Water vapor is a gas, a GHG. Always present in the atmosphere.
It is the largest GHG by a considerable margin
Other GHG, chief among which is of course CO2 , are considered as a forcing.
H20 , as a GHG is therefore also a forcing.
Has to be, variable, because it varies a lot more with temperature and pressure, but nonetheless a forcing while there are any molecules in the atmosphere.
It is always resident in the atmosphere at its saturation level for that temperature and pressure.
“And what do you think would happen on Earth if there were no non-condensing GHGs, chief among which is of course CO2?”
So many earth’s to choose from.
Which one would Tony Banton care to use?
Let us take the view that it is the earth as it is now with the unreal assumption that no CO2, Methane and the other minute trace GHG are available or possible. A lifeless* rock with lots of water and Oxygen and Nitrogen. No life or possibility of life like we know it. Unreal.
But this is science. No GHG , no life but atmospheric temperatures.
Life removed, we have a rocky silicon and iron planet with oceans atmosphere and a heat source the sun.
Might be a bit more in the Zeke knowledge range now.
We would have the same planet, the same atmosphere, and the same seas.
The temperature of the world would be the same at the TOA .
Energy in equals energy out.
The atmosphere would be hotter during the day under the sun and colder at night with a marked range of extremes.
More of the earth would be covered with ice starting from the north /south boundaries where the temperature is always below zero.
The average temperature, thanks chief, on a slowly rotating planet like this, would be more or less the same as today.
Long term there would be drastic changes as the compounds would have to find new ways to achieve stability.
*A lifeless rock Tony as basically it would have to be carbon free to be CO2 free.
Alarmists use two false arguments to claim that water vapor is not a forcing.
The first is that water vapor does not have a residence in the atmosphere because it rains.
The falsity here is that rain does not remove water from the atmosphere. It just removes excess water for that temperature and pressure.
The second is that without CO2 forcing all the water in the world would remain as ice and that CO2 was necessary to allow water vapor to get into the atmosphere.
The point is that the earth has come from a hotter to a cooler planet and the water vapor was already in the atmosphere when the earth was much warmer. Pulling the coming out of an Ice age trick does not work either. A drop of 10-12 C could never freeze all the water in the world.
The claim that it was well below zero without an atmosphere does not work either. If one had water on the moon it would be ice on the dark side and steam on the sunny side at well over 100 C. The same argument applies to water on the Earth. Wherever the sun was water would heat up, go into the atmosphere and then exert its GHG effect.
David Appell | September 3, 2021 at 1:34 pm | Reply
angech wrote: The claim that it was well below zero without an atmosphere does not work either.
Without an atmosphere?? What relevance does that have to a discussion of water vapor?
angech | September 3, 2021 at 1:15 am | Reply
Short version Water vapor is a gas, a GHG. Always present in the atmosphere.
Water is therefore a GHG just like methane and CO2.
You consider them to be forcing so by your own logic H2O is also a forcing.