The authors compare the targets and actions to which countries have committed under the Copenhagen Accord. The Accord allows participating countries to express their commitments to reduce greenhouse-gas (GHG) emissions in a variety of ways—most broadly, through economy-wide quantified emissions targets for developed countries and mitigation "actions" by developing countries. These are difficult to compare. However, even mitigation commitments that look similar can require very different levels of effort in different countries, and commitments that produce similar economic outcomes can look inequitable. These variations in effort and equity depend on historical patterns of energy use, marginal costs of greenhouse-gas abatement, choice of base year, methods for determining "business as usual" projections, and other factors.