Thanks SoM.
However there is only one external heat source for this planet, and I can understand how there could transference of energy from one wavelength to another, eg visible spectrum into IR by absorption and emission. The positive feedback that is mentioned time and time again baffles me. How can the total radiation falling on the Earth's surface be greater than the Solar radiation that enters the top of the atmosphere? Where does the energy for this process come from? Is this what the IPCC call Radiative Forcing?
Many thanks.