Abstract. We have analyzed TROPOspheric Monitoring Instrument (TROPOMI) carbon monoxide (CO) data acquired between November 2017 and March 2019 with respect to other satellite (MOPITT, Measurement Of Pollution In The Troposphere) and airborne (ATom, Atmospheric Tomography mission) datasets to understand better TROPOMI’s contribution to the global tropospheric CO record (2000 to present). TROPOMI and MOPITT are currently the only satellite instruments deriving CO from solar reflected radiances. Therefore, it is particularly important to understand how these two datasets compare. Our results indicate that TROPOMI CO retrievals over land show excellent agreement with respect to MOPITT: relative biases and their standard deviation (i.e., accuracy and precision) are on average −3.73 ± 11.51, −2.24 ± 12.38, and −3.22 ± 11.13 %, compared to the MOPITT TIR (thermal infrared), NIR (near infrared), and TIR+NIR (multispectral) products, respectively. TROPOMI and MOPITT data also show good agreement in terms of temporal and spatial patterns. Despite depending on solar reflected radiances for its measurements, TROPOMI can also retrieve CO over bodies of water if clouds are present, by approximating partial columns under cloud tops using scaled, model-based reference CO profiles. We quantify the bias of TROPOMI total column retrievals over bodies of water with respect to colocated in situ ATom CO profiles after smoothing the latter with the TROPOMI column averaging kernels (AK), which account for signal attenuation under clouds (relative bias and its standard deviation = 3.25 ± 11.46 %). In addition, we quantify enull (the null-space error), which accounts for differences between the shape of the TROPOMI reference profile and that of the ATom true profile (enull = 2.16 ± 2.23 %). For comparisons of TROPOMI and MOPITT retrievals over open water, we adopt a simpler approach, since smoothing with TROPOMI AK does not apply for MOPITT retrievals. To this effect, we compare TROPOMI total CO columns (above and below cloud tops) and partial CO columns (above cloud top) to their colocated MOPITT TIR counterparts. (This approximation would be most accurate for optically thick clouds.) We find very small changes in relative bias between TROPOMI and MOPITT TIR retrievals if total columns are considered instead of partial above-cloud-top columns (