Carbon dioxide and climate impulse response functions for the computation of greenhouse gas
metrics: A multi-model analysis
Supplementary Information Part A: Protocol V1.1
Fortunat Joos, Raphael Roth
Physics Institute, Climate and Environmental Physics and Oeschger Centre for Climate Change Research, University of Bern,
Bern, Switzerland; , [email protected], [email protected]
Jan Fuglestvedt, Glen Peters
Center for International Climate and Environmental Reseach - Oslo (CICERO), Norway; [email protected],
[email protected]
Documents and updates are available online: http://www.climate.unibe.ch/~joos/IRF_Intercomparison
Global warming potentials (GWP) of different gases are used as a metric to compare emissions of
various greenhouse gases in the Kyoto Basket approach. The response in atmospheric CO2 to an
instantaneous release of carbon into the atmosphere, the atmospheric CO2 impulse response
function (IRF), is used for the computation of global warming potentials (GWP) and global
temperature change potential (GTP) (Shine et al., 2005).
The goal of this exercise is to determine the atmospheric CO2 impulse response function (IRF) by a
suite of carbon-cycle climate models to explore model-model differences. Results will be written up
for publication in a peer-reviewed journal in spring 2012 (IPCC AR5 WG1 deadline is summer 2012) in
order to be available for calculations of GWPs in IPCC AR5. The results will also be useful for metrics
and simplified climate models in other contexts.
Model requirements
The model must be able to compute the redistribution of anthropogenic carbon among the principal
carbon reservoirs atmosphere, land biosphere, and ocean. Further compartments such as ocean
sediments may also be included. Preferentially, the model simulates changes in climate in response
to CO2 radiative forcing and includes a representation of the relevant carbon cycle-climate feedbacks.
Model runs: overview
The scenario setup is inspired by the calculation of the IRF function as done for the Second
Assessment Report (SAR) and as used in the Kyoto GWP with the Bern SAR model version and as
repeated in preparation of the Fourth Assessment. The setup relies on that described in Enting,
Wigley, Heimann, CSIRO Division of Atmospheric Research. Technical Paper No 31, 1994:
Three simulations are performed:
(a) The model is forced with historical concentration up to a reference year (here tref=2010) and then
concentration are kept fixed thereafter at a constant value (here CO2,ref=389 ppm). The allowed
emission are calculated from the change in total inventory (prescribed atmospheric change plus
modelled ocean and terrestrial uptake)
(b) A simulation with prescribed emissions from (a)
(or concentration prescribed up to the reference year and emissions prescribed thereafter )
(c) same as (b) but an impulse of carbon, here of 100 GtC, added instantaneously to the atmosphere
five years after the reference year (here in 2015).
Supplementary Information
2
The normalised IRF is then approximately:
IRF(t=tmodel-2015.0) = (CO2(tmodel)-CO2,ref)/(100 GtC/2.123GtC/ppm)
for tmodel > 2015
Model runs: detailed description
A) CO2 background concentration of 389 ppm
1. PresCO2_389ppm: The simulation starts from preindustrial conditions. Atmospheric CO2 is
prescribed and compatible emissions (=change in all carbon reservoirs) diagnosed.
Atmospheric CO2 is prescribed to follow the historical evolution up to year 2010. After 2010,
the concentration is kept fixed at the value of 389.0 ppm. The diagnosed emissions should be
written frequently (at least annually); these will be used to drive the model in run 2 and 3. An
input file with the historical concentrations is provided
(file name: co2ccn_irf_850_2010_v1.0.dat).
A restart file may be written in 2010 to start simulation 2 and 3 in 2010
2. PresEmiss_389ppm: run 2 may either start in 2010 as a continuation of run 1 or at the same
preindustrial initial conditions used in run 1. Atmospheric CO2 is evolving freely. Diagnosed
emissions from run PresCO2_389ppm are used to force the model. (Expected result: the
computed CO2 evolution should be close to the evolution prescribed in run
PresCO2_389ppm, see Figure 1).
3. PresEmiss100_389ppm: Atmospheric CO2 is evolving freely. Diagnosed emissions from run
PresCO2_389ppm are used to force the model as in run PresEmiss_389ppm. In addition, 100
GtC are released at the beginning of year 2015. (Expected results: Atmospheric CO2 will
increase by 47.1032 ppm above the background concentration (~389 ppm) in 2015 and then
slowly decline over the coming decades, see Figure 1)
Remarks:
-
-
It is crucial that the carbon pulse will be added to a constant background concentration of
389 ppm for comparability (roughly 2010 value).
run 1 (PresCO2_389ppm): An existing run or setup from the CMIP or EMIC Intercomparison
projects may be used up to a concentration of 389 ppm.
run 3 (PresEmiss100_389ppm): The atmospheric CO2 concentration should be increased at
the beginning of year 2015 by 47.1032 ppm (100 GtC/2.123 GtC/ppm) in all atmospheric grid
cells.
non-CO2 forcing agents should be included to the extent possible. Non-CO2 forcing should be
kept constant at 2010 level after 2010 (or at the year at which 389 ppm CO2 is reached).
land use and land use changes should be included to the extent possible. Land use area
should be kept constant at 2010 level after 2010.
