A reliable Ensemble Averaging(REA) is a proposed technique which provides an estimate of Associated Uncertainty Range and Reliability of future climate change projections for Indian summer monsoon (June- September), stimulated by the state of the art Coupled General Circulation Models (CGCMs) under Coupled Model Intercomparison Project 5 (CMIP5). An evaluation of historical as well as future (RCP4.5 scenario) simulations often CGCMs in the REA technique projects a mean monsoon warming of 1.215 0 C with an associated uncertainty range () of 0.22 0 C, and an all-India precipitation increase by 7.109 mm/ the month with an associated uncertainty ((P) of 2.592 mm/month for 2021–2050. REA technique also shows a considerable reduction in the uncertainty range compared with the simple average ensemble approach and is characterized by consistently high-reliability index in a comparative study with individual CGCMs. The results suggest achievability of REA methodology in constituting the realistic future Indian Monsoon Projections by preparing a performance model and a descriptive confluence criteria.