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<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" article-type="research-article" dtd-version="3.0" xml:lang="en">
<front>
<journal-meta>
<journal-id journal-id-type="publisher">ACP</journal-id>
<journal-title-group>
<journal-title>Atmospheric Chemistry and Physics</journal-title>
<abbrev-journal-title abbrev-type="publisher">ACP</abbrev-journal-title>
</journal-title-group>
<issn pub-type="epub">1680-7324</issn>
<publisher><publisher-name>Copernicus GmbH</publisher-name>
<publisher-loc>Göttingen, Germany</publisher-loc>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.5194/acp-12-4365-2012</article-id>
<title-group>
<article-title>The isotopic record of Northern Hemisphere atmospheric carbon monoxide since 1950: implications for the CO budget</article-title>
</title-group>
<contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Wang</surname>
<given-names>Z.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Chappellaz</surname>
<given-names>J.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Martinerie</surname>
<given-names>P.</given-names>
</name>
<xref ref-type="aff" rid="aff2">
<sup>2</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Park</surname>
<given-names>K.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
<xref ref-type="aff" rid="aff8">
<sup>8</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Petrenko</surname>
<given-names>V.</given-names>
</name>
<xref ref-type="aff" rid="aff3">
<sup>3</sup>
</xref>
<xref ref-type="aff" rid="aff9">
<sup>9</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Witrant</surname>
<given-names>E.</given-names>
</name>
<xref ref-type="aff" rid="aff4">
<sup>4</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Emmons</surname>
<given-names>L. K.</given-names>
</name>
<xref ref-type="aff" rid="aff5">
<sup>5</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Blunier</surname>
<given-names>T.</given-names>
</name>
<xref ref-type="aff" rid="aff6">
<sup>6</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Brenninkmeijer</surname>
<given-names>C. A. M.</given-names>
</name>
<xref ref-type="aff" rid="aff7">
<sup>7</sup>
</xref>
</contrib>
<contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Mak</surname>
<given-names>J. E.</given-names>
</name>
<xref ref-type="aff" rid="aff1">
<sup>1</sup>
</xref>
</contrib>
</contrib-group><aff id="aff1">
<label>1</label>
<addr-line>Institute for Terrestrial and Planetary Atmospheres/School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794, USA</addr-line>
</aff>
<aff id="aff2">
<label>2</label>
<addr-line>UJF – Grenoble 1/CNRS, Laboratoire de Glaciologie et Géophysique de l&apos;Environnement (LGGE) UMR5183, Grenoble, 38041, France</addr-line>
</aff>
<aff id="aff3">
<label>3</label>
<addr-line>Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA</addr-line>
</aff>
<aff id="aff4">
<label>4</label>
<addr-line>Grenoble Image Parole Signal Automatique (GIPSA-lab), Université Joseph Fourier/CNRS, BP 46, 38 402 Saint Martin d&apos;Hères, France</addr-line>
</aff>
<aff id="aff5">
<label>5</label>
<addr-line>National Center for Atmospheric Research, Atmospheric Chemistry Division, Boulder CO 80301, USA</addr-line>
</aff>
<aff id="aff6">
<label>6</label>
<addr-line>Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30,  2100 Copenhagen Ø, Denmark</addr-line>
</aff>
<aff id="aff7">
<label>7</label>
<addr-line>Max Planck Institute for Chemistry, 55128 Mainz, Germany</addr-line>
</aff>
<aff id="aff8">
<label>8</label>
<addr-line>now at: Division of Polar Climate Research, Korea Polar Research Institute, Incheon, South Korea</addr-line>
</aff>
<aff id="aff9">
<label>9</label>
<addr-line>now at: Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY, USA</addr-line>