If CPU time is an issue and if a group is sure that CO2 remains at a constant value with the
emissions diagnosed in run #1, run#2 may be skipped. This may only apply to ESMs and it is
strongly recommended to perform run #2 to avoid problems with model drift.
Supplementary Information
3
B) Preindustrial Set
Runs 4 to 5 start from preindustrial conditions
4. CTRL: Control simulation with constant boundary conditions and freely evolving atm. CO2
5. PI100: Freely evolving atm. CO2. 100 GtC are released into the atmosphere during year 10 of
the control simulation and then continued. (Expected result: atm CO2 will increase from the
preindustrial value of around 280 ppm by about 45 ppm to 325 ppm in year 10. Afterwards,
the CO2 concentration will then decrease due to uptake by the ocean and the land
biosphere).
6. PI5000: as PI100, but 5000 GtC are released instead of 100 GtC
Remark: an available control simulation may be used to minimize work
Resulting IRFs
We will use your results to compute impulse response functions for CO2 and other variables:
a) IRF_100GtC_389ppm: The difference in atm. CO2 of run PresEmiss100_389ppm and
PresEmiss_389ppm divided by the pulse size of 47 ppm will yield the (normalized) IRF for a
background concentration of 389 ppm and a pulse size of 100 GtC (see Figure 2)
b) IRF_100GtC_PI: The difference in atm. CO2 of run PI100 and CTRL will yield the IRF for
preindustrial background conditions and a pulse size of 100 GtC
c) IRF_5000GtC_PI: The difference in atm. CO2 of run PI5000 and CTRL will yield the IRF for
preindustrial background conditions and a pulse size of 5000 GtC
Duration of runs
Preferentially, simulations are run for 2000 years after the pulse release until a complete equilibrium
between atmosphere-ocean-land biosphere is re-established. If this is not feasible, runs of shorter
duration are also welcome. Usually models are close to equilibrium after 1000 years. Global Warming
Potentials for which the IRFs will be used were tabulated in past IPCC reports for 500, 100, and 20
years. A time horizon of 100 years is used in the Kyoto protocol.
A minimum of 100 years after the pulse release is requested.
Models that include ocean sediments and/or weathering and that are cost-efficient enough may also
be run over many millennia (e.g. 100 ka).
Priority of runs
The top priority is to get results needed to compute the IRF for a background concentration of 389
ppm (IRF_100GtC_389ppm). For this, runs 1, 2, and 3 are required.
Alternative: If computing requirements are too high for run 1 to 3, please provide at least results for
runs 4 and 5 (PI100, CTRL).
Conversion factor GtC to ppm
Please use a conversion factor of 2.123 GtC per ppm
Supplementary Information
4
Preindustrial condition
It is up to the researcher to define the exact preindustrial state and the exact evolution how to reach
the 2010 atmospheric CO2 value of 389 ppm. However, model runs should start before 1900 AD and
concentration should be kept fixed at a value of 389 ppm a few years before and during the pulse
release. The idea is that the carbon pulse is added for the same background concentration of 389
ppm in all models.
Other forcings
Non-CO2 forcings and land use are preferentially included in run 1 to 3; keep non-CO2 forcing and
land use area constant after 2010 at the level of year 2010. A suitable set of forcing is provided by
the EMIC Intercomparison Project (http://climate.uvic.ca/EMICAR5/forcing ).
Output
Ascii files with global mean values, provide at least 5 significant digits for each run.
a) File name: RUNNAME_MODELNAME_Modelversion_startyear_endyear.dat, e.g.
“PresCO2_2010_Bern3DLPX_v1.0_1750_4015.dat” for run 1 with the Bern3DLPX model,
version 1.0 and simulation starting at 1750 AD and ending at 4015
b) Header:
- start each comment line with: #
- indicate run name
- provide contact address,
- indicate model name and version and model components included,
- indicate climate sensitivity of model
- conversion factor used to convert GtC into ppm and/or pulse size in ppm
- description of non-CO2 forcing applied
- indicate whether tabulated data show annual averages or instantaneous values
- column headers with units
c) Tabulated data including year, global mean values of atmospheric CO2 in ppm (CO2atm),
global mean net air-to-sea carbon flux in GtC per year (Fas,net), global mean net air-to-land
carbon flux in GtC per year (Fab,net), global mean surface temperature in Celsius (T) , global
mean sea level rise in cm (SLR), ocean heat content in Joule (Heat)
# year CO2atm [ppm] Fas,net [GtC/yr] Fab,net [GtC/yr] T [deg Celsius] SLR[cm] Heat[J]
A text file in ascii describing the model, model resolution, model components, climate sensitivity, and
appropriate references. File name: MODELNAME_Modelversion_description.txt. Include contact
address.
It is assumed that group will store more output individually than just the few global numbers that we
ask for as output. It is anticipated that the runs may be very useful to diagnose response patterns for
Supplementary Information
5
a wide range of variables. In additions to IRFs for CO2, temp, and sea level, one may also want to
analyze pH, precip, etc.
