  This is a white paper in response to the National Academy of Sciences
"Exoplanet Science Strategy" call.
  We summarize recent advances in theoretical habitability studies and argue
that such studies will remain important for guiding and interpreting
observations. Interactions between 1-D and 3-D climate modelers will be
necessary to resolve recent discrepancies in model results and improve
habitability studies. Observational capabilities will also need improvement.
Although basic observations can be performed with present capabilities,
technological advances will be necessary to improve climate models to the level
needed for planetary habitability studies.
