Standing in the Himalayan valley of Langtang, Rinjin Dorje Lama remembers where he used to play as a child in the 1960s.

"When I was a kid, it was a lot longer," said Lama, pointing at the Lirung glacier surrounded by snowy peaks on Nepal's northern border with Tibet.

"We used to play on the glacier, and it came right down to the monastery, but now it's about two kilometres (1.2 miles) further back."

Temperatures in the Himalayas are rising by around 0.06 degrees Celsius (0.108 Fahrenheit) annually, according to a long-term study by the Nepalese department of hydrology.

The rate is far above the global average given last year by the UN's senior scientists, who said surface temperatures have risen by a total of 0.74 degrees C over the past 100 years.

"I don't really understand why the glacier has gone so far back, but I am told it's due to global warming," said Lama, whose weather-beaten face makes him look older than his 57 years.

Lama has witnessed other changes in the roadless valley, 60 kilometres (40 miles) northwest of Kathmandu, where sure-footed ponies remain the quickest form of transport.

"I feel that the sun is getting stronger, and in the past there used to be a lot more snow in winter. We used to get up to two metres in the winter, and it would stay for weeks. Last winter we only had two centimetres."

On top of unpredictable weather, other dangers are increasing in Nepal's mountains because of climate change.

As the meltwater flows off the glacier, lakes begin to form and grow.

When the pressure becomes too great, the lake walls burst and release millions of cubic tonnes of water that can wash away people, villages and arable land.

Researchers at the Nepal-based International Centre for Integrated Mountain Development (ICIMOD) have said five major glacial lake floods have hit Nepal since 1970, as well as at least two in Tibet and one in Bhutan.

Ang Tsering Sherpa, who grew up in Nepal's Everest region, has observed the growth of one glacial lake with growing concern.

"A small pond first appeared close to the Imja glacier in about 1962," said Sherpa, who owns a trekking and expedition company in Kathmandu.

Last year, a research team from Japan measured the Imja lake as being 1.7 kilometres long, 900 metres wide and 92 metres deep.

"If that lake bursts, it will be like a tsunami," said Sherpa, who estimates that the Imja glacier has been retreating at a rate of 60 metres per year.

"Imagine the damage that will be caused by a lake emptying within minutes into a well-inhabited valley. The loss of life will be huge."

The World Wildlife Fund (WWF) calculates there are 2,000 glacial lakes forming in Nepal and around 20 are in danger of bursting.

Mountain dwellers are seeing at first hand the effects of global warming, but the changing climate will eventually have dire consequences for a much wider section of Asia's population.

Himalayan snow and ice is a massive freshwater reserve that feeds nine of Asia's major waterways, including the Indus, Ganges and Yellow rivers.

"In the long term, water scarcity will become a big problem," said Sandeep Chamling Rai, WWF climate change officer.

"There will eventually be a tipping point where the amount of water from the glaciers is hugely reduced, which will result in loss of water resources for people downstream who rely on these Himalayan-fed rivers."

The ICIMOD said in August that climate change posed a serious threat to essential water resources in the Himalayans, putting the livelihoods of 1.3 billion people at risk.

Studies say much of the blame is due to the "Asia brown cloud" spewed from tailpipes, factory chimneys and power plants -- as well as forests and fields that are burned for agriculture, and wood and dung burned for fuel.

Back in the Langtang Valley, where around 700 people and 4,000 yaks live, Lama can only watch as the ice and snow retreat from around his home.

"I am very worried, but what can we do. We are not contributing to global warming but we feel its effects. I am scared there will be no snow and ice in these mountains within the next 15 years."