The authors show that the mean global temperature – and, therefore, climate – is determined mainly by the reflected portion of the total heat received from the Sun. The heat reflected directly by infra-red radiation is insufficient for maintenance of the temperature necessary for the Earth life, since it is limited by absorption windows created by green-house gases (mainly water molecules). The deficient heat is transported by a strong vertical convective air stream – a component of the total air circulation. This heat – limited only by Newton’s law – is delivered to the upper troposphere layers not containing water molecules, from where it is dissipated, practically unlimitedly, at the infra-red radiation wavelengths corresponding to cooled media. The convection, in compliance with Newton’s law, creates a negative feed-back, which stabilizes the processes of temperature changes on the Earth reducing them by half.