Climate forcing

Ozone is a highly reactive molecule composed of three atoms of oxygen. Ozone concentrations vary by geographical location and by altitude. In addition, ozone exerts a different climate-forcing effect, depending upon altitude. 

It is clear that human action can affect seven of eight of the major gi eenhouse forcings carbon dioxide, methane, nitrous oxide, ozone, CFCs, aerosols, and water vapor. As studies of solar variation have shown, it is also clear that human action is not the only factor involved in determining the impact of these forcings. There is still substantial uncertainty regarding the actual climate impact of the climate forcings. 

Lean, J., and Rind, U. (1998). "Climate Forcing by Changing Solar Radiation. Joiimaf of Climate 11 3069-3094. 

Ocean-Atmosphere Interactions. To determine how the ocean responds to a C02-induced climate forcing, it will be necessary to develop a combined ocean and atmospheric general circulation model. It will take 10-20 years to develop a model with appropriate chemistry and biology to the level of confidence necessary to make valid projections. In the interim, two approaches can be pursued in parallel with this model development. 

Capaldo, K., Corbett, J. Kasibhatla, P., Fischbeck, P., and Pandis, S. N. (1999). Effects of ship emissions on sulphur cycling and radiative climate forcing over the ocean. Nature, 400, 743-746. 

The Coupling of Biogeochemical Cycles and Climate Forcings, Feedbacks, and Responses... 

Fig. 17-6 Calculated geographical distribution of the climate forcing (W/m ) by anthropogenic greenhouse gases alone, from pre-industrial periods to ca. 1990. From IPCC (1995), after Kiehl and Briegleb (1993). See text for interpretation. (Reprinted by permission from IPCC.)...

Figure 17-8 summarizes and compares the anthropogenic and natural forcings for the period 1800-1990, showing the complex nature of the issue of anthropogenic climate forcing. 

Kiehl, J. T. and Briegleb, B. P. (1993). The relative roles of sulfate aerosols and greenhouse gases in climate forcing. Science 260 (16 April), 311-314. 

Table 19-1 demonstrates that with the exception of water vapor, all of these cycles have been severely perturbed by human activity. Of course, all of these cycles are also linked in many ways. For example, the combustion of fossil fuel has increased the fluxes of carbon, sulfur, and nitrogen oxides to the atmosphere. Denitrification, the production of N2O, is linked with the production of CO2 during respiration and decay. And of course, other important cycles are involved which are not depicted here. Look back at Fig. 17-8, which sums up the climate forcings by the key agents. 

Barron, E.J., Solan, J.L. and Harrison, C.G.A. (1980) Potential significance of land-sea distribution and surface albedo variations as a climatic forcing factor 180 m.y. to the present. Paleoneogr. Paleoclimatol. PaleoecoL, 30, 17- 0. 

Mann M., Bradley R.S., et al. Global-scale temprature patterns and climate forcing over the past six centuries. 1998 Nature 392 779-787. 

Schultz, M. G., Diel, T., Brasseur, G. P. and Zittel, W. (2003). Air pollution and climate-forcing impacts of a global hydrogen economy. Science, 302 (24th October, 2003). 

Another potential climate forcing agent that is not well understood is solar irradiance. (This was discussed at the end of Chapter 25.4.4.) Direct measurements have been underway only since 1978 and provide no evidence for any upward trend over the past 25 or so years, although the existence of the 11-y sunspot cycle is apparent. Variations in... 

LeUeveld I, Crutzen PI, Dentener FI. 1998. Changing concentration, lifetime and climate forcing of atmospheric methane. Tellus Series B-Chemical and Physical Meteorology 50 128-150. 

Toumi, R S. Bekki, and K. S. Law, Indirect Influence of Ozone Depletion on Climate Forcing by Clouds, Nature, 372, 348-351 (1994). 

Boucher, O., and T. L. Anderson, General Circulation Model Assessment of the Sensitivity of Direct Climate Forcing by Anthropogenic Sulfate Aerosols to Aerosol Size and Chemistry, ]. Geophys. Res., 100, 26117-26134 (1995). 

Hansen, J., M. Sato, A. Lacis, and R. Ruedy, The Missing Climate Forcing, Philos. Trans. R. Soc. London B, 352, 231-240 (1997d). 

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