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.

We develop a general equilibrium model of international trade that incorporates imperfect factor mobility, product entry, and external returns to scale into a unified framework. The effects from these microeconomic channels can be summarized by two composite elasticities that govern supply and aggregation. We structurally derive export supply and import demand curves, develop a heteroskedastic estimator, and estimate supply, aggregation, and demand elasticities across international product markets. Employing our estimated model, we evaluate the impact of recent US protectionist policies and highlight the importance of our estimates and general equilibrium effects for tariff passthrough rates and cross-industry employment reallocations.

We examine the contribution of trade to the rise of modern agriculture, taking into account interactions between trade, input requirements, and technology adoption. We develop and estimate a new multicountry general equilibrium model that incorporates producers’ choices of which crops to produce and with which technologies at the level of grid cells covering the earth’s surface. We find that trade cost reductions in agricultural inputs and the international transmission of productivity growth in the agricultural input sector since the 1980s induced large shifts from traditional, labor-intensive technologies to modern, input-intensive ones, with important global and distributional implications for productivity and welfare.