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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)

Click to get the full-size image

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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