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In common with all alpine glaciers, the Oberer Grindelwaldgletscher is shrinking fast

As this book goes to print the Swiss Alps are changing shape, and it is inevitable that some of the descriptions – not only of peaks, glaciers and snowfields, but routes to their summits – will have become outdated; such is the speed of change.

Climate change and global warming may be 21st-century buzzwords, but from about one million years ago the Alps have experienced a cycle of extended cold periods (ice ages), rapidly followed by climatically warmer intervals; each cycle lasting about 2000 years. Until these ice ages began, it is thought that the mountains consisted of bare rock peaks divided by narrow V-shaped river valleys, but then came the glaciers which covered all but the highest summits and ridges of the Central Alps, filling the valleys and stretching out into the lowlands. Reaching its peak about 25,000 years ago, the last great ice age smothered much of modern Switzerland, widening and deepening the alpine valleys, chiselling and sharpening peaks and smoothing rock walls. It was then that the Rhône glacier stretched 150km from its source near the Furkapass to the Lake of Geneva.