In recent work, we proposed the GHG index (GGI) as a central concept and administrative tool to determine border adjustments (BAs)—export rebates and import charges for covered products.1 With colleagues Jennifer Hillman and Mathew Porterfield (both at Georgetown University Law Center at the time), we initially developed the GGI in the context of a potential upstream US GHG tax. Our Framework report describes how GGIs could be used to determine border tax adjustments (BTAs) compatible with World Trade Organization (WTO) obligations.2 Among other criteria for WTO compatibility, the GGI incorporates relevant aspects of recognized international standards to determine the GHG emissions from an industrial facility and its supply chain, and then allocates them to products it manufactures (see Section 3 of the Framework). Essentially, a product’s GGI, which is expressed as tonnes of CO2 equivalent (CO2e) per tonne of product, multiplied by the GHG tax rate (US$ per tonne of CO2) determines its BTA (US$ per tonne of product). Note that the GGI itself does not depend on the policy used to set a GHG price. Rather, it is a technical metric, based on physical quantities associated with products (i.e., the carbon content of produced fossil resources and GHG process emissions required to create covered products used and produced by manufacturers). For that reason, the GGI could be used in the context of climate policies for BAs other than a GHG tax—or, more generally, as the basis for an international metric that associates GHG emissions with GHG-intensive products for various analyses and policies.