Climate Change 2001:
Working Group I: The Scientific Basis
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II.3: Radiative Forcing (Wm-2) (relative to pre-industrial period, 1750)

The concentrations of CO2 and CH4 considered here correspond to the year 2000 and differ slightly from those considered in Chapter 6 which used the values corresponding to the year 1998 (as appropriate for the time frame when Chapter 6 began its preparation). The resulting difference in the computed present day forcings is about 3% in the case of CO2 and about 2% in the case of CH4. For N2O, the difference in the computed forcings is negligible. In the case of tropospheric ozone, the forcing for the year 2000 given here and that in Chapter 6 are the results of slightly different scenarios employed which leads to about a 9% difference in the forcings. For the halogen containing compounds and aerosols, the difference in forcings between here and Chapter 6, if any, are inconsequential (note: numbers are rounded off in Chapter 6).

II.3.1: CO2 radiative forcing (Wm-2)

ISAM model (reference) - CO2 radiative forcing (Wm-2)
Year A1B A1T A1FI A2 B1 B2 A1p A2p B1p B2p IS92a IS92a/SAR
2000 1.51 1.51 1.51 1.51 1.51 1.51 1.51 1.51 1.51 1.51 1.51 1.56
2010 1.82 1.80 1.80 1.81 1.78 1.78 1.85 1.82 1.78 1.81 1.81 1.85
2020 2.21 2.10 2.17 2.17 2.10 2.05 2.27 2.19 2.07 2.13 2.14 2.18
2030 2.62 2.46 2.64 2.59 2.42 2.32 2.71 2.61 2.32 2.43 2.50 2.53
2040 3.04 2.82 3.18 3.03 2.73 2.61 3.13 3.05 2.58 2.72 2.87 2.88
2050 3.47 3.15 3.81 3.47 3.01 2.90 3.53 3.50 2.83 2.99 3.23 3.24
2060 3.86 3.43 4.44 3.93 3.24 3.18 3.91 3.96 3.11 3.27 3.58 3.59
2070 4.21 3.65 5.06 4.42 3.40 3.46 4.25 4.44 3.37 3.54 3.95 3.93
2080 4.54 3.81 5.65 4.93 3.52 3.74 4.56 4.93 3.59 3.81 4.32 4.29
2090 4.82 3.91 6.20 5.46 3.60 4.02 4.82 5.46 3.78 4.09 4.71 4.66
2100 5.07 3.95 6.69 6.02 3.64 4.30 5.05 6.02 3.92 4.38 5.11 5.05

ISAM model (low) - CO2 radiative forcing (Wm-2)
Year A1B A1T A1FI A2 B1 B2 A1p A2p B1p B2p IS92a
2000 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50
2010 1.71 1.69 1.69 1.70 1.67 1.67 1.74 1.71 1.67 1.70 1.70
2020 2.01 1.92 1.99 1.97 1.92 1.87 2.07 2.00 1.88 1.95 1.96
2030 2.36 2.19 2.37 2.32 2.16 2.08 2.43 2.35 2.08 2.17 2.25
2040 2.71 2.49 2.84 2.69 2.41 2.30 2.78 2.71 2.27 2.40 2.53
2050 3.06 2.76 3.40 3.06 2.64 2.53 3.12 3.09 2.48 2.62 2.83
2060 3.39 2.99 3.97 3.47 2.81 2.76 3.43 3.49 2.69 2.84 3.13
2070 3.69 3.15 4.52 3.90 2.92 2.99 3.72 3.91 2.91 3.05 3.44
2080 3.95 3.26 5.05 4.34 2.99 3.21 3.96 4.35 3.09 3.28 3.76
2090 4.18 3.31 5.54 4.83 3.03 3.45 4.18 4.83 3.21 3.51 4.10
2100 4.38 3.31 5.99 5.35 3.03 3.69 4.35 5.35 3.32 3.76 4.46

ISAM model (high) - CO2 radiative forcing (Wm-2)
Year A1B A1T A1FI A2 B1 B2 A1p A2p B1p B2p IS92a
2000 1.51 1.51 1.51 1.51 1.51 1.51 1.51 1.51 1.51 1.51 1.51
2010 1.91 1.87 1.87 1.88 1.87 1.85 1.92 1.89 1.85 1.89 1.89
2020 2.35 2.23 2.30 2.30 2.23 2.17 2.40 2.32 2.18 2.26 2.28
2030 2.81 2.64 2.82 2.76 2.60 2.49 2.89 2.80 2.50 2.61 2.69
2040 3.28 3.04 3.42 3.26 2.96 2.83 3.36 3.29 2.80 2.94 3.12
2050 3.75 3.42 4.09 3.76 3.29 3.16 3.82 3.78 3.10 3.27 3.54
2060 4.20 3.75 4.77 4.27 3.56 3.49 4.25 4.29 3.42 3.58 3.96
2070 4.59 4.03 5.43 4.79 3.78 3.81 4.63 4.80 3.73 3.91 4.39
2080 4.96 4.23 6.06 5.34 3.94 4.13 4.99 5.35 3.99 4.22 4.80
2090 5.30 4.39 6.64 5.90 4.06 4.46 5.30 5.90 4.21 4.54 5.23
2100 5.59 4.48 7.17 6.49 4.14 4.79 5.58 6.49 4.41 4.87 5.68

