The December 2009 Conference of the Parties to the United Nations Framework Convention on Climate Change in Copenhagen, Denmark marked a moment of truth for collective efforts to limit the greenhouse gas emissions that lead to global climate change.  The Copenhagen meeting built on efforts initiated in Bali, Indonesia at the UNFCCC's thirteenth Conference of the Parties.  The Bali Action Plan, adopted in Bali, suggests that two core principles of the current international framework for addressing climate change will carry forward.  The first principle is early action:  some parties, as a result of their level of economic development, should take early steps to reduce emissions while allowing developing countries to delay action.   The second principle is equivalent action:  similarly situated parties should take on similar commitments out of fairness to other parties.

This Note explores the tension between the principles of early action and equivalent action on the one hand, and the variable costs and benefits of addressing climate change on the other hand.  Part I maintains that the dual principles of early and equivalent action have become entrenched in the current international framework for addressing climate change.  Part II discusses how these principles are incorporated into the design of an agreement.  Part III posits that these principles have the potential to skew parties' incentives to participate in an agreement because of the variable costs of climate change.  Part IV assesses the Kyoto Protocol and argues that it failed to balance these principles successfully against the variable costs of climate change.  The Note concludes that the mechanism for managing this tension is a useful indicator of a future emission agreement's potential success.  It suggests that a successful agreement should allow short-term flexibility while measuring and verifying those actions in a way that provides long-term certainty for emissions reductions.