An introduction to Simple Climate Models used in the IPCC Second Assessment Report Rastetter, E. B., R. B. McKane, G. R. Shaver and J. M. Melillo, 1992: Changes in C storage by terrestrial ecosystems: How C-N interactions restrict responses to CO2 and temperature. Water Air and Soil Pollution, 64, 327-344. Santer, B. D. T. M. L. Wigley, M. E. Schlesinger and J. B. F. Mitchell, 1990: Developing Climate Scenarios from Equilibrium GCM Results. Max Planck Institute for Meteorology Report 47, Hamburg, Germany. Sarmiento, J. L., R. D. Slater, M. J. R. Fasham, H. W. Ducklow, J. R. Toggweiler and G. T. Evans, 1993: A seasonal threedimensional ecosystem model of nitrogen cycling in the North Atlantic euphotic zone, Glob. Biogechem. Cycles, 7, 417-450. Schlesinger, M. E. and N. Ramankutty, 1992: Implications for global warming of intercycle solar irradiance variations. Nature, 360, 330-333. Schlesinger, M. E. and N. Ramankutty, 1995: Is the recently reported 65 to 70-year surface temperature oscillation the result of climatic noise? J. Geophys. Res., 100, 13767-13774. Siegenthaler, U. and F. Joos, 1992: Use of a simple model for studying oceanic tracer distributions and the global carbon cycle. Tellus, 44B, 186-207. Soden, B. J. and R. Fu, 1995: A satellite analysis of deep convection, upper-tropospheric humidity, and the greenhouse effect, J. Clim., 8, 2333-2351. Solomon, S., R. W. Portmann, R. R. Garcia, L. W. Thomason, L. R. Poole and M. P. McCormick, 1996: The role of aerosol variations in anthropogenic ozone depletion at northern midlatitudes. J. Geophys. Res., 101, 6713-6727. Stocker, T. F. and D. G. Wright, 1991: Azonally averaged ocean model for the thermohaline circulation. Part II: Interocean circulation in the Pacific-Atlantic basin system. J. Phys. Oceanogr., 21, 1725-1739. Stocker, T. F., D. G. Wright and L. A. Mysak, 1992: A zonallyaveraged, coupled ocean-atmosphere model for paleo-climate studies. J. Clim., 5, 773-797. Stocker, T. F., W. S. Broecker and D. G. Wright, 1994: Carbon uptake experiment with a zonally-averaged global ocean circulation model. Tellus, 46B, 103-122. 39 van de Wal, R. S. W. and Oerlemans, J. 1994: An energy balance model for the Greenland ice sheet. Global and Planetary Change, 9, 115-131. van Minnen, J. G., K. Klein Goldewijk and R. Leemans, 1996: The importance of feedback processes and vegetation transition in the terrestrial carbon cycle. Journal of Biogeography, 22: 805-814. VEMAPMembers, 1995: Vegetation ecosystem modelling and analysis project: comparing biogeography and biogeochemistry models in a continental-scale study of terrestrial ecosystem responses to climate change and CO2 doubling. Global Biogeochemical Cycles, 9, 407-437. Verbitsky, M. and B. Saltzman, 1995: Behavior of the East Antarctic ice sheet as deduced from a coupled GCM/Ice-sheet model. Geophys. Res. Let., 22, 2913-2916. Wigley, T. M. L., 1989: Possible climate change due to SO2-derived cloud condensation nuclei. Nature, 339, 365-367. Wigley, T. M. L., 1991: A simple inverse carbon cycle model. Global Biogeochemical Cycles, 5, 373-382. Wigley, T. M. L. and S. C. B. Raper, 1987: Thermal expansion of sea level associated with global warming. Nature, 330, 127-131. Wigley, T. M. L. and S. C. B. Raper, 1990: Natural variability of the climate system and detection of the greenhouse effect. Nature, 344, 324-327. Wigley, T. M. L. and S. C. B. Raper, 1993: Future changes in global-mean temperature and sea level. In: Climate and Sea Level Change: Observations, Projections, and Implications, R. A. Warrick, E. M. Barrow and T. M. L. Wigley (eds.), Cambridge University Press, Cambridge, UK, pp. 111-133. Wigley, T. M. L. and S. C. B. Raper, 1995: An heuristic model for sea level rise due to the melting of small glaciers. Geophys. Res. Let., 22, 2749-2752. Wright, D. G. and T. F. Stocker, 1991: A zonally averaged ocean model for the thermohaline circulation. Part I: Model