There has been concern in the scientific community surrounding the claim that Himalayan glaciers are shrinking at an alarming rate as a result of climate change, leading to significant impacts on the water resources of populations in the downstream basins. Despite much research, there remains no clear understanding of how glacier shrinkage varies across the region, or how it might impact downstream stakeholders. Clearly this hinders well-informed, evidence-based decision and policy making. A rigorous systematic review, to discern what is the evidence about glacier shrinkage across the Himalayas, is a major step to support policy-making in the region.
This systematic review assesses the primary evidence regarding physical changes in glaciers in order to ascertain what evidence is available, whether glaciers are shrinking in mass, reducing future melt-water availability, and whether the rate of shrinkage is changing. Four main measurement types have been employed to assess such changes: terminus position, area, volume, and mass balance. Some measurements are more appropriate and indicative than others in assessing changes in glacier mass. As well as assessing the available evidence, the review provides an appraisal of current understanding and corresponding knowledge.
Application of the selected criteria identified 52 studies for review. The majority of these studies focused on Himalayan glaciers feeding the Ganges and Indus basins.
Results from the review indicate a general trend of glacial shrinkage across the Himalayan region. However, there is a lack of data from which to assess regional variation and rates of change, or provide quantitative assessments of relative changes in glacier mass. Further research should focus upon mass balance and area measurements from glaciers that have already been studied and in data sparse regions (Karakoram and Hindu-Kush), also where the threat to downstream fresh-water availability is greatest (Indus basin). Greater use of remote-sensing observations is recommended as they allow cross-border assessments and reduce the costs/difficulties in accessing such terrain. Systematic research on benchmark glaciers and standardised reporting will enable more robust analysis and provide better information for users, especially when trying to predict future impacts of climate change within the region on water resources.
There is a protocol for this systematic review
Miller, J.; Rees, G.; Warnaars, T.; Young, G.; Collins, D.; Shrestha, A. What is the evidence for glacial shrinkage across the Himalayas? Collaboration for Environmental Evidence, UK (2013) 97 pp. [CEE review 10-008]