Unprecedented glacier melting in the Andes blamed on climate change

January 24, 2013 – CLIMATE – Glaciers in the tropical Andes have been retreating at increasing rate since the 1970s, scientists write in the most comprehensive review to date of Andean glacier observations. The researchers blame the melting on rising temperatures as the region has warmed about 0.7 C over the past 50 years (1950-1994). This unprecedented retreat could affect water supply to Andean populations in the near future. These conclusions are published in The Cryosphere, an Open Access journal of the European Geosciences Union (EGU). The international team of scientists – uniting researchers from Europe, South America and the US – shows in the new paper that, since the 1970s, glaciers in tropical Andes have been melting at a rate unprecedented in the past 300 years. Globally, glaciers have been retreating at a moderate pace as the planet warmed after the peak of the Little Ice Age, a cold period lasting from the 16th to the mid-19th century. Over the past few decades, however, the rate of melting has increased steeply in the tropical Andes. Glaciers in the mountain range have shrunk by an average of 30-50% since the 1970s, according to Antoine Rabatel, researcher at the Laboratory for Glaciology and Environmental Geophysics in Grenoble, France, and lead author of the study. Glaciers are retreating everywhere in the tropical Andes, but the melting is more pronounced for small glaciers at low altitudes, the authors report. Glaciers at altitudes below 5,400 meters have lost about 1.35 meters in ice thickness (an average of 1.2 meters of water equivalent [see note]) per year since the late 1970s, twice the rate of the larger, high-altitude glaciers. “Because the maximum thickness of these small, low-altitude glaciers rarely exceeds 40 meters, with such an annual loss they will probably completely disappear within the coming decades,” says Rabatel. The researchers further report that the amount of rainfall in the region did not change much over the past few decades and, therefore, cannot account for changes in glacier retreat. Instead, climate change is to blame for the melting: regional temperatures increased an average of 0.15 C per decade over the 1950-1994 period. “Our study is important in the run-up to the next IPCC report, coming out in 2013,” says Rabatel. The Intergovernmental Panel on Climate Change (IPCC) has pointed out that tropical glaciers are key indicators of recent climate change as they are particularly sensitive to temperature changes. The tropical Andes host 99% of all tropical glaciers in the world, most of them in Peru. –SD