The vicinity of Mount Everest and the Himalayan region as a whole is sometimes called the "third pole" of the Earth due to the fact that 600 billion tons of ice are concentrated there. There are almost 650 glaciers in China, Bhutan, Nepal and India, whose behavior in the light of global warming is of great interest to scientists. Recently, researchers from Columbia University obtained access to declassified images of the area from spy satellites.
Until the 80s. virtually no one flew over the Himalayas for research purposes, and therefore there was nowhere to get data on the state of the glaciers. The Pentagon helped by sharing archival images from spy satellites. Scientists have developed a model of the three-dimensional structure of the glaciers, overlapping adjacent images, and obtained rough data on their size. They were also able to assess the change in ice thickness and compared this data with information from modern satellites, which are already able to automatically measure elevation differences.
It turned out that the rate of melting of glaciers in the Himalayas from the 1970s to 2000, on average, did not exceed 25 cm per year. But in the new century, it jumped sharply to 50 cm per year, and in some places even reached 5 m per year! One of the key reasons for this development of events, in addition to the increase in air temperature on the planet, is the industrial boom in neighboring countries. A large amount of fuel burned in the factories gave rise to mountains of soot, some of which settled on the snows of the Himalayas and began to absorb the sun's rays.