Part 1. What Water Vapor Does
Water vapor creates a hundred times as much supposed "greenhouse" effect as carbon dioxide, because there are about 30 times as many water vapor molecules in the air, while water vapor has three times as much bandwidth which can absorb infrared radiation. Bandwidth means the width of the absorption peaks where frequency of absorption is plotted.
And water vapor is highly variable, which means it swamps anything carbon dioxide does. It enters the atmosphere through evaporation, which varies with temperature and wind; and it leaves the atmosphere through precipitation, which varies with conditions.
A one percent change in water vapor would swamp the entire effect by carbon dioxide, because water vapor is doing a hundred times as much of the same thing. But this result would only be relevant if greenhouse gasses actually were creating global warming. The fact that it can be ignored demonstrates that greenhouse gasses are not creating global warming.
Neither water vapor nor carbon dioxide are relevant to global warming, because they absorb all infrared radiation available to them in such a short distance that an increase only shortens the distance rather than increasing the heat. Carbon dioxide absorbs to extinction in 10 meters. Doubling the amount of CO2 in the air would cause it to absorb all radiation available to it in 5 meters instead of 10. Water vapor would absorb to extinction in less than a meter, but I haven't seen an actual figure.
The whole reason why the global warming concept began 150 years ago is because it was observed that miniscule quantities of carbon dioxide absorb a large amount of infrared radiation in a short distance. In other words, the first 50 ppm (parts per million) of CO2 in the air does most of what CO2 does, and the next 334 ppm only shortens the distance required to absorb all available infrared radiation.
Part 2. Amplification Fraud
Since propagandists can't get enough mileage out of carbon dioxide alone (Stretching all of the numbers only gives them a 0.6°C temperature increase.), they fall back on another fraud to amplify the amount. They say that most of the heat is not produced by the carbon dioxide directly but by water vapor created by carbon dioxide. A small amount of heat is supposedly multiplied by water vapor, because heat causes water to evaporate. (They use the word "forcing" when they refer to this effect.)
Such a multiplier effect cannot occur, because it would create thermal runaway. The multiplied heat due to water vapor would cause more water to vaporize, which would create more heat and cause more water to vaporize, etc. The rationalization for thermal runaway is that only one cycle can occur before the heat escapes into space; but that explanation is not logical. There is no such thing as a cycle. A calorie of heat does the same thing at an increase of 0.1°C as for an increase of 20°C.
If small amounts of heat were multiplied, natural variations would also be multiplied, and small effects by humans would disappear in the natural variations. There are many causes of natural variation including seasons, latitude, tilt and eccentricity of the earth's orbit, variations in solar energy or volcanoes in the ocean.
Look at the ridiculous quantities. Humans are said to have increased global temperatures by 0.6°C. If most of that was due to increased water vapor, how much due to CO2? Maybe 0.2°C. Now compare that to natural variations. Night to day variations are typically 17°C. Seasonal variations are typically 60°C. Localized effects vary wildly between the equator and poles. Then there are random variations in such things as the Gulf Stream in the Atlantic Ocean which heats Europe. If each temperature increase was multiplied by a factor of 3-10 due to more water vapor, there would be explosions of heat everywhere. You can't just limit the multiplication to the 0.2°C which humans supposedly produce.
Here's another concept. A multiplier would respond more to the greatest increases, which are the natural ones, than to the long term average of humans. This would be like hitting someone on the head. A lethal blow cannot be diminished by averaging it with several small hits. Or it's like the average income in a bar. When Bill Gates walks in, the average income increases by 10,000%. Average is a human construct, not something nature sees. If multiplying temperature were possible, it would respond a lot more to the large changes than the small, average change produced by humans. But the whole concept of multiplying temperature is absurd to a point of scientific fraud.
There is also a problem with the supposed mechanism of water vapor amplifying the effect of carbon dioxide. A small amount of heat resulting from carbon dioxide would not increase evaporation of water significantly, because air has low heat capacity compared to water, and the heat of vaporization is high. Warmer air holds more water vapor, but this is not the same thing as increasing the water vapor. Increasing the holding capacity is reducing the relative humidity, which would reduce precipitation; but global precipitation is increasingthe real reason being that oceans are heating, not the atmosphere.
In other words, throughout the global warming hype, fraud is built endlessly upon fraud.
