Biogeosciences Discuss., 10, 8343-8413, 2013
© Author(s) 2013. This work is distributed
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This discussion paper has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG.
The full greenhouse gases budget of Africa: synthesis, uncertainties and vulnerabilities
R. Valentini1,2, A. Arneth3, A. Bombelli2, S. Castaldi2,4, R. Cazzolla Gatti1, F. Chevallier5, P. Ciais5, E. Grieco2, J. Hartmann6, M. Henry7, R. A. Houghton8, M. Jung9, W. L. Kutsch10, Y. Malhi11, E. Mayorga12, L. Merbold13, G. Murray-Tortarolo15, D. Papale1, P. Peylin5, B. Poulter5, P. A. Raymond14, M. Santini2, S. Sitch15, G. Vaglio Laurin2,16, G. R. van der Werf17, C. A. Williams18, and R. J. Scholes19
1Department for Innovation in Biological, Agro-food and Forest systems (DIBAF), University of Tuscia, via S. Camillo de Lellis, 01100 Viterbo, Italy
2Euro-Mediterranean Center on Climate Change (CMCC), Via Augusto Imperatore 16, 73100 Lecce, Italy
3Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research, Kreuzeckbahn Str. 19, 82467 Garmisch-Partenkirchen, Germany
4Dipartimento di Scienze Ambientali, Biologiche e Farmaceutiche (DISTABIF), Seconda Università di Napoli, via Vivaldi 43, 81100 Caserta, Italy
5LSCE, CEA-CNRS-UVSQ, L'Orme des Merisiers, Bat 701, 91191 Gif-sur-Yvette, France
6Institute for Biogeochemistry and Marine Chemistry, 20146, Hamburg, Germany
7FAO, Forestry Department, UN-REDD Programme, Viale delle terme di Caracalla 1, 00153 Rome, Italy
8Woods Hole Research Center, 149 Woods Hole Road, Falmouth, MA 02540, USA
9Biogeochemical Model Data Integration Group, Max Planck Institute for Biogeochemistry, Hans-Knöll Str. 10, 07745 Jena, Germany
10Thuenen Institute for Climate-smart Agriculture, Bundesallee 50, 38116 Braunschweig, Germany
11Environmental Change Institute, School of Geography and the Environment, University of Oxford, UK
12Applied Physics Laboratory, University of Washington, Seattle, USA
13Department of Environmental Systems Science, Institute of Agricultural Sciences IAS, ETH Zurich, 8092 Zurich, Switzerland
14Yale School of Forestry and Environmental Studies, 195 Prospect St, new Haven CT, 06511, USA
15University of Exeter, Rennes Drive, Exeter EX4 4RJ, UK
16Department of Civil Engineering and Computer Science Engineering, University of Tor Vergata, Rome, Italy
17Faculty of Earth and Life Sciences, VU University Amsterdam, De Boelelaan 1085, 1081HV Amsterdam, the Netherlands
18Graduate School of Geography, Clark University, Worcester, Massachusetts, USA
19Council for Scientific and Industrial Research, P.O. Box 395, Pretoria 0001 South Africa

Abstract. This paper, developed under the framework of the RECCAP initiative, aims at providing improved estimates of the carbon and GHG (CO2, CH4 and N2O) balance of continental Africa. The various components and processes of the African carbon and GHG budget were considered, and new and available data derived by different methodologies (based on inventories, ecosystem fluxes, models, and atmospheric inversions) were integrated. The related uncertainties were quantified and current gaps and weakness in knowledge and in the monitoring systems were also considered in order to provide indications on the future requirements. The vast majority of the results seem to agree that Africa is probably a small sink of carbon on an annual scale, with an average value of −0.61 ± 0.58 Pg C yr−1. Nevertheless the emissions of CH4 and N2O may turn Africa into a source in terms of CO2 equivalents. At sub-regional level there is a significant spatial variability in both sources and sinks, mainly due to the biome's differences and the different anthropic impacts, with southern Africa as the main source and central Africa, with its evergreen tropical forests, as the main sink. Emissions from land use change in Africa are significant (around 0.32 ± 0.05 Pg C yr−1) and even higher than the fossil fuel ones; this is a unique feature among all the continents. In addition there can be significant carbon losses from land even without changes in the land use (forest), as results from the impact of selective logging. Fires also play a significant role, with 1.03 ± 0.22 Pg C yr−1 of carbon emissions, mainly (90%) originated by savanna and woodland burning. But whether fire carbon emissions are compensated by CO2 uptake during the growing season, or are a non-reversible loss of CO2, remains unclear. Most of these figures are subjected to a significant interannual variability, on the order of ± 0.5 Pg C yr−1 in standard deviation, accounting for around 25% of the year-to-year variation in the global carbon budget.

These results, even if still highly uncertain, show the important role that Africa plays in the carbon cycle at global level, both in terms of absolute values and variability.

Citation: Valentini, R., Arneth, A., Bombelli, A., Castaldi, S., Cazzolla Gatti, R., Chevallier, F., Ciais, P., Grieco, E., Hartmann, J., Henry, M., Houghton, R. A., Jung, M., Kutsch, W. L., Malhi, Y., Mayorga, E., Merbold, L., Murray-Tortarolo, G., Papale, D., Peylin, P., Poulter, B., Raymond, P. A., Santini, M., Sitch, S., Vaglio Laurin, G., van der Werf, G. R., Williams, C. A., and Scholes, R. J.: The full greenhouse gases budget of Africa: synthesis, uncertainties and vulnerabilities, Biogeosciences Discuss., 10, 8343-8413, doi:10.5194/bgd-10-8343-2013, 2013.
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