Assessment of Climate Changes and Their Impact on Barley Yield in Mediterranean Environment Using NEX-GDDP Downscaled GCMs and DSSAT

In countries with scarce water resources, modeling the impacts of climate change on agricultural crops is highly important to assess levels of adverse impacts and to put future changes within the context of planning. In this study, climate change impacts on grain and biological yields of barley were assessed using data for three sites, representing Mediterranean environments in Jordan. Historical climatic and crop data were to calibrate DSSAT crop model to simulate grain and biological yields. Future climate data of daily air temperature and precipitation for the two future periods of 2030–2050 and 2080–2100, under the representative concentration pathway (RCP), were obtained from the downscaled NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) of General Circulation Models (GCMs) simulations. The Decision Support System for Agrotechnology Transfer (DSSAT) model was then used to simulate barley yield under RCP4.5 and RCP8.5 scenarios for the two future periods. The NEX-GDDP future climate projections showed that climate changes would be extreme in terms of declined precipitation and increased air temperature. On average, minimum air temperature would increase by 2.0–4.8 °C while maximum air temperature would increase by 2.4–5.4 °C. These changes would result in severe reductions in barley yield, as shown by the outputs from DSSAT model, except for the site of Madaba under the scenario of RCP8.5 for 2030–2050. The average reduction in grain yield would be 9–30% during 2030–2050 and 5–19% during 2080–2100. The average reduction in biological yield would be and 8–31% during 2030–2050 and 6–19% during 2080–2100. Results also showed significant correlations between DSSAT observed and simulated yield, with relatively high R 2 values and low root mean square error (RMSE). Therefore, the trends of climate change would have an adverse impact on rainfed crops in Mediterranean environments similar to the sites included in this study.