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Non-polar glacial ice holds a wealth of information about past changes in climate, the environment and, especially, atmospheric composition, such as variations in temperature, atmospheric concentrations of greenhouse gases and emissions of natural aerosols or man-made pollutants. This ice constitutes the ONLY natural record of changes in the past composition of the atmosphere. It has also offered an unmatched insight into the rise in atmospheric pollution over the past century by highlighting regional disparities, as well as by characterising the origin of that pollution.

The increase in frequency of certain positive temperature periods or events at high altitude (e.g. summer heatwaves in the Alps and strong El Niño events in the Andes) will lead in the next few years to systematic percolation of meltwater through the upper layers of snow on the glacier surface. This phenomenon will irreversibly alter the chemical composition of the snow strata, thus destroying the potential of these records forever, along with all hope of reconstructing the history of geochemical signals associated with climate, human activity and the biological evolution of our environment (e.g. mutation of the viruses or bacteria found in snowfall).

The Alps

The glaciers in the Alps are unique observation points in our region. Offering us all the advantages of a high-altitude laboratory, alpine glaciers have long been the subject of studies. The recent acceleration in their retreat is related to global warming. At the heart of an industrialised Europe, the ice of Mont Blanc has preserved traces of natural climate changes over the past millennium, as well as changes in human-induced pollution over the past century (such as sulphur and nitrogen oxides, heavy metals, organic pollutants and radioactivity).

While the temperature has increased by 1°C in France over the past century (compared to 0.6°C worldwide), it has risen between 1°C and 3°C at 1,800 m (5,900 ft) in the Alps in the winter. Similarly, on-site measurements taken from a drill hole on the Col du Dôme at 4,300 m (14,100 ft) in the French Alps indicate an increase in the temperature on the glacier surface of almost 1.5°C between 1994 and 2005. We know the temperature of the ice on the Col du Dôme is closely linked to that of the air, and future warming will accelerate this glacial warming.

The Andes

The Andean barrier, which stretches from the Equator to 50°S, is geographically unique and helps us establish a link between the tropical region – a climate driver – and high-latitude regions where there are already ice core records covering longer periods (800,000 years in Antarctica).

The rise in temperature related to global warming will be sharper in the tropical regions at an altitude of around 6,000 m (19,680 ft), potentially reaching +5.5°C by the year 2100 according to certain scenarios. Studies of Andean glaciers show substantial retreat and even disappearance in tropical regions since the late 20th century. This is particularly true in the Andes, where the sharp retreat of glaciers since 1960 has led to the disappearance of many of them, such as the Chacaltaya glacier in Bolivia. This glacial retreat is extremely worrying in terms of water resources for the local populations. For example, in Bolivia’s capital, La Paz, glacial meltwater represents almost 30% of the city’s water supply during the dry season. The rise in temperatures at high altitude in the Andes is much greater than at sea level, thus accentuating the local impacts of climate change on the glaciers.