-60- 



Volcanic Activity 



average -- Historical average optical depth value of .007 

 high — optical depth of .037 (average of highest two decades 



in last century. Both values are dimensionless ; see 



Appendix B) 



Solar Luminosity 



average -- no net change in historical luminosity 



low -- Linear decrease from historical average to 0.5 % less 



in 2100 

 high — Linear increase from historical average to 0.5% more 



in 2100 



Diffusivity Coefficient (k) 



very low — 0.20 cm2/sec 

 low — 1.18 cm2/sec 

 medium — 1.54 cm^/sec 

 high — 1.9 cm 2 /sec 

 very high — 4.0 cm2/sec 



CO? Retention (Fraction Airborne) 



ORNL — estimates from the ORNL carbon cycle model (.6 to .8) 

 low -- a constant fraction of 0.53 



