Climate and carbon-cycle variability over the last millennium

2010/10/26 by Johann Jungclaus, Stephan Lorenz, Claudia Timmreck +22 · 6 citations
Earth and Planetary Sciences · Environmental Science · #Geology and Paleoclimatology Research #Tree-ring climate responses #Climate variability and models #Climatology #Forcing (mathematics) #Environmental science #Carbon cycle #Climate model #Climate change #Greenhouse gas #Atmospheric sciences #Volcano #Radiative forcing #Climate sensitivity #Geology #Ecology

paper · pdf · doi:10.5194/cp-6-723-2010

openalex publication_date 2010/10/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/04

Abstract

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.

Citations

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Cited by

• Technical details concerning development of a 1200 yr proxy index for global volcanism
• The extra-tropical Northern Hemisphere temperature in the last two millennia: reconstructions of low-frequency variability
• Effects of Large Volcanic Eruptions on Global Summer Climate and East Asian Monsoon Changes during the Last Millennium: Analysis of MPI-ESM Simulations
• Volcanic forcing for climate modeling: a new microphysics-based data set covering years 1600–present
• The Extratropical Northern Hemisphere Temperature Reconstruction during the Last Millennium Based on a Novel Method
• Huaynaputina [wikipedia]

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