@article{c3955e55f37d465998c761b73e6f9c84,
title = "Unexpected slowdown of US pollutant emission reduction in the past decade",
abstract = "Ground and satellite observations show that air pollution regulations in the United States (US) have resulted in substantial reductions in emissions and corresponding improvements in air quality over the last several decades. However, large uncertainties remain in evaluating how recent regulations affect different emission sectors and pollutant trends. Here we show a significant slowdown in decreasing US emissions of nitrogen oxides (NOx) and carbon monoxide (CO) for 2011–2015 using satellite and surface measurements. This observed slowdown in emission reductions is significantly different from the trend expected using US Environmental Protection Agency (EPA) bottom-up inventories and impedes compliance with local and federal agency air-quality goals. We find that the difference between observations and EPA{\textquoteright}s NOx emission estimates could be explained by: (i) growing relative contributions of industrial, area, and off-road sources, (ii) decreasing relative contributions of on-road gasoline, and (iii) slower than expected decreases in on-road diesel emissions.",
keywords = "Decadal scale variation, Emission regulations, Nitrogen oxides",
author = "Zhe Jiang and McDonald, {Brian C.} and Helen Worden and Worden, {John R.} and Kazuyuki Miyazaki and Zhen Qu and Henze, {Daven K.} and Jones, {Dylan B.A.} and Arellano, {Avelino F.} and Fischer, {Emily V.} and Liye Zhu and {Folkert Boersma}, K.",
note = "Funding Information: ACKNOWLEDGMENTS. We acknowledge useful discussions with Vivienne H. Payne, Benjamin Gaubert, and Forrest Lacey. We thank the EPA for providing their national NOx and CO emission data and surface in situ NO2, CO, and O3 measurements (AQS). We acknowledge the OMI tropospheric NO2 column data from https://disc.sci.gsfc.nasa.gov, www.temis.nl, and behr.cchem.berkeley.edu/DownloadBEHRData.aspx. The MOPITT team also acknowledges the Canadian Space Agency for the instrument finance, the Natural Sciences and Engineering Research Council and Environment Canada (formerly the Meteorological Service of Canada) for help with the data processing, COMDEV (the prime contractor), and ABB BOMEM. The National Center for Atmospheric Research (NCAR) MOPITT project is supported by the NASA Earth Observing System Program. NCAR is sponsored by the National Science Foundation. Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Support for Z.Q. and D.K.H. was provided by NASA Health and Air Quality Applied Science Team NNX16AQ26G. Funding Information: We acknowledge useful discussions with Vivienne H. Payne, Benjamin Gaubert, and Forrest Lacey. We thank the EPA for providing their national NOx and CO emission data and surface in situ NO2, CO, and O3 measurements (AQS). We acknowledge the OMI tropospheric NO2 column data from https://disc.sci.gsfc.nasa.gov, www.temis.nl, and behr.cchem.Berkeley.edu/DownloadBEHRData.aspx. The MOPITT team also acknowledges the Canadian Space Agency for the instrument finance, the Natural Sciences and Engineering Research Council and Environment Canada (formerly the Meteorological Service of Canada) for help with the data processing, COMDEV (the prime contractor), and ABB BOMEM. The National Center for Atmospheric Research (NCAR) MOPITT project is supported by the NASA Earth Observing System Program. NCAR is sponsored by the National Science Foundation. Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. Support for Z.Q. and D.K.H. was provided by NASA Health and Air Quality Applied Science Team NNX16AQ26G. Publisher Copyright: {\textcopyright} 2018 National Academy of Sciences. All Rights Reserved. ",
year = "2018",
month = may,
day = "15",
doi = "10.1073/pnas.1801191115",
language = "English (US)",
volume = "115",
pages = "5099--5104",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
issn = "0027-8424",
publisher = "National Academy of Sciences",
number = "20",
}