Equivalency Analysis of State-Level Air Pollution Emissions Estimates from an Integrated Assessment Model: GCAM-USA
The use of Integrated Assessment Models (IAMs) has expanded from their primary application, global climate assessment, to examine broader environmental trends such as air pollution emissions, including those at sub-national levels. While most IAMs are evaluated for internal validity, little literature evaluates IAM performance against real-world data. In this paper, 2015 estimates from the Global Climate Assessment Model (GCAM), an IAM, of state-level air pollution from five macro-economic sectors and six air pollutants, are tested against EPA data using two equivalency analysis tests. One-sided t-tests and regression analysis determine if modeled emissions fall within 20% of U.S. Environmental Protection Agency data. The results are mixed, showing that GCAM emissions estimates from only one sector and one pollutant pass both tests, and two sectors and two pollutants pass neither test. This indicates that GCAM-USA is more appropriate for examining national trends than specific sectors or pollutants at the sub-national level.