A U.S. Cap-and-Trade System to Address Global Climate Change proposes a specific cap-and-trade system with several key features including: an upstream cap on CO2 emissions with gradual inclusion of other greenhouse gases; a gradual downward trajectory of emissions ceilings over time to minimize disruption and allow firms and households time to adapt; and mechanisms to reduce cost uncertainty. Initially, half of the program’s allowances would be allocated through auctioning and half through free distribution, primarily to those entities most burdened by the policy.