Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Decreasing emissions of NOx relative to CO2 in East Asia inferred from satellite observations


At present, global CO2 emission inventories are mainly based on bottom-up estimates that rely, for example, on reported fossil fuel consumptions and fuel types1,2. The associated uncertainties propagate into the CO2-to-NOx emission ratios that are used in pollution prediction and monitoring3, as well as into biospheric carbon fluxes derived by inverse models4. Here we analyse simultaneous and co-located satellite retrievals from SCIAMACHY (ref. 5; SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY) of the column-average dry-air mole fraction of CO2 (refs 6, 7) and NO2 (refs 8, 9, 10) for the years 2003–2011 to provide a top-down estimate of trends in emissions and in the ratio between CO2 and NOx emissions. Our analysis shows that the CO2-to-NOx emission ratio has increased by 4.2 ± 1.7% yr−1 in East Asia. In this region, we find a large positive trend of CO2 emissions (9.8 ± 1.7% yr−1), which we largely attribute to the growing Chinese economy. This trend exceeds the positive trend of NOx emissions (5.8 ± 0.9% yr−1). Our findings suggest that the recently installed and renewed technology in East Asia, such as power plants, transportation and so on, is cleaner in terms of NOx emissions than the old infrastructure, and roughly matches relative emission levels in North America and Europe.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Get just this article for as long as you need it


Prices may be subject to local taxes which are calculated during checkout

Figure 1: Expected XCO2 enhancement from nearby anthropogenic emissions (XCO2e) and corresponding NO2 levels.
Figure 2: Data-period-averaged regional weekday anomaly of ΔXCO2 (green) and ΔNO2 (red) for the regions North America/Europe (solid) and East Asia (dashed).
Figure 3: Trends of the CO2-to-NOx emission ratio (that is, conversion factor F), tropospheric NO2, XCO2e and EDGAR CO2 emissions.


  1. Olivier, J., Janssens-Maenhout, G., Muntean, M. & Peters, J. Trends in global CO2 emissions: 2013 Report (European Commission’s Joint Research Centre, 2013)

  2. Boden, T., Marland, G. & Andres, R. Global, Regional, and National Fossil-Fuel CO2 Emissions (Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, 2013).

    Google Scholar 

  3. Zhang, Q. et al. NOx emission trends for China, 1995–2004: The view from the ground and the view from space. J. Geophys. Res. 112, D22306 (2007).

    Article  Google Scholar 

  4. Peters, W. et al. An atmospheric perspective on North American carbon dioxide exchange: Carbontracker. Proc. Natl Acad. Sci. USA 104, 18925–18930 (2007).

    Article  Google Scholar 

  5. Bovensmann, H. et al. SCIAMACHY—Mission objectives and measurement modes. J. Atmos. Sci. 56, 127–150 (1999).

    Article  Google Scholar 

  6. Reuter, M. et al. A method for improved SCIAMACHY CO2 retrieval in the presence of optically thin clouds. Atmos. Meas. Tech. 3, 209–232 (2010).

    Article  Google Scholar 

  7. Reuter, M. et al. Retrieval of atmospheric CO2 with enhanced accuracy and precision from SCIAMACHY: Validation with FTS measurements and comparison with model results. J. Geophys. Res. 116, D04301 (2011).

    Article  Google Scholar 

  8. Richter, A. & Burrows, J. P. Tropospheric NO2 from GOME measurements. Adv. Space Res. 29, 1673–1683 (2002).

    Article  Google Scholar 

  9. Hilboll, A. et al. Improvements to the retrieval of tropospheric NO2 from satellite—stratospheric correction using SCIAMACHY limb/nadir matching and comparison to Oslo CTM2 simulations. Atmos. Meas. Tech. 6, 565–584 (2013).

    Article  Google Scholar 

  10. Hilboll, A., Richter, A. & Burrows, J. P. Long-term changes of tropospheric NO2 over megacities derived from multiple satellite instruments. Atmos. Chem. Phys. 13, 4145–4169 (2013).

    Article  Google Scholar 

  11. IPCC, Climate Change 2013: The Physical Science Basis (Cambridge Univ. Press, 2013).

    Google Scholar 

  12. Bovensmann, H. et al. A remote sensing technique for global monitoring of power plant CO2 emissions from space and related applications. Atmos. Meas. Tech. 3, 781–811 (2010).

    Article  Google Scholar 

  13. BP statistical review of world energy (BP, 2013);

  14. Kurokawa, J. et al. Emissions of air pollutants and greenhouse gases over Asian regions during 2000–2008: Regional Emission inventory in ASia (REAS) version 2. Atmos. Chem. Phys. 13, 11019–11058 (2013).

    Article  Google Scholar 

  15. Guan, D., Liu, Z., Geng, Y., Lindner, S. & Hubacek, K. The gigatonne gap in China’s carbon dioxide inventories. Nature Clim. Change 2, 672–675 (2012).