Deadlines
Please let us know by 15 December 2011 whether you plan to contribute and submit the runs until 15
February 2012 to [email protected] and [email protected]
Further Reading
Section 2.10, page 210 ff in:
Forster, P., et al. (2007), Changes in Atmospheric Constitutents and in Radiative Forcing, in Climate
Change 2007: The Physical Science Basis. Contribution of Working Group I to Fourth Assessment
Report of the Intergovernmental Panel on Climate Change, edited by S. Solomon, D. Qin, M. Manning,
Z. Chen, M. Marquis, K. B. Averyt, M. Tignor and H. L. Miller, pp. 129-234, Cambridge United Kingdom
and New York, NY, USA, New York, NY, USA.
Enting, I.G., Wigley, T.M.L., Heimann, M., 1994. Future Emissions and Concentrations of Carbon
Dioxide: Key Ocean/Atmosphere/Land Analyses. CSIRO Division of Atmospheric Research Technical
Paper no. 31.
Shine, K., Fuglestvedt, J., Hailemariam, K., and Stuber, N.: Alternatives to the Global Warming
Potential for Comparing Climate Impacts of Emissions of Greenhouse Gases, Climatic Change, 68,
281-302, 10.1007/s10584-005-1146-9, 2005
Supplementary Information
6
Results obtained with the Bern3D-LPJ model for a CO2 background of 389 ppm (R. Roth)
Figure 1: Simulated evolution of atmospheric CO2 for runs 2 and 3 (PresEmiss_389ppm
PresEmiss100_389ppm). 100 GtC are instantaneously released at the beginning of year 2015 in
simulations PresEmiss100_389ppm (red) in addition to the emissions prescribed in run
PresEmiss_389ppm (black). Prescribed emissions were diagnosed from a run in which atmospheric
CO2 was prescribed to follow the observed evolution until 2010 and kept constant at 389 ppm after
2010.
IRF_100GtC_389ppm
m
Figure 2: CO2 impulse response function (IRF) as obtained from the difference of the runs shown in
figure 1. The IRF is normalised by the size of the pulse input. Time is shifted such that year 0
corresponds to the time when the pulse of 100 GtC was released into the atmosphere.
Supplementary Information
7
Results of sensitivity runs with the Bern3D-LPJ model (Raphael Roth)
Differences in Impulse Response Function computed with the Bern3D-LPX model for different model setups.
Top: Results from simulations with and without anthropogenic land use. Middle: Results from simulations with
and without non-CO2 forcings. Bottom: release of pulse emissions at the beginning of the year versus a release
of 100 GtC over one year. Note that the Bern3D-LPX model considers CO2 to be well mixed in the atmosphere.
Thus differences in IRF may be larger for models that feature atmospheric carbon transport.
Supplementary Information
8
# -----------------------------------------------------------# midyear CO2 concentrations 850-2010
# to be used for the IRF intercomparison experiment "PresCO2_389ppm"
#
# author: Raphael Roth, [email protected]
# date:
24/11/2011
# -----------------------------------------------------------#
# data used:
# from 850 - 2005 EMIC AR5 forcing was used
(http://climate.uvic.ca/EMICAR5/data/UVic_data/co2ccn_850-2005.nc.gz)
#
-->PMIP3 CO2 concentration (850 to 1800) and the CMIP5 historical
CO2 concentration (1765 to 2005).
#
-->The data sets were linearly blended between 1765 and 1800.
#
# from 2005-2010, RCP6.0 midyear CO2-concentration
#
(value from 2010.5 of 389.072 was rounded to 389.00)
# from 2010constant value of 389.00 ppm
#
#
#
# year co2 [ppm]
#
850.5 279.266
851.5 279.272
852.5 279.277
853.5 279.281
854.5 279.284
855.5 279.286
856.5 279.287
857.5 279.287
858.5 279.285
859.5 279.283
860.5 279.279
861.5 279.274
862.5 279.268
863.5 279.261
864.5 279.254
865.5 279.245
866.5 279.236
867.5 279.226
868.5 279.216
869.5 279.204
870.5 279.193
871.5 279.181
872.5 279.169
873.5 279.156
874.5 279.143
875.5 279.130
876.5 279.117
877.5 279.103
878.5 279.090
879.5 279.077
880.5 279.064
881.5 279.051
882.5 279.038
883.5 279.026
Supplementary Information
884.5
885.5
886.5
887.5
888.5
889.5
890.5
891.5
892.5
893.5
894.5
895.5
896.5
897.5
898.5
899.5
900.5
901.5
902.5
903.5
904.5
905.5
906.5
907.5
908.5
909.5
910.5
