Evaluating the impact of land-use induced land-cover changes on climate
Proposed protocol for intercomparing models
Proposed acronyms:
LUCID “Land-Use and Climate, IDentification of robust impacts”
PACE: “PAtterns of Climate Evolution induced by land-use”
PALACE “PAtterns of LAnd-use on Climate Evolution” (has a meaning in both French and English)
Any ideas????
The objective of the proposed protocol is to identify and quantify the impacts of land-used induced land-cover changes on the evolution of climate between the pre-industrial epoch and present-day. The use of a) multi-model and b) ensemble simulations will allow us to assess the robustness of the identified changes. Assessment will be carried out by looking not only at the mean climate but also at climate variability . Assessment will also be made on the potential impact land-use induced land-cover change can have on the sea-surface temperatures and on ocean circulation.
Among the final objectives: make sure land-use induced land-cover changes are accounted for in simulations that will be run for the next IPCC report (5 th ).
Snap-shot simulations will be carried out first and intercompared. Four groups will carry out the simulations: a) NCAR with Gordon Bonan et al., b) IPSL with Nathalie de Noblet et al., c)
CSIRO with Andy Pitman et al., d) CNRM with Aurore Voldoire et al., e) Christine Delire.
In a second phase, transient simulations will be carried out from 1870 till 2002.
The protocol presented here addresses only the first part (snap-shots). The protocol for transient simulations will come next and will hopefully be carried out by more groups.
Protocol for intercomparing the models
The models will be run for the pre-industrial period and present-day. Both models will carry out prescribed and computed SSTs simulations. The same land-use induced land-cover change will be imposed to each model.
1) Sea-Surface Temperatures
 for the prescribed SSTs simulations, 30 years of interannually varying SSTs will be chosen for both snap-shot periods.
For the pre-industrial period: 1870-1900
For present-day: 1972-2002
The fixed SSTs used will be the same as the ones used by the climate groups participating to the C20C project (HadISST1.1, ftp://www.iges.org/pub/kinter/c20c/HadISST/ , 1870-2002).
For all years, the LSCE has extended the data set on the continent, as it is generally done for
AMIP data, to facilitate the work of some groups. Data (annual SST and Sea-ice (sic),
NetCDF files, resolution: 1°x1°) have been put on a DODS server in France
(http://dods.extra.cea.fr/cgi-bin/nph-dods/data/p25nath/DIVA/ForcingData/HadISST/).

 for the computed SSTs , the OGCM of each group will be used (POP1.4 for NCAR, OPA for IPSL, …).
2) Land-cover
The land-use maps are derived from a) the crop data base constructed by Ramankutty and
Foley (1999) for the crop area, b) the HYDE database (Goldewijk, 2000) for the anthropogenic pasture land. The IPSL group provides each group with two NetCDF files that include the distribution of crops and pasture at a 0.5°*0.5° grid. In each dataset, fractions
(between 0 and 1) of crops or pasture are provided for each continental grid cell. All datasets have been put on a DODS server in France (http://dods.extra.cea.fr/cgi-bin/nphdods/data/p25nath/DIVA/ForcingData/Vegetation/).
One specific year will be chosen for each time-period:

for the pre-industrial period: 1870

for present-day: 1992
The distribution of natural land-cover at each time period will be specified by each group. The
IPSL can help in implementing their protocol for deriving natural land-cover distribution in the past from the present-day distribution.
There will be differences in the natural land-cover maps used by each individual groups, as well as differences that arise from each land-surface model: some compute their own leaf area index (LAI), daily, others prescribe it from observations and therefore prevent their model from accounting for feedbacks from the seasonal adaptation of vegetation to the modelled climate. We therefore encourage groups who compute their LAI to carry out as well simulations with prescribed LAI .
3) Ensemble simulations
To assess the robustness of the results we will conduct ensemble simulations.

For prescribed SSTs, 6 (minimum required) to 10 realisations of each time period.
Differences between ensemble members will come from different initial atmospheric states.

For the computed SSTs , long enough simulations (at least 300 years) should be run at equilibrium, from which we’ll identify different 50-years time periods that will be used for climatological averaging.
4) Output Data
Ouput data should be provided as NetCDF files and include the minimum set is listed in the attached table.
5) Simulations to be carried out
Three ensemble simulations will be carried out with prescribed SSTs: 1) a ‘pure’ preindustrial (PI), 2) a ‘pure’ present-day (PD), 3) a hybrid pre-industrial to isolate the sole effects of land-use induced land-cover change (PIv), 4) another hybrid simulation to identify the sole effects of changing CO2 and SSTs (PDv). This forth simulation will moreover help us quantify the synergism between changes in land-cover and in CO2-SSTs.
Differences between PIv and PI will allow us to quantify the effects of changing vegetation on the pre-industrial climate.

Differences between PDv and PI will allow us to quantify the effects of changing CO2 and
SSTs on climate.
Synergisms can be computes as = PD + PI – PDv – PIv (= (PD-PI) – (PDv-PI) – (PIv-PI))
Name of simulations CO2 Vegetation map SSTs Number of simulations per ensemble
OR
Length of simulation
PI 280 ppm 1870
PD 375 ppm 1992
Prescribed
1870-1900
Prescribed
1972-2002
Ensemble
5-10 runs
Ensemble
5-10 runs
PIv 280 ppm 1992
PDv 375 ppm 1870
Prescribed
1870-1900
Prescribed
1972-2002
Ensemble
5-10 runs
Ensemble
5-10 runs
PIs
PIsv
280 ppm
280 ppm
1870
1992
Computed
Computed
300 years(More?) at equilibrium
300 years(More?) at equilibrium
We suggest that simulations to be run first are PD and PDv. They will help us identify the patterns of present-day climate that are influenced by the land-use extent.
Maps of Crop extent for 1860, 1870, 1992, 2000 (in % of 1°*1° grid)