Even the highest glaciers in the world will not escape the effects of climate change, according to a study published today (27 May) in The Cryosphere, an open access journal of the European Geosciences Union (EGU). This study shows that the glaciers in the Everest region are very sensitive to warming, and will shrink massively by 2100. The precise amount of ice loss will depend on the levels of greenhouse gas emissions, but even if these emissions were greatly reduced, the volume of ice will be greatly reduced. The projected decrease by 2100 range from 70% to 99%–a loss of at least two-thirds.
Joseph Shea, the leader of the study, states “the signal of future glacier change in the region is clear: continued and possibly accelerated mass loss from glaciers is likely given the projected increase in temperatures.”
Shea, a glacier hydrologist at the International Centre for Integrated Mountain Development (ICIMOD), Kathmandu, Nepal, and his colleagues from Nepal, the Netherlands and France, conducted a study in which they developed and applied glacier models. The researchers follow the snow that falls in the region and track it as it converts to ice and moves downslope. They worked with a set of 8 different scenarios of temperature and precipitation changes to develop a full range of estimates of accumulation and melting of glacier ice.
Walter Immerzeel of Utrecht University, one of the study’s authors, described the combination of methods in the study to GlacierHub. He writes, “In these kind of environments such a smart combination of field observations, remote sensing and modelling is the way to go. There is a huge variability in meteorological conditions over short distances and it is impossible to measure this directly in the field. With remote sensing it is possible to get spatial information, but only at specific times when the satellite passes over and usually a lot of problems due to cloud cover during the monsoon. Forcing and calibrating a model with both types of observations largely overcomes these major limitations.”
These projected lossese of glaciers are a sobering message to the whole world, because Everest is an iconic peak. They also have a regional influence in the Himalayan region, which, along with neighboring mountain ranges such as the Hindu Kush and Karakoram, contain the largest volume of ice outside the Arctic and Antarctic. And on a smaller scale, the consequences are devastating. The Dudh Kosi basin in Nepal receives the meltwater from the glaciers on and around Everest.
“Glacier changes will affect river flows downstream,” says Shea. Agriculture in the region will be affected by the loss of irrigation water, especially in the critical dry months in springtime before the monsoon rains begin.
Hydropower facilities are likely to face multiple impacts: flows will be lower, they will be concentrated in the monsoon months rather than spread more widely, and they will vary more from year to year, because glacier meltwater will be less available as a supplement in dry years. The risk of glacier lake outburst floods will also increase as new glacier lakes form and expand.
These results, published in The Cryosphere, point to the need for future research, which can narrow the range of estimates of ice loss in Himalayan glaciers as climate change advances.
Patrick Wagnon, a visiting scientist at ICIMOD and glaciologist at the Institut de Recherche pour le Développement in Grenoble, France, says “Our estimates need to be taken very cautiously, as considerable uncertainties remain.” In particular, the researchers would like to be able to model more precisely the movement of snow in avalanches and the downward flow of ice across the rugged terrain of the region. They would also like to include more fully the effects of the dust and debris on the surfaces of the glaciers.
However, the major findings are dramatic, and unlikely to be revised. As the researchers state in the paper, “the signal of future glacier change in the region is clear and compelling.” They find that decreases in ice thickness and extent are expected for “even the most conservative climate change scenario.”