</aff>
<pub-date pub-type="epub">
<day>16</day>
<month>05</month>
<year>2012</year>
</pub-date>
<volume>12</volume>
<issue>10</issue>
<fpage>4365</fpage>
<lpage>4377</lpage>
<permissions>
<license xlink:type="simple">
<license-p>This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.</license-p>
</license>
</permissions>
<self-uri xlink:href="http://www.atmos-chem-phys.net/12/4365/2012/acp-12-4365-2012.html">This article is available from http://www.atmos-chem-phys.net/12/4365/2012/acp-12-4365-2012.html</self-uri>
<self-uri xlink:href="http://www.atmos-chem-phys.net/12/4365/2012/acp-12-4365-2012.pdf">The full text article is available as a PDF file from http://www.atmos-chem-phys.net/12/4365/2012/acp-12-4365-2012.pdf</self-uri>
<abstract>
<p>We present a 60-year record of the stable isotopes of atmospheric carbon
monoxide (CO) from firn air samples collected under the framework of the
North Greenland Eemian Ice Drilling (NEEM) project. CO concentration,
&amp;delta;&lt;sup&gt;13&lt;/sup&gt;C, and &amp;delta;&lt;sup&gt;18&lt;/sup&gt;O of CO were measured by gas
chromatography/isotope ratio mass spectrometry (gc-IRMS) from trapped gases
in the firn. We applied LGGE-GIPSA firn air models (Witrant et al., 2011) to
correlate gas age with firn air depth and then reconstructed the trend of
atmospheric CO and its stable isotopic composition at high northern
latitudes since 1950. The most probable firn air model scenarios show that
&amp;delta;&lt;sup&gt;13&lt;/sup&gt;C decreased slightly from −25.8&amp;permil;  in 1950 to −26.4&amp;permil; in 2000,
then decreased more significantly to −27.2&amp;permil; in 2008. &amp;delta;&lt;sup&gt;18&lt;/sup&gt;O
decreased more regularly from 9.8&amp;permil; in 1950 to 7.1&amp;permil; in 2008. Those same
scenarios show CO concentration increased gradually from 1950 and peaked in
the late 1970s, followed by a gradual decrease to present day values
 (Petrenko et al., 2012). Results from an
isotope mass balance model indicate that a slight increase, followed by a
large reduction, in CO derived from fossil fuel combustion has occurred since
1950. The reduction of CO emission from fossil fuel combustion after the
mid-1970s is the most plausible mechanism for the drop of CO concentration
during this time. Fossil fuel CO emissions decreased as a result of the
implementation of catalytic converters and the relative growth of diesel
engines, in spite of the global vehicle fleet size having grown several fold
over the same time period.</p>
</abstract>
<counts><page-count count="13"/></counts>
</article-meta>
</front>
<body/>
<back>
<ref-list>
<title>References</title>
<ref id="ref1">
<label>1</label><mixed-citation publication-type="other" xlink:type="simple"> Assonov, S. S., Brenninkmeijer, C. A. M., Jöckel, P., Mulvaney, R., Bernard, S., and Chappellaz, J.: Evidence for a CO increase in the SH during the 20th century based on firn air samples from Berkner Island, Antarctica, Atmos. Chem. Phys., 7, 295–308, http://dx.doi.org/10.5194/acp-7-295-2007doi:10.5194/acp-7-295-2007, 2007. </mixed-citation>
</ref>
<ref id="ref2">
<label>2</label><mixed-citation publication-type="other" xlink:type="simple"> Bauer, K., Conrad, R., and Seiler, W.: Photo-oxidative production of carbon monoxide by phototropic mocroorganisms, Biochim. Biophys. Acta, 589, 46–55, 1980. </mixed-citation>
</ref>
<ref id="ref3">
<label>3</label><mixed-citation publication-type="other" xlink:type="simple"> Bergamaschi, P., Hein, R., Brenninkmeijer, C. A. M., and Crutzen, P. J.: Inverse modeling of the global CO cycle 2. Inversion of $^13$C/$^12$C and $^18$O/$^16$O isotope ratios, J. Geophys. Res.-Atmos., 105, 1929–1945, 2000a. </mixed-citation>
</ref>
<ref id="ref4">
