Forcings in GISS Climate Models

Forcings and Responses in Marvel et al. (2016)

Marvel et al. (2016) used a suite of CMIP5 "Historical Miscellaneous" simulations from the GISS CMIP5 archive. The annual mean anomalies for temperature (K) and ocean heat content (1022 J) in each 5- or 6-member ensemble, for each single forcing, and all-forcing 'Historical' runs are provided in CSV format: tas and ohc.

Figure S1 from Marvel et al (2015) (Updated: 3/12/2016)

Figure S1: (a-g): Ensemble-average instantaneous radiative forcings and ocean heat uptake rates (thick lines) and individual ensemble members (thin) for GISS-E2-R single-forcing experiments. All quantities are 10-year running means. Dots represent year-2000 effective radiative forcings (ERF). (h): Ensemble-average temperature anomalies (relative to 1850-1859) for each single-forcing simulation. (Updated: 3/12/2016)

Ocean heat content (1022 J) calculated from ocean potential temperature (CMIP5 variable 'thetao'), assuming reference specific heat capacity 3985 J/kg K and density 1025 kg/m3. Ocean heat uptake is calculated from trends in 10-year segments. Annual mean values are given for each ensemble member (r1­5) and the ensemble average. All values are anomalies with respect to the pre­industrial control values. Temperature anomalies (K) with respect to pre­industrial control values calculated from CMIP5 variable 'tas'. The forcings used come from the iRF from Miller et al (2014) supplemented by ERF values calculated as in Hansen et al (2005) using the fixed-SST method: SSTs are held fixed at 1850 values; concentrations are held fixed at year 2000 values. Simulations are run for three decades; ERF is calculated for each decadal average.

Errata (3/12/2016)

There were a couple of errors in the Early-Online version of the paper (which were fixed in the print version); 1) The definition of the F2xCO2 which was given as Fa (4.1 W/m2) instead of Fi (4.5 W/m2) and Fs (4.3 W/m2), 2) The iRF value for the historical run from Miller et al (2014) effectively did not include land-use. The subsequent modifications to Figs 1 and 2 are given below. The Supplemental Information was also corrected.

Figure 1 from Marvel et al (2016) (Updated: 3/12/2016) Figure 2 from Marvel et al (2016) (Updated: 3/12/2016)

Corrected figs. 1 and 2 from Marvel et al. (2016). Ref. 3, 4 and 21 are Lewis and Curry (201), Otto et al. (2013) and Shindell (2014), respectively.

The corrected Table S1 showing the Efficacies (E) for the transient and equilibrium cases, using the two sets of forcings:

Instantaneous RF (iRF, Fi)
Effective RF (ERF, Fs)
Etransient Eequilibrium Etransient Eequilibrium
AA 1.55 (1.05,2.05)
1.59 (1.33,1.84)
1.03 (0.85,1.21)
0.95 (0.85,1.06)
GHG 1.17 (1.06,1.27)
1.06 (0.98,1.14)
0.99 (0.90,1.09)
0.85 (0.79,0.92)
LU 4.27 (-2.42,10.95)
1.27 (0.09,2.44)
2.25 (-1.34,5.84)
1.64 (-3.44,6.73)
Oz 0.66 (0.34, 0.98)
0.52 (0.28,0.76)
0.66 (0.38,0.94)
0.70 (0.18,1.22)
Sl 1.68 (-1.27,4.63)
1.04 (0.36,1.73)
0.43 (-0.61,1.46)
0.22 (-0.41,0.86)
Vl
0.61 (0.33,0.89)
0.7 (0.39,1.02)
0.56 (-0.09,1.20)
0.73 (-0.61,2.06)
historical 1.00 (0.83,1.16)
0.82 (0.74,0.91)
0.88 (0.83,0.92)
0.76 (0.70,0.82)

Summary of corrected sensitivities. Median and likely (17-83%) range:

E=1 E (iRF) E (ERF)
Using forcings from...Shindell (2014)
TCR (ºC) 1.4 (1.2-1.7) 1.8 (1.4-2.4) 1.6 (1.3-2.0)
ECS (ºC) 2.1 (1.7-2.7) 3.4 (2.4-5.4) 3.4 (2.5-5.1)
Lewis & Curry (2014)
TCR 1.3 (1.0-1.7) 1.4 (1.0-2.5) 1.5 (1.1-2.1)
ECS 1.5 (1.2-2.2) 1.8 (1.2-3.3) 2.1 (1.5-3.6)
Otto et al (2013)
TCR 1.3 (1.0-1.8) 1.7 (1.1-2.8) 1.6 (1.2-2.2)
ECS 2.0 (1.4-3.2) 2.6 (1.4-5.9) 3.1 (1.9-6.4)

Sensitivity studies

These are additional calculations that were not included in the paper, but may be of interest.

