Assessment of Climate Change Impacts on Major Crops in the United States of America

Climate change is expected to be a significant threat to future agriculture in the United States. Three separate research efforts were made to study climate change impact assessment. In first step, PRISM Climate Group gridded data (PRISM) and the Community Collaborative Rain, Hail and Snow Network’s (CoCoRaHS) precipitation data compared at five different locations in Nebraska. The monthly precipitation amount and days in PRISM dataset deviated up to 22.3% and 40% respectively compared to CoCoRaHS. The relative error in CERES-Maize simulated grain and biological yield found up to 130 kg ha-1 and 135 kg ha-1, respectively with PRISM dataset than the CoCoRaHS. In the second part, the delta change method employed to downscale the change in mean and variability for the temperature and precipitation data at individual weather station levels across the United States. The eight global climate models projections included in Coupled Model Intercomparison Project Phase 5 under two representation concentration pathways (RCP4.5 and RCP8.5) were used. The Agricultural Model Intercomparison and Improvement Project protocols were followed to apply the changed signal to the observed climate. As an output, fifteen future climate series under each representative concentration pathways for three periods (2013-2039, 2043-2069 and 2073-2099) were generated for 3,000 weather stations. Finally, the response of crops to future climate was explored using CERES-Maize (for corn) and CROPGRO-Soybean model (for soybean) across ten major production states at the county level. The rainfed and irrigated crop simulation was performed using generated future climate series for each future period under both RCPs. Crop yields are likely to decrease under both production systems, except some temperature limited growing environments in the northern latitudes. The irrigation water requirement found to increase in the future with lower water productivity in the majority of growing regions. The future climate impact is expected to be higher under high emission (RCP8.5) than the medium-low emission scenario (RCP4.5) in different future periods. The databases of future climate series developed under this research will be valuable resources for future impact studies. The information on crop impact will be helpful in guiding future research and in developing suitable crop adaptation strategies