Estimation of mean-values of Earth's surface temperature: Mathematical robust model of thermo-balance of Earth’s heat fluxes

Mathematical robust model of thermo-balance of Earth’s heat fluxes is suggested for such an estimation. Using well-known data (albedo of the Earth’s surface, constant of heat flux from the Sun per square meter of Earth’s outer atmosphere surface, etc.), we could conclude that heating only by the Solar activity is not sufficient to obtain the real meaning of temperature of Earth’s surface. Estimation yields the mean-valued temperature about -50 degrees below zero (Celcius scale) in this case. It means that there exist other sources of heating of Earth; we suppose such sources to be the inner sources of heating of Earth itself.