Greenhouse Gas Measurements 

Program

Advancing Greenhouse Gas Emissions (GHG) 

Measurement Tools and Standards

A Climate Challenge:

Managing the Unavoidable and Avoiding the Unmanageable

(Adaptation) (Mitigation)

James R. Whetstone

Special Asst. to the Director for Greenhouse Gas 

Measurements

Special Programs Office

National Institute of Standards and Technology
NIST’s Greenhouse Gas Measurements Program

Purpose:

Equipping Mitigation Decision Makers and Managers With Quantitative 

Information Tools To Support Strategic Decisions and Charting Progress

Mitigation Measurement Challenges: 

• Authenticating carbon credits across space and time is 

fundamental to success in commercial and regulatory activities.

• Independent responsible party identification & quantification of emissions/uptake 

facilitates harmonious markets and fair regulation.

• Currently unavailable measurement tools and capabilities can 

illuminate pressing climate science questions.

Performance Needs:

• 1% - 3% Yearly Reductions Are 

Announced Mitigation Targets

• A Measurement Challenge
NIST’s Greenhouse Gas Measurements Program

Program Components:

• Measurement tools, methods, and reference data

• Urban GHG Measurement Testbed System EL,ITL,MML, PML, SPO & Others

• Stationary/point source (smokestack) emissions PML

• Remote Sensing and Optical Measurements

• A global system of GHG concentration standards traceable to the SI MML

• Optical radiocarbon measurement and GHG concentration gradient with altitude MML, PML

• Accurate spectral line shape data for atmospheric trace gases MML

• Photosynthetic activity in vegetation (solar induced fluorescence) PML

• Carbonaceous Aerosols MML

• On-Orbit Observing Instrument Radiometric Standards & Calibration PML
Improving Urban and Regional Greenhouse Gas 

Measurement Tools

An Urban Emphasis

• Cities, metropolitan areas, states, and regions 

• Concentrate populations and energy use

• Occupy a small percentage of Earth’s Land

• Estimated to be the source of ~70% of global 

GHG emissions

• Paris Agreement recognizes sub-national actors – Business, Cities, and States

• Develop & Demonstrate Emissions Measurement Tools at Urban Scales

• Business, Local & State Governments Are Mitigation Policy Implementers

• Geographic Sensitivity to Identify Responsible Parties: Building & Street Level

• Accurately Quantify Emissions at Those Locations
2nd testbed

2013

LA Megacities Project

12 public, non-govt., & private actors +

The initial testbed

2010

Indianapolis Flux Experiment (INFLUX)

9 public & private actors +

2014

Latest testbed

Northeast Corridor/Baltimore - Washington 

(NEC/BW)

5 public & private actors +

NIST’S URBAN GHG MEASUREMENTS TESTBED SYSTEM

More are planned including expansion up the Northeastern 

seaboard of the U.S. ...

Urban testbeds are collaborative and multi-institutional:

• Combining atmospheric measurements (Top-down) with emissions modeling (Bottom-up) 

using socioeconomic statistics, and demographic data, 

• Estimate urban GHG emissions and their uncertainties, and 

• Combine NIST, Federal agency, university, and private sector expertise.
2nd testbed

2013

LA Megacities Project

12 public, non-govt., & private actors +

The initial testbed

2010

Indianapolis Flux Experiment (INFLUX)

9 public & private actors +

2014

Latest testbed

Northeast Corridor/Baltimore - Washington 

(NEC/BW)

5 public & private actors +

NIST’S URBAN GHG MEASUREMENTS TESTBED SYSTEM

More are planned including expansion up the Northeastern 

seaboard of the U.S. ...

Urban testbeds are collaborative and multi-institutional:

• Combining atmospheric measurements (Top-down) with emissions modeling (Bottom-up) 

using socioeconomic statistics, and demographic data, 

• Estimate urban GHG emissions and their uncertainties, and 

• Combine NIST, Federal agency, university, and private sector expertise.
Greenhouse Gas Quantity Determination – Urban Settings

