Just posted at WUWT…
1. Clouds happen in the troposphere (well, apart from some special kinds of clouds)
2. Clouds reflect radiation back to space
3. Radiative (“feedback”) effects are negligible in the troposphere (read raypierre’s book if you don’t believe that)
Hence radiative effects have little or no roles to play wrt clouds, apart from reflection back to space.
Therefore clouds can only cool. Empirically this can be shown in days when the sky is overcast apart from where the sun is. Were clouds to warm the surface, an “oven” effect would soon establish itself. Of course it never happens with any kind of tropospheric cloud: if it did it would violate the finding that radiative effects are negligible in the troposphere.
Therefore clouds can only cool.