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A dust aerosol optical model is proposed as a result of analysis of the data obtained during the U.S.S.R.-U.S. experiment in Tadzhikistan, 1989. The model consists of spectral dependencies of the single scattering albedo, omega, the asymmetry parameter of the scattering phase function, g, and of possible values of the aerosol optical thickness, tau, for background conditions and for dust storms. This model and available published optical models of dust aerosols were used to perform simulations of radiative forcing in the dusty atmosphere. Results obtained are compared with corresponding results for Saharan aerosol. It is shown that atmospheric dust strongly decreases the total radiative balance of the underlying surface and at the same time induces general warming of the underlying surface-atmosphere system due to a decrease in the system albedo over the arid zones. The calculated heating/cooling rates in the atmosphere are analysed together with data from aerological soundings and radiation measurements.