Using a one-dimensional radiative–convective equilibrium model, we show that in clear-sky conditions, stratospheric sulfate aerosol forcing weakens with increasing surface temperature while CO₂ forcing varies much less. This effect arises as sulfate aerosol, unlike CO₂, absorbs mainly at wavelengths where the atmosphere is optically thin. It thereby masks the surface emission, which increases with warming. The spectral masking also results in weaker radiative feedback when aerosol is present.