Can we reconcile differences in estimates of carbon fluxes from land-use change and forestry for the 1990s? A. Ito1, J. E. Penner2, M. J. Prather3, C. P. de Campos4, R. A. Houghton5, T. Kato1, A. K. Jain6, X. Yang6, G. C. Hurtt7, S. Frolking7, M. G. Fearon7, L. P. Chini7, A. Wang8, and D. T. Price9 1Frontier Research Center for Global Change, JAMSTEC, Yokohama, Japan 2Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA 3Earth System Science Department, University of California at Irvine, Irvine, California, USA 4Petrobras Research & Development Center, Rio de Janeiro, Brazil 5The Woods Hole Research Center, Woods Hole, Massachusetts, USA 6Department of Atmospheric Science, University of Illinois, Urbana, Illinois, USA 7Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire, USA 8Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada 9Natural Resources Canada, Northern Forestry Centre, Edmonton, Alberta, Canada
Abstract. 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.
Differences in Brazil result from assumptions about the LUC for agricultural
purposes. The effects of CO2 fertilization and climate change also vary
significantly in Brazil. Our consolidated estimate shows that the small sink
in Latin America is within the uncertainty range from inverse models, but
that the sink in the USA is significantly smaller than the inverse models
estimates. Because there are different sources of errors at the country
level, there is no easy reconciliation of different estimates of carbon
fluxes at the global level. Clearly, further work is required to develop
data sets for historical land cover change areas and models of
biogeochemical changes for an accurate representation of carbon uptake or
emissions due to LUC.
Citation: Ito, A., Penner, J. E., Prather, M. J., de Campos, C. P., Houghton, R. A., Kato, T., Jain, A. K., Yang, X., Hurtt, G. C., Frolking, S., Fearon, M. G., Chini, L. P., Wang, A., and Price, D. T.: Can we reconcile differences in estimates of carbon fluxes from land-use change and forestry for the 1990s?, Atmos. Chem. Phys., 8, 3291-3310, doi:10.5194/acp-8-3291-2008, 2008.