Thousands of years ago, almost the whole of Switzerland lay under a thick ice sheet that was up to three kilometers thick in places. Towards the Alps, isolated rocky islands protruded from the sea of ice. In the small ice-free areas on the Central Plateau, there was sparse tundra vegetation where reindeer and mammoths foraged for food. It was the ice age!

The glaciers reached their greatest extent during the last ice age around 24,000 years ago. The Rhine, Linth, Reuss, Aare and Rhone glaciers advanced from the Alps with their enormous tongues far into the Central Plateau. The valley of Lake Zurich lay under the thick arm of the Linth Glacier. The western midlands from the Solothurn region to far beyond Lake Geneva were buried under the mighty ice mass of the Rhone Glacier. Overall, only a few areas of Switzerland remained ice-free.

A global rise in temperature caused the glacial streams to gradually recede into the Alps. Witnesses of the great glaciation and the legacy of the ice ages are omnipresent: moraines, erratic blocks, drumlins and the alpine lakes of the Central Plateau. Today's landscape, as seen from the Felsenegg and the Weissenstein, owes its diversity to the Ice Age. As it became warmer, today's vegetation developed slowly but steadily. People settled and influenced their environment through their way of life.

The last million years were characterized by a succession of cold periods lasting 40,000 - 100,000 years, interrupted by warmer but shorter intermediate phases, so-called warm periods. This sequence of climate fluctuations is called an ice age cycle. Although it may seem paradoxical, we are now living in the ice age - albeit in an intermediate phase, i.e. a warm period.

The ice age cycles are a result of slight periodic changes in the way the Earth orbits the sun. Among other things, the Earth's orbit is sometimes more elliptical and the inclination of the Earth's axis in relation to the orbital plane fluctuates (Milanković cycles). These small changes cause large differences in terms of solar radiation on the Earth's surface. This causes strong fluctuations in the global average temperature and thus leads to the cold-warm cycles. Extensive glaciation and deglaciation therefore occur at regular intervals around the world, leading to changes in sea level.

Analyses of ice cores from the Antarctic show that the global temperature and the CO₂ concentration in the atmosphere are closely linked. Climate, atmosphere, oceans and global glaciation influence each other. If it gets colder, the oceans absorb more CO₂ from the atmosphere, which makes it even colder - excellent conditions for an ice age. Conversely, as temperatures rise, the oceans release CO₂, which heats up the climate and causes the glaciers to melt. The measurements from the ice cores also show that the CO₂ concentration never exceeded 300 ppm during the ice age cycles of the last 800,000 years. The burning of fossil fuels by humans has increased the CO₂ concentration extremely sharply to over 420 ppm and will continue to rise steeply. How far depends on what we, the global community and politicians do together for the climate.

Science has outlined three scenarios up to 2100, covering socio-economic, demographic, technological, political, institutional and lifestyle trends

Numerical models are able to simulate the interaction between climate and environmental processes. Such models are valuable tools to deepen the understanding of ice age cycles, of which there is only sparse geological evidence, and to calculate the future evolution of glaciers. State-of-the-art climate and glacier models have made it possible to reconstruct the temporal evolution of glacier extent during the last glacial cycle (120,000 years) in the European Alps. New visualization techniques based on artificial intelligence make it possible to display the Alpine arc over the period of the ice age cycles as if the images were taken by a satellite.