Econometrica · 2025 · [{"name": "Farid Farrokhi", "affiliation": ["Boston College"]}, {"name": "Ahmad Lashkaripour", "affiliation": ["Indiana University – Purdue University Indianapolis"]}]
中文摘要
贸易政策常被视为解决国际气候协定中搭便车问题的一种方案。本文考察贸易政策在多大程度上能够兑现这一承诺。我们将碳的全球供应链与气候外部性纳入一个多国、多行业的一般均衡贸易模型。通过推导最优碳税与边境税的理论公式，我们量化了两种贸易政策方案应对搭便车问题的最大有效性。在现有关税基础上加征最优碳边境税基本无效，仅能实现全球最优碳定价下可达成效果的3.4%。相比之下，Nordhaus（2015）提出的气候俱乐部框架——将边境税用作威慑搭便车的或有惩罚——可实现全球最优碳减排量的33%至68%，具体取决于初始联盟（欧盟、欧盟+美国，或欧盟+美国+中国）。在所有情形下，气候俱乐部均确保普遍合规，从而维护自由贸易。
Abstract
Trade policy is often cast as a solution to the free‐riding problem in international climate agreements. This paper examines the extent to which trade policy can deliver on this promise. We incorporate global supply chains of carbon and climate externalities into a multi‐country, multi‐industry general equilibrium trade model. By deriving theoretical formulas for optimal carbon and border taxes, we quantify the maximum efficacy of two trade policy solutions to the free‐riding problem. Adding optimal carbon border taxes to existing tariffs proves largely ineffective, delivering only 3.4% of what could be achieved under globally optimal carbon pricing. In contrast, Nordhaus's (2015) climate club framework, in which border taxes are used as contingent penalties to deter free‐riding, can achieve 33–68% of the globally optimal carbon reduction, depending on the initial coalition (EU, EU + US, or EU + US + China). In all cases, the climate club ensures universal compliance, thereby preserving free trade.