<label>4</label><mixed-citation publication-type="other" xlink:type="simple"> Bergamaschi, P., Hein, R., Heimann, M., and Crutzen, P. J.: Inverse modeling of the global CO cycle 1. Inversion of CO mixing ratios, J. Geophys. Res.-Atmos., 105, 1909–1927, 2000b. </mixed-citation>
</ref>
<ref id="ref5">
<label>5</label><mixed-citation publication-type="other" xlink:type="simple"> Bousquet, P., Hauglustaine, D. A., Peylin, P., Carouge, C., and Ciais, P.: Two decades of OH variability as inferred by an inversion of atmospheric transport and chemistry of methyl chloroform, Atmos. Chem. Phys., 5, 2635–2656, http://dx.doi.org/10.5194/acp-5-2635-2005doi:10.5194/acp-5-2635-2005, 2005. </mixed-citation>
</ref>
<ref id="ref6">
<label>6</label><mixed-citation publication-type="other" xlink:type="simple"> Brenninkmeijer, C. A. M.: Measurement of the abundance of $^14$CO in the atmosphere and the $^13$C/$^12$C and $^18$O/$^16$O ratio of atmospheric CO with applications in New Zealand and Antarctica, J. Geophys. Res.-Atmos., 98, 10595–10614, 1993. </mixed-citation>
</ref>
<ref id="ref7">
<label>7</label><mixed-citation publication-type="other" xlink:type="simple"> Brenninkmeijer, C. A. M. and Röckmann, T.: Principal factors determining the $^18$O/$^16$O ratio of atmospheric CO as derived from observations in the southern hemispheric troposphere and lowermost stratosphere, J. Geophys. Res.-Atmos., 102, 25477–25485, 1997. </mixed-citation>
</ref>
<ref id="ref8">
<label>8</label><mixed-citation publication-type="other" xlink:type="simple"> Buizert, C., Martinerie, P., Petrenko, V. V., Severinghaus, J. P., Trudinger, C. M., Witrant, E., Rosen, J. L., Orsi, A. J., Rubino, M., Etheridge, D. M., Steele, L. P., Hogan, C., Laube, J. C., Sturges, W. T., Levchenko, V. A., Smith, A. M., Levin, I., Conway, T. J., Dlugokencky, E. J., Lang, P. M., Kawamura, K., Jenk, T. M., White, J. W. C., Sowers, T., Schwander, J., and Blunier, T.: Gas transport in firn: multiple-tracer characterisation and model intercomparison for NEEM, Northern Greenland, Atmos. Chem. Phys., 12, 4259–4277, doi:10.5194/acp-12-4259-2012, 2012. </mixed-citation>
</ref>
<ref id="ref9">
<label>9</label><mixed-citation publication-type="other" xlink:type="simple"> Clark, I. D., Henderson, L., Chappellaz, J., Fisher, D., Koerner, R., Worthy, D. E. J., Kotzer, T., Norman, A. L., and Barnola, J. M.: CO&lt;sub&gt;2&lt;/sub&gt; isotopes as tracers of firn air diffusion and age in an Arctic ice cap with summer melting, Devon Island, Canada, J. Geophys. Res.-Atmos., 112, D01301, http://dx.doi.org/10.1029/2006jd007471doi:10.1029/2006jd007471, 2007. </mixed-citation>
</ref>
<ref id="ref10">
<label>10</label><mixed-citation publication-type="other" xlink:type="simple"> Conrad, R. and Seiler, W.: Photooxidative production and microbial consumption of carbon monoxide in seawater, Fems Microbiol. Lett., 9, 61–64, 1980. </mixed-citation>
</ref>
<ref id="ref11">
<label>11</label><mixed-citation publication-type="other" xlink:type="simple"> Duncan, B. N., Logan, J. A., Bey, I., Megretskaia, I. A., Yantosca, R. M., Novelli, P. C., Jones, N. B., and Rinsland, C. P.: Global budget of CO, 1988–1997: Source estimates and validation with a global model, J. Geophys. Res.-Atmos., 112, D22301, http://dx.doi.org/10.1029/2007jd008459doi:10.1029/2007jd008459, 2007. </mixed-citation>
</ref>
<ref id="ref12">
<label>12</label><mixed-citation publication-type="other" xlink:type="simple"> Emmons, L. K., Walters, S., Hess, P. G., Lamarque, J.-F., Pfister, G. G., Fillmore, D., Granier, C., Guenther, A., Kinnison, D., Laepple, T., Orlando, J., Tie, X., Tyndall, G., Wiedinmyer, C., Baughcum, S. L., and Kloster, S.: Description and evaluation of the Model for Ozone and Related chemical Tracers, version 4 (MOZART-4), Geosci. Model Dev., 3, 43–67, http://dx.doi.org/10.5194/gmd-3-43-2010doi:10.5194/gmd-3-43-2010, 2010. </mixed-citation>
