International audienceAs one of the most important precursors of O3, carbon monoxide (CO) is an important trace gas for the understanding of both air quality and climate forcing. The Infrared Atmospheric Sounding Interferometer (IASI) onboard the MetOp satellite measures carbon monoxide on a global scale, twice a day. This presentation will give a preliminary and non exhaustive validation of the IASI CO retrievals obtained by the Fast Operational/Optimal Retrievals on Layers for IASI (FORLI) algorithm. The IASI global distributions are compared with CO observations available from other operational nadir looking instruments which also record surface and atmospheric signals in the thermal infrared (TIR) spectral range: MOPITT, AIRS and TES. I...