Numerical atmospheric models can generate simulations at very high spatial and temporal resolutions. Many of such models, including the Weather Research and Forecasting (WRF), assume a spherical geographic coordinate system to represent the data and for their computations. However, most if not all Geographic Information System (GIS) data use a spheroid datum because it best represents the surface of the earth. WRF and other numerical systems, simply assume that GIS layers can be input as if they were in a spherical coordinate system. <br><br> The difference when reprojecting standard GIS layers onto a sphere can result in latitudinal errors of up to 21 km in the mid-latitudes. Recent studies have suggested that for very high resolution applications, there might be an impact when the GIS input data (e.g. terrain land use, orography) are not reprojected. These impacts introduced by the difference in coordinate systems remain unclear. This research investigates the role and importance of reprojecting GIS layers used by WRF as input by performing sensitivity studies of greenhouse gas transport and dispersion in Northeast Pennsylvania.