</ref>
<ref id="ref13">
<label>13</label><mixed-citation publication-type="other" xlink:type="simple"> EPA: National air pollutant emission trends: 1900–1998, EPA Report 454/R-00-002, United States Environmental Protection Agency, Research Triangle Park, NC 27711, 2000. </mixed-citation>
</ref>
<ref id="ref14">
<label>14</label><mixed-citation publication-type="other" xlink:type="simple"> Fernandes, S. D., Trautmann, N. M., Streets, D. G., Roden, C. A., and Bond, T. C.: Global biofuel use, 1850–2000, Global Biogeochem. Cy., 21, Gb2019, http://dx.doi.org/10.1029/2006gb002836doi:10.1029/2006gb002836, 2007. </mixed-citation>
</ref>
<ref id="ref15">
<label>15</label><mixed-citation publication-type="other" xlink:type="simple"> Ferretti, D. F., Miller, J. B., White, J. W. C., Etheridge, D. M., Lassey, K. R., Lowe, D. C., Macfarling Meure, C. M. M., Dreier, M. F., Trudinger, C. M., van Ommen, T. D., and Langenfelds, R. L.: Unexpected changes to the global methane budget over the past 2000 years, Science, 309, 1714–1717, http://dx.doi.org/10.1126/science.1115193doi:10.1126/science.1115193, 2005. </mixed-citation>
</ref>
<ref id="ref16">
<label>16</label><mixed-citation publication-type="other" xlink:type="simple"> Francey, R. J., Allison, C. E., Etheridge, D. M., Trudinger, C. M., Enting, I. G., Leuenberger, M., Langenfelds, R. L., Michel, E., and Steele, L. P.: A 1000-year high precision record of $\delta ^13$C in atmospheric CO&lt;sub&gt;2&lt;/sub&gt;, Tellus B, 51, 170–193, 1999. </mixed-citation>
</ref>
<ref id="ref17">
<label>17</label><mixed-citation publication-type="other" xlink:type="simple"> Granier, C., Bessagnet, B., Bond, T., D&apos;Angiola, A., van der Gon, H. D., Frost, G. J., Heil, A., Kaiser, J. W., Kinne, S., Klimont, Z., Kloster, S., Lamarque, J.-F., Liousse, C., Masui, T., Meleux, F., Mieville, A., Ohara, T., Raut, J.-C., Riahi, K., Schultz, M. G., Smith, S. J., Thompson, A., van Aardenne, J., van der Werf, G. R., and van Vuuren, D. P.: Evolution of anthropogenic and biomass burning emissions of air pollutants at global and regional scales during the 1980-2010 period, Climatic Change, 109, 163–190, http://dx.doi.org/10.1007/s10584-011-0154-1doi:10.1007/s10584-011-0154-1, 2011. </mixed-citation>
</ref>
<ref id="ref18">
<label>18</label><mixed-citation publication-type="other" xlink:type="simple"> Haan, D. and Raynaud, D.: Ice core record of CO variations during the last two millennia: atmospheric implications and chemical interactions within the Greenland ice, Tellus B, 50, 253–262, 1998. </mixed-citation>
</ref>
<ref id="ref19">
<label>19</label><mixed-citation publication-type="other" xlink:type="simple"> Haan, D., Martinerie, P., and Raynaud, D.: Ice core data of atmospheric carbon monoxide over Antarctica and Greenland during the last 200 years, Geophys. Res. Lett., 23, 2235–2238, 1996. </mixed-citation>
</ref>
<ref id="ref20">
<label>20</label><mixed-citation publication-type="other" xlink:type="simple"> Heidt, L. E., Krasnec, J. P., Lueb, R. A., Pollock, W. H., Henry, B. E., and Crutzen, P. J.: Latitudinal distributions of CO and CH&lt;sub&gt;4&lt;/sub&gt; over the Pacific, J. Geophys. Res.-Oc. Atm., 85, 7329–7336, 1980. </mixed-citation>
</ref>
<ref id="ref21">
<label>21</label><mixed-citation publication-type="other" xlink:type="simple"> Ito, A. and Penner, J. E.: Historical emissions of carbonaceous aerosols from biomass and fossil fuel burning for the period 1870–2000, Global. Biogeochem. Cy., 19, Gb2028, http://dx.doi.org/10.1029/2004gb002374doi:10.1029/2004gb002374, 2005. </mixed-citation>
</ref>
<ref id="ref22">
<label>22</label><mixed-citation publication-type="other" xlink:type="simple"> Kato, S., Akimoto, H., Röckmann, T., Braunlich, M., and Brenninkmeijer, C. A. M.: Stable isotopic compositions of carbon monoxide from biomass burning experiments, Atmos. Environ., 33, 4357–4362, 1999. </mixed-citation>
