Recent changes in the global and regional carbon cycle: analysis of first-order diagnostics

Abstract

Abstract. We analyze global and regional changes in CO2 fluxes using two simple models, an airborne fraction of anthropogenic emissions and a linear relationship with CO2 concentrations. We show that both models are able to fit the nonanthropogenic (hereafter natural) flux over the length of the atmospheric concentration record and that departures in the airborne fraction model are largely due to departures from exponential growth of emissions. Analysis of the first-order model (including its uncertainties) suggests no significant change in the response of the natural carbon cycle. We apply the same first-order diagnostic to fluxes from atmospheric inversions. Their responses show clear regi..