It should be noted that the upper left plot is for the measured increases in CO2 concentrations and those increases in water vapor which Santer and others believed would result from the warming caused by the CO2. Most of the actual warming in this model is actually provided by the increase in the amount of water vapor, which is greatest in the Earth's warmer areas. The warming of this extra water vapor over the Equator and nearby latitudes produces the hot spot over the equator and near it. The enhanced warming due to water vapor is what is termed a positive feedback and is a situation which is inclined to be susceptible to run-away events in which a vicious cycle of CO2 and water vapor in the atmosphere lead to more and more heating, then more and more CO2 and water in the atmosphere and more and more heating. This is an important assumption of this theory and forms its primary basis for the claim that catastrophe may result.
We should note that only direct changes in the solar irradiance are modeled here. The changing flux of cosmic rays as solar activity varies with changing affects on cloud formation and the ozone layers are not included. Many other natural effects are also not included since little was known about them in 2000 and not much more is known today, thanks to the misspending of most of the climate research funds due to the alarmist scare. But, if the factors modeled are the most important factors pertaining to climate change, such features as the very prominent hot spot near and above the equator at altitudes of 8 to 12 km with elevated temperatures of 1.0 to 1.2C should be measured by balloons equipped with transmitters to send back temperatures measured as the balloon ascends to high altitudes in the atmosphere. There are good records going back to the 1960s with hundreds of balloon flights having the ability to measure temperatures with an accuracy of better than 0.1C.
The actual measured warming from 1979 to 1999 in the atmosphere by balloons is shown below. This is Part E of Fig. 5.7 on page 116 of the U.S. Climate Change Science Program Report of 2006.