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Published May 10, 2019 | public
Journal Article

Atmospheric observation-based estimation of fossil fuel CO₂ emissions from regions of central and southern California

Abstract

Combustion of fossil fuel is the dominant source of greenhouse gas emissions to the atmosphere in California. Here, we describe radiocarbon (¹⁴CO₂) measurements and atmospheric inverse modeling to estimate fossil fuel CO₂ (ffCO₂) emissions for 2009–2012 from a site in central California, and for June 2013–May 2014 from two sites in southern California. A priori predicted ffCO₂ mixing ratios are computed based on regional atmospheric transport model (WRF-STILT) footprints and an hourly ffCO₂ prior emission map (Vulcan 2.2). Regional inversions using observations from the central California site suggest that emissions from the San Francisco Bay Area (SFBA) are higher in winter and lower in summer. Taking all years together, the average of a total of fifteen 3-month inversions from 2009 to 2012 suggests ffCO₂ emissions from SFBA were within 6 ± 35% of the a priori estimate for that region, where posterior emission uncertainties are reported as 95% confidence intervals. Results for four 3-month inversions using measurements in Los Angeles South Coast Air Basin (SoCAB) during June 2013–May 2014 suggest that emissions in SoCAB are within 13 ± 28% of the a priori estimate for that region, with marginal detection of any seasonality. While emissions from the SFBA and SoCAB urban regions (containing ~50% of prior emissions from California) are constrained by the observations, emissions from the remaining regions are less constrained, suggesting that additional observations will be valuable to more accurately estimate total ffCO₂ emissions from California as a whole.

Additional Information

© 2019 Published by Elsevier B.V. Received 17 November 2018, Revised 6 January 2019, Accepted 8 January 2019, Available online 14 January 2019. We thank David Field, Dave Bush, Edward Wahl, Ken Reichl, Toby Walpert, and particularly Jon Kofler for assistance with measurements at WGC, John Lin, Christoph Gerbig, Steve Wofsy, Janusz Eluszkiewicz, Thomas Nehrkorn for sharing the STILT code and advice, and Krishna Muriki for assistance running the WRF-STILT models on the LBNL-Lawrencium cluster. WGC 14C measurements were supported by NOAA-OGP awards to Scott Lehman and John Miller. This study was in part supported by the CARB Research Division (CARB contract 11-306) under U.S. Department of Energy contract DE-AC02-05CH11231. The statements and conclusions in this article are those of the authors and not necessarily those of the California Air Resources Board. The mention of commercial products, their source, or their use in connection with material reported herein is not to be construed as actual or implied endorsement of such products. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof, or The Regents of the University of California. Ernest Orlando Lawrence Berkeley National Laboratory is an equal opportunity employer. WGC measurement data are available through https://www.esrl.noaa.gov/gmd/ccgg/flask.php, and data for CARB sites are available at https://www.arb.ca.gov/aqmis2/res/aqdselect.php?tab=hourly. The EDGAR and CARB prior emissions are available at http://edgar.jrc.ec.europa.eu and https://www.arb.ca.gov/cc/inventory/inventory.htm, respectively.

Additional details

Created:
August 22, 2023
Modified:
October 20, 2023