The Andean Glacier and Water Atlas

Key messages

Temperatures have been rising across the Andes. There is evidence of altitude amplification, with temperatures rising faster at higher altitudes. The annual mean temperature in most countries of the Tropical Andes (Venezuela, Colombia, Ecuador, and Peru) increased by approximately 0.8°C during the 20th century. The altitude of the freezing level height has also risen by an approximate average of 45 m across the region. In the Andean mountains of Chile and Argentina, temperatures have risen between 0.2 and 0.3 per decade since the mid-1970s. Temperatures could increase further in the Tropical Andes by between 2°C and 5°C by the end of the 21st century, according to certain projections. In the Southern Andes temperatures could increase by between 1°C and 7°C. The degree of warming is also likely to be greater at higher elevations. Much larger inter-annual temperature variability and a higher likelihood of extremely hot years can also be expected. Even the coldest years could become much warmer than the warmest years observed today. Past precipitation trends are less clear, but there are indications snow cover has been decreasing over the past few decades. Precipitation trends are difficult to identify in the Andes due to the lack of reliable long-term observational records. Annual precipitation is already highly variable because it depends on location and is influenced by El Niño events. However, snow cover has seen an overall decreasing trend in the past two decades, in line with rising temperatures. This has been especially significant in the Central Andes and on the eastern flanks. In the Southern Andes, the snow line is also moving upwards which is increasing the risk of flash floods downstream.

Future precipitation trends are difficult to estimate, with projections revealing a mixed picture across the Andes region.

Most models predict an increase in precipitation during the wet season and a decrease during the dry season in the tropical Andes, as well as over the Altiplano region. Under the IPCC high emission scenario, by 2100, precipitation is projected to increase along the coastal regions of Colombia and Ecuador and in some places along the eastern Andes, and south of the equator. However, by 2100, precipitation is projected to decrease in the southern (tropical) Andes, including the Altiplano regions; which would lead to increased drought. Important reductions in precipitation of more than 30 per cent are expected in the southern Andes, particularly in Chile and Argentina. Most glaciers have been retreating around the world since the beginning of the 18th century. This retreat is linked to anthropogenic climate change. The pace of retreat and loss of certain glaciers is most rapid within the Tropical Andes. In Venezuela, just one glacier remains, and it is predicted to disappear by 2021. In Colombia, rapid retreat has occurred and has accelerated over the past few decades. By the middle of this century it is likely that only the largest glaciers on the highest peaks will remain. Ecuador’s glaciers are restricted to the country’s highest peaks and within two mountain ranges, but its glacial loss has been dramatic over the past 50 to 60 years. Peru hosts the largest number of tropical glaciers on the continent. Of two major glacial systems in the country, the Cordillera Blanca glaciers have been retreating rapidly over the past few decades, although there have been some brief periods of advancement. Rapid glacial retreat has also been observed on Bolivia’s glaciers since the 1980s, with some glaciers having lost two-thirds or more of their mass. Many of the glaciers, with an area of less than 0.5 km 2 , are so small that they are even more vulnerable to glacial retreat. In Chile and Argentina, most glaciers are retreating, and the rate has increased over the last decades. Large, low-lying, tidewater and freshwater glaciers in Patagonia and Tierra del Fuego have experienced rapid retreat. Although less rapid, retreat is also occurring in glaciers at higher altitudes. A few glaciers are still advancing due to local ice dynamics. Glaciers are retreating in every Andean country. The most rapid retreat is in the Tropical Andes, in lower-altitude glaciers.

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