1School of Earth Sciences, University of Melbourne, Melbourne, Australia
2CSIRO Oceans and Atmosphere Flagship, Melbourne, Australia
3Department of Physical Geography and Ecosystem Science, Lund University, Sweden
Received: 29 May 2014 – Discussion started: 25 Jun 2014
Abstract. We analyse 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 non-anthropogenic (hereafter natural) flux over the length of the atmospheric concentration record. Analysis of the linear model (including its uncertainties) suggests no significant decrease in the response of the natural carbon cycle. Recent data points rather to an increase. We apply the same linear diagnostic to fluxes from atmospheric inversions. Flux responses show clear regional and seasonal patterns driven by terrestrial uptake in the northern summer. Ocean fluxes show little or no linear response. Terrestrial models show clear responses, agreeing globally with the inversion responses, however the spatial structure is quite different, with dominant responses in the tropics rather than the northern extratropics.
Revised: 17 Nov 2014 – Accepted: 08 Jan 2015 – Published: 11 Feb 2015
Rayner, P. J., Stavert, A., Scholze, M., Ahlström, A., Allison, C. E., and Law, R. M.: Recent changes in the global and regional carbon cycle: analysis of first-order diagnostics, Biogeosciences, 12, 835-844, doi:10.5194/bg-12-835-2015, 2015.