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
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.