Computation and analysis of atmospheric carbon dioxide annual mean growth rates from satellite observations during 2003–2016

• Main Authors: M. Buchwitz, M. Reuter, O. Schneising, S. Noël, B. Gier, H. Bovensmann, J. P. Burrows, H. Boesch, J. Anand, R. J. Parker, P. Somkuti, R. G. Detmers, O. P. Hasekamp, I. Aben, A. Butz, A. Kuze, H. Suto, Y. Yoshida, D. Crisp, C. O'Dell
• Format: Article
• Language: English
• Published: Copernicus Publications 2018-12-01
• Series: Atmospheric Chemistry and Physics
• Online Access: https://www.atmos-chem-phys.net/18/17355/2018/acp-18-17355-2018.pdf
• ISSN: 1680-7316; 1680-7324

<p>The growth rate of atmospheric carbon dioxide (<span class="inline-formula">CO₂</span>) reflects the net effect of emissions and uptake resulting from anthropogenic and natural carbon sources and sinks. Annual mean <span class="inline-formula">CO₂</span> growth rates have been determined from satellite retrievals of column-averaged dry-air mole fractions of <span class="inline-formula">CO₂</span>, i.e. <span class="inline-formula">XCO₂</span>, for the years 2003 to 2016. The <span class="inline-formula">XCO₂</span> growth rates agree with National Oceanic and Atmospheric Administration (NOAA) growth rates from <span class="inline-formula">CO₂</span> surface observations within the uncertainty of the satellite-derived growth rates (mean difference&thinsp;<span class="inline-formula">±</span>&thinsp;standard deviation: <span class="inline-formula">0.0±0.3</span>&thinsp;ppm&thinsp;year<span class="inline-formula">⁻¹</span>; <span class="inline-formula"><i>R</i></span>: 0.82). This new and independent data set confirms record-large growth rates of around 3&thinsp;ppm&thinsp;year<span class="inline-formula">⁻¹</span> in 2015 and 2016, which are attributed to the 2015–2016 El Niño. Based on a comparison of the satellite-derived growth rates with human <span class="inline-formula">CO₂</span> emissions from fossil fuel combustion and with El Niño Southern Oscillation (ENSO) indices, we estimate by how much the impact of ENSO dominates the impact of fossil-fuel-burning-related emissions in explaining the variance of the atmospheric <span class="inline-formula">CO₂</span> growth rate. Our analysis shows that the ENSO impact on <span class="inline-formula">CO₂</span> growth rate variations dominates that of human emissions throughout the period 2003–2016 but in particular during the period 2010–2016 due to strong La Niña and El Niño events. Using the derived growth rates and their uncertainties, we estimate the probability that the impact of ENSO on the variability is larger than the impact of human emissions to be 63&thinsp;% for the time period 2003–2016. If the time period is restricted to 2010–2016, this probability increases to 94&thinsp;%.</p>