911.5
912.5
913.5
914.5
915.5
916.5
917.5
918.5
919.5
920.5
921.5
922.5
923.5
924.5
925.5
926.5
927.5
928.5
929.5
930.5
931.5
932.5
933.5
934.5
935.5
936.5
937.5
938.5
939.5
940.5
941.5
942.5
279.014
279.002
278.991
278.980
278.970
278.961
278.953
278.945
278.938
278.932
278.927
278.923
278.920
278.919
278.918
278.919
278.921
278.924
278.928
278.932
278.938
278.945
278.952
278.960
278.968
278.977
278.987
278.996
279.007
279.017
279.027
279.038
279.048
279.059
279.069
279.079
279.089
279.099
279.108
279.116
279.124
279.132
279.139
279.145
279.150
279.154
279.157
279.160
279.161
279.161
279.159
279.157
279.153
279.147
279.140
279.132
279.121
279.109
279.095
9
Supplementary Information
943.5
944.5
945.5
946.5
947.5
948.5
949.5
950.5
951.5
952.5
953.5
954.5
955.5
956.5
957.5
958.5
959.5
960.5
961.5
962.5
963.5
964.5
965.5
966.5
967.5
968.5
969.5
970.5
971.5
972.5
973.5
974.5
975.5
976.5
977.5
978.5
979.5
980.5
981.5
982.5
983.5
984.5
985.5
986.5
987.5
988.5
989.5
990.5
991.5
992.5
993.5
994.5
995.5
996.5
997.5
998.5
999.5
1000.5
1001.5
279.079
279.062
279.042
279.020
278.997
278.973
278.947
278.920
278.893
278.865
278.837
278.809
278.781
278.754
278.727
278.701
278.677
278.654
278.633
278.613
278.596
278.581
278.568
278.559
278.552
278.549
278.549
278.553
278.560
278.570
278.584
278.600
278.620
278.642
278.666
278.694
278.724
278.755
278.790
278.826
278.864
278.904
278.946
278.989
279.034
279.080
279.128
279.176
279.226
279.276
279.328
279.379
279.432
279.484
279.538
279.591
279.644
279.697
279.750
10
Supplementary Information
1002.5
1003.5
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1038.5
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1054.5
1055.5
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1057.5
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1059.5
1060.5
279.803
279.856
279.907
279.959
280.009
280.059
280.107
280.154
280.199
280.243
280.285
280.325
280.363
280.398
280.431
280.461
280.488
280.513
280.533
280.551
280.564
280.574
280.580
280.581
280.579
280.573
280.565
280.556
280.549
280.544
280.543
280.546
280.557
280.575
280.603
280.641
280.691
280.752
280.822
280.901
280.987
281.081
281.180
281.283
281.391
281.500
281.612
281.724
281.836
281.947
282.055
282.160
282.260
282.355
282.444
282.526
282.599
282.662
282.717
11
Supplementary Information
1061.5
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1111.5
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1119.5
282.764
282.802
282.833
282.857
282.874
282.885
282.891
282.891
282.886
282.877
282.863
282.847
282.827
282.805
282.781
282.755
282.728
282.701
282.673
282.645
282.618
282.592
282.567
282.545
282.525
282.508
282.494
282.484
282.478
282.476
282.478
282.483
282.491
282.502
282.516
282.533
282.552
282.573
282.597
282.622
282.649
282.678
282.708
282.739
282.772
282.805
282.838
282.872
282.907
282.943
282.978
283.014
283.050
283.086
283.123
283.159
283.195
283.231
283.267
12
Supplementary Information
1120.5
1121.5
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1123.5
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1177.5
1178.5
283.302
283.337
283.372
283.406
283.439
283.472
283.504
283.535
283.565
283.594
283.622
283.649
283.674
283.698
283.721
283.743
283.763
283.781
283.797
283.812
283.826
283.838
283.849
283.858
283.867
283.874
283.880
283.886
283.891
283.895
283.898
283.901
283.904
283.906
283.908
283.910
283.911
283.913
283.915
283.917
283.919
283.922
283.925
283.928
283.931
283.935
283.938
283.942
283.946
283.949
283.953
283.956
283.959
283.962
283.965
283.967
283.969
283.970
283.971
13
Supplementary Information
1179.5
1180.5
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1199.5
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1229.5
1230.5
1231.5
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1233.5
1234.5
1235.5
1236.5
1237.5
283.972
283.972
283.972
283.970
283.969
283.966
283.963
283.958
283.953
283.948
283.941
283.933
283.924
283.914
283.903
283.891
283.877
283.862
283.845
283.827
283.807
283.786
283.763
283.737
283.709
283.680
