There are models that handle water vapor with some accuracy. They’re called weather models. They require fast supercomputers, and have some value for 3-14 days.
Weather is inherently chaotic. Therefore climate is inherently chaotic. Changes in CO2 must be correctly modeled on a daily and yearly basis before the model can be valid.
The so-called Global Climate Models (GCM) oversimplify, and cannot have the sensitivity needed to predict climate. Albedo changes (caused by changes in cloud cover at different altitudes) are critical. Ocean current changes are critical. The GCM do not model any of this in enough detail to pick up chaotic changes and their relative probability. In simple terms, Garbage In, Garbage Out (GIGO).
A good model would predict El Nino/La Nina events and their duration. A good model would have the sunspot cycle and its relation to cosmic rays, which affects cloud formation, rainfall, and albedo. A good model would have random generation of volcanoes.
A good model would have decreased high-sulfur coal burning in Russia and Eastern Europe, starting in 1989, which led to less cloud cover in the Northern Hemisphere , which led to temperatures almost as high as 1934 in 1998. A good model would have the Urban Heat Island effect, and its effects on the thermometer record in urban and rural areas.
The current GCMs, as designed by the Climate “Science” community, have none of this.
Yep. I would use the word "model" (in real world fidelity). The El Nino would not be predictable just as weather is not predictable. But in a realistic GCM it would occur with the same amplitudes and frequencies, on average, as observed in the real world. As for volcanoes, they have been added but not with decent fidelity because the dispersal of the particulates is quite complex, not well modeled and not well measured to be inputted as a parameter.