Abstract: Over the last half decade, a variety of federal legislative proposals for limiting greenhouse gas (GHG) emissions have been put forward, most of which would set a price on carbon. As of early 2013, the one politically plausible policy appears to be a carbon tax, passed as part of a larger fiscal reform package. Meanwhile, the US Environmental Protection Agency has begun regulating GHG emissions from a variety of sources using its authority under the Clean Air Act. It may be necessary to choose between these two policies, however. The Waxman–Markey cap-and-trade bill that failed in 2009 would have preempted much of this authority, and it appears likely that a carbon tax law would do the same. But how can one make this choice? What are the key questions and issues to consider? The purpose of this paper is to compare these policies. Our aim here is therefore not to determine whether an exchange is wise or unwise. Instead, our intention is to give policymakers and other interested readers an impartial assessment of both policies and, in particular, the features that are important to a comparative evaluation. We don’t give answers, but hope at least to give the right questions to ask.

Abstract: A carbon tax will interact with other policies that are intended to reduce carbon dioxide emissions and encourage clean sources of energy and energy efficiency. This paper examines these policy interactions. A well-designed carbon tax can be an efficient instrument for reducing emissions, yet whether it will be implemented in an efficient manner is uncertain. A legislatively determined tax may not fully reflect up-to-date scientific and economic information. Behavioral and institutional factors suggest that a tax may not have its fully intended effect. These considerations suggest that climate policy should and will continue to be a complex mix of regulaions at various levels of government, even with a carbon price. Nonetheless, the possibility of unintended interactions among policies remains. The role for policies to encourage renewables and energy efficiency depends on the stringency of the carbon tax and presence of externalities related to technological learning and the energy efficiency gap.