The Atmospheric Observation Approach: Top-Down

GHG Concentrations are the Observable Parameter of Atmospheric Emissions

Atmospheric Inversion Analyses Yield Emissions Fluxes

• Cities and urban centers are complex and localized

• Commercial buildings, transportation networks, residential & industrial areas, 

electric generation plants, m governmental jurisdictions

• Incoming winds contain greenhouse gases that mix with 

emissions/uptake in the city/measurement domain

• Tower-based observation networks 

• Aircraft observations: emissions snapshots 

• Numerical weather prediction & 

dispersion models simulate 

atmospheric GHG transport 

• Spatial (1 km2) & temporal resolution
Urban GHG Surface Networks

Combining Approaches to Achieve Sensitivity and Accuracy

• Atmospheric Observation and Analysis – Top-Down

• Observations of local atmospheric greenhouse gas plumes

• Communication tower-based GHG concentration 24/7 observation networks 

in urban and surrounding areas

• Spatial and temporal scales: ~1 km2 spatial & <1 hour

• Scope 1 and 2 emissions: All emission sources and sinks in the domain 

of interest and GHG concentrations of incoming air

• Emissions Modeling – Bottom-Up

• Traditional emissions factor/activity data model elaboration of 

USEPA and the IPCC Task Force on Inventory practices and methods.

• Advanced emissions modeling achieve fine spatial & temporal scales: 

• Publicly available databases of fossil fuel combustion processes 

• Currently Scope 1 anthropogenic (fossil fuel CO2) emissions

Network

Observing Node

Communication 

Tower-Based, MultiLevel Atm. Sampling

GHG Analyzer

Top-Down: Enforces GHG Mass Conservation @ NWP Scales (1 km2 ) 

Bottom-Up: Provides Spatial and Temporal Resolution – No Mass Cons.
Bottom-Up: Elaborating Traditional Emissions Methods at 

Urban Scales

Actionable Information for City Mitigation Management

Spatially and temporally-resolved (building & street level) emissions estimation using public data

• Vulcan 3.0 (Continental @1 km2) and Hestia (urban) Data Products K. Gurney

• Anthropogenic Carbon Emission System (ACES) C. Gately, L. Hutyra

• Open-Data Inventory for Anthropogenic CO2 (ODIAC) T. Oda, S. Maksyutov

• Fossil fuel emissions

• ± 3% comparison 

NOAA’s atmospheric 

radiocarbon data 

and analysis

• Can be downscaled 

to urban areas

• Agrees with US 

inventory to ~10%

benefiting from

large data sets

Vulcan 3.0 – Continental U.S @ 1 km2 

http://vulcan.rc.nau.edu/

Hestia – Indianapolis – Building & Street Resolution

http://hestia.rc.nau.edu/index.html
Gurney et al. (2021) Under-reporting of greenhouse gas emissions in U.S. cities, Nature Communications

48 U.S. City Inventory Self-Reports vs. Vulcan 3.0

• Vulcan 3.0 used as a reference for city emission 

data in Climate Action Plans

• Extracted Fossil Fuel GHG Inventory report from 48 US city 

climate action plans

• Difference Range: ~60% over to ~140% under 

reporting.

• Perhaps due to not accounting for fuels or sectors 

where local information was limited or unavailable

• Consistent in urban emission quantities across 

cities nationally is critical for comparing 

effectiveness of differing mitigation approaches 

and policies.
Whole City Emissions (~2018)

The Indianapolis Flux Experiment (INFLUX)

• Improved Analyses

• Emissions data product – Hestia

• Surface network atmospheric Inversion

• Aircraft mass-balance experiments

• Agreement among 3 methods:

• ±7% agreement on whole city emissions

• Previous estimates – 30% to 50% 

differences

J. Turnbull, ES&T, 2019, 53 (1), 287–295, 10.1021/acs.est.8b05552 – Dec. 6, 2018

Results Achieved by:

• Harmonizing spatio-temporal mole 

fraction observation and analysis.

• Minimizing biological process emissions

 Suppress vegetative emissions and uptake 

processes 

Emissions Modeling

Bottom-Up

Atm. Obs. & Analysis 

Top-Down
Recent Advance in INFLUX Data Analyses

Combined emission modeling and atm. observation & analysis

• Urban Measurement Result Convergence Over 3-years

(Black line – emissions model, Orange line – atmospheric inversion analysis

• Atmospheric Inversion Model Testing:

• Intentional offset of +15% of Hestia input data.

• Atmospheric data and Bayesian inversion analysis correct the initial estimate by -14.2%.

• Combined method confidence is increased that 3 to 5% changes over 1 to 3 years are quantifiable.

• Replication in other urban settings needed to refine methods for general applicability.
Bill Callahan

Earth Networks, Inc.

