Int. J. Environ. Res. Public Health 2011, 8 1003 The data are far from perfect, of course, perhaps in part because of a lack of effort to gather it. But the available evidence based on empirical data (rather than models) tell the same story. This means that the hypothesis should be rejected scientifically based on current information. Future testing could lead to other conclusions, of course, but for now rejection is the only rational course of action. It is quite possible that further research may yield a different conclusion, but as of the time that this is being written the evidence strongly supports a negative feedback and a much lower CSF, and this is why a much lower CSF will be used in this paper and why I believe it needs to be by other analysts as well. The important implications of this change in the CSF for the analysis of the economic benefits of CO2 emissions reductions will be discussed in Section 2.6.2 below. It may be useful to provide some explanation why it is that feedback is negative. One explanation is that the IPCC models are not able to represent the effects of clouds very well. There is some evidence, however, that clouds play a very important role and that their net effect on a worldwide basis may be negative [46]. 2.4. Hyposthesis 3a: Changes in Global Temperatures Are Primarily Influenced by Rising Levels of GHGs Other Than Water Vapor in the Atmosphere If CO2 has such a major role in determining global temperatures as the IPCC and CAGW supporters claim, it should be possible to discern its influence in the available related real world data. This line of inquiry is consistent with the theme of this article that reliance should be placed on real world data rather than computer models in determining the validity of hypotheses concerning climate. The comparisons made in this section do not prove the validity or invalidity of the various hypotheses offered by CAGW supporters. But they do serve as a credibility check on whether the above findings that the two key hypotheses 1 and 2 are invalid are likely to be correct. If there is clear evidence that hypothesis 3a is correct, one might reasonably suspect that the conclusions with regard to hypotheses 1 or 2 might be incorrect despite the overwhelming real-world evidence that the invalidity conclusions are correct, and vice versa. Five lines of evidence will be presented in this section in the following subsections: 2.4.1 Correlations of various physical attributes with global temperatures. 2.4.2 Correlations of global temperatures with other explanations for variations. 2.4.3 Decrease of temperatures during periods of rising CO2. 2.4.4 Increases in satellite-measured temperatures show no indication of CO2 influence. 2.4.5 Lack of influence of CO2 on temperatures over the last three million years. 2.4.1. Correlations of Physical Attributes with Global Ground-Based Temperatures A review of the available data correlating CO2 levels with global temperatures over the last 110 years makes hypothesis 3 highly suspect. Perhaps the simplest way to demonstrate this is to correlate various factors with global temperatures. One such study [47] found the following for three such factors (see Table 1):