Temporal variation of the satellite-derived XCO2 obtained by NIES (black), ACOS (gray), and OCO-2 (blue) in comparison with the obs. XCO2 (red) (a, b, c). Red-shaded areas are the uncertainty of the obs. XCO2 which was derived from the ±2 ppm variability in the observation-based CO2 profile at ~850 hPa. Error bars show the standard deviation of the monthly averaged XCO2.