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Four new curves reflecting the extreme values observed for a 

 and b were then specified: 



These curves bound all possible changes in temperature, given the 

 time trend in atmospheric CO2 specified previously. The four 

 combinations of values for a and b are then transmitted to the 

 ORNL model. 

 Calculating CO? v. Time Curves with the ORNL Model 



The ORNL model is next employed to estimate future increases 

 in atmospheric CC>2, using the fossil-fuel CO2 emission scenarios 

 from the IEA model and the four sea-surface-temperature time 

 trends from the GISS model. Since four separate temperature/ 

 time curves are employed, four separate C02~time curves are 

 generated as output. Each CO2 curve is represented by estimates 

 of atmospheric CO2 concentrations in 10-year intervals from 1980 

 to 2100. Thus, a 4 by 13 matrix of values (corresponding to the 

 four time v. temperature curves and the thirteen inclusive 

 decades between 1980 and 2100) is generated as output. 



Estimating Final Temperature v. Time Curves 



The four "refined" time projections of CO2 are returned to 

 the GISS model to obtain a consensus temperature versus time 



