New Delhi, May 27: Glaciers girdling Mount Everest could lose nearly all their ice below altitudes of about 6,500 metres by the end of the century under an average temperature rise of about 3.1°C, a new study has suggested.

The study by scientists at the International Centre for Integrated Mountain Development in Kathmandu has indicated that even under a lower temperature rise of about 2.6°C, glacial loss below 6,000 metres would range between 40 and 70 per cent.

The scientists say glacial loss there could impact water flow in glacier-fed rivers although downstream impacts on the Kosi that flows through Nepal and Bihar are expected to be small. Their study findings were published today in the journal, Cryosphere.

"We find that the glaciers in the Everest region could be highly sensitive to temperature changes," Joseph Shea, a Canadian glacier hydrologist working at the Kathmandu centre, told The Telegraph. "Future studies will aim at understanding how they influence streamflow downstream."

While many earlier studies have established the threat global warming poses to the world's glaciers, including those in the Himalaya, some glaciologists in India have in the past said observations of glacial loss elsewhere in the world cannot be extrapolated to the Himalaya.

They have pointed out that multiple factors influence melting - rainfall, the orientation of the glacial valleys and rock and debris cover over the ice.

In the new study, Shea and his colleagues applied anticipated temperature, rainfall and snowfall changes under various global warming scenarios to examine the sensitivity of the Everest region to future climate change.

The scientists say the retreat of glaciers could lead to the formation of pro-glacial lakes, which could pose a risk to downstream communities.

They point out that the failure of natural moraine dams in the Kosi river basin has led to 15 glacier lake outburst floods since 1965.

Their analysis suggests that under a conservative temperature rise of about 1.3°C by 2050, glaciers above 6,000 metres will remain unchanged. But below that altitude, the glacial loss could range from 40 to 70 per cent.

Under a different scenario where the world is much hotter and drier with an average temperature rise of 3.1°C and a 2.8 per cent reduction in rain or snow, glaciers below 6,500 metres could be nearly eliminated by 2100.

"This is an excellent study," said Jayaraman Srinivasan, professor at the Centre for Atmospheric and Oceanic Sciences at the Indian Institute of Science, Bangalore, who was not associated with the research.

"Among its important results is the impact of the debris cover on glaciers - debris covered glaciers melt less rapidly than those without debris. Since debris-covered glaciers occur at low altitudes, they will be separated from high altitude glaciers," Srinivasan told this newspaper.

"So glaciers are likely to get fragmented, another important result is that temperature increase is more important than change in snowfall."