ARB's Statewide Greenhouse Gas Monitoring Network

This page was last reviewed on October 20, 2016

The California Air Resources Board (ARB) has an extensive greenhouse gas (GHG) monitoring and measurement research program to study the regional and local emission sources of important GHGs in California.  ARB initiated the first subnational GHG Monitoring Network in 2010 (with pilot measurements in 2007) to study the regional GHG emissions trends throughout the state, and evaluate the regional and statewide inventories to support the AB 32 program. These efforts rely on highly accurate and precise ambient measurement of greenhouse gases, which are analyzed using complex analytical tools.

image of california map noting locations of ghg network stations

The network currently has seven ARB-operated and one ARB-funded monitoring stations located at strategically selected regional sites throughout California. In addition, we also collaborate with a number of research partners on several other monitoring locations throughout the state. ARB has equipped these stations with a variety of state-of-the-art analyzers that are able to measure the ambient pollutant concentrations at the highest level of accuracy and precision, and measure a variety of important greenhouse gases such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and black carbon (BC) (additionally, carbon monoxide [CO] is also measured as a tracer for anthropogenic emissions). ARB is also deploying analyzers capable of measuring isotopic signature of carbon dioxide and methane to further refine the source attribution of the inventory. Data from this network are used in several research studies, and formed the basis of a comprehensive statewide inverse receptor-oriented modeling and various trends assessment analyses to verify and inform the statewide GHG inventory. Collectively, this network features a unique and extremely comprehensive greenhouse gas monitoring setup, and is a “first of its kind” GHG monitoring effort around the world.

ARB GHG Monitoring Network
Site Name Coordinates Elevation (m) County Air Basin Inlet height
(m agl)
Pollutants measured
Latitude Longitude
ARB-operated stations
Mt Wilson
Los Angeles
South Coast
CH4, CO2, N2O, CO, BC
San Bernardino
San Bernardino
South Coast
CH4, CO2, N2O, CO
San Joaquin Valley
CH4, CO2, N2O, CO
San Joaquin Valley
CH4, CO2, N2O, CO
San Joaquin Valley
CH4, CO2, N2O, CO
Sutter Buttes
Sacramento Valley
CH4, CO2, N2O, CO
Tuscan Buttes
Sacramento Valley
CH4, CO2
ARB-funded station
Walnut Grove
Sacramento Valley
91, 483
CH4, CO2, N2O, CO


ARB Research Collaborations:

In order to maximize the extent of the project and to better understand the statewide inventory, ARB is also collaborating with other researchers to expand the coverage of the GHG measurement network in California. Analytical and measurement collaborators include Megacities Carbon Project, Lawrence Berkeley National Laboratory, National Oceanic and Atmospheric Administration, Lawrence Livermore National Laboratory, University of San Diego, California Institute of Technology, and Jet Propulsion Laboratory (Los Angeles).  Some of our key collaborators are shown in the figure below.

ARB Research Contracts:

ARB also sponsors extramural research contracts and collaborations to answer critical GHG research and policy questions using the state-mandated Annual Research Program.  Over the years, this effort has focused on a variety of source sectors including dairies, oil and gas, natural gas pipelines, waste sector, and many other subjects, and have important contribution to the state of science, ranging from studying sectoral emissions at the facility as well as process levels, to evaluating the inventory from both a top-down and bottom-up perspective.  In addition, our collaborations with CEC, CalRecycle, CDFA, and other sister agencies have provided critical support both for planning, policy making, research, as well as for improving our understanding of the source sectors and mitigation.  For instance, ARB has ongoing coordinated research efforts with the CEC to study the energy sector, and these have tremendously enhanced the measurement and evaluation of methane emission from the sector and improved the statewide emissions inventory.  The following projects depict a subset of ARB-funded projects that focused on GHG monitoring, and either directly utilized the data generated by the research network or collected new monitoring data to study greenhouse gas emissions in California:

