Retreat of the glaciers

Earth's glaciers are melting - and not just since the hundred-year summer in 2003. Since the end of the 19th century, in fact, the entire glacial surface of the Alps has shrunk by about 30 to 40%, and worldwide by a staggering 50%.

Often referred to as the earth's "thermometer", these ice colossuses have thus reacted to the 0.7°C rise in the global mean temperature over the same period. Although large parts of the Alps have been ice-free several times since the end of the last cold period some 10,000 years ago - most recently during Roman times - the latter-day glacier retreat is having a considerably greater impact on humans, because the Alps are much more densely populated nowadays. And the foothills, too, are now increasingly dependent on hydrological processes in the highlands.

Water balance

Glaciers have an important compensatory effect on the water balance in the mountains and their foothills: in high precipitation years, more water is retained, since the snow cover accumulating on glaciers protects the ice from melting. In warmer and drier years, glaciers offset the lower precipitation amounts with a higher meltwater input.

If the glaciers disappear, this compensatory effect will be lost as well; the seasonal fluctuations in run-off will no longer be balanced out in the lowlands. In the summer of 2004, 90% of the water at the mouth of the Rhine on the North Sea had already been in the river at Basle, and 50% of that was meltwater from ice and snow.

Low water levels not only impede shipping but also increase pollutant concentrations in rivers. Factories are forced to cut production in order to adhere to pollution thresholds. Hydropower stations generate less electricity, while nuclear power plants are unable to withdraw sufficient cooling water from rivers. Last but not least the water table is falls, which may have far-reaching effects not only on the flora but also on the production and replenishment of drinking water.

The situation is even more dramatic in the earth's arid zones: 70% of the water in the Ganges, for example, stems from Nepalese rivers which are mostly fed by meltwater. Nearly all of the water in Lake Aral comes from the glaciers of the Tien Shan and Pamir mountains.

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Global implications

At global level, melting glaciers have an impact on the sea level that is not to be neglected. In the last 100 to 150 years, the sea level has risen by approximately 10-25 cm, one fifth of this increase being due to the meltwater input from mainland glaciers, the remainder to the temperature-related expansion of the water.

Scientific forecasts assume a further rise of 50-95 cm by the year 2100. Special importance attaches here to the inland ice in the Arctic, Antarctic, and Alaska. If all of the earth's mainland ice masses were to melt, the sea level would rise by as much as 80 m. Also, the fresh water that meltwater brings with it alters the salinity of oceans and thus has an influence on global oceanic currents and the climate system.

Insurance relevance

For the insurance sector, the immediate threat emanating from the retreat of the world's glaciers is still of subordinate significance. Most of the scenarios described here involve sparsely populated regions where both the concentration of values and the insurance penetration are low.

In the Alps, glacier retreat will have a much stronger impact on humans and infrastructures, since this region is the most densely populated mountain area on earth. This being so, Switzerland has set up a monitoring programme to investigate the risk potential of glaciers.

The information compiled for this article shows that, of the 84 Swiss glaciers examined, 53 may trigger loss events in the next 10 to 20 years - mainly from glacial lake outbursts and ice avalanches.

Even today, tourism in particular is having to prepare for higher costs and falling revenue. An increase in mean temperatures and glacier retreat will jeopardise the future of numerous summer skiing areas; thawing permafrost will have an impact on the stability of lift facilities and mountain huts.

The impact of glacier retreat on the lowlands will tend to be perceptible more in the medium to long term when hydrological changes in high mountain regions begin to have an effect on areas with a greater concentration of values and lead to shortages of drinking water, loss of earnings for shipping operators, power plants, or other industrial facilities.

Munich Re therefore has a strong interest in investigating the future development of glaciers and its impact on society. In the recent past, it has given its support for several research projects mounted in collaboration with the Commission for Glaciology of the Bavarian Academy of Sciences.

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