The greenhouse effect is a process by which thermal radiation from a planetary surface is absorbed by atmospheric greenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface and the lower atmosphere, it results in an elevation of the average surface temperature above what it would be in the absence of the gases. http://en.wikipedia.org/wiki/Greenhouse_effect

• Scott Denning‏: CO2 the Greenhouse Effect explained (2010) https://climatestate.com/2020/09/14/scott-denning%e2%80%8f-co2-the-greenhouse-effect-explained-2010/
• The Greenhouse Effect – Heat trapping Explained https://climatestate.com/2013/05/03/the-greenhouse-effect-heat-trapping/