TABLE 4-2 Efficacies and Effective Forcing Calculated for a Variety of Forcings in Several Climate Models

Experiment

Forcing at the Tropopause f (W m-2)

Equilibrium Response at the Surface ΔT (K)

Efficacy E

Effective Forcing fe (W m-2)

Reference

CO2 (based on three GCMs)

1

0.38-1.12

1

0.38-1.12

Joshi et al. (2003)

Changes in snow and ice albedo due to black carbon (two scenarios)

0.16-0.17

0.2-0.24

1.97-2.22

0.32-0.38

Hansen and Nazarenko (2004)

Solar increase based on three GCMs

1

0.31-1.07

0.82-1.01

0.82-1.01

Joshi et al. (2003)

Solar increase

4.2-3.7

2.1-2.85

0.52-0.8

2.2-3.0

Gregory et al. (2004)

Tropospheric ozone

1

0.24-0.94

0.71-0.88

0.71-0.88

Joshi et al. (2003)

Tropospheric ozone

0.49

0.28

0.73

0.49

Mickley et al. (2004)

Sulfate aerosols, direct effect

−0.34

−0.24

0.83

−0.28

E. Roeckner (personal communication, May 2004)

Sulfate aerosols, first indirect effect

−0.89

−0.78

1.01

−0.90

E. Roeckner (personal communication, May 2004)

Well-mixed greenhouse gases from 1860 to 1990

2.12

1.82

1

2.12

Feichter et al. (2004)

All aerosol effects (direct and indirect on water clouds)

−1.4

−0.87

0.72

−1.01

Feichter et al. (2004),

Lohmann and Feichter (2001)

Greenhouse gases + direct sulfate aerosol forcing (1900-present) based on four GCMs

0.5-0.7

0.56-0.75

Boer et al. (2000)

All aerosol effects and greenhouse gases

0.7

0.57

0.94

0.66

Feichter et al. (2004),

Lohmann and Feichter (2001)



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