as temperatures rise, said Qin Xiang, the director at the monitoring station. REUTERS/Carlos Garcia Rawlins TPX IMAGES OF THE DAY SEARCH "RAWLINS GLACIER" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES.