The fudge factor is used to indicate that a doubling of CO2 in the atmosphere will result in a heat increase of about 4 watts per square meter. This amount is then multiplied by 0.75 to indicate a temperature increase of about 3°C.

Heat increase = 5.35 ln C/C₀
Temperature increase = 0.75 times heat increase.

Notice that the heat is in terms of square meters. The atmosphere is three dimensional. Why not a result in terms of cubic meters instead of square meters? Because there is way too much complexity in the three dimensional space of the atmosphere including a pressure gradient, convection, layering, etc. None of that can be accounted for. So the two dimensional result is an abstraction removed from the complex and unanswerable questions.

In other words, you get a magical result out of the fudge factor without a complex analysis. That's why it must be called a fudge factor instead of a scientific result.

The fudge factor apparently showed up first in the literature in 1988. At that time, a 3°C temperature increase was desirable, so the constant 5.35 was used with the natural log of two.

How come then the addition of 100 ppm CO2 by humans since the industrial revolution only produced 0.6°C temperature increase? The result should have been 1.2°C (5.35 ln 380/280 x 0.75). As usual, the contrivers missed something which didn't fit their results.

Observers would often state that they would be unconcerned about a 1.2°C temperature increase; it would have to be 3-6°C to be worth spending a lot of money on.

How do you get the 3-6°C expected result, when the past produced a lot less, for doubling CO2 in the atmosphere? You simply muddle the subject.

So the contrivers quietly changed the expected result to 1.2°C upon doubling CO2 in the atmosphere while multiplying it due to feedback effects. This would have required changing the constant from 5.35 to 2.31. Where that number might have showed up in the peer reviewed literature, no one knows. This whole subject is impossible to trace down in the all-holy peer reviewed literature.

This little adjustment was a neat fix for the next problem. The science of global warming/climate change would have ended at that point, if someone hadn't thought of something more complex to evaluate. The chosen complexity was a feedback effect called forcing. The heat would cause more water to evaporate, and since water is a stronger greenhouse gas than CO2, the CO2 effect could be multiplied by the increase water vapor effect. To pin down the amount of feedback/forcing, computer models could be used, and they would provide the rest of the subject of global warming/climate change.

To get from the 1.2°C of the fudge factor to the desired 3-6C temperature increase, the multiplying factor due to water vapor forcing was found to be three. Computer models produced this number.

But there's still another glitch (as there always is when contriving to show one and one equals three). If the future 1.2°C is going to be multiplied times a factor of three due to water vapor, why would not the past increase be multiplied by the same factor of three? But of course, it is. The increase in CO2 only increased the temperature by 0.2°C in the past, while water vapor multiplied it to 0.6°C, which is the amount humans supposedly caused based on thermometer measurement analysis of Phil Jones and cohorts.

But that fix didn't fix everything either. To get 0.2°C for the past human input out of the fudge factor, the constant would have to be 0.873. You can't change this constant for different purposes; it's supposed to be a law of physics; and there would be no fudge factor without a constant.

Now the problem is that if this new constant (0.873) is applied to the expected doubling of CO2 in the future, the end result is 0.45°C temperature increase, not the desired 1.2°C. If the 0.45°C is multiplied times a feedback factor of three, it's only a 1.35°C total temperature increase with forcing. But observers would not be concerned with that amount.

In other words, there is no way to get the desired 3-6°C temperature increase upon doubling CO2 in the atmosphere, when humans supposedly increased the temperature by only 0.6°C since the industrial revolution by increasing the CO2 in the atmosphere from 280 ppm to 380 ppm.

This contradiction cannot be resolved. Humans did not create enough supposed temperature increase in the past to point to the amount of temperature increase alarmists want to show for the future.

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