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Kaplan et al. 2003

LGM model simulations. ... vs. reconstructions. Kaplan et al. 2003. Mid-Holocene model simulations. ... vs. reconstructions. BIOME 6000 reconstruction (Prentice, Webb et al., 1999). today. mid-Holocene. Neolithic Rock Painting (Tassili-Plateau, Sahara). Insolation change.

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Kaplan et al. 2003

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  1. LGM model simulations ... vs. reconstructions Kaplan et al. 2003

  2. Mid-Holocene model simulations ... vs. reconstructions

  3. BIOME 6000 reconstruction (Prentice, Webb et al., 1999) today mid-Holocene

  4. Neolithic Rock Painting (Tassili-Plateau, Sahara)

  5. Insolation change

  6. High northern latitudes: Amplification of snow-albedo feedback by sea ice-albedo feedback GDD0 [oC] Transient model runs: tree fraction carbon storage [kgC/m2]

  7. Transient model runs

  8. Abrupt desertification Insolation northern hemisphere Monsoon rain, Northern Africa Vegetation Sahara Reconstruction B,C – CLIMBER-2 results Claussen et al., 1999 D – proxy data deMenocal et al., 2000

  9. CLIMBER Precipitation differences (NH Summer) mid-Holocene - present Niederschlagsdifferenzen (NH Sommer) mittleres Holozän - heute DP(mm/d)  Amplification of monsoonal precipitation by local ‚recycling‘

  10. Complex-model simulations of LGM: two equilibrium states (depending on initial vegetation conditions)

  11. Present-day Mid-Holocene LGM

  12. Simplified model:

  13. Conceptual model: V 2 equil green 1 V*(P) P*(V) P 0 desert Stability function Mid-Holocene 2xCO2 V 1 Modern desert green Brovkin et al. 1998

  14. Practical units • Daisyworld • Multiple equilibria • ...

  15. Climate forcing • Natural • ->Sun • Anthropogenic • ->Emission of greenhouse gases ... ->Volcanism ->Land use

  16. Effect of deforestation: biogeophysical biogeochemical sum

  17. Ruddiman‘s Hypothesis: Ruddiman 2003

  18. Cox et al. 2004

  19. Betts et al. 2004

  20. Will greenhouse greenthe Sahara? (Petit-Maire, 1990) [ppmv] Scenarios of atmospheric CO2 concentration Vegetation fraction in the Sahara Claussen et al., 2003 years of simulation

  21. mid-Holocene 2 x CO2 DTJJA DPJJA Claussen et al., 2003

  22. Northern Africa (JJA) ‘Hadley‘ ‘Monsoon‘ near-surface spec. humidity dynamic + thermodyn. component (of changes in vertical moisture flux) Claussen et al., 2003

  23. Biosphere 2:

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