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  1. Paleoclimate Models (Chapter 12)

  2. The Climate System (IPCC TAR, Ch. 1)

  3. The Climate System (IPCC TAR, Ch. 1)

  4. Feedbacks Internal couplings through linking processes Amplify or diminish initial induced climate change

  5. Adjustment Time Scales 300-3000 yr

  6. Climatic Variation and Change Additional Factors • Abrupt change • external conditions (e.g., solar output) • internal feedbacks • passing a threshold (e.g. ice caps melting) 2. Multiple climate states from the same external conditions

  7. How can a numerical model represent all of this? • Options: • “Full” complexity - short time scales • Simplified - long time scales

  8. Simplified Models • Climate simulation in general - 1960s • Paleoclimate applications: • Barry Saltzman (1931-2001) e.g., Saltzman & Maasch (1991)

  9. Simplified Models • Three-variable model for slow climate variability: I = ice mass,  = atmospheric CO2,  = mean ocean temperature R(t) = solar variation at 65 ˚N i, i, I - constants that can distill into 7 tunable parameters

  10. Simplified Models • Three-variable model for slow climate variability: (Saltzman, 1986) CO2 parameter (): from 13C core data (dashed) and simulation (solid)

  11. Simplified Models • Three-variable model for slow climate variability: (Saltzman, 1986) 18O: from SPECMAP 18O (dashed) and simulation (solid)

  12. Intermediate Models • Global, 2-5 dimensional model: • 5˚ latitudinal bands • In each band • 2 continental sectors (Eurasia-Africa, Americas) • 3 ocean sectors (Atlantic, Indian, Pacific) • Circulation dynamics: 2-level, Q-G • winds at 250 hPa, 750 hPa • temperature at 500 hPa • plus - Hadley Cell transport in tropics • 2-D ocean model for each basin • Land-atmosphere coupling processes (Crucifix et al., 2002)

  13. Intermediate Models Simulation versus observations (Crucifix et al., 2002)

  14. Intermediate Models (Crucifix et al., 2002)

  15. Intermediate Models Prescribed Changes (Crucifix et al., 2002)

  16. Intermediate Models Prescribed Changes and Responses (Crucifix et al., 2002)

  17. Intermediate Models Response (Crucifix et al., 2002)

  18. Intermediate Models Prescribed Changes - Sensitivity (Crucifix et al., 2002)

  19. Intermediate Models Sensitivity (Crucifix et al., 2002)

  20. Global Climate Models

  21. Global Climate Models Differing scales: distributed surface properties

  22. Global Climate Models

  23. GCM Simulation • Paleo-Simulation Projects: • Cooperative Holocene Mapping Project (COHMAP) • COHMAP extension • Paleoclimate Model Intercomparison Project (PMIP)

  24. GCM Simulation • Cooperative Holocene Mapping Project (COHMAP) • NCAR CCM0 • Prescribed changes in • Insolation • SST • Ice sheets • CO2 • Time slices every 3,000 yr (18k BP, 15k BP, …) • Perpetual January or July

  25. GCM Simulation • Cooperative Holocene Mapping Project (COHMAP) • Ice sheets & cold ocean • colder, drier climate • intensified jet stream • Amplified annual cycle • Intensified summer monsoons

  26. GCM Simulation • COHMAP Extension • NCAR CCM1 • Computed • SST (slab ocean, prescribed heat transport) • Sea ice • Soil moisture • Seasonal snow • Time slices every ~ 3,000 yr • Full annual cycle simulated

  27. GCM Simulation (Kutzbach et al., 1998)

  28. GCM Simulation (Kutzbach et al., 1998)

  29. GCM Simulation • 25-yr simulation • Last 5 yr analyzed (Kutzbach et al., 1998)

  30. GCM Simulation Longitudinal average overturning circulation (mean meridional circulation) (Kutzbach et al., 1998)

  31. Spruce GCM Simulation Present-Day Results Douglas Fir Sagebrush (Bartlein et al., 1998)

  32. GCM Simulation Changes with Climate (Bartlein et al., 1998)

  33. GCM Simulation Paleoclimate Model Intercomparison Project: Tropical Changes @ LGM • 17 GCMs • 9 slab ocean • 8 prescribed SST • Prescribed changes in • - insolation • - CO2 • - ice sheets

  34. GCM Simulation PMIP: LGM vs. Present Day (Pinot et al., 1999)

  35. GCM Simulation PMIP: Present Day Sea-surface temperature Land-surface temperature (Pinot et al., 1999)

  36. GCM Simulation PMIP: Present Day (Pinot et al., 1999)

  37. GCM Simulation PMIP: Present Day Ocean precipitation Land precipitation (Pinot et al., 1999)

  38. GCM Simulation PMIP: LGM vs. PD (30 S - 30 N) (Pinot et al., 1999)

  39. GCM Simulation Paleoclimate Model Intercomparison Project: Tropical Changes @ LGM Top: Sfc T change - prescribed SST RMS spead among models Bottom: Sfc T change - computed SST

  40. GCM Simulation Paleoclimate Model Intercomparison Project: Tropical Changes @ LGM Difference in simulated SST changes from reconstructed changes (LGM-PD)

  41. GCM Simulation PMIP: LGM-PD Comparison with proxies (Pinot et al., 1999)

  42. GCM Simulation Paleoclimate Model Intercomparison Project: Tropical Changes @ LGM Model changes vs. pollen record Coldest month temperature

  43. Paleoclimate Model Intercomparison Project: Tropical Changes @ LGM GCM Simulation Model changes vs. pollen record Annual surface temperature

  44. Precipitation changes vs. lake records prescribed SST models

  45. Precipitation changes vs. lake records computed SST models

  46. Paleoclimate Models (Chapter 12) END