Traditionally, analysis of the costs of cutting greenhouse gas emissions has assumed that governments would implement idealized, optimal policies such as uniform economy-wide carbon taxes. Yet actual policies in the real world, especially in large federal governments, are often highly heterogeneous and vary in political support and administrative capabilities within a country. While the benefits of heterogeneous action have been discussed widely for experimentation and leadership, little is known about its costs. Focusing on the United States, we represent plausible variation (by more than a factor of 3) in the stringency of state-led climate policy in a process-based integrated assessment model (GCAM-USA). For a wide array of national decarbonization targets, we find that the nationwide cost from heterogeneous subnational policies is only one-tenth higher than nationally uniform policies. Such results hinge on two critical technologies (advanced biofuels and electricity) for which inter-state trade ameliorates the economic efficiencies that might arise with heterogeneous action.

传统上，对减少温室气体排放成本的分析假设政府将实施理想化的最优政策，例如统一的经济范围内的碳税。然而，现实世界中的实际政策，尤其是大型联邦政府中的实际政策，通常是高度异质的，并且在一个国家内的政治支持和行政能力各不相同。虽然异类行动的好处已被广泛讨论以进行实验和领导，但对其成本知之甚少。以美国为重点，我们在基于过程的综合评估模型 (GCAM-USA) 中表示了国家主导的气候政策严格性的合理变化（超过 3 倍）。对于广泛的国家脱碳目标，我们发现，异质的地方政策在全国范围内的成本仅比全国统一的政策高出十分之一。这样的结果取决于两种关键技术（先进的生物燃料和电力），国家间贸易改善了异质行动可能产生的经济效率。