Forcings of Climate

The simplest forcing to define and describe -although by no means easy to quantify - is the change or variability of the so-called solar constant. The IPCC (1990, 1995, 1996) provides several estimates of this forcing, e.g., 

CFC-12. These manmade chemicals absorb infrared radiation in a part of the spectrum where water vapor and CO2 do not already have strong bands. On the other hand, the manmade increase of CO2 is so large (currently ca. 25% since the mid-1800s - see Chapter 11) that it is the largest anthropogenic input to the greenhouse effect (not counting feedbacks). 

CO2 where [CO2] is concentration in ppmv Valid for concentrations 1000 ppmv 

Aerosol particles - the visible haze in polluted air - reflect and absorb sunlight, directly influencing the heat balance over large ( 1000 km) 

Here B is the world average burden of anthropogenic sulfate aerosol in a column of air, in grams per square meter. The optical depth is then used in the Beer Law (which describes the transmission of light through the entire vertical column of the atmosphere). The law yields I/Iq = where I is the intensity of transmitted radiation, Iq is the incident intensity outside the atmosphere and e is the base of natural logarithms. In the simplest case, where the optical depth is much less than 1, (5 is the fraction of light lost from the solar beam because of 

---

Intergovernmental Panel on Climate Change, S cientific Assessment of Climate Change, Section 2, Kadiative Forcing of Climate, United Nations, New York, 1990, p. 14. 

Charlson, R. J., and J. Heintzenberg, Eds., Aerosol Forcing of Climate, Wiley, New York, 1995. 

Haigh, J. D., The Role of Stratospheric Ozone in Modulating the Solar Radiative Forcing of Climate, Nature, 370, 544-546 (1994). 

Lacis, A. A., and M. I. Mishchenko, Climate Forcing, Climate Sensitivity, and Climate Response A Radiative Modeling Perspective on Atmospheric Aerosols, in Aerosol Forcing of Climate (R. J. Charlson and J. Heintzenberg, Eds.), Wiley, New York, 1995. 

Lelieveld, J., and R. van Dorland, Ozone Chemistry Changes in the Troposphere and Consequent Radiative Forcing of Climate, in NATO AS 1 Series, 132, (1995). 

Liao, H., and J. H. Seinfeld, Effect of Clouds on Direct Aerosol Radiative Forcing of Climate, J. Geophys. Res., 103, 3781-3788... 

Nemesure, S., R. Wagener, and S. E. Schwartz, Direct Shortwave Forcing of Climate by the Anthropogenic Sulfate Aerosol Sensitivity to Particle Size, Composition, and Relative Humidity, J. Geophys. Res., 100, 26105-26116 (1995). 

Ramaswamy, V., M. D. Schwarzkopf, and K. P. Shine, Radiative Forcing of Climate from Halocarbon-Induced Global Stratospheric Ozone Loss, Nature, 355, 810-812 (1992). 

Schwartz, S. E., The Whitehouse Effect—Shortwave Radiative Forcing of Climate by Anthropogenic Aerosols An Overview, J. Aerosol Sci., 27, 359-382 (1996). 

Lelieveld, J. and R. van Dorland, Ozone chemistry changes in the troposphere and consequent radiative forcing of climate, in Atmospheric Ozone as a Climate Gas, edited by W-C. Wang and l.S.A. lsaksen. Springer, Berlin, 1995. 

NOx emissions are implicated in phenomena such as acidification and eutrophication, with their subsequent impacts on the biodiversity of habitats, as well as radiative forcing of climate through the formation of nitrate aerosol and tropospheric ozone, and impacts on the carbon cycle [3]. 

Schwartz, S. E. (2004). Uncertainty requirements in radiative forcing of climate change./. Air Waste Manage. Assoc. 54,1351-1359. 

Abrupt climate changes are especially substantial in transitions from one climatic state to another. Therefore, if anthropogenic forcings of climate do favor the drifting... 

There is considerable interest in volcanic emissions of sulfur compounds because of the role of atmospheric sulfur chemistry in atmospheric radiation and climate, the hydrological cycle, acid precipitation, and air quality (see Chapter 8.14). Early theories on the climatic effects of eruptions considered that ash particles were responsible for raising the planetary albedo, but it is now clear that even fine tephra sediment rapidly from the atmosphere, and that the main protagonist in volcanic forcing of climate is the... 

Aerosol Forcing Relative to Other Forcings of Climate Change over the Industrial Period... 

Nemesure S., Wagener R., and Schwartz S. E. (1995) Direct shortwave forcing of climate by anthropogenic sulfate aerosol sensitivity to particle size, composition, and relative humidity. J. Geophys. Res. 100, 26105—26116. 

Shine K. P. and Forster P. M. D. (1999) The effect of human activity on radiative forcing of climate change a review of recent developments. Global Planet. Change 20, 205—225. 

---