During the first decade of the 21st century Earth observation from satellites will be faced with two major demands: provision of continuity missions and launch of new exploratory missions. This paper addresses European plans for new Earth observations in the context of Ocean Observing System for Climate at the onset of this new millennium. It highlights three quantities: ice mass fluctuations, sea surface salinity and fine resolution marine geoid. Their relevance and importance for climate are briefly reviewed in connection with important processes such as, for example, thermohaline circulation, sea level change, and evolution of large scale salinity events. The associated satellite mission concepts approved by ESAare then presented in light of their objectives, scientific observation requirements and degree of complementarity and synergy with other relevant missions.