Local to international control of anthropogenic greenhouse gas (GHG) emissions will require systematic estimation of emissions and independent verification. California, the only state in the US with legislated controls on GHG emissions, is conducting research to enable emissions verification of the mandated emissions reductions (AB-32). The California Energy Commission supports the California Greenhouse Gas Emissions Measurement (CALGEM) project at LBNL. In collaboration with NOAA, CALGEM measures mixing ratios of all significant GHGs at two tall-towers and on aircraft in Central California. This talk describes measurements of CO2, CH4, and N2O. Urban fossil fuel CO2 emissions from the Sacramento metropolitan area are estimated using airborne campaign measurements of radiocarbon CO2 and carbon monoxide in an advection model. The urban emissions are consistent with VULCAN, a high-resolution fossil fuel CO2 emissions inventory for the continental US. Regional CH4 and N2O emissions are estimated separately using a Bayesian inverse model. Predicted mixing ratios are calculated based on spatially resolved a priori CH4 and N2O emissions inventories and a carefully evaluated model for atmospheric transport. Inverse estimates for 2008 show suggest that actual CH4 emissions are approximately consistent with the a priori inventory model in winter but significantly larger in summer, while the estimates of N2O emissions suggest that actual emissions are significantly higher than inventory estimates for all seasons. In summary, these results demonstrate the potential to quantitatively verify GHG emissions inventories, and identify areas where current emission inventories for California require improvement.