Int. J. Environ. Res. Public Health 2011, 8 1020 (1) There has been an upward trend in global temperatures since the 1970s, (2) ―Climate models predicted this well in advance, even getting the magnitude of the temperature rise roughly right.‖ This ―gives them enormous credibility.‖ (3) ―Models based on this research indicate that if we continue adding greenhouse gases to the atmosphere as we have, we will eventually face drastic changes in the climate.‖ My comments on these points are as follows: (1) Global temperatures have been trending upwards not just since the 1970s, but since the end of the Little Ice Age (see Figure 5 and Section 2.4.2), with what appears to be a superimposed 60-year cycle. So this upward trend existed long before there were significant anthropogenic GHG emissions, and the increases since the 1970s are hardly the most relevant observational data. (2) It is highly questionable whether the climate models used by the IPCC made any such predictions (see Figure 8, which shows the divergence between various IPCC scenarios shown in red, orange, and brown, with the actual satellite temperature measurements adjusted to surface in blue and adjusted ground temperature data in green; see also the green line in Figure 5). And there is no evidence that the climate models have even managed to correctly hindcast temperatures [4]. But even if they did so forecast, who predicted what and when provides no valid scientific evidence about whether the models can predict the future. So again this is not the most relevant observational data. (3) It is probably true that the IPCC models will continue to produce such results. Whether they have any predictive capability, however, is highly dubious for the reasons discussed in Section 1.2.1 Krugman‘s views on the coming apocalypse, however, are of considerable importance because they appear to form the basis on which he bases his final conclusions in the article. So Krugman recognized the importance of the science, but appears not to have asked the crucial questions necessary to validate his views in terms of whether they reflected the most relevant observational data and the scientific method. In the remainder of his article, Krugman explains that economists have supported two different approaches to climate change mitigation. He characterizes the first of these as a ―policy ramp‖ approach because it proposes that GHG emissions controls should start slowly and eventually be ramped-up to much higher levels that the proposers believe will provide adequate control to prevent CAGW. (He does not explain why this approach might make sense, but it postpones major expenditures so that the present discounted costs are much less.) He characterizes the second approach as a ―big-bang‖ approach in that emissions controls would initially be much nearer the levels that are thought to reduce emissions sufficiently to allegedly avoid CAGW. He then supports Weitzman‘s views (not referenced, but presumably [81]) concerning the difficulty that economics may have in analyzing programs that may have a low risk of uncertain but overwhelming impacts, and uses these concerns plus his own views concerning the importance and magnitude of these alleged CAGW effects of increasing atmospheric GHG levels to support the ―big bang‖ approach.