En this section, we study the aspects related to the transfer of energy. A brief revision of the atmosphere behavior against the electromagnetic radiation is carried out. Afterwards, we introduce the radiometric basic magnitudes and the laws of Radiation: Planck's Law, Law of Wien's displacement, Stefan-Boltzmann's Law, Kirchhoff's Law and Beer's Law. The blackbody is defined according to a classification of the bodies based on their emissivities. Solar constant and the terrestrial albedo are defined in order to calculate the radiative balance and to introduce the term of greenhouse effect. To finish, the greenhouse gases are analyzed. The effects provoke by thermal variations in aquatic environmnets are also studied.