In my course about climate change I got some explanation about the so-called greenhous gases. But this is not sufficient to see the complete picture and the role they play within the climate system. Being a layman, I want to find out how these work and try to get an easy to understand but yet exact enough picture for everybody. As an example I use the CO2, but the other GG are working after the same principle.
What are the properties of CO2?
- CO2 can absorb a vast spectrum of infrared (heat)rays. The CO2 molecule gets hotter and radiates again infrared radiation, partly toward the earth's surface, partly towards space.
- The time between absorbing heat for IR radiation and emitting it again lies in the fraction of a nanosecond.
- CO2 can collect heat from the earth surface or from other surrounding non-greenhouse-gas-molecules through physical contact. Even this heat is radiated in both directions.
- CO2 content of the air is about 400ppm (parts pe million, 1 ppm = 0.0001 %). In very direction of an air filled space, every 16th molecule is CO2. So it is unlikely that infrared radiation doen't meet such molecules. In fact, even after only few cm, a big amount of the IR radiation has already met CO2 molecules.
- They can collect heat through physical contact to the earth's surface and to other air molecules.
- They can't neither absorb IR rays nor emit/radiate heat away. They are insulating.
- IR radiation could pass through towards space, causing more heat loss.
- But O2 and Nitrogen are also heated up by contact to the surface, but this heat can't escape from the atmosphere, because both cannot emit heat through IR rays.
- So the whole atmosphere would have the same temperature as the surface.the only cooling could happen through contact to colder parts of the earth, heating them up, and causing them to radiate the excess heat towards space.