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Extreme climate events and precipitation depths are assessed for Iran with minimal uncertainties, considering three sources of uncertainty: general circulation models (GCMs), future scenarios, and downscaling method. The frequency, duration, severity, and intensity of extreme events, along with extreme precipitation depths for 2- to 50-year return periods, are evaluated for the baseline period (1980–2014) and three Shared Socioeconomic Pathways (SSPs): SSP1-1.9, SSP2- 4.5, and SSP5-8.5 (2021–2080). Daily precipitation and temperature data from multi-model ensemble of the Coupled Model Inter-comparison Project phase 6 are statistically downscaled for 51 stations across Iran. Extreme precipitation depths increase under SSP1-1.9, whereas the precipitation anomaly depends on location under SSP2-4.5 and SSP5-8.5. The southern coastal and southeastern regions (remaining stations) will experience more-frequent shorter (less-frequent longer) extreme events. The GCM and downscaling method are the main sources of uncertainty in projected precipitation, while climate scenario significantly contributes to the uncertainty in projected temperature. [ABSTRACT FROM AUTHOR]

Karstic aquifers, because of their conduit system, are susceptible to climate change. Ten karst springs in the Zagros region were selected to investigate the impact of climate change under three CMIP6 scenarios: SSP1-1.9, SSP2-4.5, and SSP5-8.5. This study was conducted in three steps: downscaling climate projection, analyzing spring discharge time series, and introducing a new index to assess the impact of climate change on spring flow rate. Applying LARS-WG6, precipitation was downscaled at 14 stations in the study area. Moreover, time series and trend analysis showed that the selected springs have experienced a decrease in their flow rate. Assuming the covariance function between precipitation and spring discharge is constant, new indices (i.e., I Q d , I d Q d , and I c c ) were introduced to highlight the effect of climate change according to the three scenarios. d Q d is the variability of spring discharge from past to future, I d Q d is spring discharge variability over the historical data, and I c c is the effect of precipitation and spring discharge change together. I c c has a range from −0.25 to 0.25 below and above, which is indicative that two extreme conditions including the spring dryness and overflow are in effect, respectively. The main results revealed that the degree of impact at each spring is a function of climate change scenarios and hydrogeological characteristics of the karstic systems. A more noticeable negative trend in spring flow rate is observed for the karst springs characterized by a dominant conduit flow regime and low matrix storage, located in the areas with low cumulative rainfall, and has a stronger relationship with precipitation. Based on the results, decisions on the management of karst water resources should be made considering where the springs bear free surface and pressurized flow conditions. [ABSTRACT FROM AUTHOR]

The impact of climate change on hydrology and water salinity of a valuable coastal wetland (Anzali) in northern Iran is assessed using daily precipitation and temperature data from 19 models of Coupled Model Inter-comparison Project Phase 5. The daily data are transiently downscaled using the Long Ashton Research Station Weather Generator to three climatic stations. The temperature is projected to increase by +1.6, +1.9 and +2.7°C and precipitation to decrease by 10.4%, 12.8% and 12.2% under representative concentration pathway (RCP) scenarios RCP2.6, RCP4.5 and RCP8.5, respectively. The wetland hydrology and water salinity are assessed using the water balance approach and mixing equation, respectively. The upstream river flow modelled by the Soil and Water Assessment Tool is projected to reduce by up to 18%, leading to reductions in wetland volume (154 × 106 m3), area (57.47 km2) and depth (2.77 m) by 34%, 21.1% and 20.2%, respectively, under climate change, while the mean annual total dissolved solids (1675 mg/L) would increase by 49%. The reduced volume and raised salinity may affect the wetland ecology. [ABSTRACT FROM AUTHOR]

Climate change involves increasing atmospheric carbon dioxide concentration which is driven by anthropogenic emissions. Afforestation, which is the establishment of forests on previously non‐forested lands, could be a suitable climate change mitigation strategy. The aim of this research is to evaluate the carbon sequestration capability of the Eucalyptus and Prosopis species in the Reza‐Abad afforestation park in western Iran. For this aim, three stands of any species were selected. For quantitative assessment, a transect was implemented at the length of 100 m. In trees located of transects, the general characteristics of species were measured. Also, for estimating the amount of litter, a sample plot has been measured at the center of the quadrate. These samples were taken from the afforested area, the control area inside the afforested area and another control area outside. In each stand, species were selected randomly and one‐eighth of the whole stand was taken for calculating the percentage of carbon and aerial biomass. Then the aboveground organs were weighted and after the transfer of different plant organs to the laboratory, the conversion factor of carbon sequestration of the plant organs was determined individually by combustion method. Also, soil samples were also collected from two depths of 0–15 and 15–30 cm in each of the cultivated and control parts. The results showed that there is a significant difference between the species and Prosopis has higher carbon sequestration than Eucalyptus. The carbon sequestration among different organs showed a significant difference, carbon sequestration was 19.24 t/ha for Eucalyptus and 18.43 t/ha for Prosopis. After an economic calculation, it was concluded that afforestation has a positive effect on the reduction of atmospheric carbon dioxide. Hence, these results allow decision makers to change land use from desert area to forest, and planting the Prosopis species is more recommendable than Eucalyptus for afforestation in such areas which are economically profitable. [ABSTRACT FROM AUTHOR]