<b>Trade in Transition: Three Essays on Climate-Driven Changes in Comparative Advantage and Border Interventions</b>

<p dir="ltr">This thesis focuses on the impact of climate change and climate policy on international trade and production. Chapter 1 looks directly at the US trade balance and how climate impacts on different sectors individually and combined impact trade dynamics under a 3-degree Celsius warming scenario. Under 3-degrees warming, there is estimated to be a widening agricultural trade deficit despite an overall US trade balance improvement. Current science indicates that warming and elevated atmospheric CO₂ will have ambiguous results for crop productivity depending on crop type and geographic location, while increased heat stress makes livestock and human labor less productive. The differential impacts across regions will alter comparative advantage and shift the patterns of global trade. We find that the widening agricultural trade deficits persist, even as the overall US trade balance improves due to enhanced investment inflows. Chapter 2 explores the uncertainty embedded in climate economics research through climate and crop model estimates. By simulating crop impacts under the 3-degree Celsius warming scenario across eight crop models and five climate models, it is clear that although there are some key impacts showing likely gains in agriculture by Australia and production losses in the United States, most of the results show a large amount of uncertainty. Finally, Chapter 3 examines the impact of CBAM with a deep dive into the fertilizer markets. This Chapter employs a new version of the GTAP model that that allows for substitution between fertilizer and land (GTAP-FERT) and is augmented with disaggregated data from the GTAP-CE database to analyze the impacts of CBAM on fertilizer production and global trade patterns. Under CBAM, carbon leakage seen under the integration of carbon-intensive commodities into the carbon market in the EU is eliminated. Fertilizer production in the EU increases, but agriculture tends to move out of the EU and to regions facing cheaper inputs.</p>