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ECN publication
Importance of fossil fuel emission uncertainties over Europe for CO2 modeling: model intercomparison
Peylin, P.; Houweling, S.; Krol, M.C.; Karstens, U.; Rödenbeck, C.; Geels, C.; Vermeulen, A.T.; Badawy, B.; Aulagnier, C.; Pregger, T.; Delage, F.; Pieterse, G.; Ciais, P.; Heimann, M.
Published by: Publication date:
ECN Biomass, Coal and Environmental Research 22-6-2009
ECN report number: Document type:
ECN-W--09-017 Article (scientific)
Number of pages:

Published in: Atmos. Chem. Phys. Discuss., 9, 7457–7503, 2009 (), , , Vol., p.-.

Inverse modeling techniques used to quantify surface carbon fluxes commonly assume that the uncertainty of fossil fuel CO2 (FFCO2) emissions is negligible and that intraannual variations can be neglected. To investigate these assumptions, we analyzed the differences between four fossil fuel emission maps with spatial and temporal differences over Europe and their impact on the model simulated CO2 concentration. Large temporal flux variations characterize the hourly fields (_40% and _80% for the seasonal and diurnal cycles, peak-to-peak) and annual country totals differ by 10% on average and up to 40% for some countries (i.e., The Netherlands). These emissions have been prescribed to seven different transport models, resulting in 28 different FFCO2 concentrations fields. The modeled FFCO2 concentration time series at surface sites using time-varying emissions show larger seasonal cycles (+2 ppm at the Hungarian tall tower (HUN)) and smaller diurnal cycles in summer (-1 ppm at HUN) than when using constant emissions. The concentration range spanned by all simulations varies between stations, and is generally larger in winter (up to _10 ppm peak-to-peak at HUN) than in summer (_5 ppm). The contribution of transport model differences to the simulated concentration std-dev is 2–3 times larger than the contribution of emission differences only, at typical European sites used in global inversions. These contributions to the hourly (monthly) std-dev’s amount to _1.2 (0.8) ppm and _0.4 (0.3) ppm for transport and emissions, respectively. First comparisons of the modeled concentrations with 14C-based fossil fuel CO2 observations show that the large transport differences still hamper a quantitative evaluation/validation of the emission inventories. Changes in the estimated monthly biosphere flux (Fbio) over Europe, using two inverse modeling approaches, are relatively small (less that 5%) while changes in annual Fbio (up to _0.15 Gt C/yr) are only slightly smaller than the differences in annual emission totals and around 30% of the mean European ecosystem carbon sink. These results point to an urgent need to improve not only the transport models but also the assumed spatial and temporal distribution of fossil fuel emission maps.

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