Cities across the US are under-reporting their greenhouse gas emissions by an average of 18.3%, according to a new study cited in the journal Nature Communications. The results of the study, Under-Reporting of Greenhouse Gas Emissions in US Cities, raise concerns about the self-reported inventories (SRIs) of cities, particularly when it comes to setting emissions baselines and targets.
The paper compares cities’ SRIs to data reported in the Vulcan Project, which estimates emissions consistent with atmospheric measures.
The most common differences between the SRIs of US cities and Vulcan Project data are related to three factors:
—SRI omission of petroleum fuel use and point source emissions in the industrial/commercial sector;
—different accounting perspectives on marine shipping and airborne emissions; and
—different methods in onroad emission estimation.
The findings underscore the importance of developing a standardized method of accounting for GHG emissions, the authors say. Most cities follow one of a few publicly available protocols to develop the numbers they use in their self-reported inventories (SRIs), however there is no “systematic, peer-reviewed assessment of SRI quality or accuracy.”
The challenges of inconsistent and inaccurate reporting are particularly important when placed in the context of reduction targets. For example, the city of Indianapolis has indicated that it aims to make a 20% reduction in building GHG emissions between by 2025 relative to 2016 values. However, with the 26.9% underestimate found in the study, it will be difficult to know when and if this target is truly achieved or to track progress towards it.
Other cities found to be significantly under-reporting emissions include Los Angeles, which under-reported by 50%, and Chicago and New York, each under-reporting by about 20% (via Reuters).