283.648
283.613
283.576
283.537
283.495
283.451
283.404
283.355
283.305
283.254
283.200
283.146
283.090
283.034
282.977
282.919
282.862
282.804
282.746
282.688
282.631
282.575
282.519
282.464
282.410
282.358
282.308
282.259
282.212
282.167
282.124
282.084
282.046
14
Supplementary Information
1238.5
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1265.5
1266.5
1267.5
1268.5
1269.5
1270.5
1271.5
1272.5
1273.5
1274.5
1275.5
1276.5
1277.5
1278.5
1279.5
1280.5
1281.5
1282.5
1283.5
1284.5
1285.5
1286.5
1287.5
1288.5
1289.5
1290.5
1291.5
1292.5
1293.5
1294.5
1295.5
1296.5
282.012
281.980
281.952
281.927
281.905
281.887
281.874
281.864
281.858
281.858
281.861
281.866
281.874
281.883
281.892
281.900
281.906
281.909
281.909
281.904
281.893
281.876
281.854
281.826
281.794
281.758
281.718
281.676
281.630
281.583
281.534
281.484
281.434
281.384
281.334
281.285
281.238
281.193
281.150
281.110
281.073
281.040
281.009
280.982
280.958
280.937
280.920
280.907
280.897
280.892
280.889
280.891
280.897
280.907
280.921
280.940
280.962
280.990
281.021
15
Supplementary Information
1297.5
1298.5
1299.5
1300.5
1301.5
1302.5
1303.5
1304.5
1305.5
1306.5
1307.5
1308.5
1309.5
1310.5
1311.5
1312.5
1313.5
1314.5
1315.5
1316.5
1317.5
1318.5
1319.5
1320.5
1321.5
1322.5
1323.5
1324.5
1325.5
1326.5
1327.5
1328.5
1329.5
1330.5
1331.5
1332.5
1333.5
1334.5
1335.5
1336.5
1337.5
1338.5
1339.5
1340.5
1341.5
1342.5
1343.5
1344.5
1345.5
1346.5
1347.5
1348.5
1349.5
1350.5
1351.5
1352.5
1353.5
1354.5
1355.5
281.058
281.099
281.144
281.195
281.250
281.311
281.376
281.447
281.523
281.605
281.691
281.783
281.879
281.977
282.078
282.180
282.281
282.382
282.481
282.577
282.669
282.757
282.838
282.913
282.979
283.037
283.086
283.123
283.148
283.161
283.161
283.145
283.114
283.066
283.001
282.919
282.823
282.712
282.591
282.458
282.316
282.167
282.012
281.852
281.689
281.524
281.359
281.196
281.035
280.878
280.727
280.583
280.448
280.323
280.210
280.106
280.013
279.930
279.856
16
Supplementary Information
1356.5
1357.5
1358.5
1359.5
1360.5
1361.5
1362.5
1363.5
1364.5
1365.5
1366.5
1367.5
1368.5
1369.5
1370.5
1371.5
1372.5
1373.5
1374.5
1375.5
1376.5
1377.5
1378.5
1379.5
1380.5
1381.5
1382.5
1383.5
1384.5
1385.5
1386.5
1387.5
1388.5
1389.5
1390.5
1391.5
1392.5
1393.5
1394.5
1395.5
1396.5
1397.5
1398.5
1399.5
1400.5
1401.5
1402.5
1403.5
1404.5
1405.5
1406.5
1407.5
1408.5
1409.5
1410.5
1411.5
1412.5
1413.5
1414.5
279.791
279.735
279.687
279.647
279.614
279.588
279.569
279.556
279.549
279.547
279.551
279.558
279.570
279.586
279.605
279.627
279.651
279.678
279.707
279.736
279.767
279.798
279.829
279.860
279.891
279.920
279.948
279.973
279.997
280.017
280.035
280.049
280.059
280.065
280.066
280.062
280.053
280.039
280.022
280.001
279.977
279.951
279.924
279.895
279.866
279.837
279.809
279.782
279.757
279.734
279.714
279.698
279.686
279.678
279.676
279.680
279.690
279.707
279.730
17
Supplementary Information
1415.5
1416.5
1417.5
1418.5
1419.5
1420.5
1421.5
1422.5
1423.5
1424.5
1425.5
1426.5
1427.5
1428.5
1429.5
1430.5
1431.5
1432.5
1433.5
1434.5
1435.5
1436.5
1437.5
1438.5
1439.5
1440.5
1441.5
1442.5
1443.5
1444.5
1445.5
1446.5
1447.5
1448.5
1449.5
1450.5
1451.5
1452.5
1453.5
1454.5
1455.5
1456.5
1457.5
1458.5
1459.5
1460.5
1461.5
1462.5
1463.5
1464.5
1465.5
1466.5
1467.5
1468.5
1469.5
1470.5
1471.5
1472.5
1473.5
279.760
279.796
279.839
279.888
279.944
280.006
280.074
280.149
280.230
280.318
280.412
280.512
280.619
280.731
280.850
280.975
281.098
281.213
281.316
281.409
281.491
281.563
281.624
281.675
281.715
281.745
281.765
281.775
281.775
281.764
281.745
281.715
281.675
281.626
281.568
281.500
281.424
281.340
281.250
281.155
281.056
280.954
280.849
280.745
280.640
280.536
280.435
280.338
280.245
280.158
280.077
280.004
279.941
279.887
279.844
279.814
279.796
279.789
279.795
18
Supplementary Information
1474.5
1475.5
1476.5
1477.5
1478.5
1479.5
1480.5
1481.5
1482.5
1483.5
1484.5
1485.5
1486.5
1487.5
1488.5
1489.5
1490.5
1491.5
1492.5
1493.5
1494.5
1495.5
1496.5
1497.5
1498.5
1499.5
1500.5
1501.5
1502.5
1503.5
