U.S. Cities are NOT Vastly Undercounting Emissions

City climate accounting standards are consistent methods that capture emissions most policy-relevant to local governments

For Immediate Release: 02/05/21

On February 2, 2021, Nature Communications published a study whose results indicate an under-reporting of city-level greenhouse gas (GHG) emissions across 48 U.S. cities. The GHG accounting method in the study is atypical in local GHG accounting, it is not fully comparable with city inventories, and does not address some of the key policy levers that drive cities to conduct GHG inventories and develop GHG mitigation strategies.

Key Points:

  • Two of the greenhouse gas (GHG) accounting protocols referenced in the Nature Communications Study, commonly used by U.S. cities, are consistent, accurate methods that capture the GHG emissions and removals that are most policy-relevant to local governments. Self-reported inventories are a management tool to prioritize action.
  • The Nature Communications Study approach produces insights into gross GHG emission sources in one area, but it does not attribute the emissions directly to local activities. Not all CO2 emitted within a city boundary can be influenced by city policies or advocacy.
  • The Nature Communications study highlights the need for innovation to make inventory development easier and more informative. ICLEI’s tools, data, and partnerships remove complexities and lower costs to improve cities’ ability to actively reduce their GHG emissions.

The methods aren’t wrong: cities have and use consistent protocols that measure and manage emissions and removals (see the technical FAQ)

“The common refrain ‘you can’t manage what you don’t measure’ implies that what is being measured is manageable,” stated Angie Fyfe, Executive Director at ICLEI Local Governments for Sustainability USA (ICLEI). “This is why local government practitioners developed community GHG accounting protocols to provide actionable results for decision makers and align with national inventories for multi-level collaboration. To imply that cities have erred in reporting emissions is misleading and does a disservice to the thousands of local governments doing their part to solve the climate crisis.”

For nearly a decade, communities have created GHG inventories using the U.S. Community Protocol for Accounting and Reporting of Greenhouse Gas Emissions (USCP). The USCP details science-based methodologies and best practices to guide local governments as they measure and report the GHG emissions and removals associated with their communities. ICLEI developed the USCP in 2012 with input from a field of experts at the World Resource Institute, the US Environmental Protection Agency, and more than 80 cities, state agencies, foundations, and universities. From the ICLEI USA website alone, the protocol has been downloaded more than 5,700 times as of January 2021.

A similar Global Protocol for Community Greenhouse Gas Emissions Inventories (GPC) released in 2014 was developed through a parallel process with international stakeholders including ICLEI, the World Resource Institute, and C40. The USCP and GPC are very well aligned with each other in their focus on policy-relevant emissions accounting. There are some minor differences between the GPC and USCP in which minor emissions sources are required and the USCP includes more information on data sources available in the US.

The USCP and GPC were developed to provide local policymakers and their communities with the most appropriate understanding of how their community’s activities translate into GHG emissions. It allows policymakers to focus on the actions for which they have the best opportunity to reduce emissions and increase carbon sinks.

The overall approach used in the Nature Communications study is not comparable to city inventories and is less policy-relevant for local governments

The study uses a new approach to CO2 monitoring that measures changes in fossil fuel-based CO2 concentration in the atmosphere over cities, and attempts to work backwards and allocate those changes to different sectoral emissions. There can be uncertainty in this backtracking approach based on assumptions made about the starting/background CO2 concentration in air, uncertainty in the location of industries even by a small distance in/out of city boundaries; consideration of power plant emissions within city boundaries even if the power is effectively exported; and potentially using different estimates of vehicle miles traveled compared to what was publicly available to cities. Additionally, the Vulcan method also does not capture many activities relevant to city policy such as reducing electricity use or reducing generation of municipal solid waste. It likely will provide better estimates of industrial purchases of gas and petroleum not reported to cities by utilities, and aircraft landing and take-off emissions, although some cities are going a step further and accounting for all fossil fuel used by aircrafts.

“The paper presents a novel way to track CO2 emissions directly over land. However, a purely territorial approach to CO2 accounting does not fully match up with urban policy levers. Not all CO2 emitted within a city boundary, such as from ports and large exporting power plants can be influenced by city policies. And some of the key urban policy levers, such as energy efficient buildings that save electricity (often imported into cities), or efforts to reduce waste currently being disposed to distant landfills, would not be captured by the territorial accounting approach ” said Anu Ramaswami, Professor of Civil and Environmental Engineering and the Princeton Institute for International and Regional Studies. The purely territorial approach is what the NIST / NAU team used.

ICLEI and cities continue to innovate to make inventories easier and more informative

GHG inventory development need not be complex or expensive. ICLEI’s ClearPath™ GHG emissions management software application has been used by 738 jurisdictions to create nearly 1,000 GHG Inventories, forecasts, climate action plans, and to monitor progress over time. 

There is a need to improve access to the data local governments rely on for GHG inventory development and reducing emissions. First announced last September, ICLEI USA’s partnership with Google’s Environmental Insights Explorer is an example of a streamlined and improved GHG inventory and emissions management process. Also important will be the development of benchmarks for energy usage data from utilities and mobility data emerging from new sources, such as cell phones.

We welcome new data products and tools such as Vulcan referenced in the Nature Communications study, where they can be appropriately used to improve measurement of particular emissions sources, link to human activities on the ground, and inform policy decisions.

The USCP and GPC are designed to encourage innovation and improvement in city inventories. The USCP was updated in 2019 to add guidance for cities that want to include carbon removal from the atmosphere by forests and trees, as well as emissions from loss of forests and trees. 

The USCP requires all inventories to include five emissions-generating activities associated with human activities in cities: electricity use, fuels used in buildings, on-road transportation, solid waste, and energy associated with water use. In addition, the USCP encourages cities to look at other approaches such as infrastructure supply chain and consumption-based emissions to account for goods and services consumed within the city boundary that have a carbon footprint associated with production occurring outside of the political boundary. 

The USCP provides local governments with the option to include emissions associated with production occurring outside of the boundary and resulting in consumption within the boundary – food production and consumption, for example.  ICLEI USA partnered with Philipstown, NY, to model such a consumption-based approach. Like the approach in the Nature Communications study, a consumption-based inventory yields different results than does a conventional inventory.  It is used to identify different types of actions.

ICLEI USA developed this technical FAQ for local government practitioners and policymakers in need of a detailed comparison of the methods.


ICLEI USA is the United States country office of ICLEI-Local Governments for Sustainability and the leading technical experts on greenhouse-gas emissions accounting, climate action, and resilience and sustainability planning. Along with our ClearPath tool for local greenhouse gas emissions accounting, we remain firmly positioned as the experts in the industry through our development of the U.S. Community Protocol for Accounting and Reporting of Greenhouse Gas Emissions, the Local Government Operations Protocol, and the Recycling and Composting Protocol.

ICLEI–Local Governments for Sustainability is the leading global network of more than 1,750 local and regional governments committed to sustainable urban development. Active in more than 100 countries, we support local governments to deliver their self-determined sustainability policy and drive local action for low-emission, nature-based, equitable, resilient, and circular development. Our members and team of experts work together through peer exchange, partnerships, and capacity building to create systemic change for urban sustainability.

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