The effect of clouds on this heat budget is immense. The major radiatively active components of the atmosphere are water vapor and so-called layer clouds. Recent observational studies show that these effects almost balance, but that the cooling effect is somewhat more important. In existing climate models about one third of the predicted warming due to increasing CO2 arises because of the predicted cloud changes. These predictions, however, are highly speculative because none of the models include interactive cloud physics.
Convection also plays an important role in the surface heat budget.
The main mechanism whereby the surface of the Earth cools is not radiation, but evaporation. The heat lost by evaporation is carried deep into the atmosphere by convection and is realized as heat by the atmosphere when water vapor condenses into rain and snow. Much of this heat is released above 6 km. Moreover, increased evaporation is likely to lead to increased convection. However the bulk of this water vapor condenses as it rises and falls out as precipitation leaving open how much is actually available to moisturize the atmosphere.