Modeling the Sea-Level Change from U.S. Vehicle Emissions

TL;DR

This study models U.S. vehicle emissions' impact on sea-level rise using advanced climate and sea-level models, revealing long-term and regional effects of emissions mitigation.

Contribution

It extends EPA's modeling framework with probabilistic methods and longer timescales to better quantify climate-sea level uncertainties and regional impacts.

Findings

Vehicle emissions mitigation reduces global sea-level rise by 1-2 cm by 2100.

Differences in sea-level rise grow to over 6 cm by 2200 with mitigation.

Regional effects are more pronounced along the Gulf of Mexico Coast.

Abstract

Recent U.S. Environmental Protection Agency (EPA) analyses have argued that greenhouse gas emissions from U.S. on-road vehicles contribute negligibly to global mean sea-level rise (GMSLR). Here, I replicate and extend the EPA's modeling framework using the FaIR climate model coupled with the BRICK sea-level model, incorporating a probabilistic weighting approach and a longer model timescale to better represent joint climate-sea-level uncertainty. In addition to the baseline SSP2-4.5 scenario and an EPA-consistent emissions reduction case, I examine alternative scenarios reflecting stalled technological progress and a counterfactual pre-regulation vehicle fleet. Results reproduce EPA estimates of approximately 1-2 cm of GMSLR reduction by 2100 under vehicle emissions mitigation but show that these differences grow substantially over multi-century timescales, exceeding 6 cm by 2200. Downscaling to U.S. coastlines reveals larger local effects, particularly along the Gulf of Mexico Coast. These findings highlight the long-term and regionally amplified benefits of emissions reductions from the transportation sector.