Study shows U.S. cities are underestimating their GHG emissions by nearly 20%

Cities have become increasingly involved in reducing greenhouse gas (GHG) emissions that are causing global climate change. Urban areas make up nearly 70 percent of these emissions, and city governments are proposing a number of policy actions aimed at reducing them. Many cities also make investments that detail their greenhouse gas emissions.

Now, Professor Kevin Gurney from the University of Northern Arizona School of Informatics, Computing, and Cyber ​​Systems and colleagues have compared the self-reported distribution investments published by 48 major cities of the United States. USA to estimates from a modern emissions information system. As described in Nature Communications, Gurney and his research colleagues discovered large differences and a systematic underreporting of urban-city distributions.

Gurney, who specializes in atmospheric science, ecology and climate policy, has spent the last two decades developing a standard system for measuring greenhouse gas emissions under the Projects. He has Vulcan and Hestia. The system, funded by the National Aeronautics and Space Administration (NASA) and the National Institute of Standards and Technology (NIST), will measure and image greenhouse gases emitted across the country to centers individual power, neighborhoods and roads.

The emissions estimates emanating from the system help identify problem areas and enable better decisions on where emissions will be cut most effectively. Two recent studies, both at the national (link) and inner-city Indianapolis, IN (link), have shown that Gurney’s estimates are consistent with estimates based on direct atmospheric analysis, a key independent type of assertion. independent.

Climate change policies in cities are advancing rapidly, and cities often rely on their self-reported investments when developing their policies, Gurney compared 48 of the those self-reported investments from U.S. cities to emissions assessed by its Vulcan information system. The cities in the study included New York, Chicago, Los Angeles, Dallas, Denver and Philadelphia.

“The results of this comparison were amazing,” Gurney said. “The differences were large and varied widely from one city to the next. When it was average, the self-reported emissions were nearly 20 percent lower than the estimated emissions. the Vulcan system. ” But that average doesn’t tell the whole story: for example, Cleveland, Ohio reported emissions 90.1 percent lower than the Vulcan estimate while Palo Alto, Calif., Reported 41.7 percent higher emissions the Vulcan estimates.

To prioritize emissions reduction, cities need to gain an unbiased understanding of their emissions. “The adjective‘ you can’t achieve the things you can’t measure ’is relevant here,” Gurney said. “Cities need a complete and accurate assessment of their emissions. Without it, they could focus on the wrong emission sources in their landscape to reduce emissions or think they are on a emissions path to achieve their target, when in fact they are not. “

For example, the city of Indianapolis is aiming for a 20 percent reduction in GHG emissions from buildings by 2025 compared to 2016 values. With the projection of 26.9 percent found in the study, it will be difficult to track keep track of this target or know when and if it has been achieved.

“Consistency in estimating emissions from one city to the next is also crucial for comparing and differentiating between different mitigation methods and policies,” Gurney said. “This will allow cities- large emission discount policies borrow from others with similar distribution characteristics. The inconsistencies in self-reported investments make it very difficult. “

The approach adopted by the research team uses a consistent approach across all U.S. cities, combining federal, state, and local data on a regular basis.

“Building urban greenhouse gas deposits is expensive and time consuming for cities,” said Geoffrey Roest, a NAU postdoctoral researcher and co-author of the study. “But we have emissions data for every city in the U.S., and we can collaborate with cities to help them make complete, accurate investments right from that data.” the research team found that the differences between the self-reported investments and Vulcan estimates were likely due to cities not reporting fuel or specific regions where local information was limited or difficult to come through.

“Vulcan data can be modified to meet the needs of different cities by incorporating local data” said Yang Song, NAU postdoctoral researcher and co-author of the study. “This will help cities identify the most effective strategies towards reducing real and lasting emissions with the support of the best science.”

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Data from the Vulcan project can be found on the Oak Ridge National Laboratory Data Archive. Additional images are available on the Vulcan website. A video describing Project Vulcan can be found online as is an animated video of the results of Project Vulcan. This research was supported by a grant from the Aeronautics and Space Administration NNX14AJ20G, a grant from the National Institute of Standards and Technology 70NANB16H264N, and the French research program Make Our Planet Great Again (CIUDAD project).

Gurney joined NAU in 2018, where he is continuing the research that began at Purdue and Arizona State University. He has been involved with the United Nations Climate Change Framework Convention and the Kyoto Protocol for 25 years and is a lead author for the Intergovernmental Panel on Climate Change (IPCC). In addition to his interests in carbon cycle science and policy, he has worked on stratospheric ozone depletion, radionuclide dose evaluation, energy systems and climate-economy modeling.

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