1504.5
1505.5
1506.5
1507.5
1508.5
1509.5
1510.5
1511.5
1512.5
1513.5
1514.5
1515.5
1516.5
1517.5
1518.5
1519.5
1520.5
1521.5
1522.5
1523.5
1524.5
1525.5
1526.5
1527.5
1528.5
1529.5
1530.5
1531.5
1532.5
279.810
279.837
279.872
279.917
279.970
280.032
280.100
280.176
280.258
280.345
280.438
280.535
280.637
280.742
280.849
280.959
281.071
281.184
281.298
281.412
281.525
281.638
281.749
281.857
281.963
282.066
282.165
282.260
282.349
282.434
282.513
282.588
282.658
282.723
282.784
282.840
282.892
282.940
282.983
283.023
283.059
283.092
283.121
283.147
283.169
283.188
283.204
283.217
283.228
283.236
283.241
283.244
283.245
283.244
283.240
283.235
283.228
283.219
283.209
19
Supplementary Information
1533.5
1534.5
1535.5
1536.5
1537.5
1538.5
1539.5
1540.5
1541.5
1542.5
1543.5
1544.5
1545.5
1546.5
1547.5
1548.5
1549.5
1550.5
1551.5
1552.5
1553.5
1554.5
1555.5
1556.5
1557.5
1558.5
1559.5
1560.5
1561.5
1562.5
1563.5
1564.5
1565.5
1566.5
1567.5
1568.5
1569.5
1570.5
1571.5
1572.5
1573.5
1574.5
1575.5
1576.5
1577.5
1578.5
1579.5
1580.5
1581.5
1582.5
1583.5
1584.5
1585.5
1586.5
1587.5
1588.5
1589.5
1590.5
1591.5
283.196
283.182
283.165
283.147
283.126
283.103
283.077
283.049
283.018
282.985
282.949
282.909
282.867
282.822
282.774
282.722
282.667
282.609
282.547
282.483
282.419
282.355
282.292
282.232
282.176
282.125
282.080
282.042
282.013
281.992
281.978
281.970
281.966
281.965
281.967
281.969
281.971
281.972
281.969
281.963
281.951
281.933
281.907
281.871
281.824
281.764
281.690
281.599
281.491
281.364
281.216
281.045
280.850
280.630
280.383
280.107
279.800
279.467
279.112
20
Supplementary Information
1592.5
1593.5
1594.5
1595.5
1596.5
1597.5
1598.5
1599.5
1600.5
1601.5
1602.5
1603.5
1604.5
1605.5
1606.5
1607.5
1608.5
1609.5
1610.5
1611.5
1612.5
1613.5
1614.5
1615.5
1616.5
1617.5
1618.5
1619.5
1620.5
1621.5
1622.5
1623.5
1624.5
1625.5
1626.5
1627.5
1628.5
1629.5
1630.5
1631.5
1632.5
1633.5
1634.5
1635.5
1636.5
1637.5
1638.5
1639.5
1640.5
1641.5
1642.5
1643.5
1644.5
1645.5
1646.5
1647.5
1648.5
1649.5
1650.5
278.741
278.358
277.963
277.562
277.156
276.748
276.342
275.939
275.543
275.156
274.781
274.421
274.080
273.758
273.461
273.190
272.948
272.739
272.565
272.429
272.331
272.268
272.240
272.243
272.275
272.334
272.418
272.525
272.652
272.798
272.960
273.136
273.323
273.521
273.725
273.935
274.148
274.361
274.574
274.784
274.991
275.193
275.390
275.581
275.764
275.939
276.105
276.259
276.403
276.534
276.652
276.759
276.853
276.936
277.008
277.069
277.119
277.159
277.189
21
Supplementary Information
1651.5
1652.5
1653.5
1654.5
1655.5
1656.5
1657.5
1658.5
1659.5
1660.5
1661.5
1662.5
1663.5
1664.5
1665.5
1666.5
1667.5
1668.5
1669.5
1670.5
1671.5
1672.5
1673.5
1674.5
1675.5
1676.5
1677.5
1678.5
1679.5
1680.5
1681.5
1682.5
1683.5
1684.5
1685.5
1686.5
1687.5
1688.5
1689.5
1690.5
1691.5
1692.5
1693.5
1694.5
1695.5
1696.5
1697.5
1698.5
1699.5
1700.5
1701.5
1702.5
1703.5
1704.5
1705.5
1706.5
1707.5
1708.5
1709.5
277.210
277.221
277.224
277.220
277.207
277.188
277.163
277.132
277.096
277.056
277.011
276.963
276.911
276.858
276.802
276.745
276.688
276.630
276.572
276.515
276.460
276.406
276.355
276.307
276.263
276.222
276.186
276.156
276.131
276.113
276.101
276.097
276.100
276.110
276.126
276.148
276.173
276.202
276.234
276.267
276.301
276.336
276.370
276.403
276.435
276.466
276.496
276.525
276.553
276.581
276.607
276.634
276.660
276.686
276.712
276.738
276.764
276.790
276.818
22
Supplementary Information
1710.5
1711.5
1712.5
1713.5
1714.5
1715.5
1716.5
1717.5
1718.5
1719.5
1720.5
1721.5
1722.5
1723.5
1724.5
1725.5
1726.5
1727.5
1728.5
1729.5
1730.5
1731.5
1732.5
1733.5
1734.5
1735.5
1736.5
1737.5
1738.5
1739.5
1740.5
1741.5
1742.5
1743.5
1744.5
1745.5
1746.5
1747.5
1748.5
1749.5
1750.5
1751.5
1752.5
1753.5
1754.5
1755.5
1756.5
1757.5
1758.5
1759.5
1760.5
1761.5
1762.5
1763.5
1764.5
1765.5
1766.5
1767.5
1768.5
276.845
276.874
276.903
276.934
276.965
276.998
277.032
277.068
277.106
277.145
277.187
277.230
277.276
277.324
277.374
277.425
277.474
277.521
277.563
277.600
277.630
277.651