Such extreme fraud obviously requires motives. The agitators are population controllers who feel humans are using too many resources, and their answer is to shove people out of the economy. They feel that lying is justifiable for that purpose. So they start at the end point of claiming humans are creating a problem with carbon dioxide, and then they work backwards to rationalize the claim through fraud.
Almost everything in climate analysis deals with averages. There are no averages in nature. Averaging is a human construct.
Carbon dioxide is so uniform and stable in the atmosphere that it's average is close to it's actual level. But not so with water vapor. It's concentration varies from 0 to 3%. The variations have sharp boundaries and include large and small patches, as clouds demonstrate.
If so-called greenhouse gasses were really heating the atmosphere, the heat produced by water vapor would be in patches with the water vapor.
The heating process is instantaneous, when radiation is absorbed by a gas in the atmosphere. The radiation is at a nearly constant level changing only with the temperature of the mass which emits it on the surface of the earth. So the temperature variations would track with concentration of the so-called greenhouse gas.
But no such temperature variations occur. If they were occurring, there would be a relationship between temperature and humidity. None is mentioned in meteorology, and none is noticed by humans.
Would the variations be so small as to not be noticed? Not if the planet is going to be fried by a doubling of carbon dioxide. The amount of heat that matters is supposed to be in the range of 3-6°C. Two thirds of it (2-4°C) is supposed to be due to the amplification (positive forcing) by water vapor which is increased by the heat resulting from the increase in carbon dioxide. If such a miniscule increase in water vapor fries the planet, the natural increases would do a lot more. How much more? It would be at least 100 to 400°C, because natural variations in humidity would be at least 50 to 100 times as much as the increase caused by carbon dioxide.
How do you prove it? The frauds don't allow anyone to see their numbers. They insert the numbers into computer models, and scientists are not allowed to see how it is done. But common sense shows that nature puts vastly more water vapor into the air than carbon dioxide could.
Since there is no real "greenhouse" effect of any significance due to radiation absorption in the atmosphere, all of the water vapor is due to other causes. So how much increase of nothing fries the planet? It depends upon what number is substituted for nothing in the computer models.
The Attitude Fraud
This gets to the attitude fraud. Throughout the global warming fraud, critics and the public are supposed to trust the obscure analysis of the promoters of the fraud. And anyone who doesn't gets assaulted with threats, insults and name calling.
There needs to be verification process involved. That process is inseparable from science. Verification is needed not only to determine the reliability of the authorities but to apply the information.
Then how reliable are the persons who obscure their analysis? Honest persons never go down the obscurantism path. They know other people need to get involved in the evaluation process. Congress, for example, needs to know how much money, how much effect and for how long.
So why would anyone trust obscurantists with their esoteric knowledge, which they insist is unquestionable? There is an inherent contradiction in concealing it and claiming it is unquestionable.
The attitude problem is exactly the same inside science and out. The following quote is the response from a referee rejecting a scientific paper on mathematical analysis of water vapor data in the upper atmosphere. The paper was published later in another journal.
“The only object I can see for this paper is for the authors to get something in the peer-reviewed literature which the ignorant can cite as supporting lower climate sensitivity than the standard IPCC range”. Source
The alternative is not which authority ignorant persons cite but rationality applied to evidence. I describe the basic principles of science applied to the logic of the subject, so rational persons can see the truth and the fraud.
To a large extent, scientists critical of the global warming fraud are not allowed to publish in science, as the above quote demonstrates and as explained elsewhere on this web site (Oreskes) (How the Firing Works).
Concerning propaganda: Scientists (now overrun and controlled by fakes) refer to atmospheric temperature increase as forcing. Why not call it an increase? Notice the quantities. The forcing they are talking about is in the fraction of a degree range. The daily and seasonal changes are in the dozens of degrees range. They are trying to say that nature has a rock solid set of interactions, and humans chisel into it with carbon dioxide and mess it up. It's as if engineers developed a finely tuned jet engine, and someone threw in a wrench which destroyed it.
It's all about impressions, because there isn't a trace of objective reality to the assumptions and conclusions. There are thousands of complex interactions in climate, in constant flux; and scientists cannot get a grasp of 1% of the subject. Guessing at those interdependent complexities is no more science than thirteenth century charlatanism.