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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) Provided below	same as in CMIP5 PI
Ice sheets	No changes from Pre-Ind control
Topography and coastlines	same as in CMIP5 PI

Total Solar Irradiance

Multiple reconstructions of annual total solar irradiance are provided. These are designed to either fit smoothly with the reconstructions used in the post-1850 CMIP5 simulations (Wang, Lean and Sheely (2005)), or to explore independent estimates of the long term solar trends. Each series has an 11 year solar cycle throughout the time series (synthetic for pre-1610, based on a relationship between cycle magnitude and long-term TSI) and comes with an estimate of the spectral changes (as a function of the TSI anomaly). Each reconstruction is calibrated to the WLS modern values.

Wang, Lean and Sheely (WLS): 1610-2000 CE

Spectral reconstruction based on a flux transport model of the open and closed flux using the observed sunspot record as the main input. This comes in two versions, A) a “no-background” version that just has TSI variations similar to that seen over a solar cycle today, and B) a “with background” version with longer term trends in the solar minimum.

Lean J, "Calculations of Solar Irradiance"

Wang, Y.-M., J. L. Lean, and N. R. Sheeley, Jr. (2005), Modeling the Sun’s Magnetic Field and Irradiance since 1713, ApJ, 625, 522–538, doi:10.1086/429689.

Delaygue and Bard (DB): 850-1609 CE

Reconstruction based on an Antarctica stack of 10Be records scaled linearly to the modern-to-Maunder Minimum TSI in the two WLS reconstructions.

Delaygue, G and E. Bard, (2009), Solar forcing based on Be-10 in Antarctica ice over the past millennium and beyond, EGU 2009 General Assembly, #EGU2009-6943

Muscheler, Joos, Beer, Müller, Vonmoos and Snowball (MEA): 850-1609 CE

Reconstruction based on the 14C record scaled based on an inverse regression to the two WLS reconstructions.

Muscheler, R., F. Joos, J. Beer, S.A. Müller, M. Vonmoos, and I. Snowball (2007), Solar activity during the last 1000 yr inferred from radionuclide records Quaternary Science Reviews, Vol. 26, pp. 82-97. doi:10.1016/j.quascirev.2006.07.012

Vieira, Krivova and Solanki (VK): 850-1849 CE

Reconstruction based on a model of the open and closed magnetic flux including an estimate of the 11 yr cycle. We recommend patching this into the WLS w/background values in 1850.

Vieira, L.E.A., and S. Solanki (2009), Evolution of the solar magnetic flux on time scales of years to millenia, http://eprintweb.org/S/authors/All/so/Solanki/2 arXiv/0911.4396, doi:10.1051/0004-6361/200913276

Steinhilber, Beer, and Frohlich (SBF): 850-1849 CE

Reconstruction based on a Greenland 10Be core and a different model of solar flux. 11yr cycle is synthetic. We recommend patching this into the WLS w/background values in 1850.

Steinhilber, F., J. Beer, and C. Frohlich (2009), Total solar irradiance during the Holocene, Geophys. Res. Lett., 36, L19704, doi:10.1029/2009GL040142.

Solar-driven Ozone variations

A parameterisation of ozone changes in the atmosphere (lat, lon, altitude) as a function of changing solar irradiance (including spectral variations) is available based on the results of Shindell et al (2006).

Shindell, D.T., G. Faluvegi, R.L. Miller, G.A. Schmidt, J.E. Hansen, and S. Sun, 2006: Solar and anthropogenic forcing of tropical hydrology. Geophys. Res. Lett., 33, L24706, doi:10.1029/2006GL027468,2006. http://pubs.giss.nasa.gov/docs/2006/2006_Shindell_etal_4.pdf

Volcanic Forcings

Two alternative data sets are provided below. It is up to the groups to choose the Gao-Robock-Amann or the Crowley reconstruction for their last millenium simulation.

The Gao-Robock-Ammann data set

Time series of global hemispheric total stratospheric sulphate injections from volcanic eruptions for the past 1500 years as well as estimates of stratospheric loading as a function of latitude, altitude, and month are available from IVI2link

The data are derived from 54 ice core records, 32 from the Arctic, and 22 from Antarctica. It is based on the most comprehensive set of ice cores, an updated extraction record, updated ice core deposition to global stratospheric aerosol loading conversion factors, and an advanced spatial-temporal transport parameterization scheme (Gao et al., 2008)

The stratospheric aerosol loadings (in units of Tg) provided in the IVI2 data set may be converted into aerosol optical depth (AOD) by dividing the loadings by 150 Tg (Stothers, 1984). The AOD time series can then be used to calculate the corresponding radiative forcing (in units of Wm-2) by multiplying it by (-20) (Wigley et al., 2005). The conversion to AOD is valid for aerosols with effective radius in the visible spectral range.

Further explanation is provided here : ivi2aodtsiconversion.pdf

Gao, C., A. Robock, and C. Ammann: Volcanic forcing of climate over the last 1500 years: An improved ice-core based index for climate models. J. Geophys. Res., 113, D2311, doi:10.1029/2008JD010239 (2008).

Stothers, R.B., The great Tambora eruptions in 1815 and its aftermath. Science, 224(4654), 1191-1198 (1984). Wigley, T.M.L., C.M. Ammann, B.D. santer, and S.C.B. Raper: Effect of climate sensitivity on the response of volcanic forcing. J. Geophys. Res., 110,D09107, doi:10.1029/2004JD005557

The Crowley data set

The volcanic forcing is calculated using time series of aerosol optical depth (AOD) at 0.55μm and of the effective radius (Reff) (Crowley et al., 2008). The time resolution of the series is ten days and the data are provided at four equal area latitude bands.

AOD estimates are based on a correlation between sulphate in Antarctic ice cores and satellite data (Sato et al., 1993).

Reff growth and decay is based on satellite observations of the Pinatubo eruption in 1991, with eruptions larger than that of Pinatubo (maximum is 0.15) being scaled by the theoretical calculations for very large eruptions (Pinto et al., 1989). In the model AOD is distributed between 20-86 hPa over three vertical levels, with a maximum at 50 hPa.

Sensitivity experiments for the model response to the Pinatubo eruption yield an average global temperature change (0.4 K) comparable to observations. For the largest eruption of the last millennium, the 1258 AD eruption, a NH summer temperature anomaly over land of 1.2 K is found in agreement with reconstructions (Timmreck et al., 2009)

Crowley, T. et al. Volcanism and the Little Ice Age. PAGES Newsletter, 16, 22-23 (2008).

Sato, M., Hansen, J.E., McCormick, M.P. & Pollack, J.B. Stratospheric aerosol optical depths, 1850-1990. J. Geophys. Res., 98(D12), 22,987-22,994, doi:10.1029/93JD02553 (1993).

Pinto, J.P., Turco, R.P., & Toon, O.B. Self-limiting physical and chemical effects in volcanic eruption clouds. J. Geophys. Res., 94(D8), 11,165-11,174, doi:10.1029/JD094iD08p11165 (1989).

Timmreck, C. et al. Limited temperature response to the very large AD 1258 volcanic eruption. Geophys. Res. Lett., 36, L21708, doi:10.1029/2009GL040083 (2009).

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).

To access the files, click here RECON_LAND_COVER_800-1992

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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