Presented at the 2018 AGU Fall MeetingOcean surface wind speed, sea surface temperature (SST), and integrated water vapor (W) have been derived, under clear and cloudy conditions, starting with Scanning Multichannel Microwave Radiometer (SMMR) on Seasat and Nimbus-7. The 1982-83 El Niño and Southern Oscillation episode initially escaped notice because it was obscured from spacebased visible and infrared sensors by volcanic aerosols. Nimbus-7 SMMR demonstrated for the first time the all-weather capability by monitoring the eastward migration of atmosphere convection and ocean warming along the equator during the episode. By deriving a statistical relation between W and near surface humidity, based on the coherence of vertical humidity profile, we pioneered the method of spacebased estimation of surface evaporation/latent heat flux, using bulk parameterization, in the 1980s. We also demonstrated the direct retrieval of evaporation from the radiances measured by selected channels of the microwave radiometers. In the decades that follow, microwave radiometers have been applied to study ocean-atmosphere interactions, in tropical cyclones, in mesoscale atmospheric convections and ocean eddies, in large-scales mid-latitudes anomalies. Most recently, SST from Advanced Microwave Scanning Radiometers (AMSR) and ocean surface salinity from Aquarius and Soil Moisture Active and Passive (SMAP)have been used to monitor ocean carbon dioxide partial pressure and acidification, leading the linkage of water and carbon cycles in the oceans. Past accomplishments and future potentials will be highlighted in this report.