277.661
277.659
277.644
277.614
277.571
277.518
277.457
277.390
277.320
277.250
277.181
277.117
277.058
277.005
276.957
276.912
276.871
276.832
276.796
276.761
276.727
276.695
276.665
276.638
276.614
276.595
276.582
276.575
276.576
276.585
276.604
276.634
276.675
276.728
276.830
276.943
277.067
23
Supplementary Information
1769.5
1770.5
1771.5
1772.5
1773.5
1774.5
1775.5
1776.5
1777.5
1778.5
1779.5
1780.5
1781.5
1782.5
1783.5
1784.5
1785.5
1786.5
1787.5
1788.5
1789.5
1790.5
1791.5
1792.5
1793.5
1794.5
1795.5
1796.5
1797.5
1798.5
1799.5
1800.5
1801.5
1802.5
1803.5
1804.5
1805.5
1806.5
1807.5
1808.5
1809.5
1810.5
1811.5
1812.5
1813.5
1814.5
1815.5
1816.5
1817.5
1818.5
1819.5
1820.5
1821.5
1822.5
1823.5
1824.5
1825.5
1826.5
1827.5
277.202
277.344
277.493
277.648
277.809
277.974
278.143
278.319
278.501
278.689
278.882
279.077
279.275
279.478
279.685
279.897
280.115
280.338
280.565
280.793
281.016
281.232
281.440
281.638
281.828
282.009
282.180
282.341
282.494
282.638
282.773
282.899
283.007
283.111
283.211
283.307
283.400
283.490
283.578
283.661
283.735
283.797
283.847
283.889
283.926
283.963
284.001
284.043
284.086
284.129
284.167
284.198
284.223
284.244
284.263
284.281
284.300
284.320
284.340
24
Supplementary Information
1828.5
1829.5
1830.5
1831.5
1832.5
1833.5
1834.5
1835.5
1836.5
1837.5
1838.5
1839.5
1840.5
1841.5
1842.5
1843.5
1844.5
1845.5
1846.5
1847.5
1848.5
1849.5
1850.5
1851.5
1852.5
1853.5
1854.5
1855.5
1856.5
1857.5
1858.5
1859.5
1860.5
1861.5
1862.5
1863.5
1864.5
1865.5
1866.5
1867.5
1868.5
1869.5
1870.5
1871.5
1872.5
1873.5
1874.5
1875.5
1876.5
1877.5
1878.5
1879.5
1880.5
1881.5
1882.5
1883.5
1884.5
1885.5
1886.5
284.360
284.380
284.400
284.385
284.280
284.125
283.975
283.825
283.675
283.525
283.425
283.400
283.400
283.425
283.500
283.600
283.725
283.900
284.075
284.225
284.400
284.575
284.725
284.875
285.000
285.125
285.275
285.425
285.575
285.725
285.900
286.075
286.225
286.375
286.500
286.625
286.775
286.900
287.000
287.100
287.225
287.375
287.525
287.700
287.900
288.125
288.400
288.700
289.025
289.400
289.800
290.225
290.700
291.200
291.675
292.125
292.575
292.975
293.300
25
Supplementary Information
1887.5
1888.5
1889.5
1890.5
1891.5
1892.5
1893.5
1894.5
1895.5
1896.5
1897.5
1898.5
1899.5
1900.5
1901.5
1902.5
1903.5
1904.5
1905.5
1906.5
1907.5
1908.5
1909.5
1910.5
1911.5
1912.5
1913.5
1914.5
1915.5
1916.5
1917.5
1918.5
1919.5
1920.5
1921.5
1922.5
1923.5
1924.5
1925.5
1926.5
1927.5
1928.5
1929.5
1930.5
1931.5
1932.5
1933.5
1934.5
1935.5
1936.5
1937.5
1938.5
1939.5
1940.5
1941.5
1942.5
1943.5
1944.5
1945.5
293.575
293.800
294.000
294.175
294.325
294.475
294.600
294.700
294.800
294.900
295.025
295.225
295.500
295.800
296.125
296.475
296.825
297.200
297.625
298.075
298.500
298.900
299.300
299.700
300.075
300.425
300.775
301.100
301.400
301.725
302.075
302.400
302.700
303.025
303.400
303.775
304.125
304.525
304.975
305.400
305.825
306.300
306.775
307.225
307.700
308.175
308.600
309.000
309.400
309.750
310.000
310.175
310.300
310.375
310.375
310.300
310.200
310.125
310.100
26
Supplementary Information
1946.5
1947.5
1948.5
1949.5
1950.5
1951.5
1952.5
1953.5
1954.5
1955.5
1956.5
1957.5
1958.5
1959.5
1960.5
1961.5
1962.5
1963.5
1964.5
1965.5
1966.5
1967.5
1968.5
1969.5
1970.5
1971.5
1972.5
1973.5
1974.5
1975.5
1976.5
1977.5
1978.5
1979.5
1980.5
1981.5
1982.5
1983.5
1984.5
1985.5
1986.5
1987.5
1988.5
1989.5
1990.5
1991.5
1992.5
1993.5
1994.5
1995.5
1996.5
1997.5
1998.5
1999.5
2000.5
2001.5
2002.5
2003.5
2004.5
310.125
310.200
310.325
310.500
310.750
311.100
311.500
311.925
312.425
313.000
313.600
314.225
314.848
315.500
316.272
317.075
317.795
318.397
318.925
319.647
320.647
321.605
322.635
323.902
324.985
325.855
327.140
328.677
329.742
330.585
331.747
333.272
334.848
336.525
338.360
339.728
340.793
342.198
343.783
345.283
346.797
348.645
350.737
352.487
353.855
355.017
355.885
356.777
358.128
359.837
361.462
363.155
365.323
367.348
368.865
370.467
372.522
374.760
376.813
27
Supplementary Information
2005.5
2006.5
2007.5
2008.5
2009.5
2010.5
999999.
