54 The greenhousegases
10 With the use of the formula given in the text, calculate the radiative forcing
due to carbon dioxide for atmospheric concentrations of 150, 280, 450, 560
and 1000 ppm.Notes for Chapter 3
1 It is convenient to define radiative forcing as the radiative imbalance at the
top of the troposphere rather than at the top of the whole atmosphere.
2 Reference sources for Table 3.1 are as follows:
Prentice, I. C.et al. 2001. The carbon cycle and atmospheric carbon dioxide.
Chapter 3 in Houghton,J. T., Ding, Y., Griggs,D. J., Noguer, M., vander
Linden, P. J., Dai, X., Maskell, K., Johnson, C. A. (eds.)Climate Change
2001: The Scientific Basis. Contribution of Working Group I to the Third As-
sessment Report of the Intergovernmental Panel on Climate Change. Cam-
bridge: Cambridge University Press.
House, J. I.et al. 2003. Reconciling apparent inconsistencies in estimates
of terrestrial CO 2 sources and sinks.Tellus,55B, pp. 345–63.
See also Table 1.2 in Watson, R.T., Noble, I. R., Bolin, B., Ravindranath,
N. H., Verardo, D. J., Dokken, D. J. (eds.)Land Use, Land-use Change, and
Forestry, Chapter 1. Cambridge: Cambridge University Press.
3 See Prenticeet al.,Climate Change 2001.
4 Woods, J., Barkmann, W. 1993. The Plankton multiplier – positive feedback
in the greenhouse.Journal of Plankton Research, 15 , pp. 1053–74.
5 Keeling,R. F., Piper, S. C., Heimann,M. 1996. Global and hemispheric
sinks deduced from changes in atmospheric O 2 concentration.Nature, 381 ,
pp. 218–21.
6 For more details see House, J. I.et al. 2003. Reconciling apparent incon-
sistencies in estimates of terrestrial CO 2 sources and sinks.Tellus,55B,
pp. 345–63.
7 See Jones, C. D. and Cox, P. M. 2001. Atmospheric science letters.
doi.1006/asle. 2001.0041; the respiration rate varies approximately with
a factor 2(T−10)/^10.
8Cox,P.M.et al. 2004. Amazon die-back under climate-carbon cycle pro-
jections for the 21st century.Theoretical and Applied Climatology, in press.
9 In 1992 the increase slowed to almost zero. The reason for this is not known
but one suggestionis that, because of the collapse of the Russian economy,
the leakage from Siberian natural gas pipelines was much reduced.
10 The ratio of the enhanced greenhouse effect of a molecule of methane com-
pared to a molecule of carbon dioxide is known as its global warming po-
tential (GWP); a definition of GWP is given later in the chapter. The figure
of about 8 given here for the GWP of methane is for a time horizon of
100 years – see Lelieveld, J., Crutzen, P. J.Nature, 355 , 1992, pp. 339–41;
see also Pratheret al., Chapter 4, and Ramaswamyet al., Chapter 6 in,
Houghtonet al.,Climate Change 2001. The GWP is also often expressed as
the ratio of the effect for unit mass of each gas in which case the GWP for
methane (whose molecular mass is 0.36 of that of carbon dioxide) becomes