The Effects of Changing the Solar Constant on the Climate of a General Circulation Model

It follows from the analysis of obвervation data that the вecular variation of the mean temperature of the ЕапЬ сап Ье explained Ьу the variation of short·wave radiation, arriving at the surface ofthe Earth. In connection with thiв, the influence of long.term changes of radiation, cauвed Ьу variationв of atmospheric transparency оп the ther· таl regime is being studied. Taking into account the influence of changes of planetary albedo of the Earth under the development of glaciations оп the thermal regime, it is found that comparatively атаll variations of atmospheric transparency could Ье Bufficient for the development of quaternary glaciations. Ав paleogeographical reвearch including та· terials оп paleotemperature analуаев Ьав shown (Bowen, 1966, et ш), the ЕапЬ'а climate Ьав long differed from the preвent one. During the IMt two hundred miIlion years the temperature difference between the роlеа and equator Ьав been comparatively атаlI and there were по zones of cold climate оп the Еапь. Ву the end of the Tertiary period the temperature at tempera.te and high latitudes had decreaвed ар­ precia.bly, and in the Quaternary time subsequent increase in the thermal contrast between the poles and equator took place, that was followed Ьу the development of ice cover оп the lsnd a.nd осеans at temperate and hi~ latitudes. Тhe Bize of Quaternary glaciationв changed severa.l timeв, the present еросЬ corresponding to the moment of а decreaвe in the area of glacistions that still occupy а conвiderable part of the Earth's surface. То anвwer the question of in what way the clima.te will change in future, it is necessary to eвtablish the causes of Quaternary glaciations initia.tion and to determine the direction of their development. N umerOUB studieB оп this ргоЫеm contain various and often contradictory hypotheвes оп the causeB of glaciationв. Тhe absence of the generally accepted viewpoint 8s regardв thiв веетв to Ье explained Ьу the fa.ct that the existing hypotheses were based msinly оп qualitative conвiderationв allowing different interpretation. Теllив ХХI (1969), 5 Taking into account this consideration, we аЬаll ехатinе in the preвent paper the possibility of using quantitative methods of physical climatology to stt1dy the problem in queвtion. First1y we вЬаll dwell upon the problem of climate change regularities during the last centt1ry. Fig. 1 represents the sесшаг variation of annual temperatнre in the northern hemiерЬеге that was calct11ated from the таре of temperatнre anomalies for еасЬ month for the period of 1881 to 1960 which were compiled at the Main Geophysical Observatory. Line 1 in this figнre characterizeв the values of anomalies that are not smoothed, line 2 the апотаliее averaged Ьу ten-year periodв. Ае is seen from this figure, а riвe in temperature that began at the end of last century stopped in about 1940, and а fall in temperature started. Тhe temperatt1re in the northern hemisphere that increased in the warming period Ьу 0. 6С then decreaвed Ьу the middle of the fiftieв Ьу 0. 2С. А comparatively еЬоп­ period rise in temperature with атаllег amplitude was аlео observed in the last years of the XIXth century. Тhe curve of secular temperature variation сап ье compared with the curve of sect11ar variation of direct solar radiation with cloudless sky that waв drawn Ьу the data from а group of stations in Ешоре and America with the longestperiod вeries of observationв. Тhiв curve рге­ senting the valt1es of solar radiation smoothed