A recent build-up of atmospheric CO2 over Europe. Part 1: observed signals and possible explanations

• Published in: Tellus. Series B, Chemical and physical meteorology Chemical and physical meteorology, 2010-02, Vol.62 (1), p.1-13
• Main Authors: Ramonet, Michel, Ciais, Philippe, Aalto, Tuula, Aulagnier, Céeline, Chevallier, FrédSéric, Cipriano, Domenico, Conway, Thomas, Haszpra, Laszlo, Kazan, Victor, Meinhardt, Frank, Paris, Jean-Daniel, Schmid, Martina, Simmonds, Peter, Xueref-Rémy, IRéNE, Necki, Jaroslaw
• Format: Article
• Language: English
• Subjects: Applied sciences; Atmospheric pollution; Chemical composition and interactions. Ionic interactions and processes; Earth, ocean, space; Exact sciences and technology; External geophysics; Marine; Meteorology; Pollutants physicochemistry study: properties, effects, reactions, transport and distribution; Pollution
• ISSN: 0280-6509; 1600-0889
• DOI: 10.1111/j.1600-0889.2009.00442.x

We analysed interannual and decadal changes in the atmospheric CO 2 concentration gradient (ΔCO 2 ) between Europe and the Atlantic Ocean over the period 1995-2007. Fourteen measurement stations are used, with Mace-Head being used to define background conditions. The variability of ΔCO 2 reflects fossil fuel emissions and natural sinks activity over Europe, as well as atmospheric transport variability. The mean ΔCO 2 increased by 1-2 ppm at Eastern European stations (∼30% growth), between 1990-1995 and 2000-2005. This built up of CO 2 over the continent is predominantly a winter signal. If the observed increase of ΔCO 2 is explained by changes in ecosystem fluxes, a loss of about 0.46 Pg C per year would be required during 2000-2005. Even if severe droughts have impacted Western Europe in 2003 and 2005, a sustained CO 2 loss of that magnitude is unlikely to be true.We sought alternative explanations for the observed CO 2 build-up into transport changes and into regional redistribution of fossil fuel CO 2 emissions. Boundary layer heights becoming shallower can only explain 32% of the variance of the signal. Regional changes of emissions may explain up to 27% of the build-up. More insights are given in the Aulagnier et al. companion paper.