Understanding and independently validating carbon emissions from concentrated point sources is vital to support climate policy. Satellite-based quantifications of ${text{CO}}_{2}$ point source emissions have been limited by the spatial coverage of current satellite instruments. We combine three different satellite instruments to determine carbon monoxide (CO) and carbon dioxide (${text{CO}}_{2}$) emissions of seven large cities and six industrial complexes. We first estimate CO emission rates using TROPOMI CO observations with the Cross-Sectional Flux method. Subsequently, ${text{CO}}_{2}$ emission rates are calculated by multiplying with the ratio of TROPOMI-observed CO enhancements and ${text{CO}}_{2}$ enhancements from OCO-2 and OCO-3, also representing the combustion efficiency. We use synthetic observations to validate our approach and show that the inclusion of TROPOMI CO observations increases the number of possible ${text{CO}}_{2}$ emission quantifications. Using 2018─2023 observations, we find lower CO emission rates for Delhi and Lahore than the EDGAR emission inventory version 8. In contrast, our CO emission estimates exceed bottom-up inventory estimates for most industrial sources. This is caused by observed combustion efficiencies that are generally lower than those reported in emission inventories. Our ${text{CO}}_{2}$ emission estimates show better agreement with EDGAR than the CO emissions, especially for industrial sources. We find higher ${text{CO}}_{2}$ emission rates than EDGAR for Delhi, Lahore, and Cairo that better agree with the ODIAC inventory. Our work shows the importance of CO as a co-emitted species, and paves the way for a similar approach to be applied to the combination of TROPOMI, its successor Sentinel-5, and the future CO2M satellites.
