-6be as low as 10 to 1. A great deal of the coEputer tlne ls spent ln uovlng large masses of alr around the globe and recalculatlng the enyoptlc proflles every 10 to 15 Dlnutes. Thelr Edvantage ls that latltudl.nal effects ele coupletely lncluded but the sophlstlcstlon rlth vhlch vertlcal effects ean be treated ls ll.mlted due to the tlme and e:<penge aEsoclated lrlth runDfug the Eodel. One of the best geDela1 clrculation uodels of the Greenhouse Effect, and the one whlch ls Dost frequently quoted" ls that developed by Manabe end Wetherald9. Thelr predlctlons for the eliEatlc effect of a doubllng of C02 are ptesented in Vugraph 9. Thls vugraph predicts rhar a doubllng of the aEnospherlc C02 conceDtratlon would produce a tenperatule rise at lolrer eltltudes and a temperatule decrease above twenly kiloDeters. At the surfsce the teuperature !1se would be ebout 2 to 3oC from the equator up to about 600 latltude, with a Euch greater increase predlcted for the poles, The larger lnerease at the poles results froa two effects. Fllst, vertlcal nlxlng at the poles 1s reduced due to a natursl decreese ln the helght of the lnversion layer ln these reglons, Second, the Eodel contalns a teuperature - lce and snow cover - reflectlvity lnteractlon by which lncreages in etDospherLc teDperature uelt the snolr and lee cover and reduce the aoount of heat reflecled back lnto sPace. SlDpllflcatlons lDcolporated ln this nodel include fixed cloudlnese, a ttswa&p t' ocean which has zero heat capaclly, and ldealLzed treatDent of the topography. The oodel also contalns a siupllfled treatDent of the lnfraled ladiatlon tranEfer ln the atmosphere. In a separate calculatlon, l,taoabel0 calculated that the use of a nore sophlsticated trealuent, developed by Rodgers ead Walshawfl, would reduce the indlcated teDpelature lncreases at the 6urface by about 0.5"C. Ia the 11ght of this and other Dodels, 1t Ls genela11y accepted by cllDatologlsts that a doubllng of the carbon dloxlde concenttatl.on ln the at8osphere would produce fron 1.5oC-3.0"C wanolng at the eerth's sulface ln the lower and Eld-latltudes nith about 2 to 3 tl8es greater effect at the poles. The next nalural questlon ls the slgniflcance of such a temperature tlse copared to the oagnltude of lhe Batural teEperatule changes whlch have been obsenred to occur ln the pagt. A conparlson lrlth respect to hl.sto!1cal teoperatule changes sloce 185O accordlng to Kelloggl2, is presenEed 1a Vugraph 10. In thls fLgurq the observed oeen Northern Heolsphere teEperature ls plotted as the soIld l1ne. It can be seen that thls has varled less than iloc over the last century. The extrapolatlons past 1977 reeult from the appllcetlon of llanabe and Wetherald I s nodelv wlth the aesroptloo that the earbon dloxlde leve1s w111 double by 2050 A.D. The 1olrer dashed 11ne ln the flgure represents an estlDate of nhat the recent teEperatule tleDds nould have been lf the CO2 lncrease had not occurred.