378.813
380.828
382.777
384.800
386.935
389.000
389.000
28
Supplementary Information
29
Supplementary Information: Part B
Responses in CO2 for the 100 GtC emission pulse added to a constant background of 389 ppm (PD100
case) are fitted by a sum of exponentials:
3
 t 
IRFCO2 (t )  a0   ai  exp  
i 1
 i 
for 0  t  nryears .
(S1)
For IRFCO2 the conditions is applied that the sum of the coefficients ai equals 1. Note that the fits only
apply for the period from 0 to nryears, where nryears is the number of available output years.
The mean relative error, mre, in permil is calculated from annual values:
mre 
1 nryears f i  mi
 m 1000permil ,
nryears i 1
i
(S2)
where fi are the annual data from the fit and mi from the model output.
Table S1: Coefficients to fit model responses in CO2 (IRFCO2) for the PD100 case. The mean relative
error (mre) is given in permil.
model
a0
a1
a2
a3
1
2
3
nryears
mre
NCAR
CSM1.4
HadGEM2-ES
289
11
2.935E-07
3.665E-01
3.542E-01
2.793E-01
1.691E+03
2.836E+01
5.316E+00
101
40
4.340E-01
1.973E-01
1.889E-01
1.798E-01
2.307E+01
2.307E+01
3.922E+00
MPI-ESM
101
16
1.252E-07
5.864E-01
1.826E-01
2.310E-01
1.781E+02
9.039E+00
8.989E+00
Bern3D-LPJ
(reference)
Bern3D-LPJ
(ensemble)
Bern2.5D-LPJ
1000
5
6.345E-10
5.150E-01
2.631E-01
2.219E-01
1.955E+03
4.583E+01
3.872E+00
585
3
2.796E-01
2.382E-01
2.382E-01
2.440E-01
2.762E+02
3.845E+01
4.928E+00
1000
9
2.362E-01
9.866E-02
3.850E-01
2.801E-01
2.321E+02
5.850E+01
2.587E+00
CLIMBER2LPJ
DCESS
1000
20
2.318E-01
2.756E-01
4.900E-01
2.576E-03
2.726E+02
6.692E+00
6.692E+00
1000
4
2.159E-01
2.912E-01
2.410E-01
2.518E-01
3.799E+02
3.631E+01
3.398E+00
GENIE
(ensemble)
LOVECLIM
1000
5
2.145E-01
2.490E-01
1.924E-01
3.441E-01
2.701E+02
3.932E+01
4.305E+00
1000
58
8.539E-08
3.606E-01
4.503E-01
1.891E-01
1.596E+03
2.171E+01
2.281E+00
MESMO
1000
1
2.848E-01
2.938E-01
2.382E-01
1.831E-01
4.543E+02
2.500E+01
2.014E+00
UVic2.9
1000
4
3.186E-01
1.748E-01
1.921E-01
3.145E-01
3.046E+02
2.656E+01
3.800E+00
ACC2
985
4
1.779E-01
1.654E-01
3.796E-01
2.772E-01
3.862E+02
3.689E+01
3.723E+00
Bern-SAR
1000
3
1.994E-01
1.762E-01
3.452E-01
2.792E-01
3.331E+02
3.969E+01
4.110E+00
MAGICC6
(ensemble)
TOTEM2
604
1
2.051E-01
2.533E-01
3.318E-01
2.098E-01
5.961E+02
2.197E+01
2.995E+00
984
2
7.177E-06
2.032E-01
6.995E-01
9.738E-02
8.577E+04
1.118E+02
1.583E-02
multi-model
mean
1000
6
2.173E-01
2.240E-01
2.824E-01
2.763E-01
3.944E+02
3.654E+01
4.304E+00
Supplementary Information
30
Table S2: Coefficients to fit model responses in CO2 (IRFCO2) for the PI100 and PD100 cases with and
without climate feedbacks and for the Bern3D-LPJ(reference). The mean relative error (mre) is given
in permil.
a0
a1
a2
a3
1
2
3
nryears
mre
With climate
feedback
Without
climate
feedback
1000
4
1.266E-01
2.607E-01
2.909E-01
3.218E-01
3.028E+02
3.161E+01
4.240E+00
1000
3
1.332E-01
1.663E-01
3.453E-01
3.551E-01
3.133E+02
2.999E+01
4.601E+00
With climate
feedback
Without
climate
feedback
1000
5
6.345E-10
5.150E-01
2.631E-01
2.219E-01
1.955E+03
4.583E+01
3.872E+00
1000
0.02
2.123E-01
2.444e-01
3.360e-01
2.073e-01
3.364e+02
2.789e+01
4.055e+00
PI100
PD100
Supplementary Information
Figure S1: Responses in IRFCO2 from individual models (black) and corresponding fits (red).
31