A multi-perspective approach for selecting CMIP6 scenarios to project climate change impacts on glacio-hydrology with a case study in Upper Indus river basin

Abstract

Abstract The selection of future climate change scenarios may have issues in representing the full spectrum of climate projections in glacierized mountain regions, where glaciers play an important role in hydrology. Thus, the effect of glacier storage change must be considered in the selection approaches. Here, a multi-perspective approach was proposed to select climate models from CMIP6 database, considering the full spectrum of future climate change and effects of glaciers on hydrology. This approach combines the envelope-based approach (EA), past performance approach (PPA), and additional criteria to incorporate water-energy balance and glacier storage change based on the Turc-Budyko theory. The approach physically diagnoses GCMs by investigating their effects on glacier storage change compared to reference climate and observed mass balance data. A step-wise shortlisting and selection of appropriate climate models for the Upper Indus Basin (UIB) was made under three Shared Socioeconomic Pathways (SSPs): SSP126, SSP245, and SSP585, based on (a) range of projected changes in mean values for four extreme future projections (cold-dry, cold-wet, warm-dry, and warm-wet), (b) range of projected changes in climatic extremes, (c) representation of water-energy balance and storage change, and (d) skill in representing historical climate. The future projections indicate temperature and precipitation increase by 1.7\xa0±\xa00.6\xa0°C and 7\xa0±\xa05%, 3.3\xa0±\xa01.3\xa0°C and 10\xa0±\xa06%, and 6.3\xa0±\xa02.6\xa0°C and 22\xa0±\xa013% under SSP126, SSP245, and SSP585 in 2071–2100 compared to 1985–2014, respectively. The glacier area, volume, and length are projected to decrease by 22–33%, 51–63%, and 13–22% under ensembled scenarios of full spectrum at selected glaciers. The proposed multi-perspective approach is advantageous in shortlisting a limited number of climate models, representing the full range of possible future climatic conditions, to assess the full range of expected impacts of climate changes on indigenous glacio-hydrology. Such selection eventually reduces the glacio-hydrological simulation task.