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initial warming considerably. Because the magnitudes of these 



factors are not precisely known, a large range of temperature 



changes was used to represent all of these uncertainties: 



o The high scenario used the National Academy of Sciences' 

 (NAS) estimate of a 4.5°C rise for a CO2 doubling. 



o The mid-range scenario used the NAS middle estimate 

 of 3.0°C. 



o The low scenario used the NAS low estimate of 1.5°C. 



To integrate these assumptions about thermal sensitivity 

 and the changes in atmospheric concentrations, we used an equa- 

 tion obtained from the Goddard Institute for Space Studies 

 based on a one-dimensional radiative convective model. (See 

 Appendix B). Coupled with a box-diffusion model that 

 calculates the heat absorbed by oceans, the equation allowed a 

 consistent integration of changes in greenhouse gases, thermal 

 sensitivity, and the oceans' absorption of heat . 13/ 



Thermal Expansion of Ocean Waters 



Because ocean waters circulate slowly, the deeper layers 

 of the ocean will warm very slowly, and for our purposes, can 

 be ignored. As the top layers warm, however, the ocean's 

 volume will expand. Although the percentage expansion is 

 small, the resulting sea level rise could be significant from 

 the human perspective. 



