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| Titel |
From land use to land cover: restoring the afforestation signal in a coupled integrated assessment–earth system model and the implications for CMIP5 RCP simulations |
| VerfasserIn |
A. V. Di Vittorio, L. P. Chini, B. Bond-Lamberty, J. Mao, X. Shi, J. Truesdale, A. Craig, K. Calvin, A. Jones, W. D. Collins, J. Edmonds, G. C. Hurtt, P. Thornton, A. Thomson |
| 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 ; 11, no. 22 ; Nr. 11, no. 22 (2014-11-27), S.6435-6450 |
| Datensatznummer |
250117694
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| Publikation (Nr.) |
 copernicus.org/bg-11-6435-2014.pdf |
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| Zusammenfassung |
| Climate projections depend on scenarios of fossil fuel emissions and land use
change, and the Intergovernmental Panel on Climate Change (IPCC) AR5 parallel process assumes consistent climate
scenarios across integrated assessment and earth system models (IAMs and
ESMs). The CMIP5 (Coupled Model Intercomparison Project Phase 5) project used a novel "land use harmonization" based on
the Global Land use Model (GLM) to provide ESMs with consistent 1500–2100 land
use trajectories generated by historical data and four IAMs. A direct
coupling of the Global Change Assessment Model (GCAM), GLM, and the Community
ESM (CESM) has allowed us to characterize and partially address a major gap
in the CMIP5 land coupling design: the lack of a corresponding land cover
harmonization. For RCP4.5, CESM global afforestation is only 22% of
GCAM's 2005 to 2100 afforestation. Likewise, only 17% of GCAM's 2040
afforestation, and zero pasture loss, were transmitted to CESM within the
directly coupled model. This is a problem because GCAM relied on
afforestation to achieve RCP4.5 climate stabilization. GLM modifications and
sharing forest area between GCAM and GLM within the directly coupled model
did not increase CESM afforestation. Modifying the land use translator in
addition to GLM, however, enabled CESM to include 66% of GCAM's
afforestation in 2040, and 94% of GCAM's pasture loss as grassland and
shrubland losses. This additional afforestation increases CESM vegetation
carbon gain by 19 PgC and decreases atmospheric CO2 gain by 8 ppmv
from 2005 to 2040, which demonstrates that CESM without additional
afforestation simulates a different RCP4.5 scenario than prescribed by GCAM.
Similar land cover inconsistencies exist in other CMIP5 model results,
primarily because land cover information is not shared between models.
Further work to harmonize land cover among models will be required to
increase fidelity between IAM scenarios and ESM simulations and realize the
full potential of scenario-based earth system simulations. |
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