We quantify the temperature-dependence of clear-sky radiative feedbacks in a tropical radiative-convective equilibrium model. The longwave radiative fluxes are computed using a line-by-line radiative transfer model to ensure accuracy in very warm and moist climates. The one-dimensional model is tuned to surface temperatures between 285 and 313 K by modifying a surface enthalpy sink, which does not directly interfere with radiative fluxes in the atmosphere. The total climate feedback increases from -1.7 to -0.8 Wm^-2K^-1 for surface temperatures up to 305 K due to a strengthening of the water-vapor feedback. The temperature-dependence maximizes at surface temperatures around 297 K, which is close to the present-day tropical mean temperature.
At surface temperatures above 305 K, the atmosphere becomes fully opaque and the radiative feedback is almost constant.
This near-constancy is in agreement with a theoretical model of the water-vapor feedback presented by Ingram (2010), but in disagreement with other modeling studies.