(ORDO NEWS) — Historical photographs helped to reconstruct the state of the Alpine glaciers in the first half of the 20th century. It turned out that by the beginning of the 2020s they had decreased by almost two-thirds.
The Earth’s glaciers are rapidly melting, and this is confirmed by accurate measurements that have been carried out in recent decades.
However, data on their state in the more distant past remain not always complete and accurate. A unique photo archive collected by Swiss topographers has allowed scientists to estimate the amount of ice on the Alpine peaks since the 1930s and track their changes since then.
Judging by the calculations, only until 2016, local glaciers were reduced by half, and since then they have been melting even faster.
One of the most commonly used topography methods is stereophotogrammetry . It allows you to estimate the positions, shapes and sizes of objects on the ground, reconstructing the volume from a pair of photographs taken from different angles.
Between 1916 and 1947 topographers from Switzerland were engaged in such work, surveying local mountain ranges.
During this period, almost 22 thousand photographs were taken, covering about 86 percent of all glaciers in the Swiss Alps.
Already in the 21st century, these plates were digitized and provided with detailed metadata, in accordance with field records.
This database was used by researchers from the ETH Zurich (ETH Zurich). Using photogrammetry, they estimated the volumes of glaciers at the average date of the archive – 1931 – and compared them with data obtained at the beginning of accurate measurements – 2016.
During this period, the amount of ice has decreased by 51.5 percent – more than half. This decline has not always progressed at the same pace: there were even periods of glacier growth in the 1920s and 1980s, but in general the trend is clear.
Moreover, over time, the process is only accelerating: in just six years, from 2016 to 2021, the ice has decreased by another 12 percent.
At the current rate of global warming, there are not so many left for them. The largest glaciers on the planet are melting at the same pace – in Antarctica and Greenland: according to climatologists, the process is developing according to the worst possible scenario.
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