From analysis of TRMM data, we find that warm rain accounts for 31% of the total rain amount and 72% of the total rain area in the tropics, and plays an important role in regulating the moisture content of the tropical atmosphere. There is a substantial increase in precipitation efficiency of light warm rain as the sea surface temperature increases, but precipitation efficiency of heavy rain associated with deep convection is independent of sea surface temperature. This implies that in a warmer climate, there may be more warm rain, at the expense of less cloud water available for middle and high level clouds.