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12 October, 2003
US National Assessment of
Simulations used for the U.S. National Assessment
Canadian Centre for Climate Modelling and Analysis (CCCma): First generation Coupled General Circulation Model (CGCM1)
Optional additional scenarios for the National Assessment (1 run each).
United Kingdom Meteorological Office/ Hadley Centre for Climate Prediction and Research: HADCM2
time series: 1860, scenarios start 1990
CSM (Climate System Model)
|CGCM1||HADCM2||ECHAM4/OPYC3||GFDL||NCAR CSM||DOE PCM||HADCM3|
|Atmosphere||3.75o x 3.75o/10
|2.5o x 3.75o/19
|2.8o x 2.8o/19
|3.75o x 2.25o/14
|2.8o x 2.8o/18 T42||2.8o x 2.8o/18 T42||2.5o x 3.75o/19
|Land||modified bucket||canopy processes and stomatal resistance included||canopy processes and stomatal resistance included||bucket||canopy processes and stomatal resistance included||canopy processes and stomatal resistance included||canopy processes, stomatal resistance, and CO2 processes included (MOSES)|
|Ocean||1.8o x 1.8o
Based on GFDL MOM 1.1
|2.5o x 3.75o/20||2.8o x 2.8o/9||1.875o x 2.25o /18
GFDL MOM 1.1
|2.4o x 1.2o(VAR)/45||0.66o x 0.66o (VAR)/32||1.25o x 1.25o/20|
|Sea Ice||Thermodynamic only||Dynamic and Thermodynamic||Dynamic and Thermodynamic||Dynamic and Thermodynamic||Dynamic and Thermodynamic||Dynamic and Thermodynamic||Dynamic and Thermodynamic|
|Coupler||flux-adjusted||flux-adjusted||flux-adjusted||flux-adjusted||not flux-adjusted||not flux-adjusted||not flux-adjusted|
|Multiple Greenhouse Gases||no||no||no||no||yes||yes||yes|
|Sulfate Chemistry Model||no||no||no||no||yes||no||yes|
|*Sensitivity||3.5o C||2.6o C||2.6o C||3.4o C||2.0o C||2.0o C||3.3o C|
* sensitivity is based on 2xCO2 equilibrium experiments
Figure 1a: The 1% equivalent CO2 increase per year case is scenario IS92a before present and 1% per year compounded increase of CO2 into the future. Equivalent CO2 is a way of increasing the CO2 concentration to account for the radiative effects of the other greenhouse gases (N2O, CH4, O3, Halogenated compounds). The figure shows IS92a for CO2 alone (red) and equivalent CO2 (black). The CO2 concentration by 2100 is about 700 ppmv, but increases to about 1050 ppmv when the effects of the other greenhouse gases are included. The 1% increase per year scenario (blue) leads to a slightly larger increase than the IS92a equivalent CO2 scenario, resulting in around 1250 ppmv by 2100. The 0.5% equivalent CO2 increase per year case is actually just IS92d. The CO2 alone concentration for IS92d (light blue) results in 540 ppmv by 2100, whereas the equivalent CO2 (green) case actually used in the scenarios results in 730 ppmv CO2 by 2100. These concentrations were calculated from the radiative forcings developed for IPCC from upwelling diffusion energy balance models (T. Wigley, personal communication), using the radiative forcing functions in IPCC Technical Paper II (Houghton et al., 1997).
Figure 1c: The IS92a and IS92d total sulfate emissions scenarios. Only direct effects of sulfate aerosols have been considered in these scenarios. These emissions were calculated from the radiative forcings developed for IPCC from upwelling diffusion energy balance models (T. Wigley, personal communication) , using the radiative forcing functions in IPCC Technical Paper II (Houghton et al., 1997). The HADCM2 experiments used these emission values (TgS = teragrams of sulphur) in the form of surface albedos.
Figure 2a: The actual equivalent CO2 concentration used in the HADCM2 experiments. The values from the historical period are based on the IPCC estimated greenhouse gas forcings from 1765-1990 (Shine et al., 1990, Table 2.6; Mitchell and Johns, 1997), calculated as equivalent CO2. After 1990, CO2 is increased at the rate of 1%/year.
Figure 2c: SO4 (total) radiative forcings computed from the HADCM2 GCM (note that actual emission values were not used in HADCM2, which does not have a sulfate chemistry model). The values from the historical period are scaled from present-day values to correspond with historical estimates (Mitchell and Johns, 1997). Present and future sulfate loadings were derived using the sulfur cycle model of Langner and Rodhe (1991) and IS92a estimates for the future (Mitchell and Johns, 1997).
For a complete description of the NCAR CSM forcing scenarios, go to NCAR CSM.
Note: The CGCM1 experiments used the same forcing as the HADCM2 experiments (for the 1% case).
P. , Derwent, R. G., Wuebbles, D. J., and J. J. Morcrette, 1990, "Radiative
forcing of climate", Climate Change. The IPCC Scientific
Assessment, J. T. Houghton, G. J. Jenkins, and J. J. Ephraums, Eds.,
Cambridge University Press, 41-68.
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