Techniques for inverse modeling using atmospheric tracer transport models are able to provide important information concerning regional carbon sources and sinks based on analyses of observed atmospheric carbon dioxide concentrations. Estimates of surface-atmosphere CO sub(2) fluxes are compared from an intercomparison of diverse atmospheric CO sub(2) inversion models. The systems considered in the project include 16 transport models and model variants. Findings from the project indicated that the uptake of CO sub(2) in the southern extratropical ocean is less than the value determined using ocean measurement data. This result was not sensitive to transport models of methodological techniques. Evidence of a northern land C sink distributed across the continents of the Northern Hemisphere is considered.