</ref>
<ref id="ref23">
<label>23</label><mixed-citation publication-type="other" xlink:type="simple"> Khalil, M. A. K. and Rasmussen, R. A.: Carbon monoxide in the earth&apos;s atmosphere: increased trend, Science, 224, 54–56, 1984. </mixed-citation>
</ref>
<ref id="ref24">
<label>24</label><mixed-citation publication-type="other" xlink:type="simple"> Khalil, M. A. K. and Rasmussen, R. A.: Global decrease in atmospheric carbon monoxide concentration, Nature, 370, 639–641, 1994. </mixed-citation>
</ref>
<ref id="ref25">
<label>25</label><mixed-citation publication-type="other" xlink:type="simple"> Kummer, J. T.: Catalysis for automobile emission control, Prog. Energ. Combust., 6, 177–199, 1980. </mixed-citation>
</ref>
<ref id="ref26">
<label>26</label><mixed-citation publication-type="other" xlink:type="simple"> Kummer, J. T.: Use of noble-metals in automobile exhaust catalysts, J. Phys. Chem.-US, 90, 4747–4752, http://dx.doi.org/10.1021/j100411a008doi:10.1021/j100411a008, 1986. </mixed-citation>
</ref>
<ref id="ref27">
<label>27</label><mixed-citation publication-type="other" xlink:type="simple"> Lamarque, J.-F., Bond, T. C., Eyring, V., Granier, C., Heil, A., Klimont, Z., Lee, D., Liousse, C., Mieville, A., Owen, B., Schultz, M. G., Shindell, D., Smith, S. J., Stehfest, E., Van Aardenne, J., Cooper, O. R., Kainuma, M., Mahowald, N., McConnell, J. R., Naik, V., Riahi, K., and van Vuuren, D. P.: Historical (1850–2000) gridded anthropogenic and biomass burning emissions of reactive gases and aerosols: methodology and application, Atmos. Chem. Phys., 10, 7017–7039, http://dx.doi.org/10.5194/acp-10-7017-2010doi:10.5194/acp-10-7017-2010, 2010. </mixed-citation>
</ref>
<ref id="ref28">
<label>28</label><mixed-citation publication-type="other" xlink:type="simple"> Lean, J., Beer, J., and Bradley, R.: Reconstruction of solar irradiance since 1610 – implications for climate change, Geophys. Res. Lett., 22, 3195–3198, 1995. </mixed-citation>
</ref>
<ref id="ref29">
<label>29</label><mixed-citation publication-type="other" xlink:type="simple"> Levy, H.: Normal atmosphere – Large radical and formaldehyde concentrations predicted, Science, 173, 141–143, 1971. </mixed-citation>
</ref>
<ref id="ref30">
<label>30</label><mixed-citation publication-type="other" xlink:type="simple"> Logan, J. A., Prather, M. J., Wofsy, S. C., and McElroy, M. B.: Tropospheric chemistry: a global perspective, J. Geophys. Res.-Oc. Atm., 86, 7210–7254, 1981. </mixed-citation>
</ref>
<ref id="ref31">
<label>31</label><mixed-citation publication-type="other" xlink:type="simple"> Mak, J. E. and Brenninkmeijer, C. A. M.: Measurement of $^13$CO and C$^18$O in the free troposphere, J. Geophys. Res.-Atmos., 103, 19347–19358, 1998. </mixed-citation>
</ref>
<ref id="ref32">
<label>32</label><mixed-citation publication-type="other" xlink:type="simple"> Mak, J. E. and Kra, G.: The isotopic composition of carbon monoxide at Montauk Point, Long Island, Chemosphere: Global Change Science, 1, 205–218, 1999. </mixed-citation>
</ref>
<ref id="ref33">
<label>33</label><mixed-citation publication-type="other" xlink:type="simple"> Mak, J. E., Kra, G., Sandomenico, T., and Bergamaschi, P.: The seasonally varying isotopic composition of the sources of carbon monoxide at Barbados, West Indies, J. Geophys. Res.-Atmos., 108, 4635, http://dx.doi.org/10.1029/2003jd003419doi:10.1029/2003jd003419, 2003. </mixed-citation>
</ref>
<ref id="ref34">
<label>34</label><mixed-citation publication-type="other" xlink:type="simple"> Manning, M. R., Brenninkmeijer, C. A. M., and Allan, W.: Atmospheric carbon monoxide budget of the southern hemisphere: Implications of $^13$C/$^12$C measurements, J. Geophys. Res.-Atmos., 102, 10673–10682, 1997. </mixed-citation>
