Projections of major climate change indicators over Iran from 2021 to 2080.

Abstract

This study addresses the impact of climate change (2021-2080) on the seasonal distribution of rainfall, temperature, and season lengths over Iran under three Shared Socioeconomic Pathways (SSPs) of the low (SSP1-1.9), moderate (SSP2-4.5), and high (SSP5-8.5) levels of global warming, based on the 29 model ensemble of the Coupled Model Inter-comparison Project Phase 6 (CMIP6). Results reveal that spring and autumn lengths are ~ 90 days during the baseline period (1980-2014), while summer (~ 97 days) is longer than winter (~ 87 days) by 10 days. However, global warming will result in longer summer and winter and shorter spring and autumn seasons in the future. The temperature will increase during all four seasons of spring and autumn (1.5-2.7 $_{}^{\circ }C$ ), winter (1.1-2.2 $_{}^{\circ }C$ ), and summer (2.0-3.2 $_{}^{\circ }C$ ) consistently with the level of global warming scenarios. Meanwhile, minimum and maximum temperature enhancement will occur during winter and summer, respectively, under a given climate change scenario. Rainfall over Iran will increase during all seasons (6-36%) under SSP1-1.9 but will reduce under warmer scenarios SSP2-4.5 (12-24%) and SSP5-8.5 (8-24%). The contributions of the spring, summer, autumn, and winter seasons to the annual rainfall are 32%, 5%, 20%, and 43%, respectively, implying winter and spring as wet seasons during the baseline period. However, climate change may shift the wet season from winter to spring or autumn, depending on the station and SSP, under climate change. Water managers and policymakers need to consider the highlighted issues for future sustainable management in Iran.