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Using ensemble-mean climate scenarios for future crop yield projections: a stochastic weather generator approach

Di Ma, Qi Jing, Yue-Ping Xu, Alex J. Cannon, Taifeng Dong, Mikhail A. Semenov, Budong Qian*

*Corresponding author:

ABSTRACT: Using climate scenarios from only one or a small number of global climate models (GCMs) in climate change impact studies may lead to biased assessment due to large uncertainty in climate projections. Ensemble means in impact projections derived from a multi-GCM ensemble are often used as best estimates to reduce bias. However, it is often time-consuming to run process-based models (e.g., hydrological and crop models) in climate change impact studies using numerous climate scenarios. It would be efficient if using a reduced number of climate scenarios could lead to a reasonable estimate of the ensemble mean. In this study, we generated a single ensemble-mean climate scenario (En-WG scenario) using ensemble means of the change factors derived from 20 GCMs included in CMIP5 to perturb the parameters in a weather generator, LARS-WG, for selected locations across Canada. We used the En-WG scenarios to drive crop growth models in DSSAT v4.7 to simulate crop yields for canola and spring wheat under the RCP4.5 and RCP8.5 emission scenarios. We evaluated the potential of using the En-WG scenarios to simulate crop yields, by comparing them with the crop yields simulated with the LARS-WG generated climate scenarios based on each of the 20 GCMs (WG scenarios). Our results showed that the simulated crop yields using the En-WG scenarios were often close to the ensemble means of the simulated crop yields using 20 WG scenarios with a high probability of outperforming simulations based on a randomly selected GCM. Further studies are required as the results of the proposed approach may be influenced by selected crop types, crop models, weather generators and GCM ensembles.