Antarctic ice sheet with a consequent worldwide rise in sea- level, and opening 

 of the fabled Northwest Passage. (Sununary) . 



137 HANSEN, J., LACIS, A. and RIND, D. 1983. "Climate Trends Due to 

 Increasing Greenhouse Gases," Proceedings of Coastal Zone '83 . Third Symposium 

 on Coastal and Ocean Management, American Society of Civil Engineering, 

 Vol III, pp 2796-2810. 



Climate models indicate that global mean temperature should increase 

 3+1 . 5°C if atmospheric CO, is doubled. A broad range of empirical evidence, 

 ranging from the climate on other planets to paleoclimate and recent climate 

 trends on the earth, is consistent with the climate sensitivities indicated by 

 the climate models. After reviewing the evidence, we conclude that there is 

 strong evidence that a doubling of atmospheric CO2 will lead to a global cli- 

 mate warming of at least 1 . 5°C . Such an increase will correspond to a climate 

 state near or beyond the range of human experience. 



The time required to reach an effective doubling of atmospheric COj is 

 reduced by trace gases such as methane and the chlorof luorocarbons , which have 

 begun to increase at substantial rates during the past two decades. The con- 

 tribution of trace gases to the atmospheric greenhouse effect is now compara- 

 ble to that of COt. If current trends of atmospheric composition continue, 

 effective doubling of CO2 will occur in several decades. Based on the consen- 

 sus estimate for climate sensitivity, it appears likely that substantial cli- 

 mate change due to the greenhouse warming will become apparent during the next 

 1-2 decades. The authors recommend climate model studies as high priority 

 research. It is particularly important that climate models include regional 

 climate simulation with emphasis on slowly changing atmospheric composition. 

 (Modified Abstract) . 



138 HANSEN, J., RUSSELL, G., LACIS, A., FUNG, I., RIND. D. and STONE, P. 

 1985. "Climate Response Times: Dependence on Climate Sensitivity and Ocean 

 Mixing," Science . Vol 229, No. 4716, pp 857-859. 



The factors that determine climate response times were investigated with 

 simple models and scaling statements. The response times are particularly 

 sensitive to (i) the amount that the climate response is amplified by 

 feedbacks and (ii) the representation of ocean mixing. If equilibrium climate 

 sensitivity is 3°C or greater for a doubling of the carbon dioxide 

 concentration, then most of the expected warming attributable to trace gases 

 added to the atmosphere by man probably has not yet occurred. This yet to be 

 realized warming calls into question a policy of "wait and see" regarding the 

 issue of how to deal with increasing atmospheric carbon dioxide and other 

 trace gases. (Authors). 



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