    Article  Google Scholar 

  16. Richter, A., Burrows, J. P., Nüß, H., Granier, C. & Niemeier, U. Increase in tropospheric nitrogen dioxide over China observed from space. Nature 437, 129–132 (2005).

    Article  Google Scholar 

  17. Wunch, D., Wennberg, P. O., Toon, G. C., Keppel-Aleks, G. & Yavin, Y. G. Emissions of greenhouse gases from a North American megacity. Geophys. Res. Lett. 36, L15810 (2009).

    Article  Google Scholar 

  18. Turnbull, J. C. et al. Atmospheric observations of carbon monoxide and fossil fuel CO2 emissions from East Asia. J. Geophys. Res. 116, D24306 (2011).

    Article  Google Scholar 

  19. Silva, S. J., Arellano, A. F. & Worden, H. M. Toward anthropogenic combustion emission constraints from space-based analysis of urban CO2/CO sensitivity. Geophys. Res. Lett. 40, 4971–4976 (2013).

    Article  Google Scholar 

  20. Berezin, E. V. et al. Multiannual changes of CO2 emissions in China: Indirect estimates derived from satellite measurements of tropospheric NO2 columns. Atmos. Chem. Phys. 13, 9415–9438 (2013).

    Article  Google Scholar 

  21. Schneising, O. et al. Anthropogenic carbon dioxide source areas observed from space: Assessment of regional enhancements and trends. Atmos. Chem. Phys. 13, 2445–2454 (2013).

    Article  Google Scholar 

  22. Kort, E. A., Frankenberg, C., Miller, C. E. & Oda, T. Space-based observations of megacity carbon dioxide. Geophys. Res. Lett. 39, L17806 (2012).

    Article  Google Scholar 

  23. Ummel, K. CARMA Revisited: An Updated Database of Carbon Dioxide Emissions From Power Plants Worldwide (Center for Global Development, 2012)

    Google Scholar 

  24. Beirle, S., Platt, U., Wenig, M. O. & Wagner, T. Weekly cycle of NO2 by GOME measurements: A signature of anthropogenic sources. Atmos. Chem. Phys. 3, 2225–2232 (2003).

    Article  Google Scholar 

  25. Zhou, Y., Brunner, D., Hueglin, C., Henne, S. & Staehelin, J. Changes in OMI tropospheric NO2 columns over Europe from 2004 to 2009 and the influence of meteorological variability. Atmos. Environ. 46, 482–495 (2012).

    Article  Google Scholar 

  26. Stavrakou, T., Mueller, J-F., Boersma, K. F., De Smedt, I. & van der A, R. J. Assessing the distribution and growth rates of NOx emission sources by inverting a 10-year record of NO2 satellite columns. Geophys. Res. Lett. 35, L10801 (2008).

    Article  Google Scholar 

  27. Kurokawa, J-i., Yumimoto, K., Uno, I. & Ohara, T. Adjoint inverse modeling of NOx emissions over eastern China using satellite observations of NO2 vertical column densities. Atmos. Environ. 43, 1878–1887 (2009).

    Article  Google Scholar 

  28. Gu, D., Wang, Y., Smeltzer, C. D. & Liu, Z. Reduction in NOx emission trends over China: Regional and seasonal variations. Environ. Sci. Technol. 47, 12912–12919 (2013).

    Article  Google Scholar 

  29. Crisp, D. et al. The Orbiting Carbon Observatory (OCO) mission. Adv. Space Res. 34, 700–709 (2004).

    Article  Google Scholar 

Download references


This work was in part funded by ESA/ESRIN (GHG-CCI), EU FP7 (MACC-II), DLR (SADOS), and the State and the University of Bremen. We acknowledge the use of data from the Emission Database for Global Atmospheric Research (EDGAR), BP’s statistical review of world energy, the Regional Emission inventory in ASia (REAS), the Global Carbon Project (GPC), and the CARMA (CARbon Monitoring for Action) database. Thanks also to the ECMWF for providing the meteorological reanalysis data.

Author information

Authors and Affiliations



M.R.: experimental set-up, data analysis, interpretation, design and operation of the XCO2 satellite retrieval, writing the paper. M.B., M.H., J.H., O.S., H.B., J.P.B.: experimental set-up, interpretation, design of the XCO2 satellite retrieval, improving the paper. A.H., A.R.: experimental set-up, interpretation, design and operation of the NO2 satellite retrieval, improving the paper.

Corresponding author

Correspondence to M. Reuter.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary Information (PDF 3407 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Reuter, M., Buchwitz, M., Hilboll, A. et al. Decreasing emissions of NOx relative to CO2 in East Asia inferred from satellite observations. Nature Geosci 7, 792–795 (2014).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing