Title: Segregation of Uncertainties and the Role of Internal Variability in Regional Climate Change Projections - a case study over India Presenter: Ram Singh Abstract: Various sources contribute to the total uncertainty in the future regional climate change projections. Uncertainty in future changes of temperature and precipitation over India are investigated using the CMIP5 and CESM-LE datasets for the 21st century. The uncertainty is partitioned into epistemic (model) and aleatoric (internal variability) components for each season. Role of aleatoric (internal variability) uncertainty can be more crucial at regional and sub-regional scale. CESM-LE (40 members) ensemble is also used to analyze the influence of ensemble size on aleatoric uncertainty we find that low ensemble sizes can lead to an underestimate of the uncertainty. I will present the analysed future projections with segregated components of uncertainty in temperature and precipitation change over the Indian region and various sub-regional scale homogeneous rainfall climatic zones within. Results also include the spatiotemporal characteristics of various components of uncertainty during different seasons over these regions. I will also discuss the role of internal variability at the sub-regional scale, co-evaluation of uncertainties and the impact of ensemble size on the estimation of internal variability over the regional and sub-regional scale.