Preprints
https://doi.org/10.5194/egusphere-2023-2215
https://doi.org/10.5194/egusphere-2023-2215
17 Oct 2023
 | 17 Oct 2023

Can ∆14CO2 observations help atmospheric inversions constrain the fossil CO2 emission budget of Europe?

Carlos Gómez-Ortiz, Guillaume Monteil, Sourish Basu, and Marko Scholze

Abstract. Independent estimation and verification of fossil CO2 emissions on a regional and national scale is crucial to evaluate the fossil CO2 emissions and reductions reported by countries as part of their nationally determined contributions (NDCs). Top-down methods, such as the assimilation of in situ and satellite observations of different tracers (e.g. CO2, CO, ∆14CO2, XCO2, have been increasingly used lately for this purpose. In this paper, we use the Lund University Modular Inversion Algorithm (LUMIA) to estimate fossil CO2 emissions and natural fluxes by inverting simultaneously in situ observations of CO2 and ∆14CO2 over Europe. We evaluate the inversion system by performing a series of Observing System Simulation Experiments (OSSEs). We find that in regions with a dense sampling network, such as Western/Central Europe, when we add ∆14CO2 observations in an experiment where the prior fossil CO2 and biosphere fluxes are set to zero, LUMIA is capable of recovering the time series of both categories, reducing the prior to truth RMSE from 1.26 TgC day-1 to 0.12 TgC day-1 in fossil CO2 and from 0.97 TgC day-1 to 0.17 in biosphere, and the true total CO2 budget in 91 %. In a second set of experiments, using realistic prior fluxes, we find that, in addition to retrieving the time series of the optimized fluxes, we are able to recover the true regional fossil CO2 budget in Western/Central Europe by 95 % and in Germany by 97 %. In regions with low sampling coverage, such as Southern Europe and the British Isles, the posterior fossil CO2 emissions are not well resolved in any scenario, and the biosphere fluxes can follow the seasonality with a significant bias that makes it impossible to close the total CO2 budget. We find that the prior uncertainty of fossil CO2 emissions does not significantly impact the posterior estimates, showing similar results in regions with good sampling coverage like Western/Central and Northern Europe. Finally, it is important to have a good prior estimate of the terrestrial isotopic disequilibrium to avoid including additional noise to the posterior fossil CO2 fluxes.

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Carlos Gómez-Ortiz, Guillaume Monteil, Sourish Basu, and Marko Scholze

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2215', Anonymous Referee #1, 10 Jan 2024
  • RC2: 'Comment on egusphere-2023-2215', Anonymous Referee #2, 17 Jan 2024
  • AC1: 'Answer to the referees.', Carlos Gómez-Ortiz, 10 Mar 2024
Carlos Gómez-Ortiz, Guillaume Monteil, Sourish Basu, and Marko Scholze

Data sets

Input data: Can ∆14CO2 observations help atmospheric inversions constrain the fossil CO2 emission budget of Europe? Carlos Gómez-Ortiz, Sourish Basu https://doi.org/10.6084/m9.figshare.24307162

Model code and software

Code: Can ∆14CO2 observations help atmospheric inversions constrain the fossil CO2 emission budget of Europe? Carlos Gómez-Ortiz, Guillaume Monteil https://doi.org/10.5281/zenodo.8426217

Carlos Gómez-Ortiz, Guillaume Monteil, Sourish Basu, and Marko Scholze

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Short summary
In this paper, we test the new implementations of our tool LUMIA to estimate the weekly and regional CO2 emissions from fossil fuels in Europe. We use the measurements of CO2 and radiocarbon (14CO2) levels in the atmosphere to trace emissions to their sources, while separating the natural and the fossil CO2. Our tool, LUMIA, accurately estimates fossil CO2 emissions in densely monitored regions like Western/Central Europe. This approach aids in developing strategies for reducing CO2 emissions.