Measuring the Elements of Climate Change: Greenhouse Gases

By Mark Tausig

Discussions of climate change often refer to phenomena such as global warming and increased greenhouse gas emissions.  Ever wonder how we measure such things?  How do we know that the global temperature has increased? How do we measure greenhouse gas amounts? What about decarbonization, tree canopies, auto and truck emissions, sea-level rise, glacier melting, and environmental justice? 

In this series, we will learn how climate change indicators are measured and how they change over time. The reliable and ongoing measurement of these conditions is essential for monitoring the health of our planet and promoting smart and effective policies.  

Part 2: Greenhouse Gases

Greenhouse gases are gases that trap heat from the Sun in the Earth’s atmosphere.  By allowing sunlight to pass through, but absorbing the infrared heat radiating from the planet, they drive the “greenhouse” effect. The greenhouse effect is both a natural process where atmospheric gases trap heat from the Sun, keeping the Earth warm enough to support life and one driven by human activity. Human activities—like burning fossil fuels, agricultural processes and deforestation—have intensified the natural process by adding excess gases to the atmosphere. This buildup causes the atmospheric “blanket” to become thicker, trapping more heat than the planet naturally releases. This phenomenon is the direct cause of modern global warming.

The table below charts the increase in greenhouse gases since the year 0.  The table shows that the concentration of greenhouse gases was low and stable until around 1850.  This reflects the “natural greenhouse effect.” However, since the 1850s, there has been a steep increase in such gases, referred to as “the enhanced greenhouse effect” that is driving the current global warming and climate change.  The enhanced greenhouse effect is entirely driven by human activities.  

Generally, we measure four greenhouse gases;  Carbon dioxide, responsible for 80% of such gases, Methane, responsible for 11% of gases, Nitrous oxide, 6% and Fluorinated gases, accounting for 3%.  

To measure the actual concentration of gases from a “top-down” approach, scientists use a combination of ground-based, airborne, and space instruments to measure ambient GHG concentrations in parts per million) or parts per billion in a specific region. To track emissions from human activities using a “bottom-up” approach, countries use international guidelines set by the Intergovernmental Panel on Climate Change (IPCC).  These include; activity data in which scientists multiply known polluting activities by predetermined emissions factors and, standardization in which the different gases that trap different amounts of heat, are converted to CO2 equivalents. Tracking can also be based on the actual concentration and volume of gas physically emitted from a smokestack or industrial exhaust.

Greenhouse gases are measured with different uses and objectives in mind.    Unlike the measurement of global warming that is, by definition global, greenhouse gas are measured at the global, national, regional and local levels and by industry, type of gas, source and economic sector depending on the purpose of such measurement.

Global Level

At the global level, there is no single organization that actively collects data on greenhouse gas levels.  Rather, estimates are compiled by aggregating national reports and research databases (bottom up) or from direct observation (top down).  The methods and objectives of reports vary.  The Intergovernmental Panel on Climate Change (IPCC) develops the internationally recognized methodologies and software used by countries to calculate and report their national GHG inventories. The United Nations Framework Convention on Climate Change (UNFCCC) collects and compiles those official national GHG inventories, and, the World Resources Institute (WRI) & World Business Council for Sustainable Development (WBCSD) co-convene the Greenhouse Gas Protocol, which provides the foundational accounting standards used globally by companies to measure and report emissions. The World Meteorological Organization (WMO) observes and publishes actual atmospheric greenhouse gas concentrations, utilizing a network of monitoring stations worldwide.

