A historical perspective on glacial retreat

Fieschergletscher through the ages Researchers at ETH Zurich and WSL have for the first time reconstructed the extent of Switzerland's glacier ice loss in the 20th century. For this purpose, the researchers used historical imagery and conclude that the country's glaciers lost half their volume between 1931 and 2016. Glaciers are melting rapidly - and since the 2000s, scientists have been recording and researching changes in their volume more and more precisely. In contrast, hardly anything is known about how glaciers changed during the 20th century. Although there are a handful of studies that reconstruct the surface topography of individual glaciers in the late 19th and early 20th centuries, these partially show large discrepancies with existing models when it comes to estimating the corresponding glacier volume. Old data - new insights. For their reconstruction, the glaciologists turned to what is known as stereophotogrammetry, a technique that can be used to determine the nature, shape and position of any object on the basis of image pairs.