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Glaciers of the Karakoram Himalaya
Hewitt, K. 2011. Glacier change, concentration, and elevation effects in the Karakoram Himalaya, upper Indus Basin. Mountain Research and Development 31: 188-200.

The author writes that "in recent decades the consequences of climate change for Himalayan glaciers has become of great concern," noting that it has been "widely reported that the Indus basin is threatened with severe losses," although he says that "emerging evidence suggests that such reports are, at best, exaggerated," citing Raina (2009) and Armstrong (2010).

What was done
In a review of the pertinent scientific literature, Hewitt "seeks to explain evidence of distinctive late- and post-Little Ice Age glacier change in the Karakoram Himalaya and a recent, seemingly anomalous, expansion," with attention directed to "processes that support and concentrate glacier mass, including an all-year accumulation regime, avalanche nourishment, and effects related to elevation."

What was learned
The Canadian researcher reports, first of all, that Karakoram glaciers have only declined by 5% or so since the early 20th century, "mainly between the 1920s and 1960s." Thereafter, he notes that "losses slowed in the 1970s (Mayewski and Jensche, 1979), and some glaciers underwent modest advances, as elsewhere in the region (Kotlyakov, 1997)." Retreat then prevailed from the mid-1980s through the 1990s, "but without dramatic losses." And he says that "since the late 1990s we have reports of glaciers stabilizing and, in the high Karakoram, advancing (Hewitt, 2005; Immerzeel et al., 2009)," while "total snow cover has [also] been increasing in the high Karakoram (Naz et al., 2009)."

Hewitt additionally writes that the "sheer extent and sustained high elevations" of the main Karakoram, together with the "all-year accumulation regime," both "help to buffer glaciers against 'warming'." And he says that "with high-altitude precipitation occurring as snowfall in summer and winter, they may benefit from increased moisture transport from warmer oceans." In addition, he notes that "various investigations report cooler summers recently and greater summer cloudiness and snow covers (Fowler and Archer, 2006; Naz et al., 2009; Scherler et al., 2011)," stating that these phenomena "can also reduce average ablation rates or numbers of 'ablation days'."

What it means
Considering all of these things together, and compared with "past predictions for the upper Indus," Hewitt concludes that "these observations seem good news," as indeed they are.

Armstrong, R.L. 2010. The Glaciers of the Himalayan-Hindu-Kush Region. Technical Paper of The International Centre for Integrated Mountain Development, Kathmandu, Nepal.

Fowler, H.J. and Archer, D.R. 2006. Conflicting signals of climatic change in the Upper Indus Basin. Journal of Climate 19: 4276-4293.

Hewitt, K. 2005. The Karakoram anomaly? Glacier expansion and the 'elevation effect,' Karakoram Himalaya. Mountain Research and Development 25: 332-340.

Immerzeel, W.W., Droogers, P., de Jong, S.M. and Bierkens, M.F.P. 2009. Large-scale monitoring of snow cover and runoff simulation in Himalayan river basins using remote sensing. Remote Sensing of Environment 113: 40-49.

Kotlyakov, V.M. (Ed.). 1997. World Atlas of Snow and Ice Resources. Institute of Geography, Academy of Sciences, Moscow, Russia.

Mayewski, P.A. and Jeschke, P.A. 1979. Himalayan and trans-Himalayan glacier fluctuations since AD 1812. Arctic and Alpine Research 11: 267-287.

Naz, B.S., Bowling, L.C., Diffenbaugh, N.S., Owens, P., Ashfaq, M. and Shafiqur-Rehman, S. 2009. Hydrological Sensitivity of the Upper Indus River to Glacier Changes in the Karakoram Himalaya Region. Poster no. C31C-0455 presented at the November 2009 Meeting of the American Geophysical Union, San Francisco, California, USA.

Raina, V.K. 2009. Himalayan Glaciers: A State-of-Art Review of Glacial Studies, Glacial Retreat and Climate Change. Ministry of Environment and Forests, New Delhi, India.

Scherler, D., Brookhagen, B. and Strecker, M.R. 2011. Spatially variable response of Himalayan glaciers to climate change affected by debris cover. Nature Geoscience 4: 156-159.

Reviewed 28 December 2011