Gidded Level 3 H2O total columns. The Earth's capacity to sustain life is attributed to two mechanisms: the greenhouse effect and the hydrological cycle. Water vapour in the atmosphere is a critical component of both processes and the main naturally occurring greenhouse gas in the Earth's climate system. Water in gaseous form varies more than other greenhouse gases. Monitoring atmospheric water vapour globally is essential to understand its climate impacts. Measurements of water vapor columns are derived from satellite observations of solar radiation in the ultraviolet and visible (430 – 450 nm) spectral ranges. A water vapour absorption band is detectable across some European Sentinel platforms (Sentinel-4, Sentinel-5P and 5), former (GOME and SCIAMACHY) and future instruments (CO2M). This absorption signature by water vapor is used to derive the shown concentrations with the Differential Optical Absorption Spectroscopy (DOAS) technique. The retrieval methodology, as applied to the fleet of available platforms, demonstrates several advantages, including optimal sensitivity and coverage characteristics across both oceans and continents, enhanced temporal sampling frequency for weather applications, and continuous extension of long-term datasets for climate study purposes. This is accomplished by DLR in the framework of the EUMETSAT's Satellite Application Facility on Atmospheric Composition (AC-SAF) monitoring where DLR generates operational GOME-2 / MetOp products.