Bern-CC model (reference) - CO2 radiative forcing (Wm-2)
Year A1B A1T A1FI A2 B1 B2 A1p A2p B1p B2p IS92a IS92a/SAR
2000 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.53
2010 1.78 1.76 1.76 1.76 1.76 1.74 1.81 1.78 1.74 1.77 1.77 1.82
2020 2.18 2.08 2.14 2.13 2.08 2.03 2.22 2.16 2.04 2.10 2.12 2.16
2030 2.54 2.40 2.56 2.50 2.36 2.27 2.62 2.54 2.27 2.37 2.44 2.50
2040 2.96 2.76 3.09 2.93 2.66 2.55 3.03 2.97 2.52 2.66 2.79 2.87
2050 3.37 3.10 3.70 3.37 2.94 2.84 3.44 3.40 2.78 2.93 3.13 3.21
2060 3.78 3.38 4.33 3.82 3.17 3.13 3.83 3.85 3.05 3.20 3.48 3.56
2070 4.12 3.60 4.96 4.29 3.33 3.39 4.17 4.31 3.30 3.47 3.82 3.91
2080 4.45 3.78 5.56 4.80 3.45 3.67 4.48 4.81 3.52 3.74 4.18 4.26
2090 4.74 3.86 6.12 5.34 3.53 3.94 4.74 5.34 3.70 4.01 4.57 4.63
2100 4.96 3.89 6.62 5.89 3.55 4.21 4.96 5.89 3.83 4.27 4.96 5.01

Bern-CC model (low) - CO2 radiative forcing (Wm-2)
Year A1B A1T A1FI A2 B1 B2 A1p A2p B1p B2p IS92a
2000 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49
2010 1.71 1.69 1.69 1.69 1.69 1.67 1.73 1.71 1.67 1.70 1.71
2020 2.04 1.95 2.01 2.00 1.95 1.89 2.09 2.03 1.91 1.97 1.99
2030 2.36 2.19 2.36 2.31 2.17 2.08 2.42 2.35 2.08 2.17 2.26
2040 2.69 2.48 2.83 2.68 2.41 2.30 2.76 2.71 2.27 2.38 2.55
2050 3.04 2.74 3.36 3.05 2.64 2.52 3.10 3.09 2.46 2.60 2.84
2060 3.37 2.96 3.91 3.44 2.81 2.74 3.39 3.46 2.67 2.81 3.14
2070 3.63 3.10 4.43 3.83 2.91 2.94 3.65 3.83 2.87 3.00 3.42
2080 3.89 3.19 4.94 4.27 2.98 3.16 3.89 4.26 3.03 3.21 3.74
2090 4.10 3.23 5.40 4.71 3.00 3.37 4.08 4.71 3.15 3.43 4.05
2100 4.27 3.20 5.81 5.20 2.99 3.59 4.23 5.19 3.24 3.65 4.39

Bern-CC model (high) - CO2 radiative forcing (Wm-2)
Year A1B A1T A1FI A2 B1 B2 A1p A2p B1p B2p IS92a
2000 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49 1.49
2010 1.88 1.85 1.85 1.85 1.84 1.84 1.91 1.88 1.84 1.87 1.88
2020 2.41 2.30 2.37 2.35 2.28 2.23 2.47 2.38 2.26 2.33 2.35
2030 2.96 2.78 2.97 2.89 2.73 2.62 3.04 2.94 2.64 2.75 2.82
2040 3.53 3.29 3.67 3.48 3.17 3.04 3.63 3.53 3.01 3.18 3.32
2050 4.11 3.77 4.44 4.09 3.59 3.46 4.20 4.13 3.39 3.59 3.82
2060 4.67 4.20 5.26 4.71 3.97 3.89 4.75 4.75 3.80 4.01 4.33
2070 5.18 4.57 6.04 5.33 4.27 4.29 5.23 5.36 4.19 4.39 4.82
2080 5.63 4.86 6.77 5.97 4.50 4.69 5.67 5.99 4.53 4.79 5.31
2090 6.04 5.07 7.45 6.61 4.67 5.08 6.06 6.62 4.80 5.17 5.80
2100 6.39 5.20 8.03 7.26 4.79 5.44 6.39 7.27 5.04 5.53 6.30

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