Int. J. Environ. Res. Public Health 2011, 8 1017 So although SRM and other geoengineering approaches to controlling global warming have obvious problems such as who is to make the decisions and on what basis [62], it appears that they would accomplish the goal of reducing (or increasing for that matter) global temperatures at a far more reasonable cost and to do so fairly promptly and reliably. It would appear desirable for economists to at least analyze this possibility in discussions of the costs of CAGW control. One benefit of SRM is that it can be used entirely as a very low cost insurance policy until and unless there is strong evidence that global temperatures are increasing (or decreasing) rapidly. This insurance policy should entirely eliminate the need to be concerned about low probability, high consequence CAGW effects since action could be taken if and when needed rather than decades in advance as in the case of ERD. 3.4. Implications for the Costs of Climate Change If economists had carefully considered the scientific validity of the physical aspects of the environmental benefits and the costs of alternatives to emissions reductions they would have probably been less likely to recommend reducing global GHG emissions and more likely to have recommended geoengineering that although controversial has a high likelihood and low cost of controlling global temperatures should that be needed and desired. The possibility of using geoengineering eliminates the argument for pursuing very high cost GHG-mitigation alternatives as a safety hedge against small risks of CAGW outcomes since these low-cost approaches can be implemented very rapidly if they should actually ever be needed and if minimal research has been carried out in advance and a decision-making process has been put in place. Because mitigation measures do not have to be undertaken decades in advance, even these much lower operating costs can be postponed until there should be an evident need. 4. Implications for the Benefit-Cost Analysis of Climate Change Mitigation The broad results of this analysis to this point are that the economic benefits of climate change mitigation appear to be perhaps 1/100th of those assumed by most economic analyses because of real world data showing a much lower CSF and shorter CO2 residence times in the atmosphere than assumed by the IPCC. The costs, on the other hand, would appear to be about an order of magnitude higher because of technological and implementation problems recently identified. This means that ―conventional‖ benefit-cost analysis would conclude that the proposed climate change mitigation would be much more likely to fail an economic efficiency test than previously estimated. But the costs of control can be greatly reduced by adopting an entirely different approach to mitigation (geoengineering such as SRM) based on very promising but largely ignored technology. The costs of this promising but so far not carefully validated approach appear to be many orders of magnitude less expensive, albeit with possible new and also little researched risks. These costs are so low that climate change mitigation might actually be economically efficient if global temperatures should start decreasing rapidly (since SRM can be used on the temperature downside as well as the upside). This approach also removes concern about low probability, high consequence events arising from increasing global temperatures since geoengineering options such as SRM can be implemented