Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 1 2008 10.5194/acpd-8-3843-2008 http://www.atmos-chem-phys-discuss.net/8/3843/2008/ http://www.atmos-chem-phys-discuss.net/8/3843/2008/acpd-8-3843-2008.html http://www.atmos-chem-phys-discuss.net/8/3843/2008/acpd-8-3843-2008.pdf 3843 3893 2008-02-25 Can we reconcile differences in estimates of carbon fluxes from land-use change and forestry for the 1990s? A. Ito J. E. Penner M. J. Prather C. P. de Campos R. A. Houghton T. Kato A. K. Jain X. Yang G. C. Hurtt S. Frolking M. G. Fearon L. P. Chini A. Wang D. T. Price Frontier Research Center for Global Change, JAMSTEC, Yokohama, Japan Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA Earth System Science Department, University of California at Irvine, Irvine, California, USA Petrobras Research and Development Center, Rio de Janeiro, Brazil The Woods Hole Research Center, Woods Hole, Massachusetts, USA Department of Atmospheric Science, University of Illinois, Urbana, Illinois, USA Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire, USA Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada Natural Resources Canada, Northern Forestry Centre, Edmonton, Alberta, Canada The effect of Land Use Change and Forestry (LUCF) on terrestrial carbon fluxes can be regarded as a carbon credit or debit under the UNFCCC, but scientific uncertainty in the estimates for LUCF remains large. Here, we assess the LUCF estimates by examining a variety of models of different types with different land cover change maps in the 1990s. Annual carbon pools and their changes are separated into different components for separate geographical regions, while annual land cover change areas and carbon fluxes are disaggregated into different LUCF activities and the biospheric response due to CO₂ fertilization and climate change. We developed a consolidated estimate of the terrestrial carbon fluxes that combines book-keeping models with process-based biogeochemical models and inventory estimates and yields an estimate of the global terrestrial carbon flux that is within the uncertainty range developed in the IPCC 4th Assessment Report. We examined the USA and Brazil as case studies in order to assess the cause of differences from the UNFCCC reported carbon fluxes. Major differences in the litter and soil organic matter components are found for the USA. 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