Ray Weiss

Scripps Institution of 

Oceanography

Kevin Gurney

Northern Arizona University

Ken Davis

Penn State University

Russ Dickerson

University of Maryland

Ralph Keeling

Scripps

Jocelyn Turnbull

CU/NOAA/GNS

Chip Miller

NASA/JPL

Anna Karion

NIST

Thomas Lauvaux

LSCE and 

Penn State University

Paul Shepson

Stony Brook/Purdue

INFLUX LA Megacity NEC-BW

Riley Duren

JPL/Univ. of Arizona

Paul Shepson

Stony Brook/Purdue

Urban GHG Measurements Testbed System 

Contributors
Some Recent Results and Near-Term Plans

Selected Results

• Baltimore/Washington DC network 

completion

• Initiating expansion up the Northeast 

Corridor

• Pandemic impacts on urban emissions

• Quantified in Los Angeles and 

Baltimore/Washington DC testbeds 

demonstrating similar analysis methods

• Advances in:

• Determination GHG’s of incoming air

• emissions and uptake analyses of vegetation – remote sensing applications

• Comparison of inventory self-reporting in 48 U.S. cities with US continental reference

Near Term Plans

• Strengthen NIST emissions and biogenic 

modeling capabilities

• Continue extending Northeast Corridor testbed 

observing network – Washington to Boston

• Strengthen measurements and analyses linking 

on-orbit GHG concentration observations and 

surface emissions determinations

• Initiate a landfill emissions testbed for longer 

term measurements and analyses

• Strengthen efforts linking air quality and GHG 

emissions research communities.
NIST’s Greenhouse Gas Measurements 

Program

Program Components:

• Measurement tools, methods, and reference data

• Urban GHG Measurement Testbed System EL,ITL,MML, PML, SPO & Others

• Stationary/point source (smokestack) emissions PML

• Remote Sensing and Optical Measurements

• A global system of GHG concentration standards traceable to the SI MML

• Optical radiocarbon measurement and GHG concentration gradient with altitude MML, PML

• Accurate spectral line shape data for atmospheric trace gases MML

• Photosynthetic activity in vegetation (solar induced fluorescence) PML

• Carbonaceous Aerosols MML

• On-Orbit Instrument Observing Standards & Calibration PML
Direct Greenhouse Gases Emissions Measurement

Improved Powerplant Emission Quantities

• Stack emissions are warm, turbulent, and swirling

• Challenging concentration & velocity measurement environment 

• NIST Traceable Reference Materials Program underpins EPA’s stack 

gas concentration standards requirements (±2%) for SO2, NOX, & CO2

• Flow path diameter (mature) and Gas velocity (variable, complex, & challenging)

• NIST research has demonstrated improved application of 

existing technologies achieves ~1% flow accuracy

• X-pattern ultrasonic flow metering compensates for complex velocities

• Errors of ~1% over entire flow range with no velocity dependency

• Single path installations have ~±10% estimated uncertainty

• NIST-developed in-situ stack gas velocity calibration methods: 

<2 % uncertainty

• In-Plant demonstrations – Currently on-going with EPRI

Axial Stack Gas 

Velocities 

Emission (kg/sec) =

conc. (kg/m3) x 

velocity (m/sec) x 

Area (m2)

Preferred Stack Ultrasonic 

Flow Metering Configuration

Path A

Stack

Path B
Atmospheric GHG Mole Fraction Measurements

The Standards Foundation of Atmospheric Methods

WMO Central Calibration Laboratory System

WMO Mole Fraction Scale for Atmospheric 

Measurements

(NOAA Global Monitoring Division – Boulder, CO)

(WMO/Global Atmospheric Watch (GAW) &

CIPM/Cons. Comm. On Amt. of Substance (CCQM)

Comparison of Mole Fraction Artifact Standards 

CIPM Key Comparisons & GAW Comparisons

Traceability to the SI

(NIST)

Field Standard

GHG mole fractions

Wide Availability 

of Accurate GHG 

Mole Fraction 

Measurement 

Data Traceable to 

WMO and the 

International 

System of Units

Documentary Standards

(Standardizing Methods )

Field Instrument Calibration 

in Surface Networks, 

Airborne Observations, and 

On-Orbit Spectrometers

Working 

Standards

Specialty Gas 

Manufacturers

Future Need Driven by Carbon Monetization

>5,000 – 10,000 Field Standards/Year
Atmospheric GHG Mole Fraction Measurements

The Standards Foundation of Atmospheric Methods

WMO Central Calibration Laboratory System

WMO Mole Fraction Scale for Atmospheric 

Measurements

(NOAA Global Monitoring Division – Boulder, CO)

(WMO/Global Atmospheric Watch (GAW) &

CIPM/Cons. Comm. On Amt. of Substance (CCQM)

Comparison of Mole Fraction Artifact Standards 

CIPM Key Comparisons & GAW Comparisons

Traceability to the SI

(NIST)

Field Standard

GHG mole fractions

Wide Availability 

of Accurate GHG 

Mole Fraction 

Measurement 

Data Traceable to 

WMO and the 

International 

System of Units

Documentary Standards

(Standardizing Methods )

