Is the recent build-up of atmospheric CO2 over Europe reproduced by models. Part 2: An overview with the atmospheric mesoscale transport model CHIMERE

Abstract

In this issue, Ramonet et al. revealed a positive trend in European, atmospheric CO2 concentrations relative to a marine, North Atlantic reference baseline, for the years 2001-2006. The observed build up mainly occurred during the cold season where it reaches a 0.8 ppm yr-1 at low-altitude stations to a 0.3 ppm yr-1 at mid-altitude stations. We explore the cause of this build-up using the mesoscale model CHIMERE. We first model the observed trends, using interannually varying fluxes and transport, then suppress the interannual variability in fluxes or aspects of transport to elucidate the cause. The run with no interannual variability in fluxes still matches observed trends suggesting that t..