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A new paper in Science reports that a careful study of satellite data show the assumed cooling effect of aerosols in the atmosphere to be significantly less than previously estimated. Unfortunately, the assumed greater cooling has been used in climate models for years. In such models, the global-mean warming is determined by the balance of the radiative forcings—warming by greenhouse gases balanced against cooling by aerosols. Since a greater cooling effect has been used in climate models, the result has been to credit CO2 with a larger warming effect than it really has.