The salt content of seawater (salinity, units: g/kg) is directly related to the earth's water balance. Salinity is emerging as an important climate variable. I shall briefly introduce the use of salinity as a climate variable. I shall then show facets of the space-time scales of salinity variation in the Bay of Bengal, and discuss the relation of surface salinity to (i) tropical cyclone intensity, and (ii) the active-break cycle of the monsoon. The second part of the talk is based mainly on recent measurements from research ships, instrumented moorings, and satellites.