A large number of exoplanets have been detected since 1995. Some of these are expected
to be rocky planets with Earth-like bulk composition and would have habitable
climates. Recently, the climate of exoplanets in the habitable zone has been estimated
with a three-dimensional climate model (3D GCM). Most of previous studies assumed aqua
planets that have a large enough surface water reservoir to cover most of the surface,
like the Earth. However, theoretical studies for the planet formation implied that
exo-terrestrial planets are likely to have a wider range of water contents. When planets
have a small amount of water on their surface, their climate is significantly different
from that of aqua planets. We call such climate land planet climate. I will summarize
climates of exo-terrestrial planets and the relationship between the amount of water and
the planetary climate and discuss "what should we understand for habitable exoplanets in
the next era".