Methodologies for Measuring Emissions in the US are Improving

Methodologies for Measuring Emissions in the US are Improving

This Post was submitted by Climate Scorecard US Country Manager Nathan Holman


Best Organizational Source: “Inventory of U.S. Greenhouse Gas Emissions and Sinks” published by the US Environmental Protection Agency


Inventory of GHGs

The United States’ Environmental Protection Agency (EPA) publishes an annual report on greenhouse gas emissions, called the “Inventory of U.S. Greenhouse Gas Emissions and Sinks.” The latest report (published in 2021, containing data from 2019) can be found here:‌default/files/2021-04/documents/us-ghg-inventory-2021-main-text.pdf?VersionId=wEy8wQuGr‌WS8Ef_hSLXHy1kYwKs4.ZaU. The Inventory is the official estimate of the U.S.’ contribution to climate change. Other organizations that provide data on overall emissions from the country typically rely on the Inventory or its various sources.

This comprehensive report has been published every year since the early 1990s, although methodologies for estimating emissions have changed and improved over the years. The Inventory attempts to capture all emissions of greenhouse gases, across all sectors, and all carbon sinks to estimate the United States’ net contribution to climate change. The Inventory includes detailed breakdowns of emissions and sinks by sector and by gas. It also includes measures of uncertainty in the data and a thorough explanation of how the data is collected.

The information in the GHG Inventory is collected from various official publications. The Inventory’s long list of annexes contains detailed information on the data sources for each sector: Large emitters such as fuel and industrial gas suppliers are required to report their emissions through the EPA’s Greenhouse Gas Reporting Program (GHGRP) each year. That information is published in a separate report every October and then used in the annual GHG Inventory report as well.

The Inventory is prepared according to the standards set out by the United Nations’ Intergovernmental Panel on Climate Change (IPCC). As well, in assembling the Inventory, the EPA collaborates with hundreds of experts across government, industry, academia and environmental organizations. Information for each sector is analyzed and processed by sector-specific experts within the EPA to ensure that all estimates are well-informed.

Information Gaps and Issues

  1. Inconsistency and uncertainty

In large part, the Inventory relies on information that is self-reported by emitters. For example, information pulled from the GHGRP ultimately comes from industrial facilities who measure their own emissions. While the EPA prescribes the methodologies to be used in measuring those emissions (which align with IPCC standards), a lack of consistency in measurement can be expected. Some environmental organizations suggest companies and municipalities under-report their emissions. While it is difficult to determine whether under-reporting is actually occurring, a lack of consistency in measurements between facilities is certainly likely.

To address uncertainty in the Inventory’s estimations, a robust QA/QC (quality assurance and quality control) analysis is conducted by dedicated QA/QC coordinators. Uncertainties in the data are displayed throughout the Inventory along with qualitative descriptions of methodologies for calculating those uncertainties. Those analyses are conducted according to IPCC standards.

  1. Emissions abroad

The Inventory captures emissions in the United States – that is, gases that are released on U.S. soil. However, the report does not capture all emissions created by the U.S. economy. Many American companies have industrial operations in other countries, often manufacturing goods to be sold primarily to Americans. While the companies are headquartered in the U.S. and the consumers are in the U.S., the emissions are excluded from the U.S. data. Some organizations have tried to shine a light on the amount emissions the U.S. is responsible for abroad. One perspective can be found here:

Most Accurate Emissions Data

While the Inventory does not provide a straight-forward analysis of uncertainty by sector, it does set out the relative uncertainty of emissions estimations by gas. According to the report, CO2 is the most accurately estimated GHG. In particular, this captures the transportation sector, the electric power industry, the Industry sector (including combustion from industrial processes as well as the operation of industrial furnaces, motors, lighting, etc.), residential end-use, and commercial end-use (including lighting, heating, cooling, and operating appliances).

Improvements in Climate Data

Over the years, the data reported in the Inventory has become less uncertain, according to the EPA’s analyses. As climate change garners more attention from governments and businesses, methodologies for measuring emissions are improving.

In October of 2021, the United States’ National Oceanic and Atmospheric Administration (NOAA) launched a significant upgrade to its website, making climate and weather-related data more accessible to the public. For many, climate data can be difficult to find and even more difficult to understand. Fortunately, as climate change becomes a more central social and political issue, information is becoming better and more accessible.

Quality and reliability of the climate emissions data produced by the country:

Rating: *** Good

Four Stars (****): Outstanding

Three stars (***): Good

Two stars (**): Fair

One star (*): Poor



Vincent Camobreco, Environmental Protection specialist at the EPA



Climate change is real, and what governments do matters.

Help us work with key stakeholders globally to ensure continued support of the The Paris Agreement.