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Top‐Down Constraints on Anthropogenic CO 2 Emissions Within an Agricultural‐Urban Landscape
Author(s) -
Hu Cheng,
Griffis Timothy J.,
Lee Xuhui,
Millet Dylan B.,
Chen Zichong,
Baker John M.,
Xiao Ke
Publication year - 2018
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2017jd027881
Subject(s) - environmental science , greenhouse gas , gasoline , emission inventory , diesel fuel , atmospheric sciences , radiative forcing , fossil fuel , natural gas , environmental engineering , climate change , meteorology , chemistry , ecology , air quality index , geography , organic chemistry , geology , biology
Anthropogenic carbon dioxide (CO 2 ) emissions dominate the atmospheric greenhouse gas radiative forcing budget. However, these emissions are poorly constrained at the regional (10 2 –10 6 km 2 ) and seasonal scales. Here we use a combination of tall tower CO 2 mixing ratio and carbon isotope ratio observations and inverse modeling techniques to constrain anthropogenic CO 2 emissions within a highly heterogeneous agricultural landscape near Saint Paul, Minnesota, in the Upper Midwestern United States. The analyses indicate that anthropogenic emissions contributed 6.6, 6.8, and 7.4 μmol/mol annual CO 2 enhancements (i.e., departures from the background values) in 2008, 2009, and 2010, respectively. Oil refinery, the energy industry (power and heat generation), and residential emissions (home heating and cooking) contributed 2.9 (42.5%), 1.4 (19.8%), and 1.1 μmol/mol (15.8%) of the total anthropogenic enhancement over the 3‐year period according to a priori inventories. The total anthropogenic signal was further partitioned into CO 2 emissions derived from fuel oil, natural gas, coal, gasoline, and diesel consumption using inverse modeling and carbon isotope ratio analyses. The results indicate that fuel oil and natural gas consumption accounted for 52.5% of the anthropogenic CO 2 sources in winter. Here the a posteriori CO 2 emission from natural gas was 79.0 ± 4.1% (a priori 20.0%) and accounted for 63% of the total CO 2 enhancement including both biological and anthropogenic sources. The a posteriori CO 2 emission from fuel oil was 8.4 ± 3.8% (a priori 32.5%)—suggesting a more important role of residential heating in winter. The modeled carbon isotope ratio of the CO 2 source ( δ 13 C s , −29.3 ± 0.4‰) was relatively more enriched in 13 C‐CO 2 compared to that derived from Miller‐Tans plot analyses (−35.5‰ to −34.8‰), supporting that natural gas consumption was underestimated for this region.