Assessment of climate extremes in future projections downscaled by multiple statistical downscaling methods over Pakistan

Abstract

Climate change is a phenomenon that is unequivocally altering the natural systems in all parts of the world but the alteration in climate extremes may pose more severe and unexpected impacts on Pakistan. The current study provides a comprehensive outlook of observation (1976-2005) and changes in climate extremes between the reference (1976-2005) and future periods (2020s: 2006-2035, 2050s: 2036-2065 and 2080s: 2066-2095). The analysis was conducted across six sub-regions of Pakistan including North Pakistan (NP), Monsoon Region (MR), Khyber Palchtunlchwa (1(P), Southern Punjab (SP), Balochistan and Sindh for which Coupled Model Intercomparison Project Phase 5 (CMIP5) 14 General Circulation Models (GCMs) under Representative Concentration Pathways 4.5 (RCP4.5) and RCP8.5 were downscaled and bias corrected by three statistical downscaling methods. The spatial disaggregation and quantile delta mapping (SDQDM) method was used for future projections in this study. Changes in climate extremes were detected by Expert Team on Climate Change Detection and Indices (ETCCDI). In case of temperature, the results indicate a projected increase in frequencies and magnitudes for warm extremes, while it is decreasing for cold extremes in the 21st century. The corresponding trends of maximum and minimum temperature extremes are greater than the mean temperature trend; where the frequency and magnitude of minimum temperature extremes is higher than maximum temperature extremes over Pakistan particularly over North in last half of the 21st century for both RCPs. Also, the average of temperature extremes (TXx, TXn, TNx and TNn) are severe in the order of NP (+ 4.8 degrees C), KP (+ 4.6 degrees C) and MR (+ 4.5 degrees C). In the case of precipitation extremes, most of the sub-regions across Pakistan show a higher increase in total annual precipitation and intense precipitation events with the highest increase in MR, KP and NP and the least increase in Sindh. Despite the increase in total precipitation, numbers of consecutive dry days (CDD) are increasing while consecutive wet days (CWD) are decreasing which can give rise to drought conditions particularly in Sindh. The study provides complementary and consistent climate extremes information over Pakistan for local decision makers to incorporate into policy-making, disaster management, and infrastructure planning.