Tracking Greenhouse Gas Emissions: From Field Work to Strategy

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With a delicate hand, Anna Karion slides a large, enclosed box back into its protective shelf. She’s standing on top of a hill that overlooks the Washington D.C. area. This box, a greenhouse gas (GHG) sensor, is connected to a tube that runs up a tall, metal tower that is constantly collecting air samples. Karion, a research scientist with the National Institute of Standards and Technology (NIST), is working to fine-tune GHG measuring instruments installed in a telecommunications tower. This tower is one of 15 in the D.C. area that have been fitted for air-sampling and collectively make up the Northeast Corridor Urban Testbed Project. The technology in these instruments builds on nearly 30 years of research supported by the Department of Energy’s Office of Science and others through the AmeriFlux project. AmeriFlux measures changes in the environment across North and South America, including levels of carbon dioxide (CO2). The data these towers collect will enable a consortium of research groups, including the DOE, to better understand the movement of GHG at a global scale.

“Ultimately, we’re getting contextual information that becomes extremely useful to a lot of different people,” Karion said.

This work is a part of a larger strategy developed by the Greenhouse Gas Monitoring and Measurement Interagency Working Group. The effort, as described in a recent White House release, aims to unify GHG measurement, monitoring, and information efforts across the federal government and beyond. The data from AmeriFlux provided much of the foundational science needed to develop the report.

“This is foundational, basic science,” said Dan Stover, a program manager with the DOE Office of Science who provided background expertise to the White House report. “The applied work can’t happen without it and it’s why we’re supporting it now.”

This publicly available information from AmeriFlux is being used to validate changes as CO2 levels ebb and flow in our environment. Under DOE management, this network has nearly doubled its number of observation sites and expanded to collect information from countries across the Americas. More recently, updated sensors are enabling researchers to collect valuable information about methane, a GHG that has a shorter lifespan in the atmosphere, but is twenty-eight times more potent than CO2.

“We are now able to provide data that, regarding scale and record length, are unprecedented,” said Stover.

A Warming Climate

Like a garden greenhouse keeps plants warm during the winter, greenhouse gases (GHG) influence the temperature of our planet by absorbing heat in our atmosphere. The gases remain in Earth’s atmosphere for different amounts of time depending on the type of gas. There are four types of GHGs: carbon dioxide (CO2), which lasts the longest in our atmosphere, methane, nitrous oxide, and fluorinated gases.

Although COis taken up and given off by many plants and animals naturally, human use of fossil fuels is the primary source of increased CO2 in our atmosphere today. These GHGs never move beyond Earth’s atmosphere into space, but instead cycle through the ocean, land, and atmosphere. Methane enters the atmosphere via coal and natural gas production, as well as livestock, wetlands, and landfills. Nitrous oxide is a byproduct of agricultural land use, fossil fuels, and wastewater treatment. Fluorinated gases, some of which linger in our atmosphere for over a thousand years, are industrial and commercial products and byproducts.

“We need to understand more about carbon dioxide and other GHG emissions – what’s controlling them and when they’re active – to help inform these downstream efforts and actions,” Stover said.

Across the world, net GHG emissions from human activities increased by 43% from 1990 to 2015. Historical measurements adjusted for natural fluctuations show that current atmospheric concentrations of CO2 are unprecedented in human history. In alignment with international goals, the United States has committed to net-zero emissions by 2050. To reach this goal, we must first better understand our capability to measure, monitor, and model GHGs. Only then can we more accurately understand if and how well climate policies and actions are working.

While significant expertise and knowledge exists already across federal and non-federal organizations, the recently released strategy is the first of its kind to collectively guide federal agencies toward collaboration and action.

“Nearly all federal agencies were involved in this report,” Stover said. “That’s where you start getting some traction.”

Tracing the Unseen

Tracking the quantity and movement of gas is no easy feat. But researchers must figure out a way to accurately understand GHG levels in our atmosphere. To do this, scientists are identifying and quantifying areas in the United States that both give off GHGs (known as “sources”) and remove and store GHGs (called “sinks”). This work has long been underway. Scientists are still identifying new sources and sinks almost daily, so there is still quite a bit that we still don’t know.

To measure and monitor GHG levels, scientists are using two different approaches. Activity based, or “bottom up” approaches estimate GHG emission and removal efforts through data that’s based on measured observations and computer models. Atmospheric based, or “top down” approaches, instead combine GHG amounts in our atmosphere and an understanding of how they move and interact chemically.

These tools and approaches have their strengths and limitations. But together, they have the potential to wield GHG insights like never before. “We know GHGs are out there and increasing,” said Stover. “But if we want to make an actionable decision on what we’re going to do, we need to know where it’s coming from, how it’s being transformed, where the sources are, and what controls those sources.”

A Long-Term Strategy

The National Strategy outlined by the White House puts forth an operational game-plan. In it, the tools and approaches to standardize GHG monitoring, measuring, and analyzing are described in detail. The groups involved in this strategy range from the federal level, like DOE, NASA, NOAA, and NIST (among many others), to local agencies and private companies. By collecting information about GHG sources and sinks in a uniform way, this collaborative effort will enable a holistic view of current GHG quantities and changes in the future.

Those involved in this effort will reach across disciplines and tools. Researchers are looking to gather GHG information from satellite, airborne, and surface networks across a wide range of locations and times. Using the overlapping capabilities of these tools, scientists will be able to more accurately and confidently pinpoint GHG quantities. For example, satellites struggle to make GHG measurements during cloudy days. In contrast, collecting air samples from a plane, though costly, can fill in the gap with an accurate reading no matter the cloud cover.

This work is in its first phase. Near-term activities will solidify our current understanding of GHG quantities. Some of them are already underway. In addition to standardization across tools and approaches, Phase I also includes establishing a multi-agency U.S. GHG Center. This center will enable knowledge sharing across those involved. It will also establish a clearer framework on how to work with non-federal and international groups.

One of the main goals in the first phase of this National Strategy is to expand the footprint of GHG testing sites, with the testbed in Washington, D.C. as a prototype. With so many efforts, like the NIST testbeds and AmeriFlux, long underway, this strategy is providing an official framework for how and where federal agencies can contribute to our fight against GHGs in a warming climate.

“This report is working towards this goal of improving the ways we measure carbon sources and the implications of where the gases go,” said Stover. “This all leads into the downstream implications of how we manage greenhouse gases; it’s something that really affects everyone.”


The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website.

Author: Ashleigh Papp ( is a science writer and multimedia producer in the Office of Science.

Courtesy of U.S. DOE.

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