- 9 - 



rise only five years, ^/ 



Because only a fraction of the emissions will remain in the 

 atmosphere, concentrations of atmospheric CO2 cannot be predicted 

 by emissions alone. Nevertheless, although disagreement exists 

 about the exact fraction, an almost universal consensus exists 

 that it will be great enough to ensure that atmospheric CO2 

 levels will at least double in the next century. H/ 



The future rates of increase for the other greenhouse gases 

 are less certain. Much less is known about the sources 

 of methane, nitrous oxide, and chlorof luorocarbons^/ than the 

 sources of CO2. Furthermore, scientific understanding about 

 the fate of these gases once they enter the atmosphere is also 

 insufficient. Nevertheless, atmospheric concentrations of 

 these gases are likely to increase substantially, and in the 

 case of chlorof luorocarbons , probably at a rate faster than CO2. 



THE OCEANS WILL ALSO INFLUENCE THE RATE OF FUTURE WARMING 



The rate of future warming will depend on more than the 

 earth's equilibrium temperature sensitivity and the rate of 

 increase in atmospheric CO2 and other greenhouse gases. It 

 will also depend on the time it takes for the climatic system 

 to reach the equilibrium temperature. 



The most important factor delaying the warming will be 

 the oceans' capacity to absorb heat that would otherwise warm 

 the atmosphere .-*--*/ ^ s surface air temperatures increase, a 

 temperature difference will develop between the surfaces of 

 the atmosphere and the oceans, causing heat to be moved to 