U.S. Federal Level

At the national level in the United States, the EPA is phasing out its mandatory collection of detailed corporate greenhouse gas data. Following a major policy shift under the Trump administration, the EPA released a formal proposal to permanently eliminate reporting requirements for 46 out of 47 source categories within the Greenhouse Gas Reporting Program (GHGRP). This decision effectively ends the agency’s 15-year mandate requiring the nation’s largest industrial polluters, power plants, and fuel suppliers to publicly report their facility-level emissions. The agency also announced it will not maintain its electronic collection systems—the Electronic Greenhouse Gas Reporting Tool (e-GGRT) or public databases like FLIGHT—for future reporting cycles. Historically, the EPA used facility data to build its annual Inventory of U.S. Greenhouse Gas Emissions and Sinks for the United Nations. While high-level national estimates may still be modeled using broad economic data, the loss of precise, localized facility measurements will significantly reduce the accuracy of future U.S. climate tracking.  

And on the GHG emissions side, the EPA has revoked or seeks to revoke limitations on GHG emissions from the fossil fuel, transportation, electricity production, and building industries.  It has further delayed GHGRP (greenhouse gas reporting program) deadlines, with the intent of removing the requirement before the report is due.  The annual report would document sources of GHG emissions from fuel and industrial gas suppliers, as well as from CO2 injection sites.  Without data, there is no problem to document.

However, NOAA continues to collect greenhouse gas (GHG) data through the Global Monitoring Laboratory (GML). NOAA continues to actively operate a globally distributed network of air sampling sites, measuring continuous and discrete levels of carbon dioxide, methane, nitrous oxide, and other trace gases. 

What is happening at the federal level shows how the politics of climate change can alter the means by which we measure and compile important climate related data and how we might act in regard to these data.

New York State Level

Some states continue to be committed to collecting and aggregating GHG emissions because such measures are useful for state and local purposes. 

New York State collects greenhouse gas (GHG) emissions data primarily through the Department of Environmental Conservation (DEC) via its Statewide Greenhouse Gas Emissions Report.   This emission inventory is designed to meet the requirements of the Climate Leadership and Community Protection Act (CLCPA), measure progress at reducing greenhouse gas (GHG) emissions, and to make GHG information accessible to a broad audience. 

Starting with the 2026 data collection year, New York requires direct emissions reporting. The program collects emissions data from; any site emitting 10,000 metric tons or more of CO? equivalents per year, electric power entities and fuel suppliers delivering to end-users, transporters moving waste out-of-state that generates 10,000+ metric tons of CO? equivalents and, suppliers of fertilizers, and large anaerobic digestion or liquid storage facilities. 

However, the 2026 revisions of the CLCPA also includes a modification of the GHG accounting methodology that shift from a 20-year to a 100-year global warming potential basis. Critics argue this change makes the state’s emissions appear lower without requiring any actual additional reductions. Because New York’s building and power sectors remain heavily reliant on natural gas, this accounting change meaningfully reduces the state’s reported emissions total without requiring any additional operational changes. 

Overall, however, New York State continues to collect GHG data that make it possible for state and local entities to make decisions related to climate action.

New York City Level

At the local level, in New York City, the most notable reporting requirement for property owners comes under the NYC Climate Mobilization Act (2019). The requirement affects most buildings over 25,000 gross square feet and owners must file annual reports showing whether their building complies with strict carbon intensity limits.

The Mayor’s Office of Climate & Environmental Justice also annually releases two primary inventories, the Citywide Inventory that measures all GHG emissions across the five boroughs, including energy use, transportation, and waste and, the Government Inventory that tracks and measures emissions specifically from municipal operations (e.g., city buildings, vehicle fleets, wastewater treatment).

Collecting data on GHG is foundational to responses to global warming because GHG lead to global warming.  At the same time the measurement of GHG is useful at the national, state and city levels of political organization.  GHG can be measured at local levels and by industry, type of gas, source and economic sector and that enables action to reduce the production of GHG literally at their sources despite federal efforts to eliminate documentation of GHG emissions.  

Mark Tausig, Ph.D., is a volunteer writer for the New York League of Conservation Voters. He is a retired Professor of Sociology, where he studied health disparities, social networks, work and mental health, international health, and population aging in low—and middle-income countries. His latest book, Population Aging in Societal Context: Evidence from Nepal, will be published by Routledge later this year (2025).