CYCLICAL BEHAVIOR OF CLIMATE 



global, must be carefully monitored 

 and studied. Because the environ- 

 mental balance is delicate, and be- 

 cause it can be affected not only by 

 natural changes but also by man- 

 made ones, a thorough understand- 

 ing of climatic history and dynamics 

 is important indeed. Furthermore, 

 many climatic events appear to result 

 from triggering actions involving only 

 a small amount of energy. An under- 

 standing of these actions is important 

 not only to prevent catastrophic cli- 

 matic changes (as, for instance, the 

 development of new glaciation or the 

 melting in part or in whole of the ice- 

 caps of Greenland and Antarctica) 

 but also to develop methods for cli- 

 matic control. 



Judging from the record of the past 

 interglacial ages, the present time of 

 high temperatures should be drawing 

 to an end, to be followed by a long 

 period of considerably colder temper- 

 atures leading into the next glacial 

 age some 20,000 years from now. 

 However, it is possible, or even likely, 

 that human interference has already 

 altered the environment so much that 

 the climatic pattern of the near future 

 will follow a different path. For in- 

 stance, widespread deforestation in 

 recent centuries, especially in Europe 



and North America, together with in- 

 creased atmospheric opacity due to 

 man-made dust storms and industrial 

 wastes, should have increased the 

 earth's reflectivity. At the same time, 

 increasing concentration of industrial 

 carbon dioxide in the atmosphere 

 should lead to a temperature increase 

 by absorption of infrared radiation 

 from the earth's surface. When these 

 human factors are added to such 

 other natural factors as volcanic erup- 

 tions, changes in solar activity, and 

 resonances within the hydro-atmos- 

 phere, their effect can only be esti- 

 mated in terms of direction, not of 

 amount. 



Long-Term Temperature Change — 

 Because climatic changes across in- 

 tervals of years to centuries are so 

 much affected by the time-character- 

 istics of our turbulent hydro-atmos- 

 phere, no immediate breakthroughs 

 are to be expected toward a global 

 view of climatic dynamics across 

 these intervals. Much progress has 

 been made, however, in the study of 

 climatic changes across longer time 

 intervals, in which the intractable 

 turbulent effects cancel out. Studies 

 already under way concern: the am- 

 plitude of the glacial/interglacial tem- 



perature change at different latitudes 

 and in oceans other than the Atlantic, 

 using oxygen-isotopic analysis of suit- 

 able deep-sea cores; short-range 

 (years to centuries) climatic changes 

 through oxygen-isotopic analysis of 

 deep-sea cores for anaerobic basins; 

 and climatic change in the absence of 

 ice on earth using deep-sea cores of 

 Middle and Early Cenozoic and of 

 Late Mesozoic age obtained by the 

 D. V. Glamor Challenger. 



Prospects for Controlling Change 

 — Judging from past results, the cur- 

 rent and planned research should con- 

 tribute importantly to our under- 

 standing of many climatic problems 

 related to the evolution of man's en- 

 vironment and to the possibilities for 

 altering or controlling it. Research 

 conducted so far, for instance, has 

 made much clearer the significance of 

 the earth's reflectivity as a major cli- 

 matic factor. If reflectivity is indeed 

 so important, then control of today's 

 earth reflectivity by plastic films or 

 other means may be a way to control 

 the climatic deterioration already 

 under way. Again, because glaciation 

 is essentially a runaway phenomenon, 

 early control should be much easier 

 than later attempts at modifying an 

 already established adverse situation. 



Fluctuations in Climate Over Periods of Less Than 200 Years 



Factors thought to be responsible 

 for climatic fluctuations of less than 

 200 years' duration (and the sciences 

 involved) are: 



1. Short-term fluctuations in solar 

 radiation (solar and atmospheric 

 physics) — There is no evidence 

 of changes in the solar constant 

 greater than 0.2 percent, al- 

 though variations do occur in 

 the particle (X-ray) flux and 

 also, it is thought, in the ultra- 

 violet bands shorter than 0.2 

 microns. 



Correlations have been estab- 

 lished between ultraviolet flux 

 and stratospheric ozone concen- 

 trations, but the exact nature of 

 the links between ozone and the 

 intensity of the stratospheric 

 circulation, and the conse- 

 quences for the troposphere re- 

 gime, are uncertain. 



2. Changes in atmospheric constit- 

 uents (meteorology, atmos- 

 pheric chemistry) — Carbon di- 

 oxide (CO2) is a major absorber 

 of infrared radiation from the 



earth, whereas aerosols (espe- 

 cially dust) affect solar radiation 

 by scattering and absorption. 

 The ratio of absorption to scat- 

 tering is about 5/3 for urban 

 sites and 1/5 for prairie and 

 desert areas. 



The nearly global rise of tem- 

 perature in the first forty years 

 of this century (see Figure III-4) 

 has been attributed to increas- 

 ing CO2 content, although this 

 is by no means an accepted 

 theory. The magnitude of the 



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