Assessing the climate change effects on climate variables and meteorological drought using the Climate Change Toolkit in Karkheh River Basin, Iran

Drought appears as an environmentally integral part of climate change. This study is designed to investigate the effect of climate change on meteorological drought in the Karkheh River Basin in near future (2071-2043), and distant future (2100-2072) periods. The outputs of GFDL-ESM2, HadGEM2-ES, IPSL-CM5A-LR, MIROC and NoerESM1-M models were downscaled under the RCP 2.6 and RCP8.5 scenarios using the Climate Change Toolkit (CCT) at 17 meteorological stations. To assess the uncertainty of the models and scenarios, the model outputs of the two future periods were compared with the base of the corresponding period using R2, RMSE, MAE indices. The best performing models were chosen for precipitation and maximum temperature, minimum temperature i.e. GFDL-ESM2, HadGEM2-ES and MIROC, respectively. An index, the standard precipitation-evapotranspiration index (SPEI) was also produced using the combination of all five models and under both scenarios. The climate change-induced changes were investigated by comparing the simulated data of the near and distant future periods with the statistics of the base period. The results showed that the basin annual precipitation will likely increase in both future periods, particularly in the near future. The annual maximum and minimum temperatures may also increase especially in the distant future. The rise in the maximum temperature will be possibly greater than the minimum temperature. Seasonal changes in maximum and minimum temperatures and precipitation indicate that the greatest increase in temperature and decrease in precipitation may occur in summer. Hence meteorological drought was also found to increase in the distant future.