A recent build-up of atmospheric CO 2 over Europe. Part 1: observed signals and possible explanations
Résumé
(2010) A recent build-up of atmospheric CO 2 over Europe. Part 1: observed signals and possible explanations, A B S T R A C T We analysed interannual and decadal changes in the atmospheric CO 2 concentration gradient (CO 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 CO 2 reflects fossil fuel emissions and natural sinks activity over Europe, as well as atmospheric transport variability. The mean CO 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 CO 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.
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