Identifying global CH4 sources and their emissions is important for understanding the processes that govern the increase of CH4 in the atmosphere; constraining CH4 emissions at subcontinental scales is of great value, for identifying strong emissions hot spots and attributing emissions to a particular source. In my talk, I will show CH4 emissions optimization framework from global low-resolution to subcontinental high-resolution scales using GOSAT satellite CH4 retrievals and surface flask network measurements as observational constraints. I will address challenges and limitations of quantifying CH4 emissions with current observing networks. In particular, I will develop topics of differences in GOSAT CH4 retrieval algorithms and retrieval coverage, signatures of CH4 emissions in satellite and surface flask measurements and discuss robustness of high-resolution North American CH4 emission estimates.