Paleoclimate Models (Chapter 12)

The Climate System (IPCC TAR, Ch. 1)

The Climate System (IPCC TAR, Ch. 1)

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

Adjustment Time Scales 300-3000 yr

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 Figure shows quasi-periodic behavior

How can a numerical model represent all of this? Note: More energy absorbed at surface than in atmosphere Largest net contributor of energy to atmosphere is surface latent heat flux 3. Atmosphere is heated from below 4. Note magnitude of greenhouse effect here Options: “Full” complexity - short time scales Simplified - long time scales

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

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

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

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

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)

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

Intermediate Models (Crucifix et al., 2002)

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

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

Intermediate Models Response (Crucifix et al., 2002)

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

Intermediate Models Sensitivity (Crucifix et al., 2002)

Global Climate Models

Global Climate Models Differing scales: distributed surface properties

Global Climate Models

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

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

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

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

GCM Simulation (Kutzbach et al., 1998)

GCM Simulation (Kutzbach et al., 1998)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Precipitation changes vs. lake records prescribed SST models

Precipitation changes vs. lake records computed SST models

Paleoclimate Models (Chapter 12) END