</ref>
<ref id="ref35">
<label>35</label><mixed-citation publication-type="other" xlink:type="simple"> Marland, G., Boden, T. A., and Andres, R. J.: Global, Regional, and National Fossil-Fuel CO&lt;sub&gt;2&lt;/sub&gt; Emissions, in: Trends: A Compendium of Data on Global Change, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, US Department of Energy, Oak Ridge, Tenn., USA, 2008. </mixed-citation>
</ref>
<ref id="ref36">
<label>36</label><mixed-citation publication-type="other" xlink:type="simple"> Montzka, S. A., Krol, M., Dlugokencky, E., Hall, B., Jockel, P., and Lelieveld, J.: Small Interannual Variability of Global Atmospheric Hydroxyl, Science, 331, 67–69, http://dx.doi.org/10.1126/science.1197640doi:10.1126/science.1197640, 2011. </mixed-citation>
</ref>
<ref id="ref37">
<label>37</label><mixed-citation publication-type="other" xlink:type="simple"> Novelli, P. and Masarie, K. A.: Atmospheric Carbon Monoxide Dry Air Mole Fractions from the NOAA ESRL Carbon Cycle Cooperative Global Air Sampling Network, 1988-2009, Version: 2010-07-14, Path: ftp://ftp.cmdl.noaa.gov/ccg/co/flask/event/, last access: November 2011, 2010. </mixed-citation>
</ref>
<ref id="ref38">
<label>38</label><mixed-citation publication-type="other" xlink:type="simple"> Novelli, P. C., Steele, L. P., and Tans, P. P.: Mixing ratios of carbon monoxide in the troposphere, J. Geophys. Res.-Atmos., 97, 20731–20750, 1992. </mixed-citation>
</ref>
<ref id="ref39">
<label>39</label><mixed-citation publication-type="other" xlink:type="simple"> Novelli, P. C., Masarie, K. A., Tans, P. P., and Lang, P. M.: Recent changes in atmospheric carbon monoxide, Science, 263, 1587–1590, 1994. </mixed-citation>
</ref>
<ref id="ref40">
<label>40</label><mixed-citation publication-type="other" xlink:type="simple"> Park, K.: Joint Application of Concentration and Isotope Ratios to Investigate the Global Atmospheric Carbon Monoxide Budget: An Inverse Modeling Approach, PhD Thesis, Stony Brook University, Stony Brook, NY, USA, 2010. </mixed-citation>
</ref>
<ref id="ref41">
<label>41</label><mixed-citation publication-type="other" xlink:type="simple"> Parrish, D. D.: Critical evaluation of US on-road vehicle emission inventories, Atmos. Environ., 40, 2288–2300, http://dx.doi.org/10.1016/j.atmosenv.2005.11.033doi:10.1016/j.atmosenv.2005.11.033, 2006. </mixed-citation>
</ref>
<ref id="ref42">
<label>42</label><mixed-citation publication-type="other" xlink:type="simple"> Pechony, O. and Shindell, D. T.: Driving forces of global wildfires over the past millennium and the forthcoming century, Proc. Natl. Acad. Sci. U.S.A., 107, 19167–19170, http://dx.doi.org/10.1073/pnas.1003669107doi:10.1073/pnas.1003669107, 2010. </mixed-citation>
</ref>
<ref id="ref43">
<label>43</label><mixed-citation publication-type="other" xlink:type="simple"> Petrenko, V., Martinerie, P., Novelli, P., Etheridge, D. M., Levin, I., Wang, Z., Petron, G., Blunier, T., Chappellaz, J., Kaiser, J., Lang, P., Steele, L. P., Vogel, F., Leist, M. A., Mak, J., Langenfelds, R. L., Schwander, J., Severinghaus, J. P., Forster, G., Sturges, W., Rubino, M., and White, J. W. C.: Records of Northern Hemisphere carbon monoxide and hydrogen back to $\sim $1950 from Greenland firn air, Atmos. Chem. Phys., in preparation, 2012. </mixed-citation>
</ref>
<ref id="ref44">
<label>44</label><mixed-citation publication-type="other" xlink:type="simple"> Petron, G., Granier, C., Khattatov, B., Yudin, V., Lamarque, J. F., Emmons, L., Gille, J., and Edwards, D. P.: Monthly CO surface sources inventory based on the 2000-2001 MOPITT satellite data, Geophys. Res. Lett., 31, L21107 http://dx.doi.org/10.1029/2004gl020560doi:10.1029/2004gl020560, 2004. </mixed-citation>
