Climate Change in the Mountains of Pakistan and its Water Availability Implications

Changes in precipitation and temperature directly affect the demand and supply of freshwater. This chapter presents and compares changes in these two climatic variables in the three major mountain ranges of Pakistan (Hindu-Kush, Karakoram, and Himalayan). The non-parametric Mann-Kendall, Sen’s Slope Estimator, and Mann-Whitney U-test were applied to investigate changes in the precipitation and temperature time-series for the period from 1975 to 2014. The gauge weight method was used to estimate the areal average values of both climatic variables. The time-series datasets were classified into two equal periods to enable assessment of relative changes. Results indicated that the average annual temperature had an increasing trend in all mountainous ranges, with the highest warming trend in the Karakoram range (0.08 °C/decade), followed by Hindu-Kush (0.04 °C/decade) and the Himalayas (0.03 °C/decade). The results of seasonal trend analysis indicated the highest warming trend of the spring season in the Hindu-Kush range (0.33 °C/decade), followed by Karakoram (0.28 °C/decade) and the Himalayas (0.17 °C/decade). A cooling tendency of summer temperature was found in the Karakoram range (−0.10 °C/decade), followed by the Hindu-Kush range (−0.09 °C/decade), while a warming trend of summer temperature was found in the Himalayas. Overall, a decreasing trend of total precipitation was found in the Himalayas, with a significant decreasing trend of annual (38.90 mm/decade) and spring (14.88 mm/decade) precipitation. On the contrary, annual precipitation showed an increasing trend in the Hindu-Kush (13.88 mm/decade) and Karakoram (11.86 mm/decade). Overall, our investigation confirms that the climate of the region is already changing, with an increasing trend of temperature across all mountainous ranges and a decreasing tendency of precipitation in the Himalayas.