  We propose a method for constructing the specific heat for the universe by
following standard definitions of classical thermodynamics, in a spatially flat
homogeneous and isotropic spacetime. We use cosmography to represent the
specific heat in terms of measurable quantities, and show that a negative
specific heat at constant volume and a zero specific heat at constant pressure
are compatible with observational data. We derive the most general cosmological
model which is compatible with the values obtained for the specific heat of the
universe, and show that it overcomes the fine-tuning and the coincidence
problems of the $\Lambda$CDM model.
