It is in this context that the United States and other developed countries agreed both to reduce their own emissions to help stabilize atmospheric concentrations of greenhouse gases and to take the lead in reducing greenhouse gases when they ratified the 1992 United Nations Framework Convention on Climate Change (UNFCCC). This global context raises two issues for S. 2191 : (1) whether S. 2191 ' s greenhouse gas reduction program and other provisions would be considered sufficiently credible by developing countries so that schemes for including them in future international agreements become more likely, and (2) whether S. 2191 ' s reductions meet U.S. commitments to stabilization under the UNFCCC and occur in a timely fashion so that global stabilization may occur at an acceptable level. Conclusion

This report examines six studies that project the costs of S. 2191 to 2030 or 2050. It is difficult (and some would consider it unwise) to project costs up to the year 2030, much less beyond. The already tenuous assumption that current regulatory standards will remain constant becomes more unrealistic, and other unforeseen events (such as technological breakthroughs) loom as critical issues which cannot be modeled. Hence, long-term cost projections are at best speculative, and should be viewed with attentive skepticism . First, if enacted, the ultimate cost of S. 2191 would be determined by the response of the economy to the technological challenges presented by the bill. The potential for new technology to reduce the costs of S. 2191 is not fully analyzed by any of the cases examined, nor can it be. A considerable amount of low-carbon generation will have to be built under S. 2191 in order to meet the reduction requirement. The estimated amount of capacity constructed depends on the cases' assumptions about the need for new capacity and replacement/retirement of existing capacity under S. 2191 , along with consumer demand response to the rising prices and incentives contained in S. 2191 . Third, the cases suggest that the CCS bonus allowance allocation under S. 2191 is effective in encouraging deployment of CCS, accelerating development by 5-10 years. Fourth, the cases generally indicate that offsets could be a valuable tool for covered entities not only to potentially reduce costs, but perhaps more importantly, to buy time to further develop new, more efficient technologies. Cost could be lowered further by allowing greater availability of offsets and international credits and with a broader definition of eligible international credits. Fifth, the Carbon Market Efficiency Board could have an important effect on the cost of the program through its power to increase the availability of offsets and international credits. In this sense, the Board's powers could mesh with the previous insight about the importance of offsets and banking to the cost-effectiveness of S. 2191 . Sixth, the Low Carbon Fuel Standard could significantly raise fuel prices and limit supply. The effects will depend on what fuels are included in the LCFS, the level of emissions reductions achieved by alternatives, and the ability of suppliers to produce those alternatives. Seventh, S. 2191 ' s climate-related environmental benefit is best considered in a global context and the desire to engage the developing world in the reduction effort.
This report examines six studies that project the costs of S. 2191 (S. 3036) to 2030 or 2050. It is difficult to project costs up to the year 2030, much less beyond. The already tenuous assumption that regulatory standards will remain constant becomes more unrealistic, and other unforeseen events loom as critical issues which cannot be modeled. Long-term cost projections are at best speculative, and should be viewed with attentive skepticism. Despite models' inability to predict the future, cases examined here do provide insights on the costs and benefits of S. 2191.
First, the ultimate cost of S. 2191 would be determined by the response of the economy to the technological challenges presented by the bill. The potential for technology to reduce S. 2191's costs is not fully analyzed by any of the cases, nor can it be. Technology development is not sufficiently understood currently for models to replicate with confidence. Likewise, it is difficult to determine if available incentives are directed in an optimal manner. The cases suggest that S. 2191's Carbon Capture and Storage (CCS) bonus allowances would encourage deployment of CCS, accelerating development by 5-10 years.
Second, a considerable amount of low-carbon generating capacity will have to be built under S. 2191 in order to meet the reduction requirement. How much capacity will be necessary depends on new and replacement capacity needs, along with consumer demand response to rising prices and incentives contained in S. 2191.
Third, offsets could be a valuable tool not only to potentially reduce costs, but also to buy time to permit further development of new, more efficient technologies. Cost could be lowered further by greater availability of offsets and international credits and with a broader definition of eligible international credits.
Fourth, the Carbon Market Efficiency Board could have an important effect on the cost of S. 2191 through its power to extend the availability of offsets and international credits. In this sense, the Board's powers could mesh with the previous insight about the potential effect of offsets on the bill's overall costs.
Fifth, the Low Carbon Fuel Standard could significantly raise fuel prices and limit supply. The effects will depend on what fuels are included, the emissions reductions achieved by alternatives, and the ability to produce those alternatives.
Finally, S. 2191's climate-related benefit is best considered in a global context and the desire to engage the developing world in the reduction effort. The United States and other developed countries agreed both to reduce their own emissions to help stabilize atmospheric concentrations of greenhouse gases (GHGs) and to take the lead in reducing GHGs when they ratified the United Nations Framework Convention on Climate Change (UNFCCC). This context raises two issues for S. 2191: (1) whether S. 2191's GHG program would be considered sufficiently credible by developing countries so that schemes for including them in future international agreements become more likely, and (2) whether S. 2191's reductions meet U.S. commitments under the UNFCCC.