[The] report, published in the journal Nature Geoscience, found the key factor affecting their advance or retreat is the amount of debris – rocks and mud – strewn on their surface, not the general nature of climate change.
Glaciers surrounded by high mountains and covered with more than two centimetres of debris are protected from melting.
Debris-covered glaciers are common in the rugged central Himalaya, but they are almost absent in subdued landscapes on the Tibetan Plateau, where retreat rates are higher.
In contrast, more than 50 per cent of observed glaciers in the Karakoram region in the northwestern Himalaya are advancing or stable.
The last glacier to be started, we were told, had been made 35 years earlier by the grandfather of the present rajah. It had been built to an ancient formula, with ice blocks coming from male and female glaciers (their difference was not made clear). These blocks were deposited in a high valley and covered with charcoal and thorn bushes, on top of which 50 goatskins of water were placed. The water was to help keep the ice cool and to augment the ice supply when the water froze in winter. After 20 years of gradually adding ice and snow, the glacier became strong enough to support itself and send a constant supply of water in the nonwinter months to the dry fields below.