December 2, 2022 — The most important task in confronting global climate change is the need to enforce serious quantitative limits on Greenhouse Gas emissions, such as the Nationally Defined Contributions which were originally negotiated in the 2015 Paris Agreement. The 27th Conference of Parties to the UNFCCC, which concluded in Sharm-el-Sheikh November 20, did not tackle this task. Carbon border equalization measures, including tariffs against carbon-intensive imports from lax countries, might supply the teeth that have been missing from such agreements. But they also risk advancing protectionism, which would ultimately slow the needed global energy transition. Adjudicating the fairness of carbon tariffs would be a good job for a reinvigorated WTO.