Field Instrument Calibration 

in Surface Networks, 

Airborne Observations, and 

On-Orbit Spectrometers

Working 

Standards

Specialty Gas 

Manufacturers

A CIPM working Group establish to develop 

means to meet this problem (MML)
NIST’s Greenhouse Gas Measurements 

Program

Program Components:

• Measurement tools, methods, and reference data

• Urban GHG Measurement Testbed System EL,ITL,MML, PML, SPO & Others

• Stationary/point source (smokestack) emissions PML

• Remote Sensing and Optical Measurements

• A global system of GHG concentration standards traceable to the SI MML

• Optical radiocarbon measurement and GHG concentration gradient with altitude MML, PML

• Accurate spectral line shape data for atmospheric trace gases MML

• Photosynthetic activity in vegetation (solar induced fluorescence) PML

• Carbonaceous Aerosols MML

• On-Orbit Instrument Observing Standards & Calibration PML
Optical Radiocarbon Measurement 

& Spectral Line Shape References

First linear absorption spectrometer 

for bench-top 14CO2

• Cavity ring-down spectroscopy of

14CO2 near 4.5 μm

• Absolute and calibration-free 

determination of 14CO2 concentration

• Limit-of-detection ~0. 1 fraction 

modern 14C

• Applications:

‒ Carbon-cycling studies:

fossil fuel (petrogenic vs. biogenic) 

source apportionment

‒ Radiocarbon dating

A.J. Fleisher, D.A. Long, Q. Liu, L. Gameson, and J.T. Hodges,

“Optical measurement of radiocarbon below unity fraction modern by linear absorption spectroscopy,” 

J. Phys. Chem. Lett., 8, 4550-4556 (2017).
Optical Radiocarbon 

Measurement & Spectral Line 

Shape References 

First linear absorption spectrometer 

for bench-top 14CO

2

DIAL Mixing Ratios • range resolved CO2, • range resolved H2O dry air 

Application – Improve GHG 

Satellite Data • Real-Time Vertical 

Concentrations

• Improve on-orbit observations 

for path integrated of CO

2 and 

CH

4 dry air mixing ratios 

DIAL Prototype (PML)
Urban Biogenic Processes

Measurements and Models

Urban Vegetation: Quantifying CO2

Emissions and Uptake

• Vegetation Respiration Models

• Predict CO2 emission strength at similar levels 

to anthropogenic emissions

• Few are specific to urban conditions

• Model evaluation and development are 

underway in SPO

Radiative Emissions Measurements and 

Forest Ecology

• Forested Optical Reference for Evaluating Sensor 

Technology - FOREST Project

• Uses Forested Area on NIST GaithersBurg Site

• Combines Optical Radiation and Ecological Measurements

• Solar Induced fluorescence (SIF) may not be the remote 

sensing proxy for photosynthetic activity as has been 

asserted.

Pressure 

cuff

Abscissic acid (ABA)

Closes Stomata

LI-COR 6800:

Leaf – Atm. 

Exchange

Solar Induced 

Fluorescence Obs.

Ecological 

Parameter 

Meas.
Thanks for Your Attention

Questions/Discussion
Emissions Modeling Summary

Spatially &Temporally Resolved Inventory 

Data Products

• Use publicly available data for the 

emission factor – activity data model method ‒ UNFCC-TFI approach

‒ Spatially & temporally resolved economic activity data 

coupled with emission factor for activities

• Three U.S. research groups & the EU 

‒ Northern Arizona Univ., Boston Univ., and NASA-Goddard

‒ Edgar – EU Joint Research Center & focused on 

Air Quality & GHG’s

• Substantial differences in data and methods, 

‒ Research efforts continue and are improving results

• Benefit of combined emissions modeling and atmospheric

measurement and analysis

‒ Vulcan 3.0 Data Product – Agreement with with 14CO2 atmospheric inversion results at the ~1.5% level on a yearly basis.

 1 km X 1 km data product for the Continental U.S.

‒ Vulcan 3.0 is the basis for a building – Street level 

resolution data product – Hestia

‒ Hestia is used through out the NIST Urban GHG Measurements Testbed.

• Differences between methods indicates the need for standards to 

ensure consistency and uniformity in emissions modeling 

backed by atmospheric measurement and analysis

Gately & Hutyra, 2017, J. GeoPhy. Res. - Atm, 

doi: 10.1002/2017JD027359

Comparison of 4 Data Products in the 

U.S. Northeast Corridor Show Substantial 

Spatial Differences.

EDGAR is Global