Toward robust and consistent regional CO₂ flux estimates from in situ and spaceborne measurements of atmospheric CO₂

We evaluate the robustness and consistency of global and regional posterior CO₂ flux estimates for 2010 inferred from two versions of bias-corrected CO₂ column retrievals from the Japanese Greenhouse Gases Observing Satellite (GOSAT). Six satellite-based inversions, generated from three atmospheric transport models and two independent Bayesian inference algorithms, facilitate a rigorous investigation of the uncertainty of the inverted fluxes. This ensemble shows hemispheric and regional differences in posterior flux estimates that are beyond 1 sigma uncertainties and in some regions are unrealistic. We recognize the importance of these satellite data in further understanding the contemporary carbon cycle but we argue that more resources should be invested in characterizing the errors of the prior fluxes, the systematic errors of the retrievals, and the systematic errors of the transport models, to improve confidence in the resulting posterior fluxes.