</ref>
<ref id="ref45">
<label>45</label><mixed-citation publication-type="other" xlink:type="simple"> Pongratz, J., Reick, C., Raddatz, T., and Claussen, M.: A reconstruction of global agricultural areas and land cover for the last millennium, Global Biogeochem. Cy., 22, GB3018, http://dx.doi.org/10.1029/2007gb003153doi:10.1029/2007gb003153, 2008. </mixed-citation>
</ref>
<ref id="ref46">
<label>46</label><mixed-citation publication-type="other" xlink:type="simple"> Prinn, R. G., Huang, J., Weiss, R. F., Cunnold, D. M., Fraser, P. J., Simmonds, P. G., McCulloch, A., Harth, C., Reimann, S., Salameh, P., O&apos;Doherty, S., Wang, R. H. J., Porter, L. W., Miller, B. R., and Krummel, P. B.: Evidence for variability of atmospheric hydroxyl radicals over the past quarter century, Geophys. Res. Lett., 32, L07809, http://dx.doi.org/10.1029/2004gl022228doi:10.1029/2004gl022228, 2005. </mixed-citation>
</ref>
<ref id="ref47">
<label>47</label><mixed-citation publication-type="other" xlink:type="simple"> Rinsland, C. P. and Levine, J. S.: Free tropspheric carbon monoxide concentrations in 1950 and 1951 deduced from infrared total column amount measurements, Nature, 318, 250–254, 1985. </mixed-citation>
</ref>
<ref id="ref48">
<label>48</label><mixed-citation publication-type="other" xlink:type="simple"> %Röckmann, T., Jockel, P., Gros, V., Braunlich, M., Possnert, G., and %Brenninkmeijer, C. A. M.: Using $^14$C, $^13$C, $^18$O and $^17$O %isotopic variations to provide insights into the high northern latitude %surface CO inventory, Atmospheric Chemistry and Physics, 2, 147-159, 2002. Röckmann, T., Jöckel, P., Gros, V., Bräunlich, M., Possnert, G., and Brenninkmeijer, C. A. M.: Using $^14$C, $^13$C, $^18$O and $^17$O isotopic variations to provide insights into the high northern latitude surface CO inventory, Atmos. Chem. Phys., 2, 147–159, http://dx.doi.org/10.5194/acp-2-147-2002doi:10.5194/acp-2-147-2002, 2002 </mixed-citation>
</ref>
<ref id="ref49">
<label>49</label><mixed-citation publication-type="other" xlink:type="simple"> Rommelaere, V., Arnaud, L., and Barnola, J. M.: Reconstructing recent atmospheric trace gas concentrations from polar firn and bubbly ice data by inverse methods, J. Geophys. Res.-Atmos., 102, 30069–30083, 1997. </mixed-citation>
</ref>
<ref id="ref50">
<label>50</label><mixed-citation publication-type="other" xlink:type="simple"> Santra, A. K. and Goodman, D. W.: Catalytic oxidation of CO by platinum group metals: from ultrahigh vacuum to elevated pressures, Electrochim. Acta, 47, 3595–3609, PII S0013-4686(02)00330-4, doi:10.1016/S0013-4686(02)00330-4, 2002. </mixed-citation>
</ref>
<ref id="ref51">
<label>51</label><mixed-citation publication-type="other" xlink:type="simple"> Schwander, J. and Stauffer, B.: Age Difference between Polar Ice and the Air Trapped in Its Bubbles, Nature, 311, 45–47, 1984. </mixed-citation>
</ref>
<ref id="ref52">
<label>52</label><mixed-citation publication-type="other" xlink:type="simple"> Seiler, W.: Cycle of atmospheric CO, Tellus, 26, 116–135, 1974. </mixed-citation>
</ref>
<ref id="ref53">
<label>53</label><mixed-citation publication-type="other" xlink:type="simple"> Seiler, W. and Junge, C.: Carbon monoxide in atmosphere, J. Geophys. Res., 75, 2217–2226, 1970. </mixed-citation>
</ref>
<ref id="ref54">
<label>54</label><mixed-citation publication-type="other" xlink:type="simple"> Stevens, C. M., Walling, D., Venters, A., Ross, L. E., Engelkem, A., and Krout, L.: Isotopic Composition of Atmospheric Carbon-Monoxide, Earth Planet. Sc. Lett., 16, 147–165, 1972. </mixed-citation>
</ref>
<ref id="ref55">
<label>55</label><mixed-citation publication-type="other" xlink:type="simple"> Stevens, C. M., and Wagner, A. F.: The Role of Isotope Fractionation Effects in Atmospheric Chemistry, Z. Naturforsch. A, 44, 376–384, 1989. </mixed-citation>
