Climate and carbon-cycle variability over the last millennium

By Johann Jungclaus, S. Lorenz, C. Timmreck, C. Reick, V. Brovkin, K. Six, J. Segschneider, Marco A. Giorgetta, T. Crowley, J. Pongratz and 15 more. 2010

357 citations recorded by the source corpus.

Abstract. 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 differ significantly from the internal variability across all ensemble members. The simulated atmospheric CO2 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 γ) of the global carbon cycle to temperature for a variety of climate and forcing conditions. We diagnose a distinct dependence of γ on the forcing strength and time-scales involved, thus providing a possible explanation for the systematic difference in the observational estimates for different segments of the last millennium.

Subfields: Atmospheric Science, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/f8f6468172a5402d2537d93e6df9d26a37920188

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Citations in the corpus

A reconstruction of radiocarbon production and total solar irradiance from the Holocene 14 C and CO 2 records: implications of data and model uncertainties (2013, background): “In the present study the Holocene evolution of cosmogenic radiocarbon (14C) production is reconstructed using a state of the art Earth system model of intermediate complexity and the IntCal09/SHCal04 radiocarbon records.”
The role of forcing and internal dynamics in explaining the “Medieval Climate Anomaly” (2011, methodology): “…of Earth Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands D. Shindell NASA Goddard Institute for Space Studies, New York City, NY, USA Goosse et al. 2005a; Ammann et al. 2007; Jungclaus et al. 2010; Servonnat et al. 2010; Swingedouw et al. 2011; González-Rouco et al. 2011).”
Climate and carbon cycle changes from 1850 to 2100 in MPI‐ESM simulations for the Coupled Model Intercomparison Project phase 5 (2013, result): “the key regions for ocean heat uptake is the midlatitude Southern Ocean, a region that is very sensitive to the choice of the eddy-diffusion parameterization [Kuhlbrodt and Gregory, 2012] and model resolution [Jungclaus et al., 2013]. [43] The temporal variations in ocean-heat content apart from the”
A multi-model comparison of Atlantic multidecadal variability (2014, neutral): “The strength of the AMOC is intimately tied to the three dimensional ocean density structures (Cunningham et al. 2007; Kanzow et al. 2007; Marotzke 1997; Hawkins and Sutton 2007).”