Study finds Climate TRACE database undercounts city vehicle emissions by 70%
8 reported
A new study from Northern Arizona University (NAU) has found that the Climate TRACE database, a global greenhouse gas emissions tool co-founded by former Vice President Al Gore, may significantly underestimate carbon dioxide emissions from cars and trucks in U.S. cities. Published in Environmental Research Letters, the study compared Climate TRACE data to the Vulcan onroad emissions database across 260 U.S. cities. Researchers reported that Climate TRACE’s vehicle CO2 emissions were, on average, 70% lower than those in the Vulcan database. In some cities, such as Indianapolis and Nashville, the discrepancy exceeded 90%. The study’s lead author, Kevin Gurney, a professor at NAU’s School of Informatics, Computing, and Cyber Systems, noted that a prior study had identified similar issues with Climate TRACE estimates for power plants. The researchers emphasized that while artificial intelligence has potential for emissions monitoring, transparency and rigorous scientific standards are necessary to ensure data accuracy and maintain public trust.
What’s reported
The study was conducted by Northern Arizona University and published in Environmental Research Letters on June 18, 2026.
Climate TRACE is a consortium co-founded by former Vice President Al Gore.
Researchers compared vehicle CO2 emissions data from 260 U.S. cities across the Climate TRACE and Vulcan databases.
Climate TRACE emissions were, on average, 70% lower than Vulcan’s onroad CO2 emissions.
In Indianapolis and Nashville, Climate TRACE emissions were more than 90% lower than Vulcan’s.
A prior study by the same researchers found similar issues with Climate TRACE estimates for power plants.
The Vulcan database has an uncertainty of about 14%, according to the researchers.
The study recommends strengthening Climate TRACE’s methods to improve accuracy for policymakers.
Key figures
Kevin Gurney, professor at NAU’s School of Informatics, Computing, and Cyber Systems (SICCS)
Bilal Aslam, SICCS postdoc and co-investigator
Pawlok Dass, research associate in SICCS and contributor
Al Gore, former Vice President and co-founder of Climate TRACE
Sources: ScienceDaily
