Int. J. Environ. Res. Public Health 2011, 8 1004 Table 1. Correlation of various physical attributes with global temperatures. Source: d‘Aleo [47]. Factor Years Carbon Dioxide (CO2) 1895–2007 Total Solar Irradiance (TSI) 1900–2004 Ocean Warming Index (PDO and AMO) 1900–2007 Carbon Dioxide Last Decade 1998–2007 Correlation (Pearson Coefficient) 0.66 0.76 0.92 –0.14 Correlation Strength (R-squared) 0.43 0.57 0.85 0.02 It is very clear that the strongest correlation is between the ocean warming index consisting of the Pacific Decadal Oscillation plus the Atlantic Multidecadal Oscillation (PDO + AMO) and temperatures; the next strongest is with total solar irradiance (TSI), and the weakest is with CO2. In fact, CO2 has no explanatory power over 1998–2007 decade according to this analysis. 2.4.2. Correlations of Global Temperatures with Other Explanations for Variations Another hypothesis by Orssengo [48] to explain temperature variation based on ground-based readings over the last 130 years assumes a gradually increasing trend presumably starting from the Dalton Minimum of the Little Ice Age with a 60-year cycle superimposed on it without reference to carbon dioxide or any of the other physical variables tried by d‘Aleo [47]. It is illustrated in Figure 5, which compares ground measurements of global temperatures with the hypothesis. This hypothesis may or may not prove to be accurate in forecasting future global temperatures, but Orssengo finds that it has an 88 percent correlation with past temperatures over the period studied. As shown in the figure, there are only a few years in the late 1890s and 1950s that do not appear to fit the hypothesis very well. So no strong support for the IPCC‘s CO2 hypothesis is evident here either. Figure 5. Graph depicting Orssengo‘s hypothesis concerning global temperatures. Source: Orssengo [48].