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| Titel |
Impacts of land cover and climate data selection on understanding terrestrial carbon dynamics and the CO2 airborne fraction |
| VerfasserIn |
B. Poulter, D. C. Frank, E. L. Hodson, N. E. Zimmermann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 8, no. 8 ; Nr. 8, no. 8 (2011-08-01), S.2027-2036 |
| Datensatznummer |
250006067
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| Publikation (Nr.) |
 copernicus.org/bg-8-2027-2011.pdf |
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| Zusammenfassung |
| Terrestrial and oceanic carbon cycle processes remove ~55 % of
global carbon emissions, with the remaining 45 %, known as the "airborne
fraction", accumulating in the atmosphere. The long-term dynamics of the
component fluxes contributing to the airborne fraction are challenging to
interpret, but important for informing fossil-fuel emission targets and for
monitoring the trends of biospheric carbon fluxes. Climate and land-cover
forcing data for terrestrial ecosystem models are a largely unexplored
source of uncertainty in terms of their contribution to understanding
airborne fraction dynamics. Here we present results using a single dynamic
global vegetation model forced by an ensemble experiment of climate (CRU,
ERA-Interim, NCEP-DOE II), and diagnostic land-cover datasets (GLC2000,
GlobCover, MODIS). For the averaging period 1996–2005, forcing uncertainties
resulted in a large range of simulated global carbon fluxes, up to 13 %
for net primary production (52.4 to 60.2 Pg C a−1) and 19 % for soil
respiration (44.2 to 54.8 Pg C a−1). The sensitivity of contemporary
global terrestrial carbon fluxes to climate strongly depends on forcing data
(1.2–5.9 Pg C K−1 or 0.5 to 2.7 ppmv CO2 K−1), but weakening
carbon sinks in sub-tropical regions and strengthening carbon sinks in
northern latitudes are found to be robust. The climate and land-cover
combination that best correlate to the inferred carbon sink, and with the
lowest residuals, is from observational data (CRU) rather than reanalysis
climate data and with land-cover categories that have more stringent
criteria for forest cover (MODIS). Since 1998, an increasing positive trend
in residual error from bottom-up accounting of global sinks and sources
(from 0.03 (1989–2005) to 0.23 Pg C a−1 (1998–2005)) suggests that
either modeled drought sensitivity of carbon fluxes is too high, or that
carbon emissions from net land-cover change is too large. |
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