Future Projections of Heat Waves in Pakistan Using Ensemble NEX GDDP Data Set

Abstract

Heat waves are one of the extreme weather events affecting as many people as with other climatic hazards such as droughts and floods. Due to rise in global temperatures the occurrences of heat waves are likely to exacerbate in many regions in future. The projections for future heat waves over Pakistan are analyzed in this study. The heat waves calculation has been done using the latest NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) data set which comprised of 21 Global Climate Models (GCMs) statistically downscaled at 0.25°×0.25° spatial resolution. The heat waves analysis is done with ensemble modelling approach and using two definitions of heat waves; the Heat waves Duration Index (HWDI) and fixed method approach. Two climate change scenarios; RCP4.5 and RCP8.5 are used for investigating future heat wave projections. The historical heat waves are calculated from 1976-2000 and future projected changes are analyzed in three 25 year time spans: 2025-2049, 2050-2074 and 2075-2099. Two metrics heat wave events and heat wave days are separately shown. The results indicate an increase in both number of heat wave events and heat wave days in Pakistan. The most vulnerable areas for future heat waves are northern areas, plains of Sindh and Punjab, the central and western parts of Baluchistan, and all regions of Khyber Pakhtunkhwa (KPK). The increased number of heat waves in northern areas of the country could result in rapid snow melting and can cause flooding downstream. The agricultural regions of the country would be highly vulnerable to increasing number of heat waves. Keywords: Heat waves, NEX-GDDP, Climate Change, HWDI, GCMs