The Greater Toronto Area (GTA) is responsible for more than 60% of Ontario's GHG emissions. Thus quantifying and monitoring GHG emissions from the GTA is of great importance. In this study, we have developed a high resolution CH4 emission inventory for the GTA that is going to be verified by atmospheric measurements. The overall emissions of CH4 can be identified by differencing the column-averaged abundances of CH4 measured by two ground-based Fourier Transform Spectrometers (FTS) located upwind and downwind of the GTA. In addition, a portable GHG monitoring device is used to systematically move throughout the city to gain a better understanding of the spatial distribution of the main sources of CH4. In this talk, the preliminary results from the measurements that have been done using the portable monitoring system and the FTS instruments, will be presented.