</ref>
<ref id="ref56">
<label>56</label><mixed-citation publication-type="other" xlink:type="simple"> Tarr, M. A., Miller, W. L., and Zepp, R. G.: Direct carbon monoxide photoproduction from plant matter, J. Geophys. Res.-Atmos., 100, 11403–11413, 1995. </mixed-citation>
</ref>
<ref id="ref57">
<label>57</label><mixed-citation publication-type="other" xlink:type="simple"> Trudinger, C. M., Enting, I. G., Etheridge, D. M., Francey, R. J., Levchenko, V. A., Steele, L. P., Raynaud, D., and Arnaud, L.: Modeling air movement and bubble trapping in firn, J. Geophys. Res.-Atmos., 102, 6747–6763, 1997. </mixed-citation>
</ref>
<ref id="ref58">
<label>58</label><mixed-citation publication-type="other" xlink:type="simple"> Tsunogai, U., Hachisu, Y., Komatsu, D. D., Nakagawa, F., Gamo, T., and Akiyama, K.: An updated estimation of the stable carbon and oxygen isotopic compositions of automobile CO emissions, Atmos. Environ., 37, 4901–4910, http://dx.doi.org/10.1016/j.atmosenv.2003.08.008doi:10.1016/j.atmosenv.2003.08.008, 2003. </mixed-citation>
</ref>
<ref id="ref59">
<label>59</label><mixed-citation publication-type="other" xlink:type="simple"> van Aardenne, J. A., Dentener, F. J., Olivier, J. G. J., Goldewijk, C., and Lelieveld, J.: A 1 degrees × 1 degrees resolution data set of historical anthropogenic trace gas emissions for the period 1890–1990, Global Biogeochem. Cy., 15, 909–928, 2001. </mixed-citation>
</ref>
<ref id="ref60">
<label>60</label><mixed-citation publication-type="other" xlink:type="simple"> van der Werf, G. R., Randerson, J. T., Giglio, L., Collatz, G. J., Kasibhatla, P. S., and Arellano Jr., A. F.: Interannual variability in global biomass burning emissions from 1997 to 2004, Atmos. Chem. Phys., 6, 3423–3441, http://dx.doi.org/10.5194/acp-6-3423-2006doi:10.5194/acp-6-3423-2006, 2006. </mixed-citation>
</ref>
<ref id="ref61">
<label>61</label><mixed-citation publication-type="other" xlink:type="simple"> Wang, Z. and Mak, J. E.: A new CF-IRMS system for quantifying stable isotopes of carbon monoxide from ice cores and small air samples, Atmos. Meas. Tech., 3, 1307–1317, http://dx.doi.org/10.5194/amt-3-1307-2010doi:10.5194/amt-3-1307-2010, 2010. </mixed-citation>
</ref>
<ref id="ref62">
<label>62</label><mixed-citation publication-type="other" xlink:type="simple"> Wang, Z., Chappellaz, J., Park, K., and Mak, J. E.: Large Variations in Southern Hemisphere Biomass Burning During the Last 650 Years, Science, 330, 1663–1666, http://dx.doi.org/10.1126/science.1197257doi:10.1126/science.1197257, 2010. </mixed-citation>
</ref>
<ref id="ref63">
<label>63</label><mixed-citation publication-type="other" xlink:type="simple"> Witrant, E., Martinerie, P., Hogan, C., Laube, J. C., Kawamura, K., Capron, E., Montzka, S. A., Dlugokencky, E. J., Etheridge, D., Blunier, T., and Sturges, W. T.: A new multi-gas constrained model of trace gas non-homogeneous transport in firn: evaluation and behavior at eleven polar sites, Atmos. Chem. Phys. Discuss., 11, 23029–23080, http://dx.doi.org/10.5194/acpd-11-23029-2011doi:10.5194/acpd-11-23029-2011, 2011. </mixed-citation>
</ref>
<ref id="ref64">
<label>64</label><mixed-citation publication-type="other" xlink:type="simple"> Wu, J. and Boyle, E. A.: Lead in the western North Atlantic Ocean: completed response to leaded gasoline phase-out, Geochim. Cosmochim. Acta, 61, 3279–3283, 1997. </mixed-citation>
</ref>
<ref id="ref65">
<label>65</label><mixed-citation publication-type="other" xlink:type="simple"> Young, L. C. and Finlayson, B. A.: Mathematical models of monolith catallytic converter 2: application to automobile exhaust, Aiche J., 22, 343–353, 1976. </mixed-citation>
</ref>
</ref-list>
</back>
</article>