A unique photographic archive collected by Swiss topographers has made it possible to estimate the amount of ice on top of the mountains since the 1930s. Paintings of that time were compared with modern ones.

what is known

• It uses a popular method called topography. stereophotogrammetry.
• It lets you estimate the position, shape, and size of an object using just two photos taken from different viewpoints.
• In Switzerland, this approach was widely used between 1916 and 1947 when shooting local mountain ranges.
• During this time More than 22,000 photos were taken.Covering about 86 percent of all the glaciers of the Swiss Alps.
• In the 21st century, these plates have been digitized and detailed metadata is provided based on field records.
• It was this database that was used by researchers from the Technical University of Zurich.

The researchers averaged the date the photo archive was created, choosing 1931 as the starting point. Then the materials were compared with the data obtained at the beginning of accurate measurements – in 2016.

Judging by the calculations, for this period amount of ice decreased by 51.5 percent – more than half. This decline did not always develop at the same pace: the 1920s and 1980s saw periods of glacier growth, but overall this trend continued.

Since then, the process has only accelerated: in just six years, From 2016 to 2021, ice shrank 12 percent. At the current pace of global warming, they don’t have much left.