1. Stratospherically-adjusted forcings:

Using the same set-up as in the paper, we also estimated the efficacies using adjusted radiative forcings (Fa) and applied them to the three sets of forcings used previously:

Adjusted RF (Fa)
Etransient Eequilibrium
AA 1.33 (1.09,1.56) 1.57 (1.20,1.94)
GHG 1.06 (0.96,1.16) 0.97 (0.90,1.05)
LU 1.49 (-1.17,5.07) 3.28 (-5.91,12.47)
Oz 0.90 (0.52,1.27) 1.03 (0.52,1.53)
Sl 0.79 (-1.13,2.71) 0.52 (-0.69,1.74)
Vl 4.01 (-0.63,8.65) 1.75 (-5.20,8.70)
historical 0.90 (0.86,0.95) 0.79 (0.77,0.82)

Summary of sensitivities using efficacies calculated from Fa. Median and likely (17-83%) range:

Using forcings from... Shindell (2014) Lewis & Curry (2014) Otto et al (2013)
TCR (ºC) 1.6 (1.3-2.0) 1.5 (1.1-2.1) 1.6 (1.2-2.2)
ECS (ºC) 2.9 (2.2-4.0) 1.9 (1.4-3.1) 2.8 (1.8-5.1)

2. Ocean heat content scaling:

To account for the difference between the TOA radiative imbalance and the ocean heat content change, we redid the calculation for the ECS assuming that the ocean heat content is only 94% of the TOA imbalance as in Otto et al (2013):

Eequilibrium
Instantaneous RF (iRF) Effective RF (ERF)
AA 1.64 (1.37,1.91) 0.99 (0.86,1.12)
GHG 1.09 (1.01,1.17) 0.88 (0.81,0.95)
LU 1.21 (0.07,2.34) 1.93 (-4.19,8.04)
Oz 0.52 (0.28,0.77) 0.77 (0.07,1.46)
Sl 0.98 (0.32,1.65) 0.22 (-0.41,0.85)
Vl 0.73 (0.41,1.05) 0.82 (-0.81,2.45)
historical 0.79 (0.71,0.88) 0.78 (0.71,0.84)

Summary of equilibrium sensitivities derived using efficacies from iRF and ERF. Median and likely (17-83%) range:

E=1 E (iRF) E (ERF)
Using forcings from... Shindell (2014)
ECS (ºC) 2.1 (1.7-2.7) 3.2 (2.3-5.1) 3.3 (2.4-5.2)
Lewis & Curry (2014)
ECS 1.5 (1.2-2.2) 1.7 (1.2-3.2) 2.1 (1.5-3.6)
Otto et al (2013)
ECS 2.0 (1.4-3.2) 2.5 (1.3-5.6) 3.0 (1.8-6.2)

References

Hansen, J., M. Sato, R. Ruedy, et al., 2005: Efficacy of climate forcings. J. Geophys. Res., 110, D18104, doi:10.1029/2005/JD005776. (See also Efficacy webpages).

Lewis, N., and J.A. Curry, 2014: The implications for climate sensitivity of AR5 forcing and heat uptake estimates Clim Dyn, 45, 1009-1023, doi: 10.1007/s00382-014-2342-y

Marvel, K., G.A. Schmidt, R. L. Miller and L. S. Nazarenko, 2015: Implications for climate sensitivity from the response to individual forcings. Nature Clim. Change, 6, 386-389, doi:10.1038/nclimate2888.

Miller, R.L., G.A. Schmidt, L.S. Nazarenko et al., 2014: CMIP5 historical simulations (1850-2012) with GISS ModelE2. J. Adv. Model. Earth Syst., 6, no. 2, 441-477, doi:10.1002/2013MS000266.

Otto, A., F. E. L. Otto, O. Boucher, J. Church, G. Hegerl, P. M. Forster, N. P. Gillett, J. Gregory, G. C. Johnson, R. Knutti, N. Lewis, U. Lohmann, J. Marotzke, G. Myhre, D. T. Shindell, B. Stevens, and M. R. Allen, 2013: Energy budget constraints on climate response. Nature Geosci., 6, 415-416, doi:10.1038/ngeo1836.

Shindell, D.T., 2014: Inhomogeneous forcing and transient climate sensitivity. Nature Clim. Change, 4, 274-277, doi:10.1038/nclimate2136.

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This page was written by Dr. Gavin Schmidt, with input from Drs. Kate Marvel, Ron Miller and Larissa Nazarenko.

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