  • ARCTAS-Mount Wilson GHG Monitoring “Proof of Concept” Gas Sampling and Analysis Service Contract (06-338) – Donald Blake (UCI)
  • Determination of the spatial distribution of ozone precursor and greenhouse gas concentrations and emissions on the LA-Basin (09-318) - Jochen Stutz, Qinlin Li, Stan Sander (UCLA)
  • Inverse modeling to verify California's greenhouse gas emission inventory (09-348) – Marc Fischer (CSU-East Bay)
  • Synthesis of policy relevant findings from the Calnex 2010 field study (10-326) – David Parrish and Joost de Gouw (NOAA)
  • Atmospheric measurement and inverse modeling to improve greenhouse gas emission estimates (11-306) – Marc Fischer (LBNL)
  • Mount Wilson GHG Monitoring Gas Sampling and Analysis (13-320) – Donald Blake (UCI)
  • Data Supporting GHG Emission Estimates in the South Coast Air Basin (13-329) – Yuk L. Yung (Caltech)
  • Greenhouse gas measurements at Walnut Grove Tower (15-302) – Marc Fischer (UC Davis)

Research Papers:

  • Papers from the CalNEX campaigns
  • Hsu, Y.K., VanCuren, T., Park, S., Jakober, C., Herner, J., FitzGibbon, M., Blake, D.R. and Parrish, D.D., 2010. Methane emissions inventory verification in southern California. Atmospheric Environment, 44(1), pp.1-7,
  • Gorham, K.A., Blake, N.J., VanCuren, R.A., Fuelberg, H.E., Meinardi, S. and Blake, D.R., 2010. Seasonal and diurnal measurements of carbon monoxide and nonmethane hydrocarbons at Mt. Wilson, California: Indirect evidence of atomic Cl in the Los Angeles basin. Atmospheric Environment, 44(19), pp.2271-2279,
  • Wennberg, P.O., Mui, W., Wunch, D., Kort, E.A., Blake, D.R., Atlas, E.L., Santoni, G.W., Wofsy, S.C., Diskin, G.S., Jeong, S. and Fischer, M.L., 2012. On the sources of methane to the Los Angeles atmosphere. Environmental science & technology, 46(17), pp.9282-9289,
  • Jeong, S., Y.-K. Hsu, A. E. Andrews, L. Bianco, P. Vaca, J. M. Wilczak, and M. L. Fischer, 2013. A multitower measurement network estimate of California's methane emissions, J. Geophys. Res. Atmos., 118, doi:10.1002/jgrd.50854
  • Gallagher, G., Zhan, T., Hsu, Y.K., Gupta, P., Pederson, J., Croes, B., Blake, D.R., Barletta, B., Meinardi, S., Ashford, P. and Vetter, A., 2014. High-Global Warming Potential F-gas Emissions in California: Comparison of Ambient-Based versus Inventory-Based Emission Estimates, and Implications of Refined Estimates. Environmental science & technology, 48(2), pp.1084-1093,
  • Wong, K.W., Fu, D., Pongetti,T.J., Newman, S., Kort, E.A., Duren, R., Hsu, Y.K., Miller, C.E., Yung, Y.L. and Sander, S.P., 2015. Mapping CH 4: CO 2 ratios in Los Angeles with CLARS-FTS from Mount Wilson, California. Atmospheric Chemistry and Physics, 15(1), pp.241-252,
  • Newman, S., Xu, X., Gurney, K.R., Hsu, Y. K., Li, K. F., Jiang, X., Keeling, R., Feng, S., O'Keefe, D., Patarasuk, R., Wong, K. W., Rao, P., Fischer, M. L., and Yung, Y. L.: Toward consistency between trends in bottom-up CO2 emissions and top-down atmospheric measurements in the Los Angeles megacity, Atmos. Chem. Phys., 16, 3843-3863, doi:10.5194/acp-16-3843-2016, 2016,

ARB GHG Monitoring Network Quality Assurance Project Plan (QAPP):

ARB has developed a Quality Assurance Project Plan (QAPP) that details a comprehensive project plan to develop, instrument, and implement the state-of-the-art ARB GHG Monitoring Network in California. The document also details ARB’s data processing and review processes to ensure that the Network data meets the World Meteorological Organization (WMO) standards. This stringent approach allows ARB Network data to meet the highest level of accuracy and precision for consistency with the collaborated research stations throughout California. Furthermore, ARB requires highest data quality to provide high accuracy data for evaluating the ARB GHG emissions inventory.

Data Access:

ARB GHG Monitoring Network data are a product of extensive research and technical efforts to measure, collect, and maintain high quality air monitoring data.  We take every precaution to ensure that the data are of the highest research quality, and possess the highest accuracy and precision.    

For questions regarding GHG Monitoring Network or suggestions for website improvements,
contact Dr. Abhilash Vijayan at (916) 324-0621