Title: Assessing Impact of Climate Variability and Change on Maize Yield in Gamo Zone, Southern Ethiopia: A Modelling Perspective.

Abstract Computing seasonal anomalies and Mann-Kendal trend test combined with APSIM maize crop modeling, the impact of climate variation and change on Maize crop production has been assessed; by comparing the simulated result during baseline and 3 CMIP5 climate model projections of 2 Representative Concentration Pathways (RCP 4.5&8.5) climate scenarios in Gamo Zone, Southern Ethiopia, case of 4 Woreda. Based on standardized precipitation index (SPI) analysis, a moderately wet and very wet climate condition will predominate during the 2nd rainy season (Sept - Nov). While the main rainy season (March-May), moderately dry and very dry climate conditions will predominate during the mid and end-term of the 21st century compared to the baseline period. Inconsistent decreasing and increasing temperatures and rainfall trends in response to climate change have been detected. The APSIM7.9 crop model adequately simulates the maize grain yield with a Root Mean Square Error value of (4.5 to 9.13 q/ha) across four selected woreda. The maize yield potential variation of lowest, highest limits and median ranges up to 1.2, 30.5 and 16 q/ha with a coefficient variation of 2.4% on average in future three particular periods. The median yield change showed a reduction up to 36.5% and 18.75% across all woreda during the mid term (2041-2070) and end- term (2071-2100) as compared to the baseline period (1980-2005), due to the reduction of precipitation in the main rainy season and annual total rainfall reduction; while it showed a positive change up to 29.2% during the near-term (2010-2040) period of the 21st century in both RCP scenarios.