The uncertain future of the Himalaya

Dr Shaktiman Singh, Lecturer, School of Geosciences, University of Aberdeen

Meteorological observations from mountainous regions form the basis to develop an understanding about glaciohydrological processes and the associated implications due to our changing climate. The Himalaya is the world’s highest mountain range, with enormous freshwater storage in the cryosphere, wetlands, and groundwater. Glacier and seasonal snow derived meltwater provide significant inputs to the major rivers in the region, especially during the drier season. This supply of water supports a growing population of around 1.3 billion. The fate of these water resources in the Himalaya depends on the changing climate. We can assess how this water source is changing by long-term observation of local meteorological variables that drive the exchange of energy and mass at the snow and glacier surface. The climate varies largely in different parts of the Himalaya, with the eastern side dominated by precipitation from south-east summer monsoon and the Westerlies (originating in the Mediterranean) on the western side. Because of this regional variability it is difficult to discern any general patterns for the Himalaya and therefore predict, with any degree of confidence, the impact of climate on this valuable water source.

The glaciers and seasonal snow cover are responding rapidly to ongoing climate warming, which is driving high snow ablation rates and accumulation processes, due to an increase in the proportion of liquid vs solid precipitation. Himalayan glaciers have lost mass at an accelerating rate in recent decades, resulting in a projected increase in annual and dry-season river streamflow until the 2050s (peak runoff), followed by an abrupt decrease as glaciers continue to shrink and disappear. The increasing contribution from cryosphere-derived runoff, coupled with more extreme precipitation events, is driving a rise in the magnitude and frequency of peak discharge events and natural hazards such as avalanches (snow-ice-rock mixtures), flash floods, landslides, and glacial lake outburst floods. However, due to a lack of continuous meteorological observations leading to ambiguities related to future climate projections and the need for improved understanding of the glacio-hydrological response to climate change, the uncertainties associated with existing hazard prediction and projections have realworld implications. Although in-situ observations are crucial for reducing the level of uncertainty, recent developments in availability of freely available remotely sensed data and the reanalysis of meteorological data provide an opportunity to develop a more nuanced understanding of the changing climate.

The hostile nature of the Himalaya compounds the collection of data. The inaccessibility, terrain and extreme environmental conditions are the primary hindrance behind installation and efficient maintenance of meteorological stations, limiting data to only sporadic observations. Even with the records that are available, topography makes it difficult to extrapolate data across a wider area to interpret or predict long-term climate signals. The quality of the available data is an additional major concern due to the non-uniformity of the sensors and methods used. Another problem is data sharing, including for public consumption, by the government and non-government agencies, hindered by a contentious geopolitical situation in the region. It has restricted collaborations with international research groups, and hampered attempts to develop regionally acceptable policies and to resolve the lack of certainty in current projections of future water sources and supplies.

The Himalaya is particularly vulnerable to a changing climate because of the demands placed on it by the resident population, and its dependence on the ecosystem services, in a region that has sensitive physiographic features, important biodiversity and high endemism. The problems associated with meteorological observations make it difficult to develop a resilience framework and strategy for climate change adaptation. There is an urgent need to initiate a systematic approach to create long-term meteorological data across the Himalaya, with the involvement of local and national governments and non-government organisations like International Centre for Integrated Mountain Development (ICIMOD) indigenous marginalised communities. Some nationallevel initiatives are already being developed, for example the National Mission for Sustaining the Himalayan Ecosystem (NMSHE) of the Government of India, which facilitates networking of knowledge institutions and capacity building for young researchers. There is also an international commitment from countries outside the Himalayan region; for example, during COP26 in Glasgow, the UK announced a new support of £274 million to Climate Action for a Resilient Asia (CARA), a seven-year programme to strengthen climate change resilience in Asia. All these commitments and initiatives require a cross-boundary coordination and appropriate and strategic scientific research on the ground in Himalaya.