Changing trends of thermal extremes in Pakistan

Extreme events have gained considerable scientific attention recently due to their potentially catastrophic impacts. Heat waves are thought to be more pronounced now in most parts of the world, and especially in South Asia, but doubts remain. The aim of this study is to calculate the frequency and intensity of heat waves in South Asia, focusing on Pakistan and identifying the regions within Pakistan that are most vulnerable to heat waves. Analyses have been performed both at provincial and country levels from 1961 to 2009. The provincial level analysis shows positive trends for heat waves of magnitudes a parts per thousand yen40A degrees C and a parts per thousand yen45A degrees C for 5 and 7 consecutive days. Events of magnitude a parts per thousand yen40A degrees C and a parts per thousand yen45A degrees C for 10 consecutive days also increased in frequency in Punjab, Sindh, and Balochistan. These regions are therefore considered to be the regions most vulnerable to heat wave events in Pakistan. The Balochistan region shows a consistently increasing trend throughout the study period, which may lead to more frequent drought in the future. The country level analysis indicates an increase in the frequency of 5 and 7 consecutive days heat waves at all defined temperature thresholds. The 10-days heat waves spells show a slight increase at a parts per thousand yen40A degrees C and no significant change at a parts per thousand yen45A degrees C. The Gilgit Baltistan and Azad Jammu & Kashmir areas reported no events at a parts per thousand yen45A degrees C for 5, 7 and 10 continuous days. It is anticipated that with a long term rise in temperatures around the globe, heat waves will become more frequent and intense in all parts of the world, including Pakistan.