SCOTS scientists have raised concerns that glaciers in the Himalayas are melting at an "exceptional" rate because of global warning - threatening the water supply of millions in Asia.

The study, partly authored by scientists at the University of Dundee revealed that Himalayan glaciers are shrinking far more rapidly than glaciers in other parts of the world.

Dr Simon Cook, an expert in glaciology with the University of Dundee's Geography and Environmental Science department, says that climate change is accelerating the melt of glaciers in circumstances he describes as “very concerning.”

He added that the rate of ice loss in recent decades was now ten times greater than the long-term average since the Little Ice Age, the last major period of glacier expansion that occurred 400-700 years ago.

The research, co-authored by Dr Cook and led by colleagues at the University of Leeds, published in Scientific Reports calculated that Himalayan glaciers have lost roughly 40% of their area in the past several hundred years. The glaciers are a critical source of water for about 250 million people in the mountains and an additional 1.65 billion who live in the river valleys below. These rivers include the Ganges, Indus and Brahmaputra.

The Himalayan mountain range is home to the world’s third-largest amount of glacier ice, after Antarctica and the Arctic. The region is often referred to as the world’s “Third Pole” for its huge store of ice, and it is home to Mount Everest, K2 and other iconic peaks.

Though the mountains are tens of millions of years old, their glaciers are extremely sensitive to the changing climate. Since the 1970s, when global warming first set in, these huge masses of ice have steadily thinned and retreated.

Man-made climate change is caused by the burning of fossil fuels such as gas, coal and oil, which release greenhouse gases such as carbon dioxide (CO2) and methane into the atmosphere. This extra CO2 causes temperatures of the atmosphere and oceans to rise to levels that scientists say can't be explained by natural causes.

Having mapped and reconstructed more than 14,000 glacier limits from the Little Ice Age period, the team calculated that the size of the glaciers had shrunk from a peak of 28,000 km² to around 19,600 km² today.

Furthermore, over the same period the team found that the glaciers have lost between 240 and 360 cubic miles of ice – the equivalent of all the ice contained today in the central European Alps, the Caucasus, and Scandinavia combined.

Dr Cook said “people in the region are already seeing changes that are beyond anything witnessed for centuries".

HeraldScotland:

Dr Simon Cook

He added:“Glacier melt is a normal process, and indeed desirable in terms of water supply.

“But what is alarming is the rate at which this melt is now happening and that the glaciers are losing more mass than they are gaining through snowfall."

The findings follow the recent COP26 climate summit in Glasgow, which emphasised the need for countries to unite in action to address our warming planet.

Dr Cook added: “While the outcomes of COP26 may ultimately be viewed as insufficient, we did see some positive moves and some important commitments were made by the international community. Glaciers are fragile and anything that we can do to slow down their recession should be welcomed, but there can be no doubt that we have long-term concerns about the future of these crucial water stores.

"This research is just the latest confirmation that those changes are accelerating and that they will have a significant impact on entire nations and regions."

The team used satellite images and digital elevation models to produce outlines of the glacier’s extent 400-700 years ago to ‘reconstruct’ the former ice surfaces.

The satellite images revealed sediment ridges called moraines that mark the former glacier boundaries and the researchers used the geometry of these moraine ridges to estimate the former glacier extent and ice surface elevation.

Comparing the glacier reconstruction to the glacier now, determined the volume and hence mass loss between the Little Ice Age and now.

"In the modern era, satellite imagery has allowed us to track glacier change over recent decades. However, we have looked back a lot further and this has allowed us to gauge how severely these glaciers have retreated," said Dr Cook “The acceleration in glacier loss that we have witnessed has likely been prompted by climate change, the effects of which are very concerning for millions of people who depend on these glaciers and the rivers they feed.”

Co-author Dr Jonathan Carrivick, deputy head of the University of Leeds School of Geography, said, “Our findings clearly show that ice is now being lost from Himalayan glaciers at a rate that is at least ten times higher than the average rate over past centuries. This acceleration in the rate of loss has only emerged within the last few decades and coincides with human-induced climate change.”