Spatial and temporal variability of climate change in high-altitude regions of NW Himalaya

Abstract

The high mountain areas such as the Alps, the Rockies, the Himalaya, etc. are considered as the “hotspots” over the surface of the earth where impacts of climate change are likely to be felt significantly. With regard to the Himalaya, their vulnerable ecosystem appears to have reacted to even the slightest possible changes in the temperature and precipitation conditions. The cascading effects of these changes on the vast expanse of water existing in the form of glacier ice and snow in the Himalaya, the forest cover, the health, and the socioeconomic conditions of the population inhabiting the Indo-Gangetic Plains have been the issues of serious concern. The analyses of the temperature data collected manually at different observatories during the period from 1866 to 2012 show significant rate of warming during the winter season (1.4 °C/100 years) than the monsoon temperature (0.6 °C/100 years), due to rapid increase in both the maximum and minimum temperatures, with the maximum increasing much more rapidly. Annual rate of warming (1.1 °C/100 years) is abnormally higher than the global rate (about 0.7 °C/100 years) during this period. Not all regions of the north-western Himalaya (NWH) have reacted uniformly to the specter of climate change. Studies have confirmed significant spatial and temporal variations in magnitude of winter as well as summer warming in different ranges. While the windward side of the Pir Panjal and parts of the Greater Himalayan and Karakoram Ranges have shown statistically significant winter and summer warming, leeward sides of these ranges have not shown much change. The most remarkable finding of this study is the significant decreasing trend experienced at almost all stations above the equilibrium line (>5300 m in altitude) in winter warming as well as winter precipitation in higher reaches of the Karakoram Himalaya in the last three decades. From the precipitation point of view, significant decreasing trends (at 95% confidence level) in the monsoon and overall annual precipitation during the study period are indicated. In contrast, the winter precipitation has shown an increasing but statistically insignificant trend (at 95% confidence level). Rising winter air temperatures have caused decreasing snowfall component and increasing rainfall component in total winter precipitation on the windward side of the Pir Panjal Range and parts of Greater Himalayan and the Karakoram Ranges. The analyses also show that although winter precipitation in the NWH has remained trendless in the last 140 years, there are significant increasing trends in the extreme snowfall events during winters and rainfall events during summers in Pir Panjal and Shamshawari Ranges in the last three decades and insignificant but increasing trends in the Great Himalayan and Karakoram Range. Decrease in winter snowfall amounts and increasing rainfall component at almost all stations have been affected to some extent by the increase in winter air temperature during this period. The spatial and temporal variations in winter and summer warming and consequent precipitation changes in different ranges/regions of the NWH are attributed to varying scales of anthropogenic activities and growing urbanization of the areas. Decreasing temperatures in the last three decades in the Karakoram Himalaya with altitudes above the equilibrium line (>5300 m) are attributed to prevalence of permanent snow cover which appears to have influenced their microclimatology. These studies have significant bearing on the mass balance of the glaciers in the region and the hydrological behavior of various river systems in the Himalaya.