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Review
. 1998 Oct 27;95(22):12753-8.
doi: 10.1073/pnas.95.22.12753.

Climate forcings in the industrial era

J E Hansen  1 , M Sato, A Lacis, R Ruedy, I Tegen, E Matthews
Affiliations
Review

Climate forcings in the industrial era

J E Hansen et al. Proc Natl Acad Sci U S A. .

Abstract

The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change. Anthropogenic greenhouse gases (GHGs), which are well measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. One consequence of this partial balance is that the natural forcing due to solar irradiance changes may play a larger role in long-term climate change than inferred from comparison with GHGs alone. Current trends in GHG climate forcings are smaller than in popular "business as usual" or 1% per year CO2 growth scenarios. The summary implication is a paradigm change for long-term climate projections: uncertainties in climate forcings have supplanted global climate sensitivity as the predominant issue.

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Figures

Figure 1
Figure 1
Principal anthropogenic GHGs in the Industrial era.
Figure 2
Figure 2
Estimated radiative forcings between 1850 and the present.
Figure 3
Figure 3
Optical depth, climate forcing, and simulated equilibrium temperature change for three assumed anthropogenic aerosol distributions. These are the three “more realistic” single scatter albedo (ω) cases of Table 2.
Figure 4
Figure 4
Climate forcing and simulated surface air temperature response for land-use change between the pre-Industrial era and the present.
Figure 5
Figure 5
Growth rate of greenhouse climate forcing based on gas histories shown in Fig. 1. Dashed line is forcing due to 1% CO2 increase.
Figure 6
Figure 6
Fossil fuel CO2 emissions (45). Mean annual growth rates are shown for four periods.
See this image and copyright information in PMC

References

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    1. Houghton J T, Meira Filho L G, Callander B A, Harris N, Kattenberg A, Maskell K, editors. Intergovernmental Panel on Climate Change. Climate Change (1995) Univ. Press, Cambridge, U.K.: Cambridge; 1996.
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    1. Lorenz E N. J Atmos Sci. 1963;20:130–141.
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