• GOSAT observations;
  • flux uncertainty reduction;
  • regional CO2 fluxes

[1] We investigated the utility of Greenhouse Gases Observing Satellite (GOSAT) column CO2 observations in surface CO2 flux estimation. We addressed two key issues in carbon flux estimation from satellite data: (1) reduction of the CO2 flux uncertainty and (2) bias in the constrained surface fluxes. Our results showed that GOSAT data with 1.7 ppm precision (monthly mean, land observation only) had the same utility as observational data from the existing surface network. By adding satellite observations with 2.5 ppm single-shot random error and a bias of 1 ppm, it was possible to reduce the mean regional flux uncertainty by approximately 30%. Unbiased data with 2.5 ppm single-shot precision (0.8 ppm for the monthly mean) halved the flux uncertainty. The aerosol-dependent bias in satellite data with 1 ppm mean variance led to significant absolute errors in the surface CO2 fluxes, highlighting a need for the accurate detection and rejection of biased data.