--87 - 



1700 ppm. ^-Q/ Values for the parameters in the empirical 



heat-flux equation were obtained as follows: 



A CO2 : value obtained from the IEA and ORNL models; 



A CH 4 : 1.6 ppm from 1880 to 1980; concentrations after 1980 



increase as described in section on trace gases. 

 A N2O : 0.300 ppm in from 1880 to 1980; concentrations after 



1980 increase as described in section on trace gases. 

 A CC2 and a CC3 : See Table B-5. 



A V: constant 0.007 or 0.037 each year for 1980 to 2100 



A S: for 1880 to 2100; or for 1880 to 1980 and increased 



or decreased by 0.005% per year for 1980 to 2100. 



T e : 1.5°C, 3.0*C, and 4.5°C. 



Changes in Volcano Aerosols and Solar Irradiation 



For special cases changes in aerosols and solar luminosity 



were considered. Aerosols and dust that are produced by volcanoes 



can lower global temperatures by increasing reflection of incoming 



energy. A higher estimate of optical depth than the baseline was 



used as a special case. 



Baseline optical depth = .007 each year (dimensionless units) 

 High optical depth = .037 each year (dimensionless units) 



An optical depth of 0.037 is the highest twenty-year 

 average in the last century, while 0.007 is the average over 

 the period 1900-1980. No basis exists for assigning a different 

 value across a whole century. To sustain the high value over 

 the next 120 years would require a continuation of levels of 

 volcanic activity that have been sustained for decades, at most, 

 in recorded history. 



Recent evidence indicates some possible shifts in solar 

 luminosity making the term "solar constant" a bit of a misnomer. 



