The above chart shows the absorption spectrum for CO2, assuming levels from 100 ppmv (lowest level of CO2 in the ice core record) to 200 ppmv to pre-industrial levels of about 300 ppmv to current levels of around 400 ppmv and projecting up to 500 ppmv which is where we will be in around 50 years unless we curb our carbon emissions or the Earth cools a bit.
The "hot pink" area around 10μ is where the Earth's long wave infrared radiation peaks. Notice that going from 100 ppmv to 200 ppmv almost doubles the amount of absorptivity, and increasing CO2 to 300 ppmv almost triples it. However, at 300 ppmv, the 15μ band is 100% absorbed, so increasing to 400 ppmv has little additional effect as does further increase to 500 ppmv. I have never seen "CO2 saturation" presented this way. [Get an animated version with audio narration here.]
The above chart shows how the "Greenhouse Effect" works. Rays from the Sun that strike light-colored surfaces reflect the energy back to space. Rays that strike dark-colored surfaces are absorbed, warming the Earth. Warm surfaces emit all wavelengths in all directions. Some rays pass through the atmosphere back to space. Others are absorbed by CO2 gasses that re-radiate in all directions. Radiation that comes back and warms the Earth is called the “Greenhouse Effect”. [Get an animated version with audio narration here.]
The effect of water vapor in the atmosphere is controversial. IPCC models assume it has a positive feedback effect, meaning the more water vapor in the atmosphere, the more warming. Others, including me, believe the net effect of water vapor is negative, moderating warming.
The above chart tells why. All clouds do warm the earth according to the "Greenhouse Effect". In fact, for night clouds, that is the only effect. However, there are fewer night clouds and the Earth is cooler at night, so the warming effect is moderated. Daylight clouds also warm the Earth a bit by the "Greenhouse Effect", but they also reflect incomming Sunlight back to space and cast a cooling umbra on the Earth. The net effect of daylight clouds is therefore cooling. Rain, snow, thunderstorms, wind, convection and so on also have a net cooling effect. AAs we all know, clouds are formed when water evaporates from the surface of the warm Earth. The "heat of vaporization" removes heat from the Earth and the warmed water vapor takes it higher up in the atmosphere. When water vapor condenses to droplets, the "heat of condensation" (equal to the "heat of vaporization") releases the heat into the clouds where some escapes by radiation to space, a net cooling effect. Some radiation comes back to Earth as "Greenhouse Effect". Thunderstorms suck warmed air from the surface to high up in the atmosphere, returning cooler air, a net cooling effect. Rain or snow cools the Earth when it falls to the surface.
Therefore, it is reasonable to believe that water vapor, the key element along with the Sun in driving weather, has a generally net cooling effect. Thus, the fact that more water is evaporated as the Earth warms, has a negative feedback, and moderates Global Warming. [Get an animated version with audio narration here.]