Observed, simulated and projected extreme climate indices over Pakistan in changing climate

Abstract

This article explores the observed, simulated and projected extreme climate indices from daily observed dataset for several meteorological stations as well as NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) dataset. The NEX-GDDP dataset is an extension of the General Circulation Model (GCM) runs, performed under the Coupled Model Inter-comparison Project Phase 5 (CMIP5). Two greenhouse gas emission scenarios have been considered, known as Representative Concentration Pathways, i.e., RCP4.5 and RCP8.5. The core climate indices, proposed by the Expert Team on Climate Change Detection and Indices (ETCCDI), were used for investigation of climatic extremes over different provinces of Pakistan. The results show that summer days have significantly increased in the Gilgit Baltistan and Azad Jammu Kashmir (GB-AJK) region by 24 and 18 days, respectively, triggering the frequency of Glacial Lake Outburst Flood (GLOF) events in the region. Moreover, the projected climate shows an increase of 6 days in the frequency of summer days in the GB-AJK region in the next 30 years. The frequency of heavy precipitation is significantly increasing in the Khyber Pakhtunkhwa (KP) province, which may augment the flood hazard in the region. Future projection shows an increase of 1.3 °C in the mean maximum temperature in the KP province by the year 2045. An average increase of 1.9 °C in the mean minimum temperature has been observed in the Punjab province over the past 54 years (1960-2013), whereas there is a projected increase of 1.4 °C in the mean minimum temperature in the next 30 years. Such an increasing trend in the mean minimum temperature may cause implications for food and agriculture sectors in the Punjab province. The results show a significantly increasing trend in the mean maximum temperature and summer days in the Sindh province, which may enhance the frequency and intensity of heat waves in the region. There is a projected increase of 20 days in summer days in the Sindh province. Similar rising trend in the temperature has been observed in the Balochistan province, which may ultimately enhance the dust and sand storms in this region.