development and flow dynamics. J. Phys. Oceanogr., 21, 1713-1724. Appendix 1 Summary of methods used to compute concentrations of greenhouse gases in the SAR WGI (Chapter 2 and Section 6.3) and the IPCC Technical Paper on Stabilization of Atmospheric Greenhouse Gases (IPCC TP STAB, 1997). In the above, C represents the atmospheric concentration of the corresponding gas, E the mass emission rate per year, ẞ a factor that converts from mass to concentration, and Tarm the mean lifespan of a molecule of the constituent in the atmosphere when accounting for chemical removal. In the case of methane, an additional removal process is through absorption by soils, and soil is the mean lifetime a methane molecule would have if absorption by soils were the only removal process. *VOCS = volatile organic compounds *The radiative forcing is directly computed from emissions or from the concentration of some other gas, as indicated in Appendix 2. Appendix 2 Functional dependence of radiative forcing on greenhouse gases and aerosols used in the SAR WGI (Section 6.3) and in IPCC TP STAB (1997). As discussed in the text, some of the forcing terms, as well as the natural sulphur emissions and anthropogenic sulphur emissions in 1990, are subject to considerable uncertainty. AQCH,-pure is the methane forcing before correction for overlap with N2O. C(1) and e(t) refer to concentrations and anthropogenic emissions of the gas in question at time 7, while Co is the pre-industrial concentration. Sulphate aerosol indirect forcing depends on the natural sulphur emission, ear which was assumed in the SAR WGI to be 42 TgS/yr. a higher value than currently accepted. Using a lower value leads to a slightly lower future indirect forcing (e.g., by 0.02 W m22 averaged over 1990-2100 for emission scenario IS92a). AQ = 8.62 x 10-5 AQCH, for 03 formation due to CH build-up AQ associated with O3 formation due to emissions of other gases ramps up to an assumed 1990 value of 0.32 W m2, then is held constant due to uncertainties AQ = -[0.000 552 Σ({NCI;C¡ } 1.7) + 3.048 Σ(NBr;C;)]/1 000 where C, is the concentration (pptv) of chlorine- or bromine-containing gas i, NCI; and NBr¡ are the numbers of chlorine or bromine atoms in gas i, and the summation is over all gases considered, (NBr1 = 1 for the two halons considered) AQ = e(t)/e 1990 AQ dir, 1990 where AQdir.1990 = -0.3 W m2 and e1990-69 TgS/yr * In the SAR WGL, the forcing is written as 6.3ln(C(1)/Co). The form used here is somewhat more transparent in that the coefficient in front of in (C(1)/C) is equal to the forcing that is assumed for a CO2 doubling. The forcing of 4.37 W m2 that had been used in the SAR WGI and IPCC TP STAB (1997) is about 0.5 W m2 too large. Since, for most results presented in the SAR WGI and IPCC TP STAB (1997), the climate response to a CO2 doubling is directly specified, this error will not affect the results except to the extent that the warming effect of non-CO2 gases will be slightly too small relative to the warming effect of CO2. + See First IPCC Assessment Report (IPCC, 1990), Table 2.2 for details concerning the overlap term. + The climate forcing due to loss of stratospheric ozone does not include effects of ozone loss on tropospheric chemistry. Appendix 3 Parameter values for the ice-melt module described in the text, and used to obtain the low, medium and high sea level rise estimates for this Technical Paper and IPCC TP STAB (1997). AT is a range of minimum temperatures for eventual disappearance of glaciers and ice-caps. AB, is the rise in sea level caused by the initial imbalance of the Greenland or Antarctic ice sheet. B and B are sensitivities of the mass balance (in terms of sea level rise) to global mean temperature changes. B2 is the sensitivity of the areal mean Antarctic mass balance (in terms of sea level rise) to changes in temperature through possible instability of the West Antarctic ice sheet. |