Global reductions in greenhouse gases will eventually be motivated by an international climate treaty and will entail regional or local policy decisions to mitigate emissions. Sandia’s experience in nuclear non-proliferation and treaty verification provides a strong foundation for climate treaty verification. A global climate treaty will likely be based on greenhouse gas (GHG) inventories supplied by participating countries. This “bottom-up” approach to assessing GHG emissions, however, is fraught with unacceptably large uncertainties in regional and sectoral anthropogenic emissions. A “top-down” approach based on atmospheric measurements will be required to verify compliance on a countrywide or regional scale. In addition, compliance will take place at the state and municipality level and will require feedback about the effectiveness of policies implemented to reduce emissions. Current attribution approaches are unable to estimate GHG fluxes with sufficient certainty for treaty verification or municipal decision support. This inability to estimate GHG fluxes with sufficient certainty results from large varying natural background and uncertain atmospheric transport. Sandia has substantial capabilities in GHG measurements, inverse modeling, monitoring network optimization, and uncertainty quantification that can be applied to anthropogenic GHG source attribution for treaty verification and mitigation policy support. In particular, we have developed a mobile laboratory facility for measuring greenhouse gases and tracers of their sources. Measurements from this facility are being coupled with inverse modeling and uncertainty quantification techniques to determine magnitudes and locations of anthropogenic and biogenic GHG sources and sinks.