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rise will increase water vapor levels in the atmosphere, 

 trapping more infrared radiation, and will also melt snow and 

 ice, decreasing the reflectivity of the earth. Other climatic 

 effects, such as changes in cloud cover and cloud heights, 

 could increase or diminish these amplifications by amounts 

 that cannot be predicted accurately. 



The 1979 report of the National Academy of Sciences (NAS), 

 prepared by a review panel of leading climatologists , reflected 

 the agreement of the scientific community on the effects of 

 these feedbacks. The panel members summarized their view by 

 stating: "We have tried but have been unable to find any 

 overlooked physical effect that could reduce the currently 

 estimated global warming due to a doubling of CO2 to negligible 

 proportions. . . . "_£/ Unfortunately, the panel's agreement 

 that a large warming will occur did not permit it to develop 

 a narrow range for the estimated global temperature increase. 

 However, it was able to conclude that the earth's equilibrium 

 temperature increase for doubled CO2 would be at least 1.5°C 

 (2.7°F) and not more than of 4.5° (8.1°F). 



Since 1979, scientific consensus has continued to grow 

 that the warming will be significant. In 1982, a second NAS 

 panel reviewed new evidence and confirmed the conclusions of 

 the first panel. _£/ More recently, the World Meteorological 

 Organization and other researchers have concluded that other 

 gases whose atmospheric concentrations are increasing could 

 double the warming from CO2 alone ._/ Thus, by the time CO2 



