The document analyzes satellite images from 1991, 1996, 2004, and 2011 to measure glacier areas in the Urubamba and Vilcabamba mountain ranges in Peru. It finds that over this period, all glaciers showed losses between 29.4-98.7% of their 1991 areas. For the Urubamba range, glacier coverage decreased from 64.8 km2 in 1991 to 29.4 km2 in 2011, while for the Vilcabamba range it decreased from 220.3 km2 to 129.4 km2. Losses were stronger for glaciers below 5400 meters. Analysis of precipitation data found no significant trends, suggesting losses are due to increasing air temperatures of 0.1-0.39°