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          Institute: MPI für Meteorologie     Collection: Ocean in the Earth System     Display Documents

ID: 477019.0, MPI für Meteorologie / Ocean in the Earth System
Climate and carbon-cycle variability over the last millennium
Authors:Jungclaus, J. H.; Lorenz, S. J.; Timmreck, C.; Reick, C. H.; Brovkin, V.; Six, K.; Segschneider, J.; Giorgetta, M. A.; Crowley, T. J.; Pongratz, J.; Krivova, N. A.; Vieira, L. E.; Solanki, S. K.; Klocke, D.; Botzet, M.; Esch, M.; Gayler, V.; Haak, H.; Raddatz, T.; Roeckner, E.; Schnur, R.; Widmann, H.; Claussen, M.; Stevens, B.; Marotzke, J.
Date of Publication (YYYY-MM-DD):2010
Title of Journal:Climate of the Past
Start Page:723
End Page:737
Review Status:not specified
Audience:Not Specified
Abstract / Description:A long-standing task in climate research has been to distinguish between anthropogenic climate change and natural climate variability. A prerequisite for fulfilling this task is the understanding of the relative roles of external drivers and internal variability of climate and the carbon cycle. Here, we present the first ensemble simulations over the last 1200 years with a comprehensive Earth system model including a fully interactive carbon cycle. Applying up-to-date reconstructions of external forcing including the recent low-amplitude estimates of solar variations, the ensemble simulations reproduce temperature evolutions consistent with the range of reconstructions. The 20th-century warming trend stands out against all pre-industrial trends within the ensemble. Volcanic eruptions are necessary to explain variations in pre-industrial climate such as the Little Ice Age; yet only the strongest, repeated eruptions lead to cooling trends that stand out against the internal variability across all ensemble members. The simulated atmospheric CO 2 concentrations exhibit a stable carbon cycle over the pre-industrial era with multi-centennial variations somewhat smaller than in the observational records. Early land-cover changes have modulated atmospheric CO2 concentrations only slightly. We provide a model-based quantification of the sensitivity (termed Υ) of the global carbon cycle to temperature for a variety of climate and forcing conditions. The magnitude of Υ agrees with a recent statistical assessment based on reconstruction data. We diagnose a distinct dependence of Υ on the forcing strength and time-scales involved, thus providing an explanation for the systematic difference in the observational estimates for different segments of the last millennium. © 2010 Author(s)
External Publication Status:published
Document Type:Article
Communicated by:Carola Kauhs
Affiliations:MPI für Meteorologie/Ocean in the Earth System
MPI für Meteorologie/Land in the Earth System (2005-)
MPI für Meteorologie/Atmosphere in the Earth System
Identifiers:URL:http://www.clim-past.net/6/723/2010/cp-6-723-2010.... [Final Paper]
URL:http://www.clim-past-discuss.net/6/1009/2010/cpd-6... [Discussion Paper]
DOI:10.5194/cp-6-723-2010 [Final Paper]
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