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Table of Contents
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Last Millennium Experimental Design
The basic principle is that we should strive to include all relevant transient forcings over this period if the functionality exists in the model, noting that conformability with the CMIP5 controls and 20th Century transient is crucial.
Boundary conditions
Summary of Last Millennium boundary conditions
| PMIP3 | Alternative solution | |
|---|---|---|
| Orbital parameters | Annually varying Table provided (0-2100 CE/AD), if not internally calculated | |
| Date of vernal equinox | March 21 at Noon | |
| Trace gases | Annually varying (850-1850) (Table provided) | |
| Volcanic Aerosols | Multiple reconstructions (of AOD, Effective Radius, Mass) | |
| Solar irradiance | choose at least one between Multiple reconstructions provided below | |
| Ozone | solar related variations (parameterised as function of change in solar irradiance - Drew Shindell) | same as in CMIP5 PI |
| Aerosols | biomass burning changes???? | same as in CMIP5 PI |
| Vegetation | Land use conversion (forests to C3/C4 crops) (Pongratz, 2009, Foley and Ramunkutty) Available from WDCC-Hamburg (http://cera-www.dkrz.de/WDCC/ui/Entry.jsp?acronym=LAND_COV_scen_800_1699) | same as in CMIP5 PI |
| Ice sheets | No changes from Pre-Ind control | |
| Topography and coastlines | same as in CMIP5 PI |
Total Solar Irradiance
The following figure (click to get the full-size image) has been provided by Johann Jungclaus (MPI-M Hamburg)
Time series of TSI (Wm-2) from 800AD to 2000. For the COSMOS (MPI-M) Millennium simulations (black curve), a 11 year cycle was added for consistency over the entire period.
Notes: We will impose an 11 year cycle on pre-sunspot reconstructions for consistency of the spectrum of natural variability. Additionally, we will give a spectral set of irradiance changes based on modern variability observed by satellite (Lean).
Candidate reconstructions: Krivova, Steinhilber, new Bard?, (TBD)
Volcanic Forcings
Issues: compatability of eff. rad, zonality, height distribution with modern satellite (Sato) data.
Candidate datasets: Crowley, Ammann - differences in thresholds for significant eruptions, peak forcing etc. Need merged/consistent fields. (Ammann)
Reconstructed evolution of trace gases
The evolution of CO2, CH2, N2O over past 2 millennia table has been provided by Fortunat Joos (University of Bern). Methods and references are provided in the downloadable file.
Orbital forcing
The following orbital parameters parameters should be used, if they are not internally calculated.
Note: calculation from Berger (1978), annually varying.
Precomputed table
The parameters' table has been supplied by Gavin Schmidt (GISS).
Linear regressions
Over the period 0-2100 CE, the parameters are well approximated by the following linear regressions:
| Parameter | Linear approximation |
|---|---|
| ECC | 0.017475 - 0.000000382 * Year |
| OBL | 23.697 - 0.000128 * Year |
| PERI-180 | 68.79 + 0.0170 * Year |
Vegetation
Anthropogenic land cover change is considered by applying the reconstruction of global agricultural areas and land cover (Pongratz et al., 2008).
The global maps with a spatial resolution of 0.5° and an annual timescale contain 14 vegetation types and discriminate between the agricultural categories cropland, and C3 and C4 pastures. The reconstruction merges published maps of agriculture from AD1700 to 1992 and a population-based approach to quantify agriculture from AD 800 to 1700.
The data set can be obtained from the World Data Center for Climate (doi:10.1594/WDCC/RECON_LAND_COVER_800-1992). Pongratz, J., Reick, C.H., Raddatz, T. & Claussen, M. A reconstruction of global agricultural areas and land cover for the last millennium. Global Biogeochem. Cycles, 22, GB3018, doi:10.1029/2007GB003153 (2008).
Initial conditions
| PMIP3 | Alternative solution | |
|---|---|---|
| Initial conditions | Branch off PI after adjustment | Same as in PI |
| Model spin up | Same as in PI |
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