ACCELERATING LOSS OF GLACIERS ON THE WORLD’S HIGHEST MOUNTAINS AND SOCIETAL CONSEQUENCES

Over the past 40 years climatic and environmental histories have been recovered from cores drilled on ice fields from the Polar Regions to the Tropics. These proxy records, many extending back 25,000 years, have made it possible to compare Late Glacial Stage climate conditions throughout the world. High resolution records of stable isotopes of oxygen, which, in part, indicate temperature, demonstrate that the current warming at high elevations in the lower latitudes is unprecedented over the last two millennia, although at many sites the early Holocene was warmer/dryer than today. Similarities over the last 1000 years among records from high elevations in the Himalaya and the tropical Andes argue for large-scale ENSO teleconnections across the Pacific Ocean.

Observations of glacier shrinkage during the 20^th and 21^st centuries have been made in the Andes, the Third Pole (centered on the Tibetan Plateau), East Africa (Kilimanjaro) and near Puncak Jaya, Indonesia. Ice cores from these glaciers confirm their continuous existence ranging from hundreds to thousands of years, suggesting that current climate conditions are different from those under which they originated and have been sustained. Thus, the current warming is unusual when viewed from both the millennial-scale perspective provided by proxy records and the 160-year record of direct temperature measurements. The ongoing, widespread melting of non-polar mountain glaciers provides strong evidence that a large scale, pervasive and relatively rapid change in Earth’s climate system is underway. Glaciers serve both as recorders of past climate variations and early indicators of future climate changes, and their history and fate provide a global perspective for the current warming trend. The Third Pole contains one of the largest glacier stores (total area ~100,000 km²) of fresh water that feeds Asia’s largest rivers, while the Peruvian Andes contain over 70% of Earth’s tropical glaciers which are critical for municipal water supplies, hydroelectricity, mining, irrigation and recreation. Ice core analyses, as well as glacier area and volume measurements, provide critical perceptions of modern climate change and the potential economic and social impacts of dwindling water resources, as well as new geo-hazards, in glacier-dependent nations.