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Tilicho lake with snow-capped mountains in Nepal
Photo: Frank Bienewald / imagebroker / imago images
The Himalayas have a unique flora and fauna and because of its impressive peaks it is also called "the roof of the world".
Climate researchers have given the region another nickname.
They call it "the third pole" because this is where the largest reserves of glacier snow and ice are located outside of the North and South Poles.
But as in many other cold regions of the world, climate change is also gnawing at the ice masses of the mountains there.
The ice has receded for the past three decades.
Most recently, an average of eight billion tons melted each year.
This was shown by a study from last year.
In addition to global warming, another factor also contributes significantly to ice melting: dust and soot.
It is blown in the atmosphere over long distances in spring and summer and lies on snow and ice.
This makes the snow darker and absorbs sunlight instead of reflecting it back into space.
As a result, the ice warms up faster and melts more quickly.
What influence does the dust have?
Researchers speak of so-called albedo values.
They vary in many areas of the earth's surface, wherever there are lighter and darker areas.
A fresh snow surface has a high albedo of up to 0.95, whereas a dark coniferous forest only has one of 0.05 to 0.12.
Researchers led by Yun Qian from the Pacific Northwest National Laboratory and colleagues have now investigated the effect by means of remote sensing observations for the Himalayas, the Hindu Kush and Karakoram mountains and created computer simulations.
She was particularly interested in the influence of the dust and which the soot.
The latter particles have a higher darkening effect and thus contribute more to the melt, suggested earlier studies.
According to the current results, which were published in the journal "Nature Climate Change", this is not the case at the high altitudes of the region.
Here dust seems to have a bigger impact than carbonaceous aerosols - although these are darker.
Overall, there is an inconsistent distribution.
Most of the ice and snow melts at altitudes around 4,500 meters.
Here the annual decrease is five millimeters per year.
At 6,000 meters, the mean annual shrinkage is only around three millimeters.
Further down in the valley, at a height of a thousand meters, only about a millimeter disappears.
The heterogeneous distribution seems to be due to the fact that the influence of dust on snow darkening is greater than that of soot at altitudes of over 4000 meters.
Much more dust may be deposited.
The scientists themselves were surprised by their results.
They suspect that the dust-induced melt could also play an important role in other mountains.
Soot particles arise from human activities.
They are blown into the atmosphere by car traffic, slash and burn or coal and wood heating.
The entry of dust, on the other hand, has natural causes.
It is native to Africa and the Middle East.
But in the end, humans are also partly to blame for the dust development.
As a result of changes in land use, green spaces are disappearing and soil erosion increases.
Therefore, the trend in the Himalayas is likely to intensify rather than reverse.
Melting effects from dust and soot have also been measured in other areas of the world, for example in Greenland, where the mighty ice sheet has darkened.
Similar effects have also been measured on glaciers in the Alps.
In order to curb the melting, researchers resort to a trick and cover the ice masses with light-colored foils.
This happened, for example, on the Presena Glacier in northern Italy.
In the lonely high altitude of the Himalayas, however, that should be difficult.
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