Int. J. Environ. Res. Public Health 2011, 8 991 study shows that the outcomes of economic analyses of the climate change mitigation are critically sensitive to a number of scientific judgments which need to be very carefully examined for scientific validity. 1.2.3. Some Assumptions This article will assume that most of the economists who have attempted to value the economic benefits of climate change remediation have directly or indirectly tried to use the then most recent version of the IPCC assessment reports as their guide to the science. Some may have been more or less successful in doing so, of course. But in order to make some more general points with regard to how economic analyses of such hypotheses might best be carried out, there is no other easy way to do so other than by making this assumption; further, this seems to be the underlying unifying assumption of all the previous analyses discussed in this article. Thus by questioning a particular aspect of the IPCC‘s analyses, it is assumed that all of the economic analyses are questioned in this respect. Each economic analysis is different in what it computes the benefits will be, what discount rate is used, etc., but most appear to strive towards using IPCC science in determining what the economic benefits of climate change mitigation might be as it was known at the time the analysis was done. 1.3. Why Economists Also Have a Responsibility to Consider the Lowest Cost Alternative In doing benefit-cost analysis economists can usually select from a variety of alternative ways to achieve the benefits being valued. If they select a higher cost alternative for their analysis, they are putting the action being valued at a disadvantage relative to using the lowest cost alternative. So although the action might be economically efficient using the lowest cost alternative, it might not be using the higher cost alternative. In any case it would be more efficient using the lowest cost alternative. I will take the viewpoint that economists would be able to make a more useful policy contribution by pointing out whether lower cost alternatives exist so that users can determine what the meaning of the conclusions reached might be in terms of all the options available. Some of these alternatives may have unquantifiable disadvantages compared to higher cost alternatives, but this needs to be pointed out so that policy analysis users can select the best possible option rather than simply ignoring or not discussing these lower cost alternatives as too often happens, particularly in the case of climate change. 1.4. Outline of the Article Section 2 will discuss what the economic benefits are of the major solution offered by CAGW proponents for mitigating climate change, namely reducing emissions of greenhouse gases (GHGs) into the air as a result of human activities. Section 3 will discuss several major problems with previous determinations of economic costs. Section 4 discusses how these changes affect benefit-cost analyses of the problem. Section 5 will provide selected comparisons between the conclusions reached in this paper with those of other economists. Section 6 will summarize the major conclusions from the paper.