Regulatory instruments for greenhouse gas control present a policy dilemma: Market-based instruments such as cap and trade function to reduce regulatory costs;, but because they provide no guarantee that costs will be reduced to acceptable levels it is infeasible to set caps at sustainable levels. Emission taxes provide cost certainly, but their comparatively high cost makes it infeasible to set tax rates at levels commensurate with sustainability goals. However, there is a straightforward solution to this dilemma: Just as cap and trade uses free allowance allocation to minimize regulatory costs, an emission tax's cost can be mitigated by refunding tax revenue in such a way that emission reduction becomes profitable. A refunded tax, like cap and trade with free allocation, Would be revenue-neutral within the regulated industry. Marginal competitive incentives for commercializing emission-reducing technologies would not be diminished by the refund, and the refund could actually make it politically and economically feasible to increase the incentives by an order of magnitude. Whereas cap and trade merely caps emissions at an unsustainable level while subjecting the economy to extreme price volatility, refunded emission taxes could create a stable investment environment with sustained incentives for emission reduction over a long-term investment horizon. (c) 2